Diastereoselective addition reactions of racemic chiral vinyl sulfimides

Abstract

S-Aryl S-vinyl sulfimides are prepared by a new method via Horner–Wadsworth–Emmons reagents generated in situ. Lewis acid-catalysed Diels–Alder reaction of S-ethenyl-S-phenyl-N-tosylsulfimide with cyclopentadiene leads to the endo anti product with good diastereofacial and endo–exo selectivities. A range of alcohols and amines, with the limitation that they be practically usable in large excess, add to β-aryl vinyl sulfimides with modest diastereoselectivity. The major products of both the cycloaddition and the nucleophilic additions are rationalised by a model invoking addition to the least-hindered face of the s-cisconformation of the vinyl sulfimide.

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Introduction

Compounds 1, which have the IUPAC name “sulfimide” and the Chemical Abstractsname “sulfilimine”, remain little-studied in the area of stereoselective synthesis,¹ as compared with, for example, sulfoxides 2,² sulfur ylides 3 ³ and sulfoximides (sulfoximines) 4.⁴ However, there have been a number of recent reports regarding the synthesis of enantiomerically enriched sulfimides ^1,5 and their application in enantioselective synthesis of non-racemic epoxides and aziridines,⁶ which represent a small renaissance of interest in this field.

The asymmetric chemistry of chiral vinyl sulfoxides and sulfoximides is now well-established,^2,4 but the parallel chemistry of sulfimides remains largely unexplored. We decided to study the following classes of addition to the S-vinyl group of a sulfimide:

(i) Diels–Alder additions of dienes;

(ii) additions of nucleophiles;

(iii) additions of carbon-centred radicals.

To our knowledge, previous to our work there were no examples of classes (i) and (iii) in the sulfimide series. However, there are a number of reports from Yamamoto and co-workers of additions of alcohols, thiols, amines and doubly-stabilised carbanions to β-unsubstituted sulfimides,⁷ which are useful precedents for our work on the second class (nucleophilic additions). In the β-unsubstituted examples studied by the Yamamoto group, no new chiral centre is established. We envisaged carrying out analogous reactions on β-substituted vinyl sulfimides to establish the stereochemical influence of the sulfimidyl group.

Our initial work on the third class of reactions (radical additions) has already been communicated.⁸ In this case, the major product appears to result from α-addition with subsequent elimination of the sulfimidyl group (Scheme 1). A comparative study of reactions of radicals with various vinyl sulfur compounds has recently been completed and will be published separately.⁹

Scheme 1

Herein we describe (i) a short study on the Diels–Alder reactions of two aryl vinyl sulfimides, (ii) the results of nucleophilic additions to a series of new β-substituted aryl vinyl sulfimides and (iii) a stereochemical model for the addition reactions.

Results and discussion

(i) Diels–Alder additions

Lewis acid-catalysed reaction of 5 with cyclopentadiene was attempted in toluene at room temperature, using some of the Lewis acids proposed for the analogous cycloadditions of substituted vinyl sulfoxides.¹⁰ With TiCl₄ a complex mixture of unidentified products resulted, but with ZnCl₂ a mixture of cycloadducts was isolated in low yield, in which an endo product appeared to be dominant.

Finally, using Et₂AlCl at room temperature, a 55% isolated yield of a mixture of the four possible stereoisomers 6, which were not separated, was achieved (Scheme 2). The ¹H NMR spectrum of the purified mixture was compared with those of the analogous sulfoxides ¹¹ and sulfoximides,¹² which resulted from uncatalysed reactions at relatively high temperature. Not surprisingly, the closest fit, as judged by comparison of chemical shifts, was with the sulfoximides 7 (which differ only in the oxo group at sulfur and a para methyl group on the non-sulfonyl S-aryl group) and we thus used comparison with 7 to tentatively assign structures to the four isomers.

Scheme 2

The chemical shift data for the major isomer 6a are a reasonable match for those of both of the endo sulfoximides 7a and 7d (Table 1) and we thus confidently assign the endo stereochemistry to 6a. Closer inspection reveals an excellent match between the data for 6a and sulfoximide 7a, with the greatest discrepancies being with those protons (H-1 and H-3endo) that would be expected to be the most affected by the oxo group. The configuration of another closely analogous sulfoximide was established by the Glass group by X-ray crystallography ¹² and we thus believe the assignment of the relative stereochemistry of the sulfur centre to be secure. This leads us to speculate that the major product in the sulfimide case is the endo anti compound 6a (adapting the terminology proposed by Montanari and co-workers ^13,14 and referring to approach past the S–N rather than S–O bond).

Table 1 Chemical shift data for endo sulfimide 6a and endo sulfoximides 7a and 7d

6a δ/	7a δ/	7d δ/
H-1	2.44	2.69	3.57
H-2	3.78	3.96	3.93
H-3 endo	1.32	1.69	1.33
H-3 exo	2.13	2.23	1.78
H-4	2.93	2.97	2.92
H-5 & H-6	5.97, 6.29	5.79, 6.21	5.82, 6.14
H-7 syn	1.25	1.25	1.27
H-7 anti	1.49	1.48	1.49

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The data for the 11% and 5% isomers cannot be extracted completely from the spectrum, making unambiguous structural assignments difficult. Nevertheless it can be observed that the data for these two compounds are (a) quite similar and (b) best matched to the two exo sulfoximide analogues 7b and 7c. Hence we tentatively assign the exo stereochemistry to isomers 6b and 6c. Assignment of the relative stereochemistry of the sulfur centre is not possible from these data; isolation and either crystallography or stereospecific oxidation to the sulfoximide would be required. Finally, by a process of elimination we assign the endo syn stereochemistry to the minor isomer 6d, but there are no independent data to confirm this.

If our assignments are correct, the Lewis acid-catalysed reaction of vinyl sulfimide 5 with cyclopentadiene proceeds with significant endo anti selectivity. Comparison with the thermal reactions of the corresponding sulfoxide 8 and sulfoximide 9 shows that the endo selectivity is as expected (Table 2). However, there is a significant change in both the magnitude and sense of the diastereofacial selectivity (Table 2). We have followed De Lucchi in extending the syn/anti nomenclature to sulfoximides by reference to the oxo group rather than the imido group,¹⁴ but note that this is necessarily somewhat artificial. The variations in syn/anti selectivity (if correctly assigned) need not be surprising considering the differences in reaction conditions (115 °C for the sulfoxide, refluxing dichloromethane for the sulfoximide and Et₂AlCl at room temperature for the sulfimide). Indeed, prior conversion of the vinyl sulfoxide to a sulfoxonium salt leads to the endo anti product with good stereoselectivities.^11c

Table 2 Stereoselectivities in reactions of cyclopentadiene with sulfoxide 8, sulfoximide 9 and sulfimide 5

	endo∶exo	syn∶anti
a  Assuming 11% exo isomer is syn, otherwise 13∶87.
Sulfoxide 8	64∶36	50∶50
Sulfoximide 9	81∶19	55∶45
Sulfimide 5	84∶16	7∶93 ^a

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We proceeded to attempt the same Et₂AlCl-catalysed reaction of the Z-β-substituted analogue 11. Sulfimide 11 was prepared by imidation of the known sulfide 10 which is the isomerically pure product of addition of thiocresol to phenylacetylene (Scheme 3). Reaction with cyclopentadiene under our previous best conditions led to a crude product with signals in the ¹H NMR spectrum at around 6.0 and 6.45 ppm (cf. 6.0 and 6.3 ppm for the alkene protons in 11) and no signal for the upfield vinylic proton of the starting material 11 at 6.3 ppm. However, on work-up only unreacted starting material 11 could be isolated. It seems that the Diels–Alder reaction does indeed occur, but that a retro-reaction occurs during work-up to give back the starting material. This observation is significant since, as pointed out by Paquette and Magnus,¹⁵ low yields in sulfoxide-mediated Diels–Alder reactions are often attributed to low reactivity, without consideration of the possibility of the existence of a relatively fast equilibrium. It may be that in our case the Et₂AlCl is not a true catalyst (three equivalents were used), but remains coordinated to the product, thus preventing the reverse reaction occurring until the Lewis acid is removed.

Scheme 3

We wished to extend the cycloaddition chemistry to acyclic dienes, but starting material was recovered from reactions of both sulfimides 5 and 11 with Danishefsky’s diene 12.

(ii) Nucleophilic additions to vinyl sulfimides

As mentioned in the introduction, we were interested in the stereochemical influence of the sulfimidyl group on nucleophilic additions to the β-vinylic carbon of sulfimides of general structure 13. Since the sulfimidyl group is readily reduced to the corresponding sulfide,¹⁶ additions of alcohols and amines would lead to derivatives of β-hydroxy- and β-aminosulfides respectively, which have potential as chiral ligands for metals.¹⁷ Hence, it was important that our chemistry was readily adaptable to the enantiomerically pure analogues.

The two main literature routes to vinyl sulfimides are direct imidation of sulfides, as used in Section (i) above, of which no asymmetric version yet exists for vinyl analogues,^5a and elimination from β-halo sulfimides.¹⁸ Although a good ee was reported for one example of an asymmetric version of this elimination reaction (Scheme 4),^18b we did not feel that this procedure had general potential.

Scheme 4

At the start of our work, one of the few readily-available enantiomerically-pure sulfimides was compound 14 prepared from the corresponding commercially available enantiomerically-pure sulfoxide using the procedure of Cram et al.¹⁹ We therefore decided to use this methyl sulfimide as our starting material and to adapt the method used by Craig’s group for the synthesis of related vinyl sulfoximides 15.²⁰ This involves the in situ generation of Horner–Wadsworth–Emmons type reagents from the methyl sulfoximide and their reaction with aldehydes (Scheme 5).

Scheme 5

Using the identical conditions to Craig’s group,²⁰ we were able to isolate a range of new racemic chiral β-substituted aryl vinyl sulfimides 16 (Table 3), albeit in lower yield than observed with the sulfoximides. In all cases the (E ) isomer was the major product, but the selectivities varied considerably with the substituent. The aryl derivatives gave separable (E )∶(Z ) mixtures, in which the predominance of the (E ) product increased with increasing electron demand of the substituent (Table 3), whereas for the isopropyl and tert-butyl compounds, the (Z ) isomer was not observed. However, another alkyl derivative, the cyclopropyl product 16g, showed virtually no selectivity.

Table 3 Yields and stereoselectivities for syntheses of vinyl sulfimides 16

16	R	Yield (%) ^a	E∶Z
a  Yield of (E∶Z) mixture. b  Not determined.
a	p-MeOC6H4	60	80∶20
b	Ph	48	85∶15
c	p-ClC6H4	40	95∶5
d	p-O2NC6H4	5	^b
e	i-Pr	64	98∶2
f	t-Bu	39	98∶2
g	cyclopropyl	39	53∶47

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Although all the products described here are racemic we did undertake a small-scale preparation of 16b using enantiomerically-enriched 14 and determined that the ees of product and starting material were the same (by integration of the p-tosyl methyl signals in the ¹H NMR spectrum in the presence of trifluoroanthrylethanol). Hence this method should be applicable to asymmetric synthesis.

The reactions of some of the new aryl sulfimides with some representative alcohols and amines are summarised in Scheme 6 and Table 4. Unfortunately, the effect of the β-substituent meant that these reactions only gave useful yields, as compared with the unsubstituted literature examples,⁷ when the alcohol or amine was used as the solvent; a similar phenomenon was reported by Pyne et al. in the sulfoxide series.²¹ Hence, the scope of this reaction is limited to cheap, volatile alcohols and amines which can feasibly be used as solvents.

Table 4 Yields and stereoselectivites for nucleophilic additions to vinyl sulfimides 16

	X	Y	R	Yield (%)	17∶18
a  Isolated yield of 17. b  Mixture of 17 and 18. c  Major isomer not identified.
a	O	H	PhCH2	64 ^a	>97∶3
b	O	H	Et	73 ^a	90∶10
c	O	OMe	Et	32 ^b	90∶10
d	NH	H	PhCH2	63 ^a	80∶20
e	NH	Cl	PhCH2	57 ^a	80∶20
f	NH	H	i-Pr	53 ^b	80∶20
g	NH	Cl	i-Pr	69 ^b	80∶20
h	NEt	H	Et	46 ^b	70% de ^c
i	NEt	Cl	Et	56 ^b	70% de ^c

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Scheme 6

The diastereoselectivities of the reactions were modest (Table 4), with the exception of the addition of benzyl alcohol which proceeded in at least 95% de. The stereochemistry of the major isomer was inferred by comparison with some sulfoxide analogues 19.²² The benzylic proton in Pyne et al.’s examples of (R,S) 19 are doublets of doublets with coupling constants of around 3.0 and 10.5 Hz, in excellent agreement with our major isopropylamine adducts 17f and 17g (3.0 and 10.5 Hz for both examples) and the major benzylamine adducts 17d and 17e (2.3 and 10.7 Hz approximately). Furthermore, the major alcohol adducts 17a–c have even more disparate coupling constants (2.1 and 10.9 Hz approximately). We therefore propose the (RS,SR) stereochemistry for all these adducts.

The same coupling constants for the diastereoisomeric (R,R) sulfoxides 20 are less easy to extract from the literature data, but can be seen to be significantly closer to each other in value. With sulfimides 18f and 18g we were able to interpret the ¹H NMR data for the minor isomer; the coupling constants for the benzylic proton (dd, J 7.2, 7.2 Hz in both cases) resembled those of sulfoxides 20 and thus gave support to our stereochemical assignments. The equivalent multiplets for the diethylamine adducts 17h, 17i, 18h and 18i have a different pattern, presumably due to the significant increase in the steric demand of the amino group, and we are thus reluctant to assign the relative stereochemistry of these adducts.

Additions of alcohols and amines to the tert-butyl derivative 16f were unsuccessful, presumably due to steric hindrance. However, the isopropyl derivative 16e did react with ethanol, but with a different result. In this case the product was the known sulfonamide 22 which we presume to have been formed via alkene 21 (Scheme 7). Rearrangements of closely related allylic sulfimides are well-known.^5a,23

Scheme 7

Finally, we wished to demonstrate that the chiral sulfimide products 17 could be readily transformed to sulfides, to permit synthesis of potentially useful chiral ligands. The most challenging substrates were the benzyl alcohol and benzylamine adducts 17a, 17d and 17d, since selective hydrogenolysis of the S–N bond in the presence of the benzyl groups was required. In fact, with both 17a and 17d the reduction proceeded cleanly to furnish the target sulfides 23 with the O- and N-benzyl groups intact (Scheme 8).

Scheme 8

(iii) Rationalisation of the sense of stereoselectivity

Pyne and co-workers have remarked that one simple model can account for the majority of stereoselective reactions of vinyl sulfoxides.²⁴ Direct extension of this model leads to Fig. 1, where the reactive conformation of the vinyl sulfimide is s-cis and addition occurs from the least hindered face. In the cycloaddition, there is a need to invoke the usual endo preference and it should be noted that a Lewis acid is also involved in this case.

Fig. 1

The model correctly predicts (i) the anti cycloadduct 6a to be the major Diels–Alder product and (ii) the observed outcome of the addition of amines and alcohols to yield the (RS,SR) major products 17 (as with vinyl sulfoxides ²¹).

Conclusion

S-Aryl S-vinyl sulfimides were prepared by a literature route and by a new method starting from S-aryl S-methyl sulfimides via Horner–Wadsworth–Emmons reagents generated in situ, this route being appropriate for the synthesis of enantiomerically enriched vinyl sulfimides.

Lewis acid-catalysed Diels–Alder reaction of one unsubstituted vinyl sulfimide with cyclopentadiene was successful, leading to the endo anti product with good diastereofacial and endo–exo selectivities, but extension to other examples failed. A range of alcohols and amines, with the limitation that they be practically usable in large excess, add to β-aryl vinyl sulfimides with modest diastereoselectivity. The major products of both the cycloaddition and the nucleophilic additions are predicted by a model invoking addition to the least-hindered face of the s-cis conformation of the vinyl sulfimide.

Experimental

General

Melting points were determined on a Stuart Scientific SMP1 melting point apparatus and are uncorrected. Microanalyses were performed at the University of Warwick. Mass spectra were recorded on a Kratos MS90 spectrometer. Infra-red spectra were recorded on a Perkin-Elmer 1720X Fourier transform spectrometer. NMR spectra were recorded on Bruker ACF 250 or Bruker ACP 400 instruments. Flash chromatography was performed on silica gel (Merck Kieselgel 60F₂₅₄, 230–400 mesh). Racemic methyl sulfimide 14 was prepared by the literature route.^23a

S-Ethenyl-S-phenyl-N-p-tosylsulfimide 5 ^18a

Phenyl vinyl sulfide (1.0 g, 7.3 mmol) and glacial acetic acid (0.2 cm³, 3.5 mmol) were added to a solution of chloramine-T hydrate (2.07 g, 7.3 mmol) in absolute ethanol (200 cm³). The mixture was stirred at 40 °C for 1 hour. The mixture was cooled to room temperature and stirred overnight. The solvent was removed and water (100 cm³) and dichloromethane (100 cm³) were added. The organic layer was separated, dried over anhydrous magnesium sulfate and concentrated in vacuo to give the crude product. Trituration with ether followed by filtration and flash chromatography on silica gel using chloroform–ethyl acetate (8∶1) as eluant furnished white crystals of sulfimide 5 (1.01 g, 45%), mp 109–110 °C (lit.,^18a 111–113 °C); R_f 0.61 (EtOAc) (Found: C, 59.02; H, 4.94; N, 4.55. C₁₅H₁₅NO₂S₂ requires C, 59.02; H, 4.92; N, 4.59%); ν_max(CHCl₃)/cm⁻¹ 1599, 1494, 1478, 1446, 1298, 1284, 1143, 1089, 962; δ_H(250 MHz; CDCl₃) 2.34 (3H, s, Me), 6.03 (1H, dd, J = 8.4, 0.6 Hz, H-trans), 6.29 (1H, dd, J = 15.6, 0.6 Hz, H-cis), 6.41 (1H, dd, J = 8.4, 15.6 Hz, CHS), 7.17 (2H, AA′ of AA′BB′, J = 8.5 Hz, tosyl), 7.44–7.55 (3H, m, meta and para Ph), 7.64 (2H, m, ortho Ph), 7.75 (2H, BB′ of AA′BB′, J = 8.5 Hz, tosyl); δ_C(62.9 MHz; CDCl₃) 21.26 (Me), 126.02 (2), 126.80 (2), 129.10 (2), 129.68, 129.90 (2), 132.47, 132.78, 134.36, 141.18, 141.67; m/z (CI; NH₃) 306 (65%, MH⁺), 198 (38), 189 (100), 155 (24), 137 (100), 108 (64), 91 (61), 65 (21).

Reaction of ethenyl phenyl sulfimide 5 with cyclopentadiene

Diethylaluminium chloride (0.3 cm³ of a 1 M solution in hexanes, 0.30 mmol) was added to a solution of freshly distilled cyclopentadiene (0.10 cm³, 0.76 mmol) and vinyl sulfimide 5 (30 mg, 0.10 mmol) in dry toluene (10 cm³) under nitrogen at 0 °C. The mixture was stirred at 0 °C for 2 hours and then at room temperature for a further 12 hours. The solvent was removed under vacuum and the residue was subjected to flash chromatography on silica gel using chloroform–ethyl acetate (4∶1) as eluant furnishing white crystals of S-norbornenyl-S-phenyl-N-tosylsulfimide 6 in a ratio of 82∶11∶5∶2 (endo anti∶exo∶exo∶ endo syn), (20 mg, 55%); R_f (CHCl₃): 0.32 (Found: C, 64.41; H, 5.52; N, 3.44. C₂₀H₂₁NO₂S₂ requires C, 64.69; H, 5.66; N, 3.77%).

endo-anti-S-(Bicyclo[2.2.1]hept-5-en-2-yl)-S-phenyl-N-tosylsulfimide 6a.. δ _H(400 MHz; CDCl₃) 1.25 (1H, d, J = 8.9 Hz, H-7syn), 1.32 (1H, ddd, J = 13.6, 3.3, 3.3 Hz, H-3endo), 1.49 (1H, d, J = 8.9 Hz, H-7anti), 2.13 (1H, ddd, J = 13.1, 8.7, 3.5 Hz, H-3exo), 2.27 (3H, s, tosyl Me), 2.44 (1H, s, H-1), 2.93 (1H, s, H-4), 3.78 (1H, ddd, J = 8.7, 3.5, 3.5 Hz, H-2), 5.97 (1H, dd, J = 5.7, 2.7 Hz, [double bond, length half m-dash]CH), 6.29 (1H, dd, J = 5.7, 3.1 Hz, [double bond, length half m-dash]CH), 7.04 (2H, AA′ of AA′BB′, J = 8.1 Hz, tosyl), 7.46 (2H, m, Ph), 7.50 (1H, m, Ph), 7.59 (2H, BB′ of AA′BB′, J = 8.2 Hz, tosyl), 7.68 (2H, m, Ph); δ_C(100.6 MHz; CDCl₃) 21.38 (Me), 29.69 (C-3), 42.30 (C-1/C-4), 44.53 (C-1/C-4), 49.38 (C-7), 66.93 (C-2), 126.23 (2), 127.37 (2), 128.96 (2), 129.90 (2), 131.43, 132.71, 135.36, 139.72, 141.33, 141.44.

exo-S-(Bicyclo[2.2.1]hept-5-en-2-yl)-S-phenyl-N-tosylsulfimide 6b and 6c.. Discernible data for the 11% isomer: δ_H(400 MHz; CDCl₃) 0.82 (1H, dd, J = 12.7, 3.0, 3.0 Hz), 1.40 (1H, ddd, J = 12.0, 9.0, 4.0 Hz), 2.29 (3H, s), 2.36 (1H, s), 3.35 (1H, s), 5.70 (1H, dd, J = 5.7, 2.8 Hz), 6.22 (1H, dd, J = 5.7, 3.1 Hz), 7.10 (2H, AA′ of AA′BB′, J = 8.1 Hz), 7.39 (2H, m), 7.65 (2H, m); δ_C(100.6 MHz; CDCl₃) 21.38, 29.02, 42.52, 45.01, 48.29, 65.70, 126.37 (2), 127.37 (2), 129.05 (2), 129.76 (2), 131.43, 132.81, 133.95, 139.04, 141.33, 141.44. Discernible data for the 5% isomer: δ_H(400 MHz; CDCl₃) 1.67 (1H, ≈d, J = 10.0 Hz), 1.91 (1H, ddd, J = 13.0, 4.0, 4.0 Hz), 2.42 (1H, s), 2.61 (1H, s), 3.25 (1H, s), 5.85 (1H, dd, J = 5.0, 4.0 Hz), 6.20 (1H, dd, J = 6.0, 3.6 Hz), 7.22 (2H, AA′ of AA′BB′, J = 8.0 Hz), 7.78 (2H, m); δ_C(100.6 MHz; CDCl₃) 21.05, 29.32, 41.94, 44.83, 46.05, 63.93.

endo-syn-S-(Bicyclo[2.2.1]hept-5-en-2-yl)-S-phenyl-N-tosylsulfimide 6d.. The only discernible peak in the ¹H NMR spectrum was: δ_H(400 MHz; CDCl₃) 6.15 (dd, J = 6.0, 3.6 Hz). Mixture: ν_max(CHCl₃)/cm⁻¹ 1598, 1494, 1476, 1445, 1338, 1295, 1282, 1142, 1089, 1022, 1006, 971, 816; m/z (CI; NH₃) 372 (2%, MH⁺), 203 (22), 136 (33), 84 (100), 65 (37).

(Z )-Phenylethenyl p-tolyl sulfide 10 ²⁵

To a solution of sodium (1.85 g, 80.4 mmol) in absolute ethanol (100 cm³) was added thiocresol (10.0 g, 80.5 mmol) and phenylacetylene (9.70 cm³, 80.4 mmol). The mixture was refluxed for 2 days. After standing for a further 2 days, the mixture was poured into water (100 cm³) and dichloromethane (100 cm³) was added. The organic layer was separated, and the aqueous layer was extracted twice with dichloromethane (100 cm³). The combined organic layers were dried over anhydrous magnesium sulfate and concentrated in vacuo, giving exclusively sulfide 10 (14.72 g, 81%), mp 62–64.5 °C (lit.,²⁵ 64–65.5 °C); R_f (MeOH): 0.80 (Found: C, 79.57; H, 6.22. C₁₅H₁₄S requires C, 79.64; H, 6.19%); ν_max(CHCl₃)/cm⁻¹ 1599, 1588, 1494, 1445, 1358, 1094, 1019, 849, 810; δ_H(250 MHz; CDCl₃) 2.42 (3H, s, Me), 6.56 (1H, d, J = 10.8 Hz, CHPh), 6.64 (1H, d, J = 10.8 Hz, CHS), 7.23 (2H, AA′ of AA′BB′, J = 7.9 Hz, p-tolyl), 7.30 (5H, m, Ph), 7.65 (2H, BB′ of AA′BB′, J = 7.9 Hz, p-tolyl); δ_C(62.9 MHz; CDCl₃) 21.10 (Me), 126.49 (2), 127.02 (2), 127.05 (2), 128.32 (2), 128.74, 129.96, 130.50, 132.67, 136.58, 137.38; m/z (EI) 226 (100%, M⁺), 211 (30), 91 (25), 77 (23).

(Z )-S-2-Phenylethenyl-S-p-tolyl-N-p-tosylsulfimide 11

An adaptation of a literature method was used.^23a To a solution of sulfide 10 (6.00 g, 26.5 mmol) and hexadecyltributylphosphonium bromide (0.675 g, 1.3 mmol) in dichloromethane (200 cm³) was added N-chloramine-T hydrate (7.75 g, 27.5 mmol) and the mixture was stirred for 2 days. The reaction mixture was washed with 5% aqueous sodium hydroxide solution (200 cm³) and the organic layer was separated and dried over anhydrous magnesium sulfate. The solvent was then evaporated, leaving a yellow oil, which was purified by flash chromatography on silica gel using chloroform–ethyl acetate (9∶1) as eluant. White crystals of a mixture of (E ) and (Z ) sulfimides (10∶90) were obtained which on trituration yielded (Z )-11 (7.95 g, 75%); R_f (CHCl₃): 0.35; mp 123.5–125 °C (Found: C, 66.32; H, 5.33; N, 3.61. C₂₂H₂₁NO₂S₂ requires C, 66.84; H, 5.32; N, 3.54%); ν_max(CHCl₃)/cm⁻¹ 1597, 1492, 1446, 1297, 1284, 1143, 1088, 967; δ_H(250 MHz; CDCl₃) 2.32 (3H, s, tolyl Me), 2.38 (3H, s, tosyl Me), 6.33 (1H, d, J = 10.0 Hz, [double bond, length half m-dash]CHPh), 7.10 (2H, AA′ of AA′BB′, J = 7.8 Hz, tolyl), 7.13 (1H, d, J = 10.0 Hz, [double bond, length half m-dash]CHS), 7.27 (2H, AA′ of AA′BB′, J = 7.8 Hz, tosyl), 7.38 (5H, m, Ph), 7.54 (2H, BB′ of AA′BB′, J = 7.8 Hz, tolyl), 7.70 (2H, BB′ of AA′BB′, J = 7.8 Hz, tosyl); δ_C(62.9 MHz; CDCl₃) 21.30 (2 × Me), 126.05 (2), 126.24 (2), 128.76 (2), 128.99 (2), 129.43 (2), 130.09, 130.51 (2), 132.42, 132.58, 141.20, 141.36, 141.40, 142.77 (one C missing); m/z (CI; NH₃) 396 (5.4%, MH⁺), 227 (100), 226 (74), 189 (34), 124 (28), 108 (21), 91 (45).

(E )-S-[2-(4-Methoxyphenyl)ethenyl]-S-p-tolyl-N-p-tosylsulfimide 16a

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (1.0 g, 3.26 mmol) in THF (100 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 1.3 cm³, 3.26 mmol), potassium tert-butoxide (1.0 M, 3.27 cm³, 3.26 mmol) and diethyl chlorophosphate (0.47 cm³, 3.26 mmol). After stirring for 10 min, p-anisaldehyde (0.4 cm³, 3.26 mmol) in THF (2 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (100 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 80 cm³). The combined organic layers were washed with water (150 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (60% yield) showed an (E∶Z) ratio of 80∶20. Column chromatography of the yellow oil on silica using ether as eluant separated the stereoisomers. The major product was the (E) isomer 16a (0.67 g, 48%), mp 122–124 °C; R_f 0.30 (ether) (Found: C, 64.91; H, 5.45; N, 3.29. C₂₃H₂₃NO₃S₂ requires C, 64.81; H, 5.39; N, 3.23%); ν_max(Nujol)/cm⁻¹ 1602, 1512, 1465, 1307, 1293, 1170, 1136, 1087, 959, 802; δ_H(250 MHz; CDCl₃) 2.29 (3H, s, Me tolyl), 2.36 (3H, s, Me tosyl), 3.79 (3H, s, MeO), 6.42 (1H, dd, J = 15.1, 0.9 Hz, [double bond, length half m-dash]CHAr), 6.85 (2H, AA′ of AA′BB′, MeOC₆H₄), 7.13 (AA′ of AA′BB′, tolyl), 7.25 (AA′ of AA′BB′, tosyl), 7.26 (1H, d, J = 15.1 Hz, [double bond, length half m-dash]CHS), 7.30 (2H, BB′ of AA′BB′, MeOC₆H₄), 7.55 (BB′ of AA′BB′, tolyl), 7.76 (BB′ of AA′BB′, tosyl); δ_C(62.9 MHz; CDCl₃) 21.3 (2 × Me), 55.4 (MeO), 114.3, 119.8 ([double bond, length half m-dash]CHAr), 125.3, 126.2, 126.6, 129.0, 129.7, 130.5, 132.3, 141.3, 141.4, 141.5, 142.9, 161.6 ([double bond, length half m-dash]CHS); m/z (EI) 426 (2%, MH⁺), 256 (100), 241 (21), 211 (35), 91 (76).

(E )-S-(2-Phenylethenyl)-S-p-tolyl-N-p-tosylsulfimide 16b

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (4.0 g, 0.013 mol) in THF (300 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 5.2 cm³, 0.013 mol), potassium tert-butoxide (1.0 M, 13 cm³, 0.013 mol) and diethyl chlorophosphate (1.88 cm³, 2.0 mol). After stirring for 10 min, benzaldehyde (1.32 cm³, 0.013 mmol) in THF (5 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (300 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 150 cm³). The combined organic layers were washed with water (300 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (48% yield) showed an (E∶Z) ratio of 85∶15. Column chromatography of the yellow oil on silica using chloroform–ethyl acetate 4∶1 as eluant separated the stereoisomers. The major product was the (E ) isomer 16b (1.95 g, 38%), mp 121–122 °C; R_f 0.33 (ether) (Found: C, 66.80; H, 5.35; N, 3.54. C₂₂H₂₁NO₂S₂ requires C, 66.90; H, 5.33; N, 3.46%); ν_max(Nujol)/cm⁻¹ 1662, 1601, 1491, 1307, 1138, 661; δ_H(400 MHz; CDCl₃) 2.30 (3H, s, Me tolyl), 2.37 (3H, s, Me tosyl), 6.55 (1H, d, J = 15.2 Hz, [double bond, length half m-dash]CHPh), 7.14 (2H, AA′ of AA′BB′, tolyl), 7.26 (2H, AA′ of AA′BB′, tosyl), 7.32 (1H, d, J = 15.2 Hz, [double bond, length half m-dash]CHS), 7.35 (5H, m, Ph), 7.55 (2H, BB′ of AA′BB′, tolyl), 7.76 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 21.30 (Me tolyl), 21.38 (Me tosyl), 122.70 ([double bond, length half m-dash]CHPh), 126.23, 126.82, 128.91, 129.07, 129.43, 130.56, 130.76, 132.00, 132.70, 141.07 ([double bond, length half m-dash]CHS), 141.40, 141.54, 143.20; m/z (FAB) 396 (100%, MH⁺), 227 (92), 226 (100).

The minor isomer (Z )-S-(2-phenylethenyl)-S-p-tolyl-N-p-tosylsulfimide 11 was also isolated (9%), mp 124–125 °C; spectra identical to 11 above.

(E )-S-[2-(4-Chlorophenyl)ethenyl]-S-p-tolyl-N-p-tosylsulfimide 16c

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (4.0 g, 0.013 mol) in THF (300 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 5.2 cm³, 0.013 mol), potassium tert-butoxide (1.0 M, 13 cm³, 0.013 mol) and diethyl chlorophosphate (1.88 cm³, 2.0 mol). After stirring for 10 min, benzaldehyde (1.32 cm³, 0.013 mmol) in THF (5 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (300 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 150 cm³). The combined organic layers were washed with water (300 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (40% yield) showed an (E∶Z) ratio of 95∶5. Column chromatography of the yellow oil on silica using chloroform–ethyl acetate 4∶1 as eluant was used to isolate the (E ) isomer (1.95 g, 38%), mp 108–109 °C; R_f 0.43 (ether) (Found: C, 61.16; H, 4.66; N, 3.18. C₂₂H₂₀ClNO₂S₂ requires C, 61.45; H, 4.69; N, 3.18%); ν_max(Nujol)/cm⁻¹ 1652, 1491, 1307, 1138, 955, 803, 774, 661; δ_H(400 MHz; CDCl₃) 2.32 (3H, s, Me tolyl), 2.40 (3H, s, Me tosyl), 6.54 (1H, d, J = 15.1 Hz, [double bond, length half m-dash]CHPh), 7.16 (2H, AA′ of AA′BB′, tolyl), 7.26 (1H, d, J = 15.1 Hz, [double bond, length half m-dash]CHS), 7.31 (6H, m, tosyl and p-ClC₆H₄), 7.55 (2H, BB′ of AA′BB′, tolyl), 7.76 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 21.4 (Me tolyl and tosyl), 123.26 ([double bond, length half m-dash]CHPh), 126.11, 126.80, 129.02, 129.07, 129.21, 131.22, 131.61, 132.07, 136.32, 139.07, 141.36 ([double bond, length half m-dash]CHS), 141.58, 143.21; m/z (FAB) 430 (49%, MH⁺).

(E )-S-(3-Methylbut-1-enyl)-S-p-tolyl-N-p-tosylsulfimide 16e

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (1.0 g, 3.26 mmol) in THF (100 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 1.3 cm³, 3.26 mmol), potassium tert-butoxide (1.0 M, 3.27 cm³, 3.26 mmol) and diethyl chlorophosphate (0.47 cm³, 3.26 mmol). After stirring for 10 min, isobutyraldehyde (0.30 cm³, 3.26 mmol) in THF (1 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (100 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 80 cm³). The combined organic layers were washed with water (150 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (64% yield) showed an (E∶Z) ratio of >98∶2. Column chromatography of the yellow oil on silica using ether as eluant separated the stereoisomers. The major product was the (E ) isomer 16e (0.41 g, 35%), mp 108–110 °C; R_f 0.37 (ether); ν_max(Nujol)/cm⁻¹ 1602, 1490, 1284, 1138, 1088, 1021, 962; δ_H(250 MHz; CDCl₃) 0.97 (6H, 2 × d, J = 7.0 Hz, Me), 2.33 (3H, s, Me tolyl), 2.36 (3H, s, Me tosyl), 2.41 (1H, m, CHMe), 5.94 (1H, dd, J = 15.0, 1.3 Hz, [double bond, length half m-dash]CHS), 6.55 (1H, dd, J = 15.0, 6.4 Hz, [double bond, length half m-dash]CHR), 7.15 (AA′ of AA′BB′, tolyl), 7.25 (AA′ of AA′BB′, tosyl), 7.47 (BB′ of AA′BB′, tolyl), 7.72 (BB′ of AA′BB′, tosyl); δ_C(62.9 MHz; CDCl₃) 20.8 (Me), 20.9 (Me), 21.3 (2 × ArMe), 31.3 (CHMe), 123.1 ([double bond, length half m-dash]CHR), 126.2, 126.5, 129.0, 130.4, 132.0, 141.1, 141.5, 142.9, 151.7 ([double bond, length half m-dash]CHS); m/z (CI/NH₃) 362 (100%, MH⁺).

(E )-S-(3,3-Dimethylbut-1-enyl)-S-p-tolyl-N-p-tosylsulfimide 16f

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (1.0 g, 3.26 mmol) in THF (100 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 1.3 cm³, 3.26 mmol), potassium tert-butoxide (1.0 M, 3.27 cm³, 3.26 mmol) and diethyl chlorophosphate (0.47 cm³, 3.26 mmol). After stirring for 10 min, pivalaldehyde (0.354 cm³, 3.26 mmol) in THF (1 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (100 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 80 cm³). The combined organic layers were washed with water (150 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (39% yield) showed an (E∶Z) ratio of >98∶2. After column chromatography of the yellow oil on silica using ether as eluant, the major product was the (E ) isomer 16f (0.48 g, 39%), mp 146–147 °C; R_f 0.46 (ether) (Found: C, 63.96; H, 6.76; N, 3.73. C₂₀H₂₅NO₂S₂ requires C, 63.82; H, 6.66; N, 3.71%); ν_max(Nujol)/cm⁻¹ 1598, 1492, 1284, 1141, 1089, 1021, 962; δ_H(250 MHz; CDCl₃) 0.98 (9H, s, Me), 2.32 (3H, s, Me tolyl), 2.36 (3H, s, Me tosyl), 5.89 (1H, d, J = 15.0 Hz, [double bond, length half m-dash]CHS), 6.53 (1H, d, J = 15.0 Hz, [double bond, length half m-dash]CHR), 7.15 (AA′ of AA′BB′, tolyl), 7.25 (AA′ of AA′BB′, tosyl), 7.47 (BB′ of AA′BB′, tolyl), 7.73 (BB′ of AA′BB′, tosyl); δ_C(62.9 MHz; CDCl₃) 21.3 (2 × ArMe), 28.3 (Me), 126.2 ([double bond, length half m-dash]CHR), 126.5, 126.6, 129.0, 130.4, 132.1, 141.4, 141.6, 142.9, 155.3 ([double bond, length half m-dash]CHS); m/z (CI/NH₃) 376 (100%, MH⁺), 220 (43), 207 (26), 206 (17).

S-(2-Cyclopropylethenyl)-S-p-tolyl-N-p-tosylsulfimide 16g

To a solution of S-methyl-S-p-tolyl-N-p-tosylsulfimide 14 (614 mg, 2.0 mmol) in THF (40 cm³) at −78 °C under nitrogen were added dropwise n-BuLi (2.5 M, 0.80 cm³, 2.0 mmol), potassium tert-butoxide (1.0 M, 2.0 cm³, 2.0 mmol) and diethyl chlorophosphate (0.29 cm³, 2.0 mmol). After stirring for 10 min, cyclopropanecarbaldehyde (0.149 cm³, 2.0 mmol) in THF (1 cm³) was added dropwise and the reaction left to warm to 0 °C over 30 min. Saturated aqueous ammonium chloride (40 cm³) was added, along with sufficient water to dissolve any salts precipitated, and the reaction extracted with dichloromethane (3 × 50 cm³). The combined organic layers were washed with water (100 cm³) and dried over magnesium sulfate, filtered and concentrated under reduced pressure. A ¹H NMR spectrum of the crude product (39% yield) showed an (E∶Z) ratio of 53∶47. Column chromatography of the yellow oil on silica using ether as eluant led to a mixture of inseparable stereoisomers (0.28 g, 39%) (Found: MH⁺ 360.1104. C₂₀H₂₅NO₂S₂ requires 360.1092); ν_max(Nujol)/cm⁻¹ 1606, 1292, 1280, 1142, 1089, 981, 734, 661.

(E )-S-(2-Cyclopropylethenyl)-S-p-tolyl-N-p-tosylsulfimide 16g.. δ _H(250 MHz; CDCl₃) 0.59 (2H, m, CH₂), 0.99 (2H, m, CH₂), 2.03 (1H, m, CH), 2.36 (3H, s, Me tolyl), 2.39 (3H, s, Me tosyl), 5.58 (1H, dd, J = 10.8, 9.0 Hz, [double bond, length half m-dash]CHR), 6.04 (1H, dd, J = 9.0, 0.6 Hz, [double bond, length half m-dash]CHS), 7.18 (AA′ of AA′BB′, tolyl), 7.28 (AA′ of AA′BB′, tosyl), 7.57 (BB′ of AA′BB′, tolyl), 7.79 (BB′ of AA′BB′, tosyl); δ_C(62.9 MHz; CDCl₃) 8.7 (CH₂), 9.1 (CH₂), 12.4 (CH), 21.3 (2 × ArMe), 123.9 ([double bond, length half m-dash]CHR), 125.9, 126.3, 129.0, 130.4, 132.6, 141.3, 141.7, 142.3, 150.6 ([double bond, length half m-dash]CHS).

(Z )-S-(2-Cyclopropylethenyl)-S-p-tolyl-N-p-tosylsulfimide.. δ _H(250 MHz; CDCl₃) 0.58 (2H, m, CH₂), 0.93 (2H, m, CH₂), 1.53 (1H, m, CH), 2.35 (3H, s, Me tolyl), 2.38 (3H, s, Me tosyl), 6.01 (1H, dd, J = 10.8, 14.5 Hz, [double bond, length half m-dash]CHR), 6.02 (1H, d, J = 14.5 Hz, [double bond, length half m-dash]CHS), 7.16 (AA′ of AA′BB′, tolyl), 7.26 (AA′ of AA′BB′, tosyl), 7.49 (BB′ of AA′BB′, tolyl), 7.74 (BB′ of AA′BB′, tosyl); δ_C(62.9 MHz; CDCl₃) 8.7 (2 × CH₂), 14.5 (CH), 21.3 (2 × ArMe), 121.2 ([double bond, length half m-dash]CHR), 126.2, 126.5, 129.0, 130.4, 132.3, 141.3, 141.6, 142.7, 150.7 ([double bond, length half m-dash]CHS); m/z (FAB) 360 (100%, MH⁺), 190 (14), 123 (46).

(RS,SR)-S-[2-Phenyl-2-(phenylmethoxy)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17a

A solution of vinyl sulfimide 16b (200 mg, 0.5 mmol) and sodium hydride (60%; hexane washed, 4 mg, 20 mol%) in benzyl alcohol (30 cm³) was stirred at room temperature for 3 days. Water (50 cm³) was added and then the aqueous solution was extracted with CH₂Cl₂ (3 × 20 cm³). The combined organic extracts were dried over magnesium sulfate and evaporated to dryness to leave a white residue (>95% de). Column chromatography on silica with 10% chloroform–ethyl acetate as eluant followed by recrystallisation from ether–petroleum ether yielded 17a as a white powder (165 mg, 64%), mp 146–148 °C; R_f 0.44 (10% chloroform–ethyl acetate) (Found: C, 68.83; H, 5.79; N, 2.77. C₂₉H₂₉NO₃S₂ requires C, 69.15; H, 5.80; N, 2.78%) (Found: 504.1670; MH⁺ requires 504.1669); ν_max(Nujol)/cm⁻¹ 1283, 1140, 1116, 1090, 967, 725, 656; δ_H(400 MHz; CDCl₃) 2.33 (3H, s, Me tolyl), 2.35 (3H, s, Me tosyl), 3.15 (dd, J = 10.7, 12.8 Hz, CH^aS), 3.27 (1H, dd, J = 2.3, 12.8 Hz, CH^bS), 4.05 (1H, AB, J = 10.5, CH₂Ph), 4.20 (1H, AB, J = 10.5 Hz, CH₂Ph), 4.84 (1H, dd, J = 2.3, 10.7 Hz, CHPh), 7.18 (2H, AA′ of AA′BB′, tolyl), 7.25 (2H, AA′ of AA′BB′, tosyl), 7.30 (10H, m, Ar), 7.60 (2H, BB′ of AA′BB′, tolyl), 7.81 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 21.27 (Me tolyl), 21.34 (Me tosyl), 62.43 (CH₂S), 70.99 (CH₂Ph), 74.96 (CH), 125.89, 126.80, 126.52, 127.74, 127.81, 128.25, 128.74, 128.99, 129.13, 130.45, 132.10, 137.23, 137.98, 141.28, 141.50, 142.99; m/z (CI/NH₃) 504 (35%, MH⁺).

(RS,SR)-S-(2-Phenyl-2-ethoxyethyl)-S-p-tolyl-N-p-tosylsulfimide 17b

A solution of vinyl sulfimide 16b (200 mg, 0.5 mmol) and sodium hydride (60%; hexane washed, 4 mg, 20 mol%) in ethanol (40 cm³) was stirred at room temperature for 5 days. Water (40 cm³) was added and then the aqueous solution was extracted with CH₂Cl₂ (3 × 40 cm³). The combined organic extracts were dried over magnesium sulfate and evaporated to dryness to leave a white residue (80% de). Column chromatography on silica with ether–petroleum ether (8∶1) as eluant followed by recrystallisation from ether–petroleum ether (8∶1) yielded 17b as a white powder (165 mg, 73%), mp 127–129 °C; R_f 0.33 (ether–petroleum ether) (Found: C, 64.96; H, 6.04; N, 3.34. C₂₄H₂₇NO₃S₂ requires C, 65.28; H, 6.16; N, 3.17%); ν_max(Nujol)/cm⁻¹ 1295, 1282, 1140, 1090, 969, 722, 656; δ_H(400 MHz; CDCl₃) 1.07 (3H, dd, J = 7.0, 7.0 Hz), 2.33 (3H, s, Me tolyl), 2.35 (3H, s, Me tosyl), 2.96 (dq, J = 8.8, 7.0 Hz, CH₂O), 3.05 (dd, J = 10.9, 12.9 Hz, CH^aS), 3.19 (1H, dd, J = 2.3, 12.9 Hz, CH^bS), 3.23 (1H, dq, J = 8.8, 7.0 Hz, CH₂O), 4.60 (1H, dd, J = 2.3, 10.9 Hz, CHPh), 7.18 (2H, AA′ of AA′BB′, tolyl), 7.24 (2H, AA′ of AA′BB′, tosyl), 7.25 (5H, m, Ph), 7.60 (2H, BB′ of AA′BB′, tolyl), 7.82 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 15.0 (Me), 21.2 (Me tolyl), 21.3 (Me tosyl), 62.3 (CH₂S), 64.6 (CH₂O), 74.6 (CH), 125.9, 126.3, 128.4, 128.7, 129.0, 130.4, 132.4, 138.5, 141.3, 141.4, 142.9; m/z (CI/NH₃) 442 (12%, MH⁺).

(RS,SR)-S-[2-(4-Methoxyphenyl)-2-ethoxyethyl]-S-p-tolyl-N-p-tosylsulfimide 17c

A solution of vinyl sulfimide 16a (50 mg, 0.12 mmol) and sodium hydride (60%; hexane washed, ≈1 mg) in ethanol (5 cm³) was stirred at room temperature for 5 days. Water (10 cm³) was added and then the aqueous solution was extracted with CH₂Cl₂ (3 × 10 cm³). The combined organic extracts were dried over magnesium sulfate and evaporated to dryness to leave a white residue (80% de). Column chromatography on silica with ethyl acetate–petroleum ether (2∶3) as eluant followed by recrystallisation from ethyl acetate–petroleum ether (2∶3) yielded a mixture of inseparable diastereoisomers 17c and 18c as a white gum (18 mg, 32%), R_f 0.33 (ethyl acetate–petroleum ether 2∶3); δ_H(for 17c only; 400 MHz; CDCl₃) 1.05 (3H, dd, J = 7.0, 7.0 Hz), 2.33 (3H, s, Me tolyl), 2.35 (3H, s, Me tosyl), 2.92 (dq, J = 8.8, 7.0 Hz, CH₂O), 3.04 (dd, J = 10.9, 12.8 Hz, CH^aS), 3.17 (1H, dd, J = 1.8, 12.8 Hz, CH^bS), 3.20 (1H, dq, J = 8.8, 7.0 Hz, CH₂O), 3.76 (3H, s, MeO), 4.55 (1H, dd, J = 1.8, 10.9 Hz, CHAr), 6.83 (2H, AA′ of AA′BB′, MeOC₆H₄), 7.17 (2H, BB′ of AA′BB′, MeOC₆H₄), 7.18 (2H, AA′ of AA′BB′, tolyl), 7.25 (2H, AA′ of AA′BB′, tosyl), 7.60 (2H, BB′ of AA′BB′, tolyl), 7.81 (2H, BB′ of AA′BB′, tosyl).

(RS,SR)-S-[2-Phenyl-2-(phenylmethylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17d

A solution of vinyl sulfimide 16b (20 mg, 0.05 mmol) and sodium hydride (60%; hexane washed, 0.5 mg, 20 mol%) in benzylamine (4 cm³) was stirred at room temperature for 24 h. Water (5 cm³) was added and then the aqueous solution was extracted with dichloromethane (3 × 4 cm³). The combined organic extracts were dried over magnesium sulfate and evaporated to dryness to leave a white residue (60% de). The major isomer was isolated by column chromatography on silica with 10% chloroform–ethyl acetate as eluant followed by recrystallisation from ether–petroleum ether to yield 17d as a white powder (16.1 mg, 63%), mp 146–148 °C; R_f 0.66 (10% EtOAc–CHCl₃) (Found: C, 69.27; H, 6.07; N, 5.50. C₂₉H₃₀N₂O₂S₂ requires C, 69.29; H, 6.02; N, 5.57%); ν_max(Nujol)/cm⁻¹ 3321, 1283, 1140, 1116, 1090, 813, 725; δ_H(400 MHz; CDCl₃) 2.25 (3H, s, Me tolyl), 2.35 (3H, s, Me tosyl), 3.13 (1H, dd, J = 10.5, 12.9 Hz, CH^aS), 3.35 (1H, dd, J = 2.2, 12.9 Hz, CH^bS), 4.06 (1H, AB, J = 10.5 Hz, CH₂Ph), 4.27 (1H, AB, J = 10.5 Hz, CH₂Ph), 4.81 (1H, dd, J = 2.2, 10.5 Hz, CHPh), 7.10 (2H, AA′ of AA′BB′, tolyl), 7.24 (2H, AA′ of AA′BB′, tosyl), 7.30 (10H, m, Ph), 7.66 (2H, BB′ of AA′BB′, tolyl), 7.84 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 21.2 (Me tolyl), 21.3 (Me tosyl), 62.5 (CH₂S), 71.0 (CH₂Ph), 74.96 (CH), 125.90, 126.34, 126.89, 127.58, 127.77, 128.26, 128.96, 129.10, 130.45, 132.2, 134.04, 138.0, 139.14, 139.94, 141.12, 141.92; m/z (CI/NH₃) 503 (3%, MH⁺), 310 (42), 210 (53), 188 (100).

(RS,SR)-S-[2-(4-Chlorophenyl-2-(phenylmethylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17e

A solution of vinyl sulfimide 16c (21.5 mg, 0.05 mmol) and sodium hydride (60%; hexane washed, 0.5 mg, 20 mol%) in benzylamine (4 cm³) was stirred at room temperature for 24 h. Water (5 cm³) was added and then the aqueous solution was extracted with dichloromethane (3 × 4 cm³). The combined organic extracts were dried over magnesium sulfate and evaporated to dryness to leave a yellow oil (60% de). The major isomer was isolated by column chromatography on silica with 10% chloroform–ethyl acetate as eluant followed by recrystallisation from ether–petroleum ether to yield 17e as a yellow solid (18.2 mg, 57%); R_f 0.64 (CHCl₃–EtOAc 4∶1) (Found: C, 64.24; H, 5.27; N, 5.26. C₂₉H₂₉ClN₂O₂S₂ requires C, 64.85; H, 5.44; N, 5.21%); ν_max(Nujol)/cm⁻¹ 3321, 1281, 1142, 1090, 813, 755, 736; δ_H(400 MHz; CDCl₃) 2.33 (3H, s, Me tolyl), 2.35 (3H, s, Me tosyl), 2.92 (1H, AB, CH₂Ph), 3.04 (1H, dd, J = 10.9, 12.8 Hz, CH^aS), 3.18 (1H, dd, J = 2.4, 12.8 Hz, CH^bS), 3.35 (1H, AB, CH₂Ph), 4.62 (1H, dd, J = 2.4, 10.9 Hz, CHAr), 6.83 (2H, AA′ of AA′BB, p-ClC₆H₄), 7.17 (2H, BB′ of AA′BB′, p-ClC₆H₄), 7.18 (2H, AA′ of AA′BB′, tolyl), 7.24 (2H, AA′ of AA′BB′, tosyl), 7.35 (5H, m, Ar), 7.60 (2H, BB′ of AA′BB′, tolyl), 7.81 (2H, BB′ of AA′BB′, tosyl); δ_C(100.6 MHz; CDCl₃) 21.2 (Me tolyl), 21.3 (Me tosyl), 62.45 (CH₂S), 71.09 (CH₂Ph), 75.06 (CH), 125.98, 126.84, 127.00, 127.67, 127.97, 128.00, 128.47, 128.96, 129.19, 130.49, 132.42, 134.08, 138.0, 139.98, 141.22, 143.12; m/z (CI/NH₃) 538 (5%, MH⁺).

General procedure for the reaction of vinyl sulfimides 16 with isopropylamine

Vinyl sulfimide 16 was stirred with a small amount of NaH in isopropylamine (15 cm³) under nitrogen at room temperature. The reaction was monitored by TLC. On completion (about 6 h) the excess amine was removed in vacuo. The remaining solid was extracted into ether (30 cm³) and washed with water (2 × 20 cm³), dried using magnesium sulfate and concentrated in vacuo yielding a yellow oil. The crude product was purified by column chromatography on silica gel (chloroform–ethyl acetate 4∶1).

S-[2-Phenyl-2-(isopropylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17f (RS,SR) and 18f (RR,SS).. Using vinyl sulfimide 16b (90 mg, 0.22 mmol), the desired product was obtained as a yellow oil as an inseparable mixture of the two diastereoisomers 17f and 18f (80∶20) (55.7 mg, 53%); R_f 0.43 (Found: C, 60.04; H, 6.62; N, 5.82. C₂₅H₃₀N₂O₂S₂ requires C, 59.99; H, 6.65; N, 6.06%); ν_max(Nujol)/cm⁻¹ 3431 (N–H stretch), 1598, 1342, 1089, 803; δ_H(400 MHz; CDCl₃) 0.82 (d, J = 6.1 Hz, Me(17)), 0.92 (m, Me(17), 2 × Me(18)), 2.32 (s, Me tolyl(17)), 2.34 (s, Me tolyl(18)), 2.35 (s, Me tosyl(17)), 2.38 (s, Me tosyl(18)), 2.48 (m, CHMe(17) and CHMe(18)), 3.02 (m, CH^aS(17) and CH^aS(18)), 3.23 (dd, J = 3.0, 12.8 Hz, CH^bS(17)), 3.47 (dd, J = 7.5, 12.8 Hz, CH^bS(18)), 3.79 (dd, J = 7.2, 7.2 Hz, CHPh(18)), 4.24 (dd, J = 3.0, 10.5 Hz, CHPh(17)), 7.00 (AA′ of AA′BB, J = 8.0 Hz, tolyl), 7.13 (AA′ of AA′BB, J = 8.0 Hz, tosyl), 7.24 (m, Ph), 7.68 (BB′ of AA′BB′, J = 8.2 Hz, tolyl), 7.73 (BB′ of AA′BB′, J = 8.2 Hz, tosyl); δ_C(for 17f; 100.6 MHz; CDCl₃) 21.44 (Me tolyl), 22.57 (Me tosyl), 23.82 (Me), 29.59 (Me), 45.53 (CH₂S), 55.30 (CHMe), 61.72 (CHPh), 126.04, 126.70, 126.83, 127.71, 128.13, 128.96, 129.43, 130.29, 131.01, 139.95, 141.29, 143.33; m/z (EI) 455 (M^+·, 15.2%).

S-[2-(4-Chlorophenyl)-2-(isopropylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17g (RS,SR) and 18g (RR,SS).. Vinyl sulfimide 16c (21.5 mg, 0.05 mmol) gave the desired product as a yellow oil as an inseparable mixture of the two diastereoisomers 17g and 18g (80∶20) (18.3 mg, 69%); R_f 0.54 (Found: C, 61.37; H, 5.96; N, 5.76. C₂₅H₂₉ClN₂O₂S₂ requires C, 61.39; H, 5.98; N, 5.73%); ν_max(Nujol)/cm⁻¹ 3431 (N–H), 1598, 1342, 1089, 809; δ_H(400 MHz; CDCl₃) 0.82 (d, J = 6.1 Hz, Me(17)), 0.92 (m, Me(17), 2 × Me(18)), 2.32 (s, Me tolyl(17)), 2.34 (s, Me tolyl(18)), 2.35 (s, Me tosyl(17)), 2.38 (s, Me tosyl(18)), 2.48 (m, CHMe(17) and CHMe(18)), 3.02 (m, CH^aS(17) and CH^aS(18)), 3.25 (dd, J = 3.0, 12.8 Hz, CH^bS(17)), 3.47 (dd, J = 7.2, 12.8 Hz, CH^bS(18)), 3.79 (dd, J = 7.2, 7.2 Hz, CHAr(18)), 4.24 (dd, J = 3.0, 10.5 Hz, CHAr(17)), 6.83 (AA′ of AA′BB, p-ClC₆H₄), 7.01 (BB′ of AA′BB′, p-ClC₆H₄), 7.17 (AA′ of AA′BB′, J = 8.2 Hz, tolyl), 7.28 (AA′ of AA′BB′, J = 8.2 Hz, tosyl), 7.68 (BB′ of AA′BB′, J = 8.2 Hz, tolyl), 7.73 (BB′ of AA′BB′, J = 8.2 Hz, tosyl); δ_C(for 17g; 100.6 MHz; CDCl₃) 21.32 (Me tolyl), 22.47 (Me tosyl), 23.75 (Me), 29.59 (Me), 45.65 (CH₂S), 54.77 (CHMe), 61.32 (CHPh), 123.90, 126.25, 126.64, 128.24, 128.99, 129.43, 130.46, 130.96, 133.88, 138.32, 141.29, 143.09; m/z (EI) 454 (65%, M − Cl^+·).

General procedure for the reaction of vinyl sulfimides 16 with diethylamine

Vinyl sulfimide 16 was stirred with a small amount of NaH in diethylamine (5 cm³) under nitrogen at room temperature. The reaction was refluxed (3 days), then the excess amine was removed in vacuo and the resulting white solid extracted into ether (10 cm³) and washed with water (2 × 10 cm³) and dried using magnesium sulfate. The ether layer was concentrated in vacuo to yield a brown solid. The product was purified by column chromatography on silica using chloroform–ethyl acetate 4∶1.

S-[2-Phenyl-2-(diethylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17h and 18h.. Using vinyl sulfimide 16b (20 mg, 0.05 mmol), the desired product was obtained as a yellow oil as an inseparable mixture of the two diastereoisomers 17h and 18h (11.4 mg, 46%) in 70% de. The configurations of the two isomers are uncertain. ¹H NMR data for the minor isomer are indicated by a prime; R_f 0.78 (CHCl₃–EtOAc 4∶1) (Found: C, 66.60; H, 6.81; N, 5.95. C₂₆H₃₂N₂O₂S₂ requires C, 66.63; H, 6.88; N, 5.98%); ν_max(neat)/cm⁻¹ 3030, 1455, 1337, 1092, 805; δ_H(400 MHz; CDCl₃) 1.29–1.42 (m, 2 × Me and 2 × Me′), 2.31 (s, Me tolyl), 2.34 (s, Me tolyl′), 2.35 (s, Me tosyl), 2.37 (s, Me tosyl′), 2.85 (m, CH^aS and CH^aS′), 3.00 (m, 2 × CH₂N and 2 × CH₂N′), 3.54 (m, CH^bS and CH^bS′), 4.67 (dd, J = 6.2, 12.9 Hz, CHPh), 5.00 (dd, J = 6.2, 6.2 Hz, CHPh′), 7.01 (AA′ of AA′BB′, J = 8.4 Hz, tolyl), 7.14 (AA′ of AA′BB′, J = 8.4 Hz, tosyl), 7.24 (m, Ph), 7.52 (BB′ of AA′BB′, J = 8.4 Hz, tolyl), 7.80 (BB′ of AA′BB′, J = 8.4 Hz, tosyl); δ_C(major isomer only; 100.6 MHz; CDCl₃) 22.99 (Me tolyl), 23.22 (Me tosyl), 29.01 (Me), 30.01 (Me), 41.85 (CH₂S), 51.14 (2 × CH₂N), 61.57 (CH), 125.71, 126.64, 127.50, 127.96, 128.32, 129.00, 129.43, 130.46, 130.96, 133.88, 138.32, 141.29; m/z (EI) 468 (100%, M^+·).

S-[2-(4-Chlorophenyl-2-(diethylamino)ethyl]-S-p-tolyl-N-p-tosylsulfimide 17i and 18i.. Using vinyl sulfimide 16c (21.5 mg, 0.05 mmol), the desired product was obtained as a yellow oil as an inseparable mixture of the two diastereoisomers 17i and 18i (14.9 mg, 56%) in 70% de. The configurations of the two isomers are uncertain. ¹H NMR data for the minor isomer are indicated by a prime (Found: C, 62.02; H, 6.17; N, 5.52. C₂₆H₃₁ClN₂O₂S₂ requires C, 62.07; H, 6.21; N, 5.57%); ν_max(neat)/cm⁻¹ 2963, 1457, 1380, 1093, 806; δ_H(400 MHz; CDCl₃) 1.36 (m, 2 × Me and 2 × Me′), 2.32 (s, Me tolyl), 2.34 (s, Me tolyl′), 2.35 (s, Me tosyl), 2.37 (s, Me tosyl′), 2.85 (m, CH^aS and CH^aS′), 3.14 (m, 2 × CH₂N and 2 × CH₂N′), 3.83 (m, CH^bS and CH^bS′), 4.69 (dd, J = 6.2, 12.9 Hz, CHAr), 5.00 (dd, J = 6.2, 6.2 Hz, CHAr′), 6.83 (AA′ of AA′BB, p-ClC₆H₄), 7.13 (BB′ of AA′BB′, p-ClC₆H₄), 7.19 (AA′ of AA′BB′, J = 8.4 Hz, tolyl), 7.30 (AA′ of AA′BB′, J = 8.4 Hz, tosyl), 7.52 (BB′ of AA′BB′, J = 8.4 Hz, tolyl), 7.80 (BB′ of AA′BB′, J = 8.4 Hz, tosyl); δ_C(for major isomer only; 100.6 MHz; CDCl₃) 22.97 (Me tolyl), 23.21 (Me tosyl), 29.05 (Me), 30.11 (Me), 41.95 (CH₂S), 51.04 (2 × CH₂N), 61.35 (CH), 125.21, 126.61, 127.70, 127.69, 128.23, 129.08, 129.46, 130.43, 130.69, 133.68, 138.22, 141.19; m/z (EI) 502 (100%, M^+·).

Reaction of vinyl sulfimide 16e with ethanol

The experimental conditions for the synthesis of 17b, but with isopropyl sulfimide 16e in place of 16b, were used. The crude ¹H NMR spectrum of the product mixture showed, by comparison with the literature data,²⁶ that the major product was N-(1,1-dimethylprop-2-enyl)toluene-p-sulfonamide 22.

4-Methyl-1-[2-(phenylmethoxy)-2-phenylethylsulfanyl]benzene 23a

A solution of 17a (8 mg, 0.016 mmol) and 10% palladium on carbon (1 mg) in degassed EtOAc (2 cm³) was stirred at room temperature under a positive pressure of hydrogen gas for 5 days. Filtration through Celite using EtOAc as eluant and concentration under reduced pressure afforded a yellow oil. Column chromatography on silica using 10% chloroform–ethyl acetate as eluant gave a pale yellow oil (3 mg, 56%); δ_H(400 MHz; CDCl₃) 2.30 (3H, s, Me), 3.10 (1H, dd, J = 5.2, 13.4 Hz, CH^aS), 3.35 (1H, dd, J = 8.0, 13.4 Hz, CH^bS), 4.29 (1H, AB, J = 11.8 Hz, CH₂Ph), 4.47 (1H, dd, J = 5.2, 8.0 Hz, CHPh), 4.48 (1H, AB, J = 11.8 Hz, CH₂Ph), 7.04 (2H, AA′ of AA′BB′, tolyl), 7.21 (2H, BB′ of AA′BB′, tolyl), 7.30 (10H, m, Ar); δ_C(100.6 MHz; CDCl₃) 20.95 (Me), 42.32 (CH₂Ph), 70.75 (CH₂S), 79.98 (CH), 126.82, 127.65, 127.83, 128.05, 128.21, 128.53, 129.60, 130.03, 132.74, 136.03, 137.96, 140.60; m/z (CI/NH₃) 352 (100%, M + NH₄⁺).

4-Methyl-1-[2-(phenylmethylamino)-2-phenylethylsulfanyl]benzene 3d

A solution of 17d (8 mg, 0.016 mmol) and 10% palladium on carbon (1 mg) in degassed EtOAc (2 cm³) was stirred at room temperature under a positive pressure of hydrogen gas for 5 days. Filtration through Celite using EtOAc as eluant and concentration under reduced pressure afforded a yellow oil. Column chromatography on silica using 10% chloroform–ethyl acetate as eluant gave a pale yellow oil (3 mg, 56%); δ_H(400 MHz; CDCl₃) 2.30 (3H, s, Me), 3.18 (1H, dd, J = 5.2, 13.4 Hz, CH^aS), 3.42 (1H, dd, J = 8.0, 13.4 Hz, CH^bS), 4.35 (1H, AB, J = 11.8 Hz, CH₂Ph), 4.52 (1H, dd, J = 5.2, 8.0 Hz, CHPh), 4.68 (1H, AB, J = 11.8 Hz, CH₂Ph), 7.04 (2H, AA′ of AA′BB′, tolyl), 7.21 (2H, BB′ of AA′BB′, tolyl), 7.30 (10H, m, Ar); δ_C(100.6 MHz; CDCl₃) 21.21 (Me), 42.39 (CH₂Ph), 70.80 (CH₂S), 80.02 (CH), 126.89, 127.67, 127.93, 128.15, 128.26, 128.53, 129.66, 130.02, 132.76, 136.08, 17.99, 140.63; m/z (CI/NH₃) 351 (100%, M + NH₄⁺).

Acknowledgements

We thank the EPSRC for studentships to C. P. R., S. M. R. and T. J. S. and the EPSRC Mass Spectrometry Service.

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