Substituted diethynyldithia[3.3]paracyclophanes—synthetically more accessible new building blocks for molecular scaffolding

Abstract

A series of dialkyne building blocks based on the dithia[3.3]paracyclophane unit have been synthesized in good yields. The electronic properties of these novel dialkynes can be tuned through a transannular substitution effect. These synthetically more accessible diethynyldithia[3.3]paracyclophanes are promising candidates for the building of relatively carbon rich molecular scaffolds.

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Introduction

The molecular building block associated with paracyclophanes is widely used in chiral catalysis,¹ the design of new optoelectronic (NLO) materials,²polymer chemistry and materials science,³electron transfer processes,⁴ molecular electronics,⁵ novel nanoscale materials,⁶ and even organic solar cells.⁷ The unique structural and electronic properties of these derivatives result from the characteristic interactions between the two cofacial π-electron systems.⁸

Acetylenic cyclophanes as a series of carbon-rich compounds not only show interesting and important structural and chemical behavior themselves, but also have been incorporated into ‘extended’ π-systems and polymers through coupling reactions such as the Sonogashira or Glaser couplings. Besides addition reactions, ethynyl cyclophanes can be employed to prepare novel iron, platinum and cobalt metal complexes.^9a By polycondensation reactions, monomeric cyclophanes can be converted into novel polymers displaying lateral π-conjugation. Marrocchi, Taticchi^7,9b–h and Hopf^9i–k have done excellently work in this area.

Up to now, although the unique transannular π–π interaction associated with [2.2]paracyclophanes has been extensively studied and documented^1,2,5,7,10 (Fig. 1), dithia[3.3]paracyclophane building blocks, which are synthetically more accessible, have received less attention.

Fig. 1 The structure of [2.2]paracyclophane and dithia[3.3]paracyclophane

In our opinion, the dithia[3.3]paracyclophane unit also represents a particularly valuable core system. It has been shown that the transannular effect in the [3.3]cyclophane unit is sufficiently strong to allow tuning of the optical properties of copolymers.¹¹ In addition, dithia[3.3]paracyclophanes could be readily prepared by coupling reactions under high dilution conditions if different substituents on the cyclophane are desired.

We have now focused on the synthesis and studies of transannular π–π interactions in the dithia[3.3]paracyclophane unit. Here, we report the synthesis of a series of novel functionalized diethynyldithia[3.3]paracyclophane building blocks (9a–e, 10 and 11), as well as a preliminary study on the transannular substitution effect on their optical and electronic structures.

Results and discussion

Dithiaparacyclophanes 3a–e, 5a and 5b were prepared by coupling the corresponding pair of dithiol and dibromide under high dilution conditions according a modified procedure found in the literature (Scheme 1).¹¹ The trimethylsilyl-protected bis-(ethynyl)ligand precursors 6a–e and 7 were synthesized by the Pd(PPh₃)₄/CuI-catalyzed Sonogashira cross-coupling reaction between 3a–e, 5a and trimethylsilylacetylene (Scheme 2). In the case of tetrafluoro substituents dibromo-dithiaparacyclophane 5b, however, this reaction did not proceed satisfactorily. Diethynyl precursor 8 was formed by the coupling of 5b and 2-methylbut-3-yn-2-ol under the same conditions. The ligand precursors were smoothly converted into the corresponding diethynyldithia[3.3]paracyclophanes 9a–e and 10 by removal of the trimethylsilyl protecting groups with dilute aqueous KOH in MeOH–THF, while 11 was obtained by treating 8 with NaH in toluene after refluxing for 2.5 h (Scheme 3).

Scheme 1 Synthetic route to 3a–e, 5a and 5b.

Scheme 2 Synthesis of protected diethynyl precursors 6a–e, 7 and 8.

Scheme 3 Synthesis of the dialkyne complexes 9a–e, 10 and 11.

All of the synthetic compounds were characterized well by NMR and elemental analysis, and the molecular structure of 9a–e, 10 and 11 was also unambiguously supported by high resolution ESI mass spectra. The structure of 5b was determined by X-ray crystallography, and an ORTEP drawing of 5b is shown in Fig. 2.† The interplane distance between the two benzene rings of 3.258 Å is less than the normal packing distance of aromatic rings in organic aromatic molecules (3.4 Å), thus supporting a potential transannular π–π interaction between the two rings in the cyclophane unit.

Fig. 2 An ORTEP drawing of compound 5b with 20% probability ellipsoids.

The electronic properties of diethynyldithia[3.3]-paracyclophanes 9a–e, 10 and 11 were investigated by absorption and emission spectroscopy (Table 1). The absorption spectra of 9b, 9c and 9e exhibit a clear red shift of about 13 nm relative to 9a, while compound 10 (tetramethyl-substituted on the cyclophane) shows a significant blue shift (about 17 nm) in absorption bands in comparison to 9a.

Table 1 UV-vis and fluorescence spectral data of compounds 9a–e, 10 and 11

Compound	λ max/nm		Φ PL (%)^a
	Absorption	Emission
a The PL efficiency (ΦPL) of the diethynyldithia[3.3]-paracyclophanes in CH2Cl2 solutions was measured by using quinine sulfate (ca. 1 × 10^−5 M solution in 0.1 M H2SO4, assuming a ΦPL of 0.55) as a standard.
9a	240, 271	398	12
9b	240, 284	402	9
9c	240, 283	402	20
9d	240, 274	400	22
9e	241, 284	399	18
10	241, 254	400	5
11	240, 274	399	15

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A comparison (Table 1) of the photoluminescence (PL) spectra of compounds 9a–e, 10 and 11 in CH₂Cl₂ (ca. 1 × 10⁻⁵ M) is illustrated in Fig. 3. The PL intensity of 9d (Φ_PL = 22%) is significantly higher than that of 9a (Φ_PL = 12%). An unexpected observation is that the Φ_PL of 9c (dicyano-substituted, 20%) is considerably larger than that of 9a, while the PL of 9b (Φ_PL = 9%) and 10 (Φ_PL = 5%) are essentially decreased; the electron-donating dimethoxy substituents seem to behave as a quencher,^11a,12,13 and the additional two methyls substituted in the pseudo-gem position appear to have a significant affect on the electronic properties of 10 (see also the absorption spectra and electronic structure, in which the dialkyne C≡C unit is involved in the HOMO orbits, in contrast to the relevant dithia[3.3]paracyclophane disubstituted in the pseudo-meta position).

Fig. 3 PL spectra of complexes 9a–e, 10 and 11 measured from solutions (ca. 1 × 10⁻⁵ M) in CH₂Cl₂ at room temperature.

Furthermore, DFT computations at the B3LYP/6-31+G(d,p) level reveal that the electron density distribution in the relevant HOMO and LUMO are significantly different after the introduction of various substituents (Fig. 4). The above result is a good indication that the introduction of different substituents causes significant changes to the electronic and optical properties of the [3.3]paracyclophane core system via a transannular substitution effect.

Fig. 4 Optimized ground state structures, and the HOMO (H) and LUMO (L) electron densities of 9a–e, 10 and 11, as calculated by DFT (B3LYP/6-31+G(d,p)).

Conclusions

In conclusion, a series of substituted dithia[3.3]paracyclophane dialkyne building blocks have been synthesized. UV-vis and photoluminescence studies and DFT calculations show that the electronic properties of these dialkynes can be tuned through a transannular substitution effect after the introduction of different substituents into the dithia[3.3]paracyclophane unit. These novel dialkyne building blocks should be valuable for extended carbon-rich π-systems,¹⁴ since their ethynyl functions can easily be connected by various reactions.

Experimental

General considerations

All manipulations were carried out under a nitrogen atmosphere using standard Schlenk techniques, unless otherwise stated. ¹H, ¹³C and ¹⁹F NMR spectra were collected on an American Varian Mercury Plus 400 (400 MHz) or 600 (600 MHz) spectrometer. ¹H and ¹³C NMR chemical shifts are relative to TMS, and ¹⁹F NMR chemical shifts are relative to C₆F₆. High resolution ESI mass spectra were obtained on Bruker Apex IV FTMS spectrometers. UV-vis spectra were obtained on a S-3100 PDA UV-vis spectrometer (Scinco Co., Ltd.). Fluorescence spectra were acquired on a Fluoromax-P luminescence spectrometer (Horiba Jobin Yvon Inc.).

2,5-Dibromo-1,4-bis(mercaptomethyl)benzene (1), ¹⁵2e¹⁶ and 4b¹⁷ were prepared by standard literature methods. 2d, 4a were purchased from Tokyo Chemical Industry Co., Ltd. All other reagents were commercially available.

General procedure for the preparation of 3a–e, 5a and 5b

The compounds 3a–c were prepared according to a modified literature procedure.^11c

General procedure: A solution with equimolar amounts of the dithiol and the dibromide in de-gassed THF (500 mL) was added dropwise under N₂ over 12 h to a refluxing solution of K₂CO₃ (5 equiv.) in EtOH (1.2 L). After an additional 2 h at the reflux temperature, the mixture was cooled and the solvent removed. The resulting residue was treated with CH₂Cl₂ (300 mL) and water (300 mL). The organic phase was separated and the aqueous extracted three times with CH₂Cl₂. The combined organic layers were dried over Na₂SO₄, the solvent removed and the resulting solid chromatographed on silica gel using CH₂Cl₂/petroleum ether (1 : 1, v/v) as the eluent. The product was further purified by recrystallization from toluene.

3a . Received from 1 (3.28 g, 10 mmol) and 2a (2.64 g, 10 mmol) as a white solid 2.16 g (yield: 50%). ¹H NMR (600 MHz, CDCl₃): δ 3.60 (d, J(HH) = 15 Hz, 2H, CH₂), 3.78 (d, J(HH) = 15 Hz, 2H, CH₂), 3.86 (d, J(HH) = 15 Hz, 2H, CH₂), 4.13 (d, J(HH) = 15 Hz, 2H, CH₂), 7.01 (d, J(HH) = 7.2 Hz, 2H, Ar), 7.16 (d, J(HH) = 7.2 Hz, 2H, Ar), 7.18 (s, 2H, Ar).

3b . Received from 1 (3.28 g, 10 mmol) and 2b (3.24 g, 10 mmol) as a white solid 2.02 g (yield: 41%). ¹H NMR (600 MHz, CDCl₃): δ 3.48 (d, J(HH) = 15 Hz, 2H, CH₂), 3.65 (d, J(HH) = 15.6 Hz, 2H, CH₂), 3.90 (s, 8H, CH₂, OCH₃), 4.05 (d, J(HH) = 15.6 Hz, 2H, CH₂), 6.74 (s, 2H, Ar), 7.32 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 31.82, 37.02 (CH₂), 55.79 (OCH₃), 112.61, 123.27, 124.14, 134.13, 136.47, 150.35 (Ar). Anal. calc. for C₁₈H₁₈Br₂O₂S₂: C, 44.10; H, 3.70; Found: C, 43.95, H, 3.96.

3c . Received from 1 (2.95 g, 9 mmol) and 2c (2.83 g, 9 mmol) as a white solid 2.55 g (yield: 59%). ¹H NMR (400 MHz, CDCl₃): δ 3.76 (d, J = 15.2 Hz, 2H, CH₂), 3.86 (d, J = 15.6 Hz, 2H, CH₂), 3.99 (d, J = 15.6 Hz, 2H, CH₂), 4.09 (d, J = 15.6 Hz, 2H, CH₂), 7.42 (s, 2H, Ar), 7.75 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 35.00, 37.07 (CH₂), 115.67 (CN), 116.83, 123.73, 133.56, 135.10, 136.54, 140.30 (Ar). Anal. calc. for C₁₈H₁₂Br₂N₂S₂: C, 45.02; H, 2.52; N, 5.83. Found: C, 45.47; H, 2.83; N, 5.98.

3d . Received from 1 (2.82 g, 8.6 mmol) and 2d (2.50 g, 8.6 mmol) as a white solid 2.97 g (yield: 75%). ¹H NMR (400 MHz, CDCl₃): δ 2.28 (s, 6H, CH₃), 3.58 (d, J = 10.8 Hz, 2H, CH₂), 3.72 (s, 4H, CH₂), 4.01 (d, J = 10.8 Hz, 2H, CH₂), 6.88 (s, 2H, Ar), 7.41 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 18.68 (CH₃), 35.87, 36.10 (CH₂), 123.40, 131.43, 133.04, 133.52, 134.01, 136.65 (Ar). Anal. calc. for C₁₈H₁₈Br₂S₂: C, 47.18; H, 3.96. Found: C, 46.95; H, 4.04.

3e . Received from 1 (2.95 g, 9 mmol) and 2e (2.70 g, 9 mmol) as a white solid 1.53 g (yield: 36%). ¹H NMR (400 MHz, CDCl₃): δ 3.53 (d, J = 14.8 Hz, 2H, CH₂), 3.70 (d, J = 14.8 Hz, 2H, CH₂), 3.94 (q, J = 10.8 Hz, 4H, CH₂), 6.97 (t, J = 8.4 Hz, 2H, Ar), 7.39 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 30.23, 36.99 (CH₂), 116.63 (d, J = 29.3 Hz), 123.64, 124.57 (t), 134.57, 136.43, 154.50, 156.91 (Ar). ¹⁹F NMR (376 MHz, CDCl₃): δ −122.28. Anal. calc. for C₁₆H₁₂Br₂F₂S₂: C, 41.22; H, 2.59. Found: C, 41.54; H, 2.53.

5a . Received from 1 (2.56 g, 7.8 mmol) and 4a (2.50 g, 7.8 mmol) as a white solid 2.41 g (yield: 64%). ¹H NMR (400 MHz, CDCl₃): δ 2.29 (s, 6H, CH₃), 2.35 (s, 6H, CH₃), 3.59 (d, J = 16 Hz, 2H, CH₂), 3.73 (d, J = 14.8 Hz, 2H, CH₂), 4.13 (d, J = 15.6 Hz, 2H, CH₂), 4.33 (d, J = 14.4 Hz, 2H, CH₂), 7.52 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 16.91, 18.07 (CH₃), 32.21, 35.36 (CH₂), 122.31, 131.62, 133.32, 133.70, 136.78 (Ar). Anal. calc. for C₂₀H₂₂Br₂S₂: C, 49.39; H, 4.56. Found: C, 49.21; H, 4.65.

5b . Received from 1 (3.28 g, 10 mmol) and 4b (3.36 g, 10 mmol) as a white solid 2.40 g (yield: 48%). Crystals suitable for X-ray diffraction were grown from a dichloromethane solution layered with hexane. Yield: 2.40 g, 48%. ¹H NMR (400 MHz, CDCl₃): δ 3.71 (q, J = 16 Hz, 4H, CH₂), 4.03 (d, J = 14.8 Hz, 2H, CH₂), 4.20 (d, J = 16 Hz, 2H, CH₂), 7.62 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 24.33, 36.12 (CH₂), 122.91, 134.64, 136.7 (Ar). The other signals for the aromatic ring were unseen due to poor solubility. Anal. calc. for C₁₆H₁₀Br₂F₄S₂: C, 38.27; H, 2.01. Found: C, 38.58, H; 1.88.

General procedure for the preparation of 6a–e

A mixture of the appropriate dibromo-substituted paracyclophane 3a–e, Pd(PPh₃)₄ (10 mol%) and CuI (15 mol%) in toluene/Et₃N (v/v = 5 : 2) was stirred at room temperature for 2 h under N₂; then (trimethylsilyl)acetylene (in the molecular ratio 1 : 10) was added to the stirred solution. The mixture was stirred at 100 °C for 2 d under an N₂ atmosphere. The precipitated ammonium salts were filtered off and the filtrate was evaporated under vacuum. The residue was subjected to column chromatography on silica gel using CH₂Cl₂/petroleum ether (1 : 1, v/v) as the eluent.

6a . Received from 3a (2.16 g, 5 mmol) as a white solid 1.30 g (yield: 56%). ¹H NMR (600 MHz, CDCl₃): δ 0.33 (s, 18H, SiMe₃), 3.53 (d, J = 15 Hz, 2H, CH₂), 3.81 (q, J = 12 Hz, 4H, CH₂), 4.28 (d, J = 15 Hz, 2H, CH₂), 7.01 (s, 2H, Ar), 7.05 (d, J = 7.8 Hz, 4H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ 0.07 (SiMe₃), 35.08, 37.83 (CH₂), 100.53, 103.55 (C≡C), 122.82, 128.22, 129.15 133.47, 135.18, 137.80 (Ar). Anal. calc. for C₂₆H₃₂S₂Si₂: C, 67.18; H, 6.94. Found: C, 67.21; H, 6.62.

6b . Received from 3b (2.45 g, 5 mmol) as a white solid 0.52 g (yield: 20%). ¹H NMR (600 MHz, CDCl₃): δ 0.29 (s, 18H, SiMe₃), 3.48 (d, J = 15 Hz, 2H, CH₂), 3.61 (d, J = 14.4 Hz, 2H, CH₂), 3.91 (s, 6H, CH₃), 4.04 (q, J = 15 Hz, 4H, CH₂), 6.66 (s, 2H, Ar), 7.22 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ −0.09 (SiMe₃), 32.14, 35.39 (CH₂), 55.17 (OCH₃), 101.48, 103.86 (C≡C), 112.67, 122.76, 123.89, 132.72, 137.89, 150.18 (Ar). Anal. calc. for C₂₈H₃₆O₂S₂Si₂: C, 64.07; H, 6.91. Found: C, 64.17; H, 7.07.

6c . Received from 3c (2.16 g, 4.5 mmol) as a white solid 1.52 g (yield: 65%). ¹H NMR (400 MHz, CDCl₃): δ 0.35 (s, 18H, SiMe₃), 3.69 (d, J = 14.8 Hz, 2H, CH₂), 3.82 (d, J = 15.6 Hz, 2H, CH₂), 4.08 (d, J = 15.6 Hz, 2H, CH₂), 4.13 (d, J = 14.4 Hz, 2H, CH₂), 7.28 (s, 2H, Ar), 7.64 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ −0.14 (SiMe₃), 35.19, 35.56 (CH₂), 101.86, 103.32 (C≡C), 114.25 (CN), 115.83, 116.75, 123.49, 133.65, 137.41, 140.18 (Ar). Anal. calc. for C₂₈H₃₀N₂S₂Si₂: C, 65.32; H, 5.87; N, 5.44. Found: C, 65.40; H, 5.43; N, 5.45.

6d . Received from 3d (2.29 g, 5 mmol) as a white solid 1.92 g (yield: 79%). ¹H NMR (400 MHz, CDCl₃): δ 0.33 (s, 18H, SiMe₃), 2.26 (s, 6H, CH₃), 3.56 (d, J = 15.2 Hz, 2H, CH₂), 3.72 (s, 4H, CH₂), 4.16 (d, J = 15.2 Hz, 2H, CH₂), 6.78 (s, 2H, Ar), 7.33 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 0.06 (SiMe₃), 18.51 (CH₃), 34.36, 36.09 (CH₂), 100.48, 103.25 (C≡C), 122.95, 131.73, 132.17, 132.84, 133.93, 137.51 (Ar). Anal. calc. for C₂₈H₃₆S₂Si₂: C, 68.23; H, 7.36. Found: C, 68.38; H, 7.79.

6e . Received from 3e (1.63 g, 3.5 mmol) as a white solid 1.26 g (yield: 72%). ¹H NMR (600 MHz, CDCl₃): δ 0.32 (s, 18 H, SiMe₃), 3.51 (d, J = 15.6 Hz, 2H, CH₂), 3.64 (d, J = 14.4 Hz, 2H, CH₂), 3.91 (d, J = 15.6 Hz, 2H, CH₂), 4.11 (d, J = 14.4 Hz, 2H, CH₂), 6.85 (t, J = 7.2 Hz, 2H, Ar), 7.26 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ −0.12 (SiMe₃), 30.65, 35.48 (SCH₂), 101.89, 102.75 (C≡C), 116.91 (d, J = 29.85 Hz, Ar), 123.25, 124.39 (d, J = 25.35 Hz, Ar), 132.94, 137.64, 154.94, 156.53 (Ar). ¹⁹F NMR (376 MHz, CDCl₃): δ −122.34. Anal. calc. for C₂₆H₃₀F₂S₂Si₂: C, 62.35; H, 6.04. Found: C, 62.36; H, 6.17.

Synthesis of 7. According to the same procedure as for 6a, received from 5a (2.43 g, 5 mmol) as a white solid 2.12 g (yield: 82%). ¹H NMR (400 MHz, CDCl₃): δ 0.29 (s, 18H, SiMe₃), 2.28 (s, 6H, CH₃), 2.32 (s, 6H, CH₃), 3.58 (d, J = 15.6 Hz, 2H, CH₂), 3.67 (d, J = 14.8 Hz, 2H, CH₂), 4.32 (d, J = 16 Hz, 2H, CH₂), 4.39 (d, J = 15.2 Hz, 2H, CH₂), 7.46 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ −0.14 (SiMe₃), 16.96, 17.73 (CH₃), 32.09, 33.72 (CH₂), 100.90, 103.65 (C≡C), 121.55, 131.32, 132.48, 133.44, 134.16, 137.72 (Ar). Anal. calc. for C₃₀H₄₀S₂Si₂: C, 69.17; H, 7.74. Found: C, 69.14; H, 7.89.

Synthesis of 8. To a stirred solution of 5b (2.43 g, 4.84 mmol) and 2-methylbut-3-yn-2-ol (1.63 g, 19.36 mmol) in THF-ⁱPr₂NH (180 mL, v/v = 2 : 1) was added Pd(PPh₃)₂Cl₂ (340 mg, 10 mol%) and CuI (91 mg, 10 mol%) under N₂; the mixture was then refluxed for 48 h. The cooled reaction mixture was filtered and the filtrate evaporated under vacuum. The residue was subjected to column chromatography on silica gel using ethyl acetate/petroleum ether (1 : 2, v/v) as the eluent to give 0.76 g of 8 as a white solid (yield: 31%). ¹H NMR (400 MHz, DMSO): δ 1.52 (s, 12H, CH₃), 3.83 (q, J = 15.2 Hz, 4H, CH₂), 3.99 (d, J = 14.8 Hz, 2H, CH₂), 4.15 (d, J = 14.8 Hz, 2H, CH₂), 5.49 (s, 2H, OH), 7.31 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 23.81 (CH₃), 31.48, 33.91 (CH₂), 63.87 (C–OH), 78.06, 102.29 (C≡C), 121.97, 131.97, 137.27 (Ar); no other signals for the aromatic ring carbons were detected due to poor solubility. Anal. calc. for C₂₆H₂₄F₄O₂S₂: C, 61.40; H, 4.76. Found: C, 61.16; H, 4.40.

General procedure for the preparation of 9a–e

To a stirred solution of bis(trimethylsilylethynyl)[3.3]dithia-paracyclophane (6a–e) in THF/MeOH (v/v = 1 : 1) was added 2.5 equiv. of KOH under N₂; the reaction mixture was then stirred at room temperature for 2 h. The reaction mixture was diluted with dichloromethane and washed with brine. The organic layer was then dried over NaSO₄ and the solvent removed in vacuo. The crude product was purified by chromatography on silica gel eluted with CH₂Cl₂/petroleum ether (1 : 1, v/v).

9a . Received from 6a (1.14 g, 2.45 mmol) as a white solid 0.75 g (yield: 96%). ¹H NMR (600 MHz, CDCl₃): δ 3.42 (s, 2H, ≡CH), 3.57 (d, J(HH) = 15.6 Hz, 2H, CH₂), 3.78 (d, J(HH) = 14.4 Hz, 2H, CH₂), 3.85 (d, J(HH) = 14.4 Hz, 2H, CH₂), 4.28 (d, J(HH) = 15 Hz, 2H, CH₂), 7.01 (d, J(HH) = 7.8 Hz, 2H, Ar), 7.05 (d, J(HH) = 7.8 Hz, 2H, Ar), 7.12 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ 34.87 (CH₂), 37.79 (CH₂), 81.94, 83.12 (C≡C), 122.15, 128.34, 129.26, 134.17, 135.25, 138.15 (Ar). MS(m/z): 320.8 (M⁺). HRMS (ESI): m/z [M + H]⁺ calc. for C₂₀H₁₇S₂: 321.07662. Found: 321.07673. Anal. calc. for C₂₀H₁₆S₂: C, 74.96; H, 5.03. Found: C, 75.21; H, 5.03.

9b . Received from 6b (0.43 g, 0.82 mmol) as a white solid 0.2 g (yield: 64%). ¹H NMR (400 MHz, CDCl₃): δ 3.48 (s, 2H, C≡CH), 3.50 (d, J = 16.8 Hz, 2H, SCH₂), 3.64 (d, J = 16 Hz, 2H, SCH₂), 3.89 (s, 6H, OCH₃), 4.06 (q, J = 14.4 Hz, 4H, SCH₂), 6.67 (s, 2H, Ar), 7.27 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 31.99, 35.17 (SCH₂), 55.38 (OCH₃), 82.13, 83.94 (C≡C), 112.74, 122.01, 123.85, 133.21, 138.16, 150.16 (Ar). HRMS (ESI): m/z [M + H]⁺ calc. for C₂₂H₂₁O₂S₂: 381.09775. Found: 381.09759. Anal. calc. for C₂₂H₂₀O₂S₂: C, 69.44; H, 5.30. Found: C, 69.54; H, 5.23.

9c . Received from 6c (1.84 g, 3.57 mmol) as a white solid 1.19 g (yield: 90%). ¹H NMR (400 MHz, CDCl₃): δ 3.58 (s, 2H, C≡CH), 3.74 (d, J = 14.4 Hz, 2H, CH₂), 3.86 (d, J = 16 Hz, 2H, CH₂), 4.08 (d, J = 14.4 Hz, 2H, CH₂), 4.17 (d, J = 14.8 Hz, 2H, CH₂), 7.36 (s, 2H, Ar), 7.67 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 35.13, 35.33 (CH₂), 80.40, 85.34 (C≡C), 115.83 (CN), 116.78, 122.85, 133.81, 134.07 137.94, 140.33 (Ar). HRMS (ESI): m/z [M + H]⁺ calc. for C₂₂H₁₅N₂S₂: 371.06712. Found: 371.06711. Anal. calc. for C₂₂H₁₄N₂S₂: C, 71.32; H, 3.81; N, 7.56. Found: C, 71.66; H, 3.47; N, 7.42.

9d . Received from 6d (1.67 g, 3.4 mmol) as a white solid 1.08 g (yield: 92%). ¹H NMR (600 MHz, CDCl₃): δ 2.27 (s, 6H, CH₃), 3.44 (s, 2H, C≡CH), 3.59 (d, J = 15.6 Hz, 2H, CH₂), 3.74 (q, J = 15.6 Hz, 4H, CH₂), 4.18 (d, J = 15.6 Hz, 2H, CH₂), 6.80 (s, 2H, Ar), 7.38 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ 18.50 (CH₃), 34.24, 35.90 (CH₂), 81.57, 83.05 (C≡C), 122.21, 131.77, 132.51, 132.88, 133.96, 137.90 (Ar). HRMS (ESI): m/z [M + H]⁺ calc. for C₂₂H₂₁S₂: 349.10792. Found: 349.10833. Anal. calc. for C₂₂H₂₀S₂: C, 75.82; H, 5.78. Found: C, 75.63; H, 5.96.

9e . Received from 6e (2.98 g, 5.95 mmol) as a white solid 1.08 g (yield: 75%). ¹H NMR (400 MHz, CDCl₃): δ 3.50 (s, 2H, C≡CH), 3.54 (d, J = 16 Hz, 2H, SCH₂), 3.68 (d, J = 14.4 Hz, 2H, SCH₂), 3.91 (d, J = 14.4 Hz, 2H, SCH₂), 4.14 (d, J = 14.8 Hz, 2H, SCH₂), 6.88 (t, J = 8.8 Hz, 2H, Ar), 7.34 (s, 2H, Ar). ¹³C NMR (100 MHz, CDCl₃): δ 30.56, 35.32 (SCH₂), 81.23, 84.21 (C≡C), 117.08 (d, J = 29.3 Hz, Ar), 122.69, 124.55 (t, J = 12.2 Hz, Ar), 133.57, 138.06, 154.60, 157.00 (Ar). ¹⁹F NMR (376 MHz, CDCl₃): δ −122.41. HRMS (ESI): m/z [M + H]⁺ calc. for C₂₀H₁₅F₂S₂: 357.05777. Found: 357.05793. Anal. calc. for C₂₀H₁₄F₂S₂: C, 67.39; H, 3.96. Found: C, 67.12; H, 3.64.

Synthesis of 10. According to the same procedure as for 9a, received from 7 (1.60 g, 3.1 mmol) as a white solid 0.82 g (yield: 70%). ¹H NMR (600 MHz, CDCl₃): δ 2.28 (s, 6H, CH₃), 2.31 (s, 6H, CH₃), 3.39 (s, 2H, C≡CH), 3.61 (d, J = 15.6 Hz, 2H, CH₂), 3.68 (d, J = 15 Hz, 2H, CH₂), 4.33 (d, J = 15.6 Hz, 2H, CH₂), 4.38 (d, J = 15.6 Hz, 2H, CH₂), 7.50 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ 17.10, 17.73 (CH₃), 32.11, 33.69 (CH₂), 81.99, 83.60 (C≡C), 120.84, 131.42, 132.77, 133.41, 134.10, 138.12 (Ar). HRMS (ESI): m/z [M + H]⁺ calc. for C₂₄H₂₅S₂: 377.13922. Found: 377.13963. Anal. calc. for C₂₄H₂₄S₂: C, 76.55; H, 6.42. Found: C, 76.50; H, 6.15.

Synthesis of 11. To a stirred solution of 8 (0.75 g, 1.47 mmol) in dried toluene (100 mL) was added NaH (78 mg, 3.25 mmol) under N₂, the reaction mixture was refluxed for 2.5 h. Then the reaction was cooled to room temperature, the solvent was removed in vacuo and the remaining solid residue treated with CH₂Cl₂ and washed with water, the organic phase was separated, dried with Na₂SO₄. Then the solvent was removed, the crude products was purified by column chromatography on silica gel (CH₂Cl₂/petroleum ether, v/v = 1 : 1) to yield 0.37 g of 11 as a white solid, yield: 64%. ¹H NMR (600 MHz, CDCl₃): δ 3.47 (s, 2H, ≡CH), 3.69 (q, J = 15.6 Hz, 4H, SCH₂), 4.04 (d, J = 15 Hz, 2H, SCH₂), 4.36 (d, J = 15.6 Hz, 2H, SCH₂), 7.55 (s, 2H, Ar). ¹³C NMR (150 MHz, CDCl₃): δ 24.34, 34.58 (SCH₂), 80.60, 84.34 (C≡C), 114.74, 122.24, 133.50, 137.95, 143.09, 144.11, 144.82, 145.78 (Ar). ¹⁹F NMR (376 MHz, CDCl₃): δ −142.18. HRMS (ESI): m/z [M + H]⁺ calc. for C₂₀H₁₃F₄S₂: 393.03893. Found: 393.03932. Anal. calc. for C₂₀H₁₂F₄S₂ : C, 61.21; H, 3.08. Found: C, 61.30; H, 3.33.

Acknowledgements

The authors acknowledge financial support from the National Natural Science Foundation of China (nos. 2072039, 20931006, 21072070) and the Program for Changjiang Scholars and Innovative Research Team in University (no. IRT0953).

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Footnote

† Electronic supplementary information (ESI) available: Tables of bond distances and angles, X-ray crystal data for complex 5b, and UV-vis absorption spectra of 9a–e, 10 and 11. See DOI: 10.1039/c0nj00553c

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