Palladium-catalyzed direct C–H arylation of ferrocenecarboxamides with aryl halides

Abstract

A simple and facile protocol for the palladium-catalyzed ortho-arylation of ferrocenecarboxamides with aryl halides was developed with the assistance of the bidentate directing group. The substrate scope could be extended to aryl iodides, bromides and even chlorides, as well as heterocyclic halides, affording diarylated products in moderate to good yields.

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Introduction

Ferrocenyl derivatives have wide applications in organic synthesis,¹ materials science,² medicinal chemistry,³ and biological science⁴ due to their unique structures, chemical and thermal stabilities, and redox properties. Furthermore, some of the ortho-difunctionalized ferrocenes can also serve as excellent planar chiral ligands in efficient enantioselective catalysis.⁵ Therefore, many efforts have been devoted to the development of economical and environmentally-friendly routes to ortho-functionalized ferrocenyl derivatives.⁶

During the past decades, transition metal-catalyzed C–H functionalization has become a robust and facile tool in organic synthesis and a series of transformations from C–H to C–C and C–heteroatom bonds have been demonstrated.^7–9 In particular, the pioneering work of C–H arylation of ferrocenes was carried out by You and co-workers, who developed a protocol of direct arylation of simple arenes with ferrocenyl oxazolines in 2007 (Scheme 1a), but this reaction employed a stoichiometric loading of the palladium salt (1 equiv.).^6b Subsequently, You's group developed another successful palladium-catalyzed C–H arylation of N,N-dimethylaminomethyl ferrocene with arylboronic acids (Scheme 1b),^6g albeit some of functionalized arylboronic acids are not very cheap and their preparation needs a multi-step synthesis. After that, palladium-catalyzed intramolecular C–H arylation of ferrocenyl derivatives was reported by Gu,⁶ⁱ You^6j and Liu^6l respectively (Scheme 1c), although the starting materials needed to be prefunctionalized.

Scheme 1 Transition metal-promoted C–H arylation of ferrocenyl derivatives.

Just recently, Kumar's group reported palladium-catalyzed C–H arylation of N-(quinolin-8-yl)ferrocenecarboxamide with aryl iodides (Scheme 1d).^6o Nevertheless, aryl iodides are usually expensive, not very easily available. Aryl bromides and chlorides are much cheaper and commercially available, and therefore, using them as the aryl sources would be the promising choice. However, the relative reports remain rare until now (on the ferrocenyl ring). Our research interest is to demonstrate a simple and easy protocol for ortho-arylation on the ferrocenyl ring. And we envisioned developing the catalytic intermolecular C–H arylation of ferrocenecarboxamides with aryl bromides and even some chlorides (Scheme 1e).

Results and discussion

We commenced our investigation by the reaction of ferrocenecarboxamide [DG = quinolin-8-ylamino moiety (Q-amino)] (1a) with bromobenzene (2a) in toluene in the presence of Pd(OAc)₂ as the model reaction (Table 1), and the desired product 3a was obtained in 8% yield (Table 1, entry 1). After extensive solvents were screened, and to our delight, the desired product 3a was obtained in 30% yield using o-xylene as the solvent (Table 1, entry 2); other solvents such as 1,2-dichloroethane, dioxane, acetonitrile and DMF could not facilitate the reaction (see ESI†). A thorough screening of bases revealed that K₂CO₃ was proved to be the most effective base (Table 1, entry 2 vs. entries 3–6). When the catalyst was switched to PdCl₂, Pd₂dba₃, Pd(CF₃COO)₂, Ni(OAc)₂ and [RuCl₂(cymene)]₂, they could not match the efficacy of Pd(OAc)₂ in our reaction, and the reaction could not take place at all without catalyst (see ESI†). Moreover, the results demonstrated that the choice of a ligand was also crucial, tricyclohexyl phosphine (PPy₃), 1,1′-bis(diphenylphosphino)ferrocene (DPPF), 2-dicyclohexylphosphino-2′,6′-diisopropoxy-1,1′-biphenyl (RuPhos), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos), 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (XantPhos) and 2-di-tert-butylphosphino-2′,4′,6′-trisopropyl-1,1′-biphenyl (^tBuXPhos) were also tested in this transformation, in which XPhos gave the best result affording the desired product 3a in 83% yield (Table 1, entries 7–12). PivOH played an important role in the reaction,¹⁰ as the pivalate anion might be a key component in C–H bond cleaving, which could lower the energy of C–H bond cleavage and act as a catalytic proton shuttle.^10b However, other additives such as AcOH, AcOK, and benzoic acid showed the lower effect (see ESI†). And the absence of the PivOH resulted in the decrease of the yield of 3a (Table 1, entry 13). When the reaction temperature was increased to 150 °C or decreased to 130 °C, no much better results were observed and the coupling products were afforded in 82% and 51%, respectively (Table 1, entries 14 and 15). In addition, it is worthwhile to mention that the same type of product 5a could be obtained in 72% yield when we use the 2-(pyridine-2-yl)isopropylamino (PIP-amino) moiety as a directing group.

Table 1 Optimization of the reaction conditions^a

Entry	Solvent	Base	Ligand	Yield^b (%)
a Reaction conditions: 1a (0.2 mmol), 2a (0.6 mmol), catalyst (0.02 mmol), ligand (0.02 mmol), PivOH (0.06 mmol), base (0.4 mmol) and solvent (1.0 mL) under nitrogen at 140 °C for 21 h unless otherwise noted.b Isolated yield based on 1a.c Without PivOH.d At 150 °C.e At 130 °C.
1	Toluene	K2CO3	PPh3	8
2	o-Xylene	K2CO3	PPh3	30
3	o-Xylene	Na2CO3	PPh3	20
4	o-Xylene	Cs2CO3	PPh3	Trace
5	o-Xylene	K3PO4	PPh3	18
6	o-Xylene	KHCO3	PPh3	Trace
7	o-Xylene	K2CO3	PPy3	23
8	o-Xylene	K2CO3	DPPF	49
9	o-Xylene	K2CO3	RuPhos	61
10	o-Xylene	K2CO3	XPhos	83
11	o-Xylene	K2CO3	XantPhos	42
12	o-Xylene	K2CO3	^tBuXPhos	60
13^c	o-Xylene	K2CO3	XPhos	72
14^d	o-Xylene	K2CO3	XPhos	82
15^e	o-Xylene	K2CO3	XPhos	51

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With the optimized reaction conditions in hand, the scope of aryl bromides was examined and the results were summarized in Table 2. Generally, a variety of aryl bromides bearing electron-donating and electron-withdrawing groups are well tolerated, generating the desired products in moderate to high yields. Whether the directing group is Q-amino or PIP-amino, electron-donating substituents (1b–g, R = Me, OMe, and ^tBu) resulted in higher yields than those of the electron-withdrawing substituents (1h–m, R = CF₃, F, Cl, COOMe, and NO₂). Moreover, a heterocyclic bromide (such as 2-bromothiophene) could also participate in the coupling, producing the target products in moderate yields (3n and 5n). Overall, the two bidentate directing groups Q-amino and PIP-amino could work well in this reaction and the results of quinolin-8-ylamino moiety as the directing group are a little better than those of 2-(pyridine-2-yl)isopropylamino group. The molecular structures of 3a¹¹ and 5a¹² were unambiguously confirmed by single crystal X-ray diffraction study.

Table 2 Substrate scope of aryl bromides^a,b

a Reaction conditions: 1a or 4a (0.2 mmol), 2 (0.6 mmol), Pd(OAc)₂ (0.02 mmol), XPhos (0.02 mmol), PivOH (0.06 mmol), K₂CO₃ (0.4 mmol) and o-xylene (1.0 mL) under nitrogen at 140 °C for 21 h.b Isolated yield based on 1a or 4a.

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To demonstrate the synthetic value of this protocol, a gram-scale reaction of 1a with 2a was performed (Scheme 2). This reaction could generate the desired product in an isolated yield of 75%.

Scheme 2 The gram scale reaction.

Moreover, 4-iodobromobenzene could also participate in the coupling with 1a, generating the desired product 3o in 82% yield (Scheme 3). This reaction did not involve the phosphine ligand (XPhos) and high temperature (only at 100 °C). It could also work well in air, which is easier to operate than that of Kumar's protocol for aryl iodides (at 120 °C under argon).^6o Furthermore, the product 3o was easily converted into the interesting more complicated compound 6 in 97% yield.

Scheme 3 Further functionalization of ferrocenyl derivatives.

Finally, we also explored the reaction of aryl chlorides shown in Scheme 4. Both 4-chlorotoluene and 1-(tert-butyl)-4-chlorobenzene were well tolerated in this reaction, leading to the desired products in moderate yields (3b and 3d).

Scheme 4 The arylation of ferrocenecarboxamides with aryl chlorides.

Conclusions

In conclusion, we have developed a Pd(II)-catalyzed intermolecular ortho C–H arylation of ferrocenecarboxamides with aryl halides using the bidentate directing groups, i.e., quinolin-8-ylamino and 2-(pyridine-2-yl)isopropylamino groups. The protocol exhibits excellent functional group tolerance for both electron-rich (e.g., Me, OMe and ^tBu) and electron-poor (e.g., CF₃, F, Cl, COOMe and NO₂) groups. Moreover, gram-scale reaction of this arylation is also successfully realized, which demonstrates its potential applicable value in organic synthesis. In addition, some aryl chlorides could also participate in the coupling, affording the desired products in moderate yields.

Experimental

General information

¹H, ¹³C and ³¹P NMR spectra were recorded on a Bruker DPX-400 spectrometer with CDCl₃ as the solvent and TMS as an internal standard. Melting points were measured using a WC-1 microscopic apparatus and are uncorrected. Mass spectra were measured on an LC-MSD-Trap-XCT instrument. High resolution mass spectra were ensured on a MALDI-FTMS. All solvents were used directly without further purification. Dichloromethane, ethyl acetate, and hexane were used for column chromatography. Chemicals were obtained from commercial sources and used as-received without further purification unless otherwise noted.

Typical procedure for the products

(a) For aryl bromides. A 25 mL Schlenk tube was equipped with a magnetic stir bar and charged with 1a or 4a (0.2 mmol), 2a–2n (0.6 mmol, 3 equiv.), K₂CO₃ (55.3 mg, 0.4 mmol, 2 equiv.), Pd(OAc)₂ (4.5 mg, 0.02 mmol, 10 mol%), XPhos (9.5 mg, 0.02 mmol, 10 mol%), PivOH (6.2 mg, 0.06 mmol, 30 mol%) in o-xylene (1.0 mL). The resulting mixture was heated under nitrogen at 140 °C for 21 h, and cooled to room temperature. Upon completion, CH₂Cl₂ (20 mL) was added to the reaction system, and the resulting mixture was filtered through a pad of Celite. The filtrate was extracted with H₂O (20 mL), and the aqueous layer was extracted with CH₂Cl₂ (2 × 10 mL). The combined organic layer was dried over anhydrous Na₂SO₄ and filtered. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (100–200 mesh) using hexane–EtOAc as an eluent to afford the pure product 3 or 5.
2,5-Diphenyl-N-(quinolin-8-yl)ferrocenecarboxamide (3a). Orange solid (84 mg, 83%); mp 184–185 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.80 (s, 1H), 8.87 (d, J = 7.5 Hz, 1H), 8.57 (d, J = 3.7 Hz, 1H), 8.11 (d, J = 8.2 Hz, 1H), 7.65 (d, J = 7.5 Hz, 4H), 7.56 (t, J = 7.6 Hz, 1H), 7.49 (d, J = 8.1 Hz, 1H), 7.36 (dd, J = 6.3 Hz, J = 2.2 Hz, 1H), 7.22 (t, J = 7.3 Hz, 4H), 7.15 (t, J = 7.2 Hz, 2H), 4.79 (s, 2H), 4.44 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.9, 147.8, 138.5, 136.8, 136.0, 134.7, 128.8, 128.0, 127.8, 127.4, 126.7, 121.4, 116.1, 88.6, 82.2, 72.7, 69.3; HRMS (ESI+) calcd for C₃₂H₂₄FeN₂O [M + H]⁺: 509.1311, found: 509.1313.
N-(Quinolin-8-yl)-2,5-di-p-tolylferrocenecarboxamide (3b). Orange solid (87 mg, 81%); mp 149–150 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.80 (s, 1H), 8.89 (dd, J = 4.2 Hz, J = 3.3 Hz, 1H), 8.59 (dd, J = 2.5 Hz, J = 2.2 Hz, 1H), 8.11 (dd, J = 4.9 Hz, J = 3.5 Hz, 1H), 7.59–7.49 (m, 6H), 7.36 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 7.02 (d, J = 8.0 Hz, 4H), 4.78 (s, 2H), 4.42 (s, 5H), 2.24 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 168.1, 147.7, 138.6, 136.3, 136.0, 134.8, 133.8, 128.7, 128.7, 127.8, 127.4, 121.3, 116.2, 88.5, 82.1, 72.5, 69.0, 21.0; HRMS (ESI+) calcd for C₃₄H₂₈FeN₂O [M + H]⁺: 537.1624, found: 537.1629.
N-(Quinolin-8-yl)-2,5-di-m-tolylferrocenecarboxamide (3c). Orange solid (86 mg, 80%); mp 209–210 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.78 (s, 1H), 8.85 (d, J = 7.5 Hz, 1H), 8.58 (dd, J = 2.8 Hz, J = 1.2 Hz, 1H), 8.11 (dd, J = 5.0 Hz, J = 3.5 Hz, 1H), 7.56 (t, J = 8.1 Hz, 1H), 7.51–7.47 (m, 3H), 7.42 (s, 2H), 7.37 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 7.11 (t, J = 7.6 Hz, 2H), 6.95 (d, J = 7.5 Hz, 2H), 4.75 (s, 2H), 4.42 (s, 5H), 2.21 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 168.0, 147.7, 138.5, 137.3, 136.7, 136.0, 134.9, 129.6, 127.8, 127.5, 127.4, 126.2, 121.3, 121.3, 116.1, 88.7, 82.4, 72.5, 69.2, 21.3; HRMS (ESI+) calcd for C₃₄H₂₈FeN₂O [M + H]⁺: 537.1624, found: 537.1628.
2,5-Bis(4-(tert-butyl)phenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3d). Yellow solid (111 mg, 90%); mp 279–282 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.72 (s, 1H), 8.87 (d, J = 7.4 Hz, 1H), 8.52 (d, J = 4.5 Hz, 1H), 8.06 (dd, J = 8.4 Hz, 1H), 7.59–7.47 (m, 6H), 7.33 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 7.21 (d, J = 8.0 Hz, 4H), 4.76 (s, 2H), 4.42 (s, 5H), 1.23 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 168.2, 149.5, 147.6, 138.5, 135.9, 134.9, 133.7, 128.6, 127.7, 127.4, 121.2, 121.1, 116.0, 88.7, 81.5, 72.6, 69.2, 34.4, 31.2; HRMS (ESI+) calcd for C₄₀H₄₀FeN₂O [M + H]⁺: 621.2563, found: 621.2569.
2,5-Bis(4-methoxyphenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3e). Orange solid (99 mg, 87%); mp 180–181 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.80 (s, 1H), 8.88 (dd, J = 4.2 Hz, J = 3.3 Hz, 1H), 8.59 (dd, J = 2.8 Hz, J = 1.2 Hz, 1H), 8.11 (dd, J = 5.0 Hz, J = 3.4 Hz, 1H), 7.58–7.48 (m, 6H), 7.36 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 6.76 (d, J = 8.4 Hz, 4H), 4.69 (s, 2H), 4.40 (s, 5H), 3.70 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 168.2, 158.5, 147.7, 138.5, 136.0, 134.8, 129.9, 128.9, 127.8, 127.3, 121.3, 121.3, 116.1, 113.5, 88.4, 81.5, 72.4, 68.8, 55.1; HRMS (ESI+) calcd for C₃₄H₂₈FeN₂O₃ [M + H]⁺: 569.1522, found: 569.1524.
2,5-Bis(3-methoxyphenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3f). Orange solid (95 mg, 84%); mp 111–112 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.90 (s, 1H), 8.88 (dd, J = 4.3 Hz, J = 3.2 Hz, 1H), 8.60 (dd, J = 2.8 Hz, J = 1.2 Hz, 1H), 8.10 (dd, J = 5.0 Hz, J = 3.4 Hz, 1H), 7.57–7.48 (m, 2H), 7.37 (dd, J = 6.3 Hz, J = 2.0 Hz, 1H), 7.25 (d, J = 6.0 Hz, 2H), 7.21 (m, 2H), 7.13 (t, J = 8.2 Hz, 2H), 6.69 (dd, J = 5.1 Hz, J = 3.1 Hz, 2H), 4.78 (s, 2H), 4.44 (s, 5H), 3.63 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.9, 159.1, 147.8, 138.5, 138.3, 136.1, 134.8, 128.9, 127.8, 127.3, 121.5, 121.4, 121.4, 116.1, 114.0, 112.7, 88.2, 82.9, 72.7, 69.2, 55.0; HRMS (ESI+) calcd for C₃₄H₂₈FeN₂O₃ [M + H]⁺: 569.1522, found: 569.1518.
2,5-Bis(3,5-dimethylphenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3g). Orange solid (87 mg, 77%); mp 189–190 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.78 (s, 1H), 8.84 (d, J = 7.5 Hz, 1H), 8.60 (dd, J = 2.8 Hz, J = 1.2 Hz, 1H), 8.12 (dd, J = 4.8 Hz, J = 3.4 Hz, 1H), 7.57 (t, J = 8.0 Hz, 1H), 7.50 (m, 1H), 7.38 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 7.26 (s, 4H), 6.77 (s, 2H), 4.73 (s, 2H), 4.44 (s, 5H), 2.18 (s, 12H); ¹³C NMR (100 MHz, CDCl₃) δ 168.1, 147.7, 138.6, 137.2, 136.6, 135.9, 135.0, 128.5, 127.8, 127.4, 126.9, 121.3, 121.2, 116.0, 88.8, 82.5, 72.6, 69.1, 21.2; HRMS (ESI+) calcd for C₃₆H₃₂FeN₂O [M + H]⁺: 565.1937, found: 565.1938.
N-(Quinolin-8-yl)-2,5-bis(4-(trifluoromethyl)phenyl)ferrocenecarboxamide (3h). Orange solid (97 mg, 75%); mp 168–169 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.70 (s, 1H), 8.83 (dd, J = 4.2 Hz, J = 2.9 Hz, 1H), 8.51 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.14 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 7.75 (d, J = 8.4 Hz, 4H), 7.61–7.53 (m, 2H), 7.47 (d, J = 8.4 Hz, 4H), 7.38 (dd, J = 6.3 Hz, J = 2.1 Hz, 1H), 4.87 (s, 2H), 4.43 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.1, 147.9, 141.0, 138.4, 136.2, 134.3, 129.0, 128.9 (q, J_C–F = 33.1 Hz), 127.9, 127.3, 125.0 (q, J_C–F = 3.7 Hz), 123.0 (q, J_C–F = 272.5 Hz), 121.9, 121.5, 116.3, 87.3, 82.5, 73.1, 70.0; HRMS (ESI+) calcd for C₃₄H₂₂F₆FeN₂O [M + H]⁺: 645.1059, found: 645.1057.
2,5-Bis(4-fluorophenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3i). Yellow solid (84 mg, 77%); mp 165–166 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.72 (s, 1H), 8.84 (dd, J = 4.3 Hz, J = 3.1 Hz, 1H), 8.59 (dd, J = 2.8 Hz, J = 1.4 Hz, 1H), 8.13 (dd, J = 4.8 Hz, J = 3.5 Hz, 1H), 7.62–7.59 (m, 4H), 7.56–7.51 (m, 2H), 7.39 (dd, J = 6.2 Hz, J = 2.1 Hz, 1H), 6.92 (t, J = 8.7 Hz, 4H), 4.72 (s, 2H), 4.40 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.6, 161.9 (d, J_C–F = 247.7 Hz), 147.8, 138.4, 136.1, 134.5, 132.6, 132.6, 130.4 (d, J_C–F = 8.3 Hz), 127.9, 127.4, 121.6, 121.5, 116.1, 114.9 (d, J_C–F = 21.6 Hz), 87.9, 81.8, 72.7, 69.3; HRMS (ESI+) calcd for C₃₂H₂₂F₂FeN₂O [M + H]⁺: 545.1122, found: 545.1118.
2,5-Bis(4-chlorophenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3j). Orange solid (92 mg, 80%); mp 213–214 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.73 (s, 1H), 8.84 (dd, J = 4.4 Hz, J = 3.0 Hz, 1H), 8.59 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.13 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 7.59–7.52 (m, 6H), 7.39 (dd, J = 6.2 Hz, J = 2.1 Hz, 1H), 7.18 (d, J = 8.0 Hz, 4H), 4.76 (s, 2H), 4.41 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.4, 147.9, 138.4, 136.1, 135.4, 134.4, 132.6, 130.0, 128.2, 127.9, 127.3, 121.7, 121.5, 116.2, 87.5, 82.1, 72.7, 69.4; HRMS (ESI+) calcd for C₃₂H₂₂Cl₂FeN₂O [M + H]⁺: 577.0531, found: 577.0531.
Dimethyl-4,4′-(2-(quinolin-8-ylcarbamoyl)ferrocene-1,3-diyl)dibenzoate (3k). Orange solid (67 mg, 54%); mp 197–199 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.81 (s, 1H), 8.84 (dd, J = 4.4 Hz, J = 3.0 Hz, 1H), 8.55 (dd, J = 2.5 Hz, J = 2.2 Hz, 1H), 8.12 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 7.88 (d, J = 8.4 Hz, 4H), 7.68 (d, J = 8.4 Hz, 4H), 7.59–7.51 (m, 2H), 7.36 (dd, J = 6.2 Hz, J = 2.1 Hz, 1H), 4.88 (s, 2H), 4.42 (s, 5H), 3.85 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.2, 166.8, 147.9, 138.4, 136.2, 134.4, 129.3, 128.5, 128.4, 127.9, 127.4, 121.8, 121.5, 116.3, 87.2, 83.1, 73.0, 69.9, 51.9; HRMS (ESI+) calcd for C₃₆H₂₈FeN₂O₅ [M + H]⁺: 625.1420, found: 625.1421.
2,5-Bis(4-nitrophenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3l). Dark red solid (67 mg, 56%); mp 223–226 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.75 (s, 1H), 8.83 (dd, J = 4.4 Hz, J = 2.5 Hz, 1H), 8.55 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.15 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 8.07 (d, J = 8.4 Hz, 4H), 7.78 (d, J = 8.4 Hz, 4H), 7.62–7.55 (m, 2H), 7.39 (dd, J = 6.2 Hz, J = 2.1 Hz, 1H), 4.97 (s, 2H), 4.46 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 166.5, 148.0, 146.5, 144.7, 138.3, 136.5, 134.0, 129.2, 128.0, 127.4, 123.4, 122.3, 121.7, 116.4, 86.4, 83.4, 73.4, 70.6; HRMS (ESI+) calcd for C₃₂H₂₂FeN₄O₅ [M + H]⁺: 599.1012, found: 599.1009.
2,5-Bis(3-nitrophenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3m). Dark red solid (56 mg, 47%); mp 165–166 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.68 (s, 1H), 8.79 (dd, J = 4.4 Hz, J = 2.8 Hz, 1H), 8.54 (t, J = 2.0 Hz, 1H), 8.51 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.13 (dd, J = 5.0 Hz, J = 3.4 Hz, 1H), 8.02–8.00 (m, 2H), 7.95–7.92 (m, 2H), 7.59–7.51 (m, 2H), 7.39–7.33 (m, 3H), 4.94 (s, 2H), 4.48 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 166.6, 148.1, 148.0, 138.9, 138.3, 136.3, 134.7, 134.0, 129.0, 127.8, 127.4, 123.6, 122.0, 121.8, 121.6, 116.4, 86.8, 82.2, 73.1, 70.3; HRMS (ESI+) calcd for C₃₂H₂₂FeN₄O₅ [M + H]⁺: 599.1012, found: 599.1013.
N-(Quinolin-8-yl)-2,5-di(thiophen-2-yl)ferrocenecarboxamide (3n). Orange solid (43 mg, 41%); mp 170–171 °C; ¹H NMR (400 MHz, CDCl₃) δ 11.13 (s, 1H), 8.95 (dd, J = 4.3 Hz, J = 3.2 Hz, 1H), 8.70 (dd, J = 2.8 Hz, J = 1.3 Hz, 1H), 8.16 (dd, J = 4.8 Hz, J = 3.5 Hz, 1H), 7.62–7.53 (m, 2H), 7.42 (dd, J = 6.2 Hz, J = 2.1 Hz, 1H), 7.22 (d, J = 3.5 Hz, 2H), 7.14 (d, J = 5.1 Hz, 2H), 6.82 (dd, J = 4.4 Hz, J = 0.7 Hz, 2H), 4.79 (s, 2H), 4.51 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 166.9, 148.0, 139.7, 138.6, 136.2, 134.8, 128.0, 127.5, 127.2, 126.0, 124.5, 121.7, 121.6, 116.4, 82.8, 81.2, 73.3, 69.4; HRMS (ESI+) calcd for C₂₈H₂₀FeN₂OS₂ [M + H]⁺: 521.0439, found: 521.0435.
2,5-Bis(4-bromophenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (3o). Orange solid (109 mg, 82%); mp 229–230 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.71 (s, 1H), 8.82 (dd, J = 4.4 Hz, J = 2.8 Hz, 1H), 8.59 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.14 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 7.59–7.48 (m, 6H), 7.40 (dd, J = 6.2 Hz, J = 2.0 Hz, 1H), 7.33 (d, J = 8.6 Hz, 4H), 4.74 (s, 2H), 4.40 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.4, 148.0, 138.5, 136.2, 135.9, 134.5, 131.2, 130.4, 128.0, 127.4, 121.8, 121.6, 120.8, 116.3, 87.6, 82.1, 72.9, 69.5; HRMS (ESI+) calcd for C₃₂H₂₂Br₂FeN₂O [M + H]⁺: 664.9521, found: 664.9524.
2,5-Diphenyl-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5a). Yellow solid (72 mg, 72%); mp 143–144 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.70 (s, 1H), 8.36 (d, J = 3.6 Hz, 1H), 7.64 (d, J = 7.6 Hz, 5H), 7.32–7.11 (m, 8H), 4.66 (s, 2H), 4.29 (s, 5H), 1.77 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.6, 164.4, 147.2, 137.3, 136.9, 128.8, 127.8, 126.6, 121.7, 119.4, 87.6, 85.0, 72.4, 68.1, 57.1, 26.9; HRMS (ESI+) calcd for C₃₁H₂₈FeN₂O [M + H]⁺: 501.1624, found: 501.1624.
N-(2-(Pyridin-2-yl)propan-2-yl)-2,5-di-p-tolylferrocenecarboxamide (5b). Yellow solid (74 mg, 70%); mp 179–180 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.72 (s, 1H), 8.41–8.39 (m, 1H), 7.69–7.64 (m, 1H), 7.55 (d, J = 8.2 Hz, 4H), 7.34 (d, J = 8.4 Hz, 1H), 7.16–7.13 (m, 1H), 7.07 (d, J = 8.2 Hz, 4H), 4.63 (s, 2H), 4.30 (s, 5H), 2.31 (s, 6H), 1.77 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.8, 164.5, 147.2, 136.9, 136.1, 134.2, 128.6, 128.5, 121.6, 119.4, 87.5, 84.7, 72.2, 67.8, 57.1, 26.9, 21.1; HRMS (ESI+) calcd for C₃₃H₃₂FeN₂O [M + H]⁺: 529.1937, found: 529.1936.
N-(2-(Pyridin-2-yl)propan-2-yl)-2,5-di-m-tolylferrocenecarboxamide (5c). Orange solid (73 mg, 69%); mp 141–142 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.80 (s, 1H), 8.41 (d, J = 4.6 Hz, 1H), 7.69–7.65 (m, 1H), 7.48 (s, 1H), 7.46 (s, 3H), 7.34 (d, J = 8.0 Hz, 1H), 7.18–7.13 (m, 3H), 7.01 (d, J = 7.4 Hz, 2H), 4.65 (s, 2H), 4.30 (s, 5H), 2.31 (s, 6H), 1.80 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.7, 164.5, 147.2, 137.2, 137.1, 137.0, 129.4, 127.7, 127.3, 125.9, 121.7, 119.4, 87.6, 85.1, 72.3, 68.0, 57.2, 26.9, 21.4; HRMS (ESI+) calcd for C₃₃H₃₂FeN₂O [M + H]⁺: 529.1937, found: 529.1938.
2,5-Bis(4-(tert-butyl)phenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5d). Orange solid (87 mg, 71%); mp 151–153 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.51 (s, 1H), 8.39–8.37 (m, 1H), 7.66–7.62 (m, 1H), 7.58–7.55 (m, 4H), 7.32 (d, J = 8.1 Hz, 1H), 7.29–7.27 (m, 4H), 7.14–7.11 (m, 1H), 4.63 (s, 2H), 4.29 (s, 5H), 1.79 (s, 6H), 1.30 (s, 18H); ¹³C NMR (100 MHz, CDCl₃) δ 167.7, 164.5, 149.3, 147.2, 136.8, 134.1, 128.6, 124.6, 121.5, 119.3, 87.8, 84.0, 72.3, 68.0, 57.1, 34.4, 31.3, 26.9; HRMS (ESI+) calcd for C₃₉H₄₄FeN₂O [M + H]⁺: 613.2876, found: 613.2880.
2,5-Bis(4-methoxyphenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5e). Orange solid (88 mg, 79%); mp 203–205 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.69 (s, 1H), 8.40–8.39 (m, 1H), 7.68–7.64 (m, 1H), 7.58–7.54 (m, 4H), 7.33 (d, J = 8.2 Hz, 1H), 7.16–7.12 (m, 1H), 6.82–6.78 (m, 4H), 4.58 (s, 2H), 4.37 (s, 5H), 3.78 (s, 6H), 1.79 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.9, 164.5, 158.4, 147.2, 136.9, 129.8, 121.6, 119.4, 113.3, 87.4, 84.3, 72.1, 67.6, 57.1, 55.2, 27.0; HRMS (ESI+) calcd for C₃₃H₃₂FeN₂O₃ [M + H]⁺: 561.1836, found: 561.1830.
2,5-Bis(3-methoxyphenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5f). Orange solid (87 mg, 78%); mp 127–128 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.77 (s, 1H), 8.41 (d, J = 4.4 Hz, 1H), 7.68–7.64 (m, 1H), 7.34 (d, J = 8.2 Hz, 1H), 7.28 (s, 1H), 7.26 (s, 3H), 7.21–7.13 (m, 3H), 6.79–6.76 (m, 2H), 4.67 (s, 2H), 4.34 (s, 5H), 3.79 (s, 6H), 1.80 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.5, 164.3, 159.0, 147.1, 138.6, 136.9, 128.7, 121.6, 121.4, 119.3, 114.4, 112.3, 87.5, 85.4, 72.4, 68.1, 57.1, 55.1, 26.9; HRMS (ESI+) calcd for C₃₃H₃₂FeN₂O₃ [M + H]⁺: 561.1836, found: 561.1836.
2,5-Bis(3,5-dimethylphenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5g). Orange solid (76 mg, 68%); mp 162–164 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.89 (s, 1H), 8.45–7.43 (m, 1H), 7.71–7.66 (m, 1H), 7.36 (d, J = 8.2 Hz, 1H), 7.29 (s, 4H), 7.18–7.15 (m, 1H), 6.86 (s, 2H), 4.64 (s, 2H), 4.33 (s, 5H), 2.30 (s, 12H), 1.83 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.7, 164.6, 147.1, 137.1, 137.0, 137.0, 128.3, 126.6, 121.7, 119.3, 87.5, 85.3, 72.2, 67.8, 57.2, 26.9, 21.2; HRMS (ESI+) calcd for C₃₅H₃₆FeN₂O [M + H]⁺: 557.2250, found: 557.2251.
N-(2-(Pyridin-2-yl)propan-2-yl)-2,5-bis(4-(trifluoromethyl)phenyl)ferrocenecarboxamide (5h). Orange solid (77 mg, 61%); mp 152–154 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.93 (s, 1H), 8.34–8.33 (m, 1H), 7.75 (d, J = 8.1 Hz, 4H), 7.72–7.68 (m, 1H), 7.51 (d, J = 8.2 Hz, 4H), 7.36 (d, J = 8.1 Hz, 1H), 7.18–7.15 (m, 1H), 4.76 (s, 2H), 4.32 (s, 5H), 1.80 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.0, 164.0, 147.1, 141.5, 137.2, 128.8, 128.6 (q, J_C–F = 31.1 Hz), 124.8 (q, J_C–F = 3.7 Hz), 124.3 (q, J_C–F = 272.0 Hz), 122.0, 119.4, 86.2, 85.4, 72.7, 68.9, 57.2, 26.9; HRMS (ESI+) calcd for C₃₃H₂₆F₆FeN₂O [M + H]⁺: 637.1372, found: 637.1372.
2,5-Bis(4-fluorophenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5i). Yellow solid (72 mg, 67%); mp 177–179 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.80 (s, 1H), 8.38–8.37 (m, 1H), 7.71–7.66 (m, 1H), 7.62–7.57 (m, 4H), 7.34 (d, J = 8.1 Hz, 1H), 7.18–7.14 (m, 1H), 6.98–6.92 (m, 4H), 4.61 (s, 2H), 4.29 (s, 5H), 1.78 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.4, 164.2, 161.7 (d, J_C–F = 246.6 Hz), 147.1, 137.1, 133.1, 133.1, 130.2 (d, J_C–F = 8.0 Hz), 121.8, 119.4, 114.7 (d, J_C–F = 21.3 Hz), 86.9, 84.7, 72.3, 68.1, 57.1, 26.9; HRMS (ESI+) calcd for C₃₁H₂₆F₂FeN₂O [M + H]⁺: 537.1436, found: 537.1440.
2,5-Bis(4-chlorophenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5j). Orange solid (78 mg, 69%); mp 169–170 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.85 (s, 1H), 8.38 (d, J = 4.4 Hz, 1H), 7.71–7.68 (m, 1H), 7.55 (d, J = 8.5 Hz, 4H), 7.35 (d, J = 8.2 Hz, 1H), 7.22 (d, J = 8.5 Hz, 4H), 7.17 (dd, J = 6.0 Hz, J = 0.9 Hz, 1H), 4.64 (s, 2H), 4.28 (s, 5H), 1.79 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.2, 164.1, 147.1, 137.1, 135.9, 132.3, 129.9, 128.0, 121.9, 119.4, 86.4, 85.0, 72.5, 68.2, 57.2, 26.9; HRMS (ESI+) calcd for C₃₁H₂₆Cl₂FeN₂O [M + H]⁺: 569.0845, found: 569.0850.
Dimethyl-4,4′-(2-(2-(pyridin-2-yl)propan-2-ylcarbamoyl)ferrocene-1,3-diyl)dibenzoate (5k). Orange solid (60 mg, 49%); mp 157–159 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.98 (s, 1H), 8.35 (d, J = 4.2 Hz, 1H), 7.92 (d, J = 8.5 Hz, 4H), 7.70–7.66 (m, 5H), 7.36 (d, J = 8.1 Hz, 1H), 7.15 (dd, J = 5.9 Hz, J = 1.0 Hz, 1H), 4.77 (s, 2H), 4.29 (s, 5H), 3.88 (s, 6H), 1.81 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 167.1, 167.0, 164.1, 147.1, 142.8, 137.2, 129.2, 128.3, 121.9, 119.4, 86.4, 86.0, 72.7, 68.8, 57.3, 52.0, 26.9; HRMS (ESI+) calcd for C₃₅H₃₂FeN₂O₅ [M + H]⁺: 617.1734, found: 617.1738.
2,5-Bis(4-nitrophenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5l). Dark red solid (48 mg, 41%); mp 162–164 °C; ¹H NMR (400 MHz, CDCl₃) δ 9.09 (s, 1H), 8.32 (d, J = 4.3 Hz, 1H), 8.12 (d, J = 8.8 Hz, 4H), 7.75–7.71 (m, 5H), 7.39 (d, J = 8.4 Hz, 1H), 7.18 (dd, J = 6.3 Hz, J = 0.9 Hz, 1H), 4.87 (s, 2H), 4.34 (s, 5H), 1.83 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 166.5, 163.7, 147.0, 146.4, 145.3, 137.5, 128.9, 123.3, 122.2, 119.5, 86.3, 85.3, 73.1, 69.6, 57.3, 26.9; HRMS (ESI+) calcd for C₃₁H₂₆FeN₄O₅ [M + H]⁺: 591.1326, found: 591.1328.
2,5-Bis(3-nitrophenyl)-N-(2-(pyridin-2-yl)propan-2-yl)ferrocenecarboxamide (5m). Orange solid (44 mg, 37%); mp 127–128 °C; ¹H NMR (400 MHz, CDCl₃) δ 9.24 (s, 1H), 8.50 (t, J = 1.9 Hz, 2H), 8.29 (d, J = 4.3 Hz, 1H), 8.07–7.92 (m, 2H), 7.93 (d, J = 8.0 Hz, 2H), 7.73–7.69 (m, 1H), 7.42 (t, J = 8.2 Hz, 2H), 7.37 (d, J = 8.4 Hz, 1H), 7.17–7.14 (m, 1H), 4.82 (s, 2H), 4.36 (s, 5H), 1.82 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 166.4, 163.9, 148.1, 146.9, 139.5, 137.4, 134.5, 128.8, 123.4, 122.0, 121.6, 119.5, 85.7, 85.3, 72.8, 69.1, 57.3, 26.9; HRMS (ESI+) calcd for C₃₁H₂₆FeN₄O₅ [M + H]⁺: 591.1326, found: 591.1328.
N-(2-(Pyridin-2-yl)propan-2-yl)-2,5-di(thiophen-2-yl)ferrocenecarboxamide (5n). Orange solid (31 mg, 30%); mp 101–102 °C; ¹H NMR (400 MHz, CDCl₃) δ 9.20 (s, 1H), 8.45–8.43 (m, 1H), 7.72–7.68 (m, 1H), 7.40 (d, J = 8.1 Hz, 1H), 7.22 (dd, J = 2.4 Hz, J = 1.2 Hz, 2H), 7.18–7.15 (m, 3H), 6.88 (dd, J = 4.4 Hz, J = 0.8 Hz, 2H), 4.68 (s, 2H), 4.37 (s, 5H), 1.87 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 166.7, 164.5, 147.1, 140.1, 137.1, 127.0, 125.8, 124.2, 121.8, 119.5, 84.9, 80.5, 73.0, 68.6, 57.3, 27.0; HRMS (ESI+) calcd for C₂₇H₂₄FeN₂OS₂ [M + H]⁺: 513.0753, found: 513.0753.

(b) For gram reaction. A 100 mL Schlenk tube was equipped with a magnetic stir bar and charged with 1a (1.07 g, 3.0 mmol), 2a (0.945 mL, 9.0 mmol, 3 equiv.), K₂CO₃ (829.5 mg, 6.0 mmol, 2 equiv.), Pd(OAc)₂ (67.5 mg, 0.3 mmol, 10 mol%), XPhos (142.5 mg, 0.3 mmol, 10 mol%), PivOH (93.0 mg, 0.9 mmol, 30 mol%) in o-xylene (15 mL). The resulting mixture was heated under nitrogen at 140 °C for 21 h, and cooled to room temperature. Upon completion, CH₂Cl₂ (100 mL) was added to the reaction system, and the resulting mixture was filtered through a pad of Celite. The filtrate was extracted with H₂O (50 mL), and the aqueous layer was extracted with CH₂Cl₂ (2 × 50 mL). The combined organic layer was dried over anhydrous Na₂SO₄ and filtered. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (100–200 mesh) using hexane–EtOAc as an eluent to afford the pure product 3a.

(c) For aryl iodide. A 10 mL round-bottomed flask was equipped with a magnetic stir bar and charged with 1a (71.2 mg, 0.2 mmol), aryl iodide (0.6 mmol, 3 equiv.), K₂CO₃ (55.3 mg, 0.4 mmol, 2 equiv.), Pd(OAc)₂ (4.5 mg, 0.02 mmol, 10 mol%), PivOH (6.2 mg, 0.06 mmol, 30 mol%) in o-xylene (1.0 mL). The resulting mixture was heated under air at 100 °C for 21 h, and cooled to room temperature. Upon completion, CH₂Cl₂ (20 mL) was added to the reaction system, and the resulting mixture was filtered through a pad of Celite. The filtrate was extracted with H₂O (20 mL), and the aqueous layer was extracted with CH₂Cl₂ (2 × 10 mL). The combined organic layer was dried over anhydrous Na₂SO₄ and filtered. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (100–200 mesh) using hexane–EtOAc as an eluent to afford the pure product 3.

(d) For aryl chlorides. A 25 mL Schlenk tube was equipped with a magnetic stir bar and charged with 1a (71.2 mg, 0.2 mmol), aryl chlorides (1 mL), K₂CO₃ (55.3 mg, 0.4 mmol, 2 equiv.), Pd(OAc)₂ (4.5 mg, 0.02 mmol, 10 mol%), ligand (9.5 mg, 0.02 mmol, 10 mol%) and PivOH (6.2 mg, 0.06 mmol, 30 mol%). The resulting mixture was heated under nitrogen at 190 °C for 21 h, and cooled to room temperature. Upon completion, CH₂Cl₂ (20 mL) was added to the reaction system, and the resulting mixture was filtered through a pad of Celite. The filtrate was extracted with H₂O (20 mL), and the aqueous layer was extracted with CH₂Cl₂ (2 × 10 mL). The combined organic layer was dried over anhydrous Na₂SO₄ and filtered. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (100–200 mesh) using hexane–EtOAc as an eluent to afford the pure product 3.

(e) For the product 6. A 25 mL Schlenk tube was equipped with a magnetic stir bar and charged with 3o (33.2 mg, 0.05 mmol), diphenylphosphine oxide (40.5 mg, 0.2 mmol, 4 equiv.), K₃PO₄ (42.5 mg, 0.2 mmol, 4 equiv.), Pd(PPh₃)₂Cl₂ (3.5 mg, 0.005 mmol, 10 mol%) in dioxane (1.0 mL). The resulting mixture was heated under nitrogen at 110 °C for 24 h, and cooled to room temperature. Upon completion, CH₂Cl₂ (20 mL) was added to the reaction system, and the resulting mixture was filtered through a pad of Celite. The filtrate was extracted with H₂O (20 mL), and the aqueous layer was extracted with CH₂Cl₂ (2 × 10 mL). The combined organic layer was dried over anhydrous Na₂SO₄ and filtered. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (100–200 mesh) using hexane–EtOAc as an eluent to afford the pure product 6.
2,5-Bis(4-(diphenylphosphoryl)phenyl)-N-(quinolin-8-yl)ferrocenecarboxamide (6). Orange solid (44 mg, 97%); mp 139–141 °C; ¹H NMR (400 MHz, CDCl₃) δ 10.76 (s, 1H), 8.80–8.76 (m, 1H), 8.58 (dd, J = 2.9 Hz, J = 1.3 Hz, 1H), 8.15 (dd, J = 4.9 Hz, J = 3.4 Hz, 1H), 7.71 (dd, J = 5.4 Hz, J = 2.9 Hz, 4H), 7.59–7.47 (m, 18H), 7.41–7.33 (m, 9H), 4.87 (s, 2H), 4.39 (s, 5H); ¹³C NMR (100 MHz, CDCl₃) δ 167.3, 148.1, 141.3, 141.3, 138.4, 136.2, 134.3, 132.9, 132.8, 132.1, 132.0, 132.0, 131.9, 131.9, 131.8, 131.1, 130.0, 128.8, 128.7, 128.5, 128.5, 128.4, 128.4, 127.9, 127.4, 121.8, 121.7, 116.2, 87.3, 82.5, 73.1, 70.2; ³¹P NMR (163 MHz, CDCl₃) δ 29.02; HRMS (ESI+) calcd for C₅₆H₄₂FeN₂O₃P₂ [M + H]⁺: 909.2093, found: 909.2093.

Acknowledgements

We are grateful to the National Natural Science Foundation of China (no. 21102134, 21172200) for financial support.

Notes and references

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11. CCDC 1446343 (3a).† Crystal data for compound 3a: C₃₂H₂₄FeN₂O, M = 508.38, monoclinic, a = 11.3423(6) Å, α = 90°, b = 14.2822(5) Å, β = 107.980(5)°, c = 16.0589(7) Å, γ = 90°, V = 2474.4(2) ų, T = 291.15 K, space group = P2₁/c, Z = 4, number of reflections = 9066, independent reflections = 4408, [R(int) = 0.0267], final R indices [I > 2σ(I)] R₁ = 0.0401, wR₂ = 0.0962, R indices (all data) R₁ = 0.0531, wR₂ = 0.1034.
12. CCDC 1446344 (5a).† Crystal data for compound 5a: C₆₃H₅₈Cl₂Fe₂N₄O₂, M = 1085.73, monoclinic, a = 14.7314(2) Å, α = 90°, b = 10.30632(19) Å, β = 95.6050(17)°, c = 17.8542(4) Å, γ = 90°, V = 2697.78(9) ų, T = 291.15 K, space group = P2₁/c, Z = 2, number of reflections = 9723, independent reflections = 4818, [R(int) = 0.0292], final R indices [I > 2σ(I)] R₁ = 0.0497, wR₂ = 0.1388, R indices (all data) R₁ = 0.0625, wR₂ = 0.1497.

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Footnote

† Electronic supplementary information (ESI) available. CCDC 1446343 and 14463434. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ra11972g

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