Syntheses, Structures, and Reactions of Cyclometalated Rhodium

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Article Cite This: Organometallics XXXX, XXX, XXX−XXX

Syntheses, Structures, and Reactions of Cyclometalated Rhodium, Iridium, and Ruthenium Complexes of N‑Methoxy-4-nitrobenzamide Tao Zhou,† Liubo Li,† Bin Li,† Haibin Song,† and Baiquan Wang*,†,‡,§ †

State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, and ‡Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, PR China § State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China S Supporting Information *

ABSTRACT: The cyclometalated rhodium, iridium, and ruthenium complexes of N-methoxy-4-nitrobenzamide were synthesized by treatment of N-methoxy-4nitrobenzamide with [Cp*MCl2]2] (M = Rh and Ir) or [(p-cymene)RuCl2]2 via C−H bond activation. The molecular structures of all these complexes were determined by single-crystal X-ray diffraction analysis. When the cyclometalated rhodium and ruthenium complexes were used as catalysts in the C−H bond functionalization reactions reported before, the desired products were obtained in high yields, proving that these cyclometalated complexes were probably the key catalytic intermediates of the C−H bond functionalization reactions of N-methoxybenzamide derivatives. The stoichiometric reactions of the cyclometalated rhodium, iridium, and ruthenium complexes with diphenylacetylene afforded the corresponding seven-membered metallacycles with insertion of two molecules of diphenylacetylene in 24, 6, and 20% yields, respectively, through the tandem reaction. However, the cyclometalated iridium complex could not catalyze the reaction of N-methoxy-4-nitrobenzamide with diphenylacetylene. This work provides a further understanding for the mechanisms of rhodium- and ruthenium-catalyzed C−H bond functionalization reactions of N-methoxybenzamide derivatives.

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INTRODUCTION The emergence of diverse catalytic functionalization of C−H bonds has become an increasingly efficient and reliable approach to the synthesis and functionalization of heterocycles in recent years.1 [Cp*RhCl2]2 (Cp* = C5Me5) and [(pcymene)RuCl2]2 were found to be competent catalysts for the C−H bond functionazation reactions between arenes/heteroarenes and unsaturated coupling partners,2,3 among which Nmethoxybenzamide derivatives have been paid great attention since they can act as an internal oxidant and also increase reactivity under mild conditions. The elegant work was first reported by Fagnou’s group which developed a conceptually new approach to C−C and C−N bonds formation through annulation reactions of N-methoxybenzamides with alkynes and without need of an external oxidant by utilizing N−O bond as an instrument for C−N bond formation and catalyst release.4a In the last few years, a lot of work about the reactions of Nmethoxybenzamides with different unsaturated coupling partners (alkenes, alkynes, allenes, etc.) catalyzed by [Cp*RhCl2]2 or [(p-cymene)RuCl2]2] have been reported.4,5 One work was also reported using [Cp*IrCl2]2 as catalyst.6 Jones and co-workers have isolated the intermediate compounds in the [Cp*RhCl 2]2 -mediated synthesis of isoquinoline salts, and a Rh(III)−Rh(IV)−Rh(II)−Rh(III) mechanism has been proposed for these stoichiometric reactions.7 Our group reported a detailed study for the mechanism of the Ru(II)- and Rh(III)-catalyzed oxidative annulations of isoquinolones with alkynes by isolation and © XXXX American Chemical Society

single-crystal X-ray diffraction analysis of all three key catalytic intermediates.8 These work has made a clear understanding of reaction process which contribute to design new reactions. In 2014, Chang’s group reported the molecular structure of an iridacycle species of N-(tert-butyl)benzamide and found that the iridium is coordinated with the oxygen atom rather than the nitrogen atom of the amide group.9 Although there are many reports on the transition metal catalyzed C−H functionalization reactions of N-methoxybenzamide, only the cyclometalated intermediate of palladium has been reported.10 Herein, we will report the synthesis, structures, and reactions of the cyclometalated rhodium, iridium, and ruthenium complexes of Nmethoxybenzamide.

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RESULTS AND DISCUSSION When N-methoxybenzamide was used as the starting material to react with [Cp*MCl2]2 (M = Rh, Ir) or [(p-cymene)RuCl2]2, we cannot isolate the corresponding cyclometalated complex. We suspected that these cyclometalated intermedates were too reactive to be isolated for their electron-rich property,8 so N-methoxy-4-nitrobenzamide with a strong electron-withdrawing group was used instead of N-methoxybenzamide to react with [Cp*MCl2]2 (M = Rh and Ir) or [(pcymene)RuCl2]2 in CH2Cl2 at room temperature in the presence of pyridine, NaOAc, and Na2CO3 for 12 h. The Received: December 9, 2017

A

DOI: 10.1021/acs.organomet.7b00879 Organometallics XXXX, XXX, XXX−XXX

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Organometallics corresponding cyclometalated complexes 2-Rh, 2-Ir, and 2-Ru were obtained in 99, 97, and 99% yields, respectively (Scheme 1). The molecular structures of these complexes were Scheme 1. Synthesis of Cyclometalated Complexes

characterized by 1H and 13C NMR spectra and mass spectrometry and further confirmed by single-crystal X-ray diffraction analysis (Figures 1−3). A piano-stool-type geometry

Figure 2. ORTEP diagram of 2-Ir. Thermal ellipsoids are shown at the 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Ir(1)−C(1) 2.062(5), Ir(1)−N(2) 2.073(4), Ir(1)−N(3) 2.104(4), C(1)−Ir(1)−N(2) 76.37(17), C(1)− Ir(1)−N(3) 85.38(16), N(2)−Ir(1)−N(3) 84.81(17).

Figure 1. ORTEP diagram of 2-Rh. Thermal ellipsoids are shown at the 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Rh(1)−C(7) 2.0259(15), Rh(1)−N(1) 2.0616(12), Rh(1)−N(2) 2.0963(12), C(7)−Rh(1)− N(1) 77.59(5), C(7)−Rh(1)−N(2) 86.21(5), N(1)−Rh(1)−N(2) 86.48(5).

Figure 3. ORTEP diagram of 2-Ru. Thermal ellipsoids are shown at the 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Ru(1)−C(18) 2.065(6), Ru(1)−N(1) 2.070(5), Ru(1)−N(3) 2.111(5), C(18)−Ru(1)−N(1) 76.3(2), C(18)−Ru(1)−N(3) 86.3(2), N(1)−Ru(1)−N(3) 84.79(19).

that consisted of a five-membered metallacycle with a coordinated pyridine was observed in all complexes. The bond lengths and angles are comparable to those in the reported cyclometalated Cp*Rh(III), Cp*Ir(III), and (pcymene)Ru(II) complexes.7,8 The M−C bond lengths in 2Rh, 2-Ir, and 2-Ru are 2.0259(15), 2.062(5), and 2.065(6) Å, respectively. Subsequently, complexes 2-Rh, 2-Ir, and 2-Ru were used as the catalysts for verifying the cyclometalated complexes to be the intermediates of the reactions reported before. First, we tested the coupling reaction between N-methoxy-4-nitrobenzamide and diphenylacetylene reported by Fagnou’s group.4a To our delight, when 2-Rh was used as the catalyst under the standard condition, the corresponding product 6nitro-3,4-diphenylisoquinolin-1(2H)-one 4 was obtained in 90% isolated yield (Scheme 2, eq 1). Our group reported the

coupling reaction between N-methoxybenzamide and alkynes using [(p-cymene)RuCl2]2 as catalyst.5a When 2-Ru was used as the catalyst under the standard conditions, 6-nitro-3,4diphenylisoquinolin-1(2H)-one, 4, was isolated in 75% yield (Scheme 2, eq 2). These results implied that 2-Rh and 2-Ru probably were the key catalytic intermediates in the coupling reaction between N-methoxybenzamide and alkynes reported before. Complex 2-Ir was also used as the catalyst under the same conditions with 2-Rh, but almost no desired product 4 was isolated (Scheme 2, eq 3). The low reactivity of iridium complex can be attributed to the electronrichness and low electronegativity of Ir(III). These factors make Ir(III) difficult to reduce to Ir(I) and thus lead to a high activation energy of the reductive elimination step.11 When stoichiometric 2-Rh reacted with diphenylacetylene in MeOH at 40 °C, a seven-membered metallacycle 5-Rh with B

DOI: 10.1021/acs.organomet.7b00879 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Scheme 2. Coupling Reaction of N-Methoxy-4nitrobenzamide and Alkynes Catalyzed by Cyclometalated Complexes

In 2011, Glorius’s group reported [Cp*RhCl2]2-catalyzed directed C−H olefination of N-methoxybenzamide.4c When 2Rh was used as the catalyst for the coupling reaction between N-methoxy-4-nitrobenzamide and styrene under the standard conditions, the desired olefination product was obtained in 87% yield (Scheme 4, eq 7). Our group reported the [(pScheme 4. Coupling Reaction of N-Methoxy-4nitrobenzamide with other Unsaturated Compounds Catalyzed by Cyclometalated Complexes

insertion of two molecules of diphenylacetylene was isolated in 24% yield through the tandem reaction, and 2-Rh was recovered in 37% yield at the same time (Scheme 3, eq 4). Scheme 3. Stoichiometric Reaction of Cyclometalated Complexes with Diphenylacetylene

cymene)RuCl2]2-catalyzed oxidative C−H bond olefination of N-methoxybenzamides.5c When 2-Ru was used as the catalyst for the coupling reaction between N-methoxy-4-nitrobenzamide and butyl acrylate, the corresponding olefination product was isolated in 30% yield (Scheme 4, eq 8). In 2015, our group reported the Rh(III)-catalyzed annulation reactions between Nmethoxybenzamide and diazo compounds.4u When 2-Rh was used as the catalyst for the coupling reaction between Nmethoxy-4-nitrobenzamide and ethyl diazoacetoacetate, the desired isoquinolone was obtained in 63% yield (Scheme 4, eq 9). In 2014, Li group reported the Ir(III)-catalyzed C−H bond alkynylation of N-methoxybenzamides using hypervalent iodine-alkyne reagents.6 When 2-Ir was used as the catalyst for the coupling reaction between N-methoxy-4-nitrobenzamide and 1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)one (TIPS-EBX), the desired alkynylation product was obtained in 18% yield (Scheme 4, eq 10). These results proved that the five-membered metallacycles probably were the key catalytic intermediates in these reactions.

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When stoichiometric 2-Ir reacted with diphenylacetylene in MeOH at 40 °C the seven-membered metallacycle 5-Ir with insertion of two molecules of diphenylacetylene was isolated in 6% yield, and 2-Ir was recovered in 52% yield (Scheme 3, eq 5). This indicated that 2-Ir could react with diphenylacetylene to form isoquinolin in low yield in stoichiometric reaction, although 2-Ir cannot catalyze the reaction of N-methoxybenzamides and alkynes. The reaction of 2-Ru, in situ prepared by the reaction of 1a and [(p-cymene)RuCl2]2, with diphenylacetylene under one-pot conditions was also done, and sevenmembered metallacycle 5-Ru and 6-nitro-3,4-diphenylisoquinolin-1(2H)-one 4 were obtained in 20 and 12% yields, respectively, with the isolation of 2-Ru in 20% yield at the same time (Scheme 3, eq 3).

CONCLUSION

In conclusion, we have synthesized three five-membered cyclometalated complexes by treating N-methoxy-4-nitrobenzamide with [Cp*MCl2]2] (M = Rh and Ir) or [(pcymene)RuCl2]2. The molecular structures of all these complexes were determined by single-crystal X-ray diffraction. The corresponding coupling products could be obtained in high yields when the cyclometalated rhodium and ruthenium complexes were used as the catalysts in the C−H bond functionalization reactions of N-methoxy-4-nitrobenzamide. These results proved that the five-membered metallacycles probably were the key catalytic intermediates in these reactions. The stoichiometric reactions of the cyclometalated rhodium C

DOI: 10.1021/acs.organomet.7b00879 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/5 to 1/2 as eluent, desired product 4 (61.7 mg, 0.18 mmol) was obtained in 90% yield. 1 H NMR (CDCl3, 400 MHz):5a δ 10.46 (s, 1H), 8.57 (d, J = 8.5 Hz, 1H), 8.24−8.21 (m, 1H), 7.38−7.37 (m, 3H), 7.32−7.28 (m, 5H), 7.2−7.19 (m, 2H). 13C NMR (CDCl3, 100 MHz): δ 161.8, 150.6, 139.8, 139.5, 134.3, 134.1, 131.6, 129.6, 129.3, 129.2, 128.9, 128.6, 128.4, 128.1, 121.1, 120.1, 117.1. Typical Procedure for the Preparation of 4 Using 2-Ru as Catalyst. A mixture of 1 (98 mg, 0.50 mmol), 3 (106.8 mg, 0.60 mmol), 2-Ru (15.3 mg, 6.0 mol %), and NaOAc (8.2 mg, 0.10 mmol) were weighed in a Schlenk tube equipped with a stir bar. Dry MeOH (2.5 mL) was added, and the mixture was stirred at room temperature for 8 h under Ar. Afterward, it was transferred to a round-bottomed flask. Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/5 to 1/2 as eluent, desired product 4 (129.0 mg, 0.375 mmol) was obtained in 75% yield. Reactions of Complexes 2-Rh and 2-Ir with Diphenylacetylene. Complex 2-Rh or 2-Ir (0.20 mmol, 1.0 equiv) and diphenylacetylene 3 (0.20 mmol, 1.0 equiv) were weighed into a Schlenk tube equipped with a stir bar. Dry MeOH (4.0 mL) was added, and the mixture was stirred at 40 °C for 12 h under an Ar atmosphere. Afterward, the mixture was diluted with CH2Cl2 and transferred into a round-bottomed flask. Silica was added to the flask and the volatile compounds were evaporated under reduced pressure. Purification was performed by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/10 to 1/5 as eluent. Compound 5-Rh.8b Red solid. Yield: 37.0 mg (0.048 mmol, 24%). 1 H NMR (CHCl3, 400 MHz): δ 8.42 (d, J = 8.9 Hz, 1H), 8.2 (d, J = 2.1 Hz, 1H), 8.11 (dd, J = 8.9 Hz, 2.2 Hz, 1H), 7.54 (d, J = 7.4 Hz, 1H), 7.45 (t, J = 7.3 Hz, 1H), 7.35 (d, J = 7.2 Hz, 1H), 7.30 (dd, J = 6.9 Hz, 1.5 Hz, 1H), 7.22 (t, J = 7.5 Hz, 1H), 7.12−7.07 (m, 2H), 7.07−7.02 (m, 4H), 6.97−6.93 (m, 4H), 6.90 (d, J = 6.9 Hz, 1H), 6.88−6.86 (m, 2H), 6.35 (d, J = 7.5 Hz, 1H), 1.29 (s, 15H). 13C NMR (CDCl3, 100 MHz): δ 168.9, 168.6, 168.3, 149.3, 148.7, 145.8, 142.5, 138.8, 135.6, 133.8, 133.6, 132.2, 131.7, 131.2, 129.2, 128.8, 128.5, 128.3, 127.9, 127.9, 127.5, 127.4, 127.3, 127.1, 125.8, 125.2, 124.8, 124.5, 121.1, 118.7, 118.1, 94.95, 94.87, 9.1. Compound 5-Ir.8b Red solid. Yield: 9.9 mg (0.012 mmol, 6%). 1H NMR (CHCl3, 400 MHz): δ 8.29 (d, J = 8.9 Hz, 1H), 8.24 (d, J = 2.1 Hz, 1H), 8.14 (dd, J = 8.9, 2.2 Hz, 1H), 7.58 (d, J = 7.8 Hz, 1H), 7.49 (t, J = 7.5 Hz, 1H), 7.31−7.28 (m, 2H), 7.20 (dt, J = 7.3, 1.5 Hz, 1H), 7.05−6.98 (m, 4H), 6.96−6.91 (m, 3H), 6.87−6.81 (m, 6H), 6.57 (d, J = 7.5 Hz, 1H), 1.38 (s, 15H). 13C NMR (CDCl3, 100 MHz): δ 169.8, 160.4, 148.9, 148.8, 148.3, 145.3, 139.6, 138.5, 137.7, 135.4, 133.3, 131.8, 131.5, 130.8, 130.5, 130.0, 128.7, 128.1, 128.0, 127.3, 127.1, 126.3, 124.8, 124.7, 124.2, 121.5, 119.9, 118.3, 86.9, 9.3. Reaction of 1, [(p-Cymene)RuCl2]2, and Diphenylacetylene under One-Pot Conditions. Pyridine (15.8 mg, 0.20 mmol) was added to a solution of [(p-cymene)RuCl2]2 (0.10 mmol) in CH2Cl2 (8 mL) at room temperature. After vigorous stirring for 4 h, NaOAc (41.0 mg, 0.50 mmol), N-methoxy-4-nitrobenzamide (39.2 mg, 0.2 mmol), and Na2CO3 (21.6 mg, 0.2 mmol) were added to the solution, and vigorous stirring was continued for a further 12 h. Then, diphenylacetylene 3 (0.20 mmol, 1.0 equiv) was added into the Schlenk tube. The mixture was stirred at 40 °C for 12 h under an Ar atmosphere. Afterward, the mixture was diluted with CH2Cl2 and transferred into a round-bottomed flask. Silica was added to the flask and the volatile compounds were evaporated under reduced pressure. Purification was performed by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/10 to 1/2 as eluent. Compounds 5-Ru (red solid, 30.0 mg, 0.04 mmol), 4 (8.0 mg, 0.024 mmol), and 2Ru (20.0 mg, 0.04 mmol) were obtained in 20, 12, and 20% yields, respectively. Compound 5-Ru.8a 1H NMR (CDCl3, 400 MHz): δ 8.21 (1H, d, J = 1.7 Hz), 8.09−7.99 (m, 2H), 7.65 (d, J = 7.5 Hz, 1H), 7.53 (t, J = 7.3 Hz, 1H), 7.38−7.27 (m, 2H), 7.22−7.08 (m, 3H), 6.98−6.76 (m, 10H), 6.65 (d, J = 7.0 Hz, 2H), 5.61 (d, J = 5.8 Hz, 1H), 4.74 (t, J =

and iridium complexes with diphenylacetylene afforded the corresponding seven-membered metallacycles with insertion of two molecules of diphenylacetylene in 24 and 6% yields, respectively, through the tandem reaction. However, the cyclometalated iridium complex could not catalyze the reaction of N-methoxy-4-nitrobenzamide with diphenylacetylene.

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EXPERIMENTAL SECTION

General Considerations. All reactions were carried out under argon atmosphere using standard Schlenk technique. 1H NMR (400 MHz) and 13C NMR (100 MHz) were recorded on a Bruker AV400 NMR spectrometer with CDCl3 or DMSO as solvent. Chemical shifts of 1H and 13C NMR spectra are reported in parts per million (ppm). The residual solvent signals were used as reference and the chemical shifts converted to the TMS scale (CDCl3: δH = 7.26 ppm, δC = 77.00 ppm; DMSO: δH = 2.5 ppm, δ C = 39.43 ppm). Column chromatography was performed on silica gel 200−300 mesh. Analytical thin-layer chromatography (TLC) was performed on precoated, glass-backed silica gel plates. Visualization of the developed chromatogram was performed by UV absorbance (254 nm). Highresolution mass spectrometry (HRMS) were done on a Varian 7.0 T FTICR-mass spectrometer. Typical Procedure for the Preparation of Cyclometalated Complexes 2. Pyridine (15.8 mg, 0.20 mmol) was added to a solution of [Cp*MCl2]2 or [(p-cymene)RuCl2]2 (0.10 mmol) in CH2Cl2 (8 mL) at room temperature. After vigorous stirring for 4 h, NaOAc (41.0 mg, 0.50 mmol), N-methoxy-4-nitrobenzamide (39.2 mg, 0.2 mmol), and Na2CO3 (21.6 mg, 0.2 mmol) were added to the solution, and vigorous stirring was continued for a further 12 h. After the reaction was completed, the solution was transferred into a roundbottomed flask. Silica was added to the flask, and the volatile compounds were evaporated under reduced pressure. The crude product was purified by column chromatography on silica gel with MeOH/CH2Cl2 = 1/10 as eluent to afford complexes 2. Compound 2-Rh. Red solid. Yield: 104.3 mg (0.199 mmol, 99%). Mp: 197−202 °C. 1H NMR (CDCl3, 400 MHz): δ 8.47 (d, J = 1.7 Hz, 1H), 8.43 (d, J = 5.5 Hz, 2H), 7.87 (dd, J = 8.2, 1.4 Hz, 1H), 7.66− 7.62 (m, 2H), 7.19 (t, J = 6.6 Hz, 2H), 4.04 (s, 3H), 1.64 (s, 15H). 13C NMR (CDCl3, 100 MHz): δ 153.5, 147.9, 147.6, 137.5, 137.5, 127.6, 125.9, 125.6, 119.0, 96.1, 96.0, 63.0, 9.3. HRMS (ESI, m/z): calcd for C18H22N2O4Rh [M + H − C5H5N]+ 433.0629, found: 433.0631. Anal. Calcd. for C23H26N3O4Rh: C, 54.02; H, 5.12; N, 8.22; Found: C, 53.97; H, 5.17; N, 8.32. Compound 2-Ir. Red solid. Yield: 117.0 mg (0.194 mmol, 97%). Mp: 214−218 °C. 1H NMR (CDCl3, 400 MHz): δ 8.41 (d, J = 2.1 Hz, 2H), 7.84 (dd, J = 8.2, 2.0 Hz, 1H), 7.61−7.58(m, 2H), 7.13 (t, J = 6.8 Hz, 2H), 4.05 (s, 3H), 1.67 (s, 15H). 13C NMR (CDCl3, 100 MHz): δ 175.2, 154.4, 151.2, 148.6, 147.4, 137.4, 127.1, 126.4, 126.0, 118.4, 88.9, 62.8, 9.1. HRMS (ESI, m/z): calcd for C23H26N3O4Ir [M + H]+ 602.1625, found: 602.1600. Anal. Calcd. for C23H26IrN3O4: C, 45.99; H, 4.36; N, 7.00; Found: C, 46.11; H, 4.50; N, 6.95. Compound 2-Ru. Red solid. Yield: 115.4 mg (0.199 mmol, 99%). Mp: 199−203 °C. 1H NMR (CDCl3, 400 MHz): δ 8.76 (d, J = 2.1 Hz, 1H), 8.54 (d, J = 5.3 Hz, 2H), 7.79 (d, J = 8.1 Hz, 1H), 7.52 (d, J = 8.1 Hz, 2H), 7.06 (d, J = 5.3 Hz, 2H), 5.83 (d, J = 5.7 Hz, 1H), 5.74 (d, J = 5.8 Hz, 1H), 5.38 (d, J = 5.8 Hz, 1 H), 4.88 (d, J = 5.7 Hz, 1H), 4.05 (s, 3H), 2.32 (dt, J = 13.6, 6.7 Hz, 1H), 1.70 (s, 3H), 1.03 (d, J = 6.9 Hz, 3H), 0.88 (d, J = 6.8 Hz, 3H). 13C NMR (CDCl3, 100 MHz): δ 173.5, 172.1, 172.0, 154.7, 147.9, 147.3, 137.0, 130.9, 125.9, 124.7, 118.7, 102.9, 102.4, 90.9, 89.5, 83.7, 80.7, 61.4, 31.2, 23.0, 22.0, 18.2. HRMS (ESI, m/z): calcd for C23H26N3O4Ru [M + H]+ 510.0961, found: 510.0963. Anal. Calcd. for C23H25N3O4Ru: C, 54.32; H, 4.96; N, 8.26; Found: C, 53.97; H, 5.39; N, 7.98. Typical Procedure for the Preparation of 4 Using 2-Rh as Catalyst. A mixture of 1 (39.2 mg, 0.2 mmol), 3 (39.2 mg, 0.22 mmol), 2-Rh (5.12 mg, 5.0 mol %), and CsOAc (11.5 mg, 30 mol %) were weighed in a Schlenk tube equipped with a stir bar. Dry MeOH (1.0 mL) was added, and the mixture was stirred at 60 °C for 16 h under Ar. Afterward, it was transferred to a round-bottomed flask. D

DOI: 10.1021/acs.organomet.7b00879 Organometallics XXXX, XXX, XXX−XXX

Organometallics

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5.5 Hz, 2H), 4.31 (d, J = 5.8 Hz, 1H), 2.45 (m, 1H), 2.10 (s, 3H), 1.17 (d, J = 6.9 Hz, 3H), 1.05 (d, J = 6.9 Hz, 3H). 13C NMR (CDCl3, 100 MHz): δ 170.9, 149.3, 149.1, 148.6, 144.7, 138.3, 135.7, 132.1, 132.0, 131.5, 130.5, 129.3, 128.7, 128.0, 127.6, 127.6, 127.5, 127.2, 127.0, 124.9, 124.6, 124.3, 123.9, 121.9, 121.0, 119.9, 118.5, 107.6, 98.2, 87.7, 80.1, 77.9, 31.7, 23.3, 23.0, 19.2. Typical Procedure for the Preparation of 7 Using 2-Rh as Catalyst. A mixture of 1 (39.2 mg, 0.2 mmol), 6 (31.2 mg, 0.30 mmol), 2-Rh (2.0 mg, 2.0 mol %), and CsOAc (11.5 mg, 30 mol %) were weighed in a Schlenk tube equipped with a stir bar. Dry MeOH (1.0 mL) was added, and the mixture was stirred at 60 °C for 16 h under Ar. Afterward, it was transferred to a round-bottomed flask. Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/3 to 2/1 as eluent, desired product 7 (46.8 mg, 0.174 mmol) was obtained in 87% yield. 1 H NMR (DMSO, 400 MHz):4c δ 8.62 (d, J = 1.9 Hz, 1H), 8.17−8.13 (m, 2H), 7.83 (s, 1H), 7.66 (d, J = 8.4 Hz, 1H), 7.59−7.58(m, 2H), 7.54−7.50 (m, 1 H), 7.47−7.39 (m, 3H), 7.34 (t, J = 7.3 Hz). 13C NMR (DMSO, 100 MHz): δ 169.2, 148.1, 141.9, 136.4, 136.01, 132.6, 128.9, 128.8, 128.5, 126.8, 123.7, 121.6, 119.9, 40.1. Typical Procedure for the Preparation of 9 Using 2-Ru as Catalyst. A mixture of 1 (98.1 mg, 0.5 mmol), 6 (115.4 mg, 0.90 mmol), 2-Ru (25.4 mg, 10 mol %), and NaOAc (12.3 mg, 30 mol %) were weighed in a Schlenk tube equipped with a stir bar. Dry MeOH (1.0 mL) was added, and the mixture was stirred at 60 °C for 24 h under Ar. Afterward, it was transferred to a round-bottomed flask. Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/3 to 2/1 as eluent, desired product 9 (43.5 mg, 0.15 mmol) was obtained in 30% yield. 1 H NMR (DMSO-d6, 400 MHz):5c δ 8.66 (d, J = 2.1 Hz, 1H), 8.29− 8.21 (m, 2H), 7.93 (s, 1H), 7.88 (d, J = 16.0 Hz, 1H), 7.72 (d, J = 8.4 Hz, 1H), 6.87 (d, J = 16.0 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 1.63 (dt, J = 14.5, 6.6 Hz, 2H), 1.43−1.33 (m, 2H), 0.92 (t, J = 7.4 Hz, 3H). 13C NMR (DMSO-d6, 100 MHz): δ 168.5, 165.7, 148.1, 143.2, 139.6, 133.0, 129.0, 124.2, 122.3, 121.7, 64.0. Typical Procedure for the Preparation of 11 Using 2-Rh as Catalyst. A mixture of 1 (39.2 mg, 0.2 mmol), 10 (37.5 mg, 0.24 mmol), 2-Rh (10.2 mg, 10 mol %), AgOAc (10.0 mg, 30 mol %), and AgSbF6 (13.7 mg, 20 mol %) were weighed in a Schlenk tube equipped with a stir bar. Dry THF (2.0 mL) was added, and the mixture was stirred at 60 °C for 12 h under Ar. Afterward, it was transferred to a round-bottomed flask. Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/2 as eluent, desired product 11 (38.6 mg, 0.13 mmol) was obtained in 63% yield. 1H NMR (CDCl3, 400 MHz):4u δ 8.67 (d, J = 1.6 Hz, 1H), 8.55 (d, J = 8.8 Hz, 1H), 8.20− 8.17 (m, 1H), 4.50 (q, J = 7.1 Hz, 2H), 4.10 (s, 3H), 2.62 (s, 3H), 1.46 (t, J = 7.1 Hz, 3H). 13C NMR (CDCl3, 100 MHz): δ 165.6, 156.9, 150.4, 144.6, 133.8, 129.8, 128.6, 120.2, 120.1, 108.9, 64.0, 62.1, 15.2, 14.2. Typical Procedure for the Preparation of 13 Using 2-Ir as Catalyst. A mixture of 1 (39.2 mg, 0.2 mmol), 10 (94.2 mg, 0.22 mmol), 2-Ir (9.6 mg, 8 mol %), and AgNTf2 (12.4 mg, 16 mol %) were weighed in a Schlenk tube equipped with a stir bar. Dry DCE (2.0 mL) was added, and the mixture was stirred at 30 °C for 16 h under Ar. Afterward, it was transferred to a round-bottomed flask. Silica was added to the flask, and volatiles were evaporated under reduced pressure. After purification by flash column chromatography on silica gel with EtOAc/petroleum ether = 1/2 as eluent, desired product 13 (13.8 mg, 0.036 mmol) was obtained in 18% yield. 1H NMR (CDCl3, 400 MHz):6 δ 10.38 (s, 1H), 8.35 (d, J = 2.3 Hz, 1H), 8.32−8.22 (m, 2H), 3.90 (s, 3H), 1.21−1.15 (m, 21H). 13C NMR (CDCl3, 100 MHz): δ 162.4, 148.9, 138.0, 131.9, 128.8, 123.4, 121.2, 103.1, 103.0, 64.7, 18.6, 11.1.

Article

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00879. NMR spectra for all compounds (PDF) Accession Codes

CCDC 1590225−1590227 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel/Fax: +86-22-23504781. ORCID

Bin Li: 0000-0003-3909-3796 Baiquan Wang: 0000-0003-4605-1607 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (Grants 21672108 and 21421062) and the Natural Science Foundation of Tianjin (16JCZDJC31700) for financial support.

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REFERENCES

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DOI: 10.1021/acs.organomet.7b00879 Organometallics XXXX, XXX, XXX−XXX