Synlett 2006(8): 1193-1196  
DOI: 10.1055/s-2006-939077
LETTER
© Georg Thieme Verlag Stuttgart · New York

New Phosphine-Functionalized N-Heterocyclic Carbene Ligands for Palladium-Catalyzed Hydroarylation Reaction

Jun Zhong, Jian-Hua Xie, Ai-E Wang, Wei Zhang, Qi-Lin Zhou*
State Key Laboratory and Institute of Elemento-organic Chemistry, Nankai University, Tianjin 300071, P. R. of China
Fax: +86(22)23506177; e-Mail: qlzhou@nankai.edu.cn;
Further Information

Publication History

Received 6 December 2005
Publication Date:
05 May 2006 (online)

Abstract

Novel triarylphosphine-functionalized imidazolinium salts have been prepared and successfully applied in palladium-­catalyzed hydroarylation of bicyclic olefins. Under reductive conditions (HCOOH, Et3N), the complexes generated in situ from imidazolinium salts and Pd(OAc)2 catalyzed the hydroarylation of bicyclic alkenes with aryl iodides, providing the hydroarylation products with high turnover numbers (TON, up to 1.9·105) and ­turnover frequencies (TOF, up to 6.3·104).

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Physical Data of Amide 5.
White solid, mp 94-96 °C. 1H NMR (300 MHz, CDCl3): δ = 1.41 (s, 9 H, CH3), 6.88 (m, 1 H, Ar-H), 6.92 (t, J = 7.2 Hz, 1H, Ar-H), 7.26-7.36 (m, 12 H, Ar-H, NH), 7.93 (dd, J = 8.1, 4.5 Hz, 1 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 28.2, 80.4, 120.6, 123.6, 125.0, 125.2, 128.7, 128.8, 129.1, 130.4, 133.5, 133.7, 134.1, 134.9, 135.0, 141.7, 142.0, 152.9. 31P NMR (121 MHz, CDCl3): δ = -21.2. MS (ESI): m/z = 378 [M + 1]. Anal. Calcd for C23H24NO2P: C, 73.19; H, 6.41; N, 3.71. Found: C, 73.01; H, 6.26; N, 3.68.

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Physical Data.
Compound 6a: oil. 1H NMR (300 MHz, CDCl3): δ = 1.09 (s, 9 H, CH3), 3.12 (m, 1 H, NCH2), 3.21 (m, 1 H, NCH2), 3.40 (m, 1 H, NCH2), 4.25 (br s, 2 H, NCH2, NH), 6.44 (d, J = 8.1 Hz, 2 H, Ar-H), 6.58 (t, J = 7.2 Hz, 1 H, Ar-H), 6.93-7.22 (m, 16 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 27.8, 42.5, 49.0, 49.1, 79.9, 112.1, 116.6, 127.4, 128.1, 128.2, 128.3, 128.4, 128.9, 129.6, 129.7, 133.4, 133.6, 133.7, 134.9, 136.0, 136.1, 136.7, 136.8, 145.8, 146.2, 148.0. 31P NMR (121 MHz, CDCl3): δ = -17.9. HRMS (ESI): m/z calcd for C31H34N2O2P: 497.2352; found: 497.2359.
Compound 6b: white solid, mp 92-93 °C. 1H NMR (300 MHz, CDCl3): δ = 1.16 (s, 9 H, CH3), 2.18 (s, 6 H, CH3), 2.21 (s, 3 H, CH3), 3.01-3.35 (m, 4 H, NCH2), 4.18 (br s, 1 H, NH), 6.78 (s, 2 H, Ar-H), 7.03 (m, 1 H, Ar-H), 7.15-7.31 (m, 13 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 18.7, 20.6, 28.1, 47.2, 50.8, 80.0, 127.7, 128.4, 128.5, 128.6, 128.8, 129.5, 130.5, 133.7, 134.0, 135.3, 136.4, 136.6, 137.1, 137.2, 143.8, 146.5, 146.9, 155.5. 31P NMR (121 MHz, CDCl3): δ = -18.2. MS (ESI): m/z = 539 [M + 1]. Anal. Calcd for C34H39N2O2P: C, 75.81; H, 7.30; N, 5.20. Found: C, 75.71; H, 7.16; N, 5.25.
Compound 6c: oil. 1H NMR (300 MHz, CDCl3): δ = 1.15 (s, 9 H, CH3), 1.19 (d, J = 5.4 Hz, 12H, CH3), 2.97 (m, 1 H, NCH2), 3.21 (m, 4 H, NCH2, CH), 3.45 (m, 1 H, NCH2), 4.29 (br s, 1 H, NH), 7.05 (m, 4 H, Ar-H), 7.23-7.32 (m, 13 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 24.4, 24.5, 27.9, 28.2, 50.2, 50.9, 76.9, 77.2, 50.9, 80.1, 123.7, 127.8, 128.6, 128.7, 128.8, 128.9, 130.0, 130.2, 133.9, 134.0, 134.1, 135.4. 31P NMR (121 MHz, CDCl3): δ = -17.1. HRMS (ESI): m/z calcd for C37H46N2O2P: 581.3291; found: 581.3297.

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Physical Data. Compound 7a: white foam. 1H NMR (300 MHz, CDCl3): δ = 3.83 (s, 2 H, NCH2), 3.89 (s, 2 H, NCH2), 6.98 (s, 2 H, Ar-H), 7.17-7.37 (m, 15 H, Ar-H), 7.71 (s, 2 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 49.5, 50.3, 123.6, 128.8, 128.9, 129.1, 129.2, 129.5, 129.8, 130.2, 130.3, 130.6, 130.9, 131.0, 131.6, 133.9, 134.1, 135.7, 136.1. 31P NMR (121 MHz, CDCl3): δ = -18.6. HRMS (ESI): m/z calcd for C26H26N2P: 397.1828; found: 397.1834.
Compound 7b: white foam. 1H NMR (300 MHz, CDCl3): δ = 2.23 (s, 3 H, CH3), 2.48 (s, 6 H, CH3), 3.87 (m, 2 H, NCH2), 4.21 (m, 2 H, NCH2), 6.80 (s, 2 H, Ar-H), 7.22 (m, 2 H, Ar-H), 7.37-7.65 (m, 12 H, Ar-H). 8.56 (br s, 2 H), 10.84 (br s, 2 H). 13C NMR (75 MHz, CDCl3): δ = 19.0, 19.1, 20.7, 44.3, 48.2, 118.6, 118.7, 123.3, 124.1, 129.1, 129.2, 130.8, 131.0, 132.1, 133.3, 133.8, 134.0, 135.9, 139.2, 145.6, 145.7, 145.9. 31P NMR (121 MHz, CDCl3): δ = -17.9. MS (ESI): m/z = 439 [M - 2 HCl + 1]. Anal. Calcd for C29H33Cl2N2P: C, 68.10; H, 6.50; N, 5.48. Found: C, 68.07; H, 6.68; N, 5.56.
Compound 7c: white foam. 1H NMR (300 MHz, CDCl3): δ = 1.19 (d, J = 6.0 Hz, 6 H, CH3), 1.32 (d, J = 6.0 Hz, 6 H, CH3), 3.37 (m, 1 H, NCH2), 3.47 (m, 2 H, NCH2), 3.57 (m, 2 H, CH), 4.04 (m, 1 H, NCH2), 4.23 (m, 1 H, NCH2), 6.66 (t, J = 7.2 Hz, 1 H, Ar-H), 6.78 (m, 2 H, Ar-H), 7.14-7.40 (m, 14 H, Ar-H), 10.90 (br s, 4 H). 13C NMR (75 MHz, CDCl3): δ = 23.9, 27.3, 27.4, 36.5, 38.7, 50.8, 52.8, 109.8, 117.5, 119.0, 119.1, 123.2, 124.6, 124.7, 127.5, 127.6, 127.8, 128.5, 128.7, 128.9, 129.0, 129.9, 132.6, 132.8, 133.9, 134.1, 134.2, 142.2, 142.4, 148.2, 148.4. 31P NMR (121 MHz, CDCl3): δ = -22.5. HRMS (ESI): m/z calcd for C32H36N2P: 481.2767; found: 481.2770.

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Physical Data. Compound 2a: white solid, mp 235-237 °C. 1H NMR (300 MHz, CDCl3): δ = 4.50 (s, 4 H, NCH2), 6.90 (m, J = 6.8, 4.0 Hz, 1 H, Ar-H), 7.25-7.45 (m, 17 H, Ar-H), 8.17 (dd, J = 7.6, 4.0 Hz, 1 H, Ar-H), 8.85 (s, 1 H, NCH). 13C NMR (75 MHz, CDCl3): δ = 49.8, 52.9, 119.3, 127.9, 128.9, 129.4, 130.1, 130.2, 130.6, 131.3, 133.9, 134.2, 134.3, 134.5, 135.4, 135.5, 135.7, 138.5, 138.7, 155.6. 31P NMR (121 MHz, CDCl3): δ = -14.6. HRMS (ESI): m/z calcd for C27H24N2P: 407.1593; found: 407.1593.
Compound 2b: white solid, mp 255-257 °C. 1H NMR (300 MHz, CDCl3): δ = 2.28 (s, 3 H, CH3), 2.36 (s, 6 H, CH3), 4.40 (m, 2 H, NCH2), 4.83 (m, 2 H, NCH2), 6.89 (m, 3 H, Ar-H), 7.25 (m, 4 H, Ar-H), 7.40 (m, 7 H, Ar-H), 7.58 (m, 1 H, Ar-H), 8.13 (s, 1 H, NCH), 8.53 (m, J = 7.8, 4.5 Hz, 1 H, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 18.1, 18.2, 18.3, 21.0, 52.0, 53.7, 53.8, 119.0, 129.2, 129.3, 129.9, 130.5, 131.7, 133.7, 133.9, 134.4, 135.5, 140.5, 158.1, 158.2. 31P NMR (121 MHz, CDCl3): δ = -18.1. MS (ESI): m/z = 449 [M - Cl]. Anal. Calcd for C30H30ClN2P: C, 74.29; H, 6.23; N, 5.78. Found: C, 74.32; H, 6.38; N, 5.80.
Compound 2c: white solid, mp 268-270 °C. 1H NMR (300 MHz, CDCl3): δ = 1.28 (d, J = 6.6 Hz, 6 H, CH3), 1.32 (d, J = 6.6 Hz, 6 H, CH3), 3.35 (m, 2 H, CH), 4.39 (m, 2 H, NCH2), 4.80 (m, 2 H, NCH2), 6.95 (dd, J = 7.5, 3.6 Hz, 1 H, Ar-H), 7.21-7.28 (m, 6 H, Ar-H), 7.36-7.48 (m, 8 H, Ar-H), 7.60 (t, J = 7.5 Hz, 1 H), 8.13 (s, 1 H, NCH), 8.53 (dd, J = 7.8, 4.5 Hz, Ar-H). 13C NMR (75 MHz, CDCl3): δ = 24.6, 25.2, 28.5, 53.9, 54.6, 125.0, 128.8, 129.1, 129.2, 129.3, 129.6, 130.0, 130.5, 131.2, 131.8, 133.5, 133.6, 133.9, 134.1, 134.2, 134.4, 138.7, 139.0, 146.8, 157.4, 157.5. 31P NMR (121 MHz, CDCl3): δ = -18.6. HRMS (ESI): m/z calcd for C33H36N2P: 491.2611; found: 491.2606.

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General Experimental Procedure.
Under an atmosphere of nitrogen, 5.0 mL DMSO were injected to a Schlenk tube charged with Pd(OAc)2 (0.01 mmol), imidazolinium salt 2 (0.01 mmol) and t-BuOK (0.01 mmol). The mixture was stirred at r.t. for 2 h. An appropriate amount of this catalyst solution was taken and added to the solution of iodobenzene (204 mg, 1 mmol), norbornene (320 mg, 3.4 mmol), Et3N (379 mg, 3.75 mmol) and formic acid (138 mg, 3 mmol) in 5.0 mL of DMSO. The mixture was stirred at 120 °C, and the course of reaction was monitored by GC. After the starting material was completely consumed the reaction mixture was cooled to r.t., and 50 mL of H2O was added. The product was extracted with pentane (3 × 30 mL), and the extract was dried over anhyd Na2SO4. The product was purified by column chromatography on silica gel eluting with PE.

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Catalyst loading for the reaction of 13c is 0.5 mol%.