Synlett 2008(4): 551-554  
DOI: 10.1055/s-2008-1032073
LETTER
© Georg Thieme Verlag Stuttgart · New York

Chloroesterification of Enynes Catalyzed by NHC Rhodium Compounds

Ji Young Baek, Sang Ick Lee, So Hee Sim, Young Keun Chung*
Intelligent Textile System Research Center and Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151747, Korea
Fax: +82(2)8890310; e-Mail: ykchung@snu.ac.kr;
Further Information

Publication History

Received 24 August 2007
Publication Date:
23 January 2008 (online)

Abstract

An efficient rhodium N-heterocyclic carbene (NHC)-catalyzed chloroesterification of terminal alkynes and enynes has been developed. The reaction was highly regio- and stereospecific: the Z-isomer was obtained as the sole product.

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General Procedure for Rh-NHC-Catalyzed Chloroesterification of Alkyne: To an oven-dried 10-mL tube containing toluene (5 mL), Rh-NHC (14 mg, 1 mol%) and alkyne (0.7 mmol) were added sequentially. After sealing the tube, the reaction temperature was elevated to 100 °C. The reaction was carried out in a test tube capped with a rubber septum. The rubber septum was tied with an aluminum binder. Thus, the reaction could be monitored by taking a small amount of the reaction mixture using a syringe. After the reactant was consumed, the solvent was removed under reduced pressure. Flash column chromatography gave the product.
3ab: 1H NMR (300 MHz, CDCl3): δ = 1.33 (t, J = 7.1 Hz, 3 H), 1.61 (m, 2 H), 1.71 (dd, J = 5.4, 9.2 Hz, 2 H), 2.25 (d, J = 4.1 Hz, 4 H), 4.22 (q, J = 7.1 Hz, 2 H), 6.11 (s, 1 H), 6.76 (t, J = 3.6 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 14.4, 21.7, 22.6, 26.4, 60.5, 112.9, 133.6, 136.0, 148.9, 165.0. HRMS (EI): m/z calcd for C11H15ClO2: 214.0761; found: 214.0764. IR: 1414 (w), 1433 (w), 1539 (w), 1601 (s), 1720 (s), 2120 (w), 2240 (w), 2296 (s), 2400 (w), 2504 (w), 2672 (m), 2920 (s), 2984 (m), 3048 (s), 3408 (br), 3680 (w), 3736 (w), 3936 (w) cm-1.
3ac: 1H NMR (300 MHz, CDCl3): δ = 1.58 (m, 2 H), 1.68 (m, 2 H), 2.22 (d, J = 6.0 Hz, 4 H), 6.15 (s, 1 H), 6.77 (s, 1 H), 7.35 (m, 5 H) 13C NMR (75 MHz, CDCl3): δ = 21.6, 22.5, 26.3, 66.3, 112.4, 128.3, 128.5, 128.7, 133.6, 136.0, 136.4, 147.6, 164.1. HRMS (EI): m/z calcd for C15H15ClO2: 262.0761; found: 262.0755. IR: 1416 (w), 1454 (w), 1486 (w), 1595 (s), 1723 (s), 1764 (w), 2128 (w), 2304 (s), 2408 (w), 2512 (w), 2672 (w), 2864 (w), 2928 (m), 2976 (w), 3048 (s), 3400(br), 3680 (w), 3744 (w), 3936 (m) cm-1.
3ba: 1H NMR (300 MHz, CDCl3): δ = 3.78 (s, 3 H), 6.20 (s, 1 H), 6.82 (d, J = 15.3 Hz, 1 H), 7.25-7.38 (m, 4 H), 7.47-7.50 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 51.8, 117.8, 125.9, 127.8, 129.1, 129.7, 135.4, 138.9, 144.6, 164.9. HRMS (EI): m/z calcd for C12H11ClO2: 222.0447; found: 222.0445. IR: 1416 (w), 1596 (w), 1723 (s), 2296 (m), 2968 (s), 3048 (s) cm-1.
3da: 1H NMR (300 MHz, CDCl3): δ = 3.77 (s, 3 H), 3.83 (s, 3 H), 6.70 (d, J = 15.2 Hz, 2 H), 6.90 (d, J = 7.0 Hz, 2 H), 7.32 (d, J = 15.2 Hz, 1 H), 7.42 (d, J = 7.0 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 51.7, 55.6, 114.6, 116.6, 123.8, 128.2, 129.4, 138.6, 145.1, 161.0, 165.1. HRMS (EI): m/z calcd for C13H13ClO3: 252.0553; found: 252.0555. IR: 1539 (w), 1584 (w), 1721 (s), 2296 (m), 2968 (s), 3048 (s) cm-1.
3ea: 1H NMR (300 MHz, CDCl3): δ = 2.02 (s, 3 H), 3.78 (s, 3 H), 5.43 (s, 1 H), 5.92 (s, 1 H), 6.24 (s, 1 H). 13C NMR (75 MHz, CDCl3): δ = 20.7, 51.9, 115.7, 122.9, 139.7, 146.1, 165.1. HRMS (EI): m/z calcd for C7H9Cl1O2: 160.0291; found: 160.0294. IR: 1417 (w), 1435 (w), 1596 (m), 1729 (s), 2296 (s), 2400 (w), 2572 (w), 2672 (w), 2976 (m), 3048 (s), 3416 (br), 3672 (w), 3736 (w), 3928 (m) cm-1.
3ga: 1H NMR (300 MHz, CDCl3): δ = 0.00 (s, 6 H), 0.84 (s, 9 H), 3.67 (s, 3 H), 4.28 (m, 2 H), 6.01 (s, 1 H), 6.34 (m, 1 H), 6.54 (td, J = 3.7, 14.7 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = -5.2, 18.6, 26.0, 26.1, 51.7, 62.6, 117.1, 126.4, 140.8, 144.3, 165.1. HRMS (FAB): m/z calcd for C12H23ClO3Si: 290.1105; found: 291.1185. IR: 1420 (br), 1460 (w), 1603 (s), 1640 (w), 1728 (s), 2304 (m), 2400 (w), 2512 (w), 2672 (w), 2848 (w), 2944 (s), 3056 (m), 3360 (br), 3672 (w), 3736 (w), 3936 (w) cm-1.