Synlett 2011(11): 1559-1562  
DOI: 10.1055/s-0030-1260770
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Highly Enantioselective Conjugate Addition of 3-Substituted Oxindoles to Vinyl Sulfone Catalyzed by Binaphthyl-Modified Tertiary Amines

Hyun Joo Lee, Seung Hee Kang, Dae Young Kim*
Department of Chemistry, Soonchunhyang University, Asan, Chungnam 336-745, Korea
Fax: +82(41)5301247; e-Mail: dyoung@sch.ac.kr;
Further Information

Publication History

Received 25 February 2011
Publication Date:
01 June 2011 (online)

Abstract

The enantioselective conjugate addition reaction of 3-substituted oxindoles with 1,1-bis(benzenesulfonyl)ethylene by binaphthyl-modified bifunctional organocatalysts was investigated. The corresponding Michael adducts, containing a quaternary center at C3 position of the oxindoles, were generally obtained in high yields with excellent enantioselectivities (up to 99% ee).

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Typical Procedure for the Conjugate Addition Reaction of 3-Phenyl Oxindole 1f with Vinyl Sulfone 2
To a solution of 3-phenyl oxindole 1f (0.3 mmol, 92 mg) and catalyst VIII (0.03 mmol, 21.4 mg) in CH2Cl2 (1.2 mL) was added 1,1-bis(benzenesulfonyl)ethylene (2, 0.45 mmol, 138.7 mg). Reaction mixture was stirred for 6 h at r.t., concentrated, and purified by flash column chromatography (EtOAc-hexane = 1:5) to afford the Michael adduct (3f, 168 mg, 90%). ( R )- tert -Butyl 3-[2,2-bis(phenylsulfonyl)ethyl]-2-oxo-3-phenylindoline-1-carboxylate (3f) [α]D ²7 26.0 (c 0.4, CHCl3). ¹H NMR (200 MHz, CDCl3): δ = 8.07-7.97 (m, 3 H), 7.77-7.67 (m, 3 H), 7.64-7.46 (m, 6 H), 7.38-7.16 (m, 7 H), 4.45-4.41 (m, 1 H), 3.40-3.29 (m, 2 H), 1.59 (s, 9 H). ¹³C NMR (50 MHz, CDCl3): δ = 175.2, 149.2, 141.2, 140.8, 138.0, 134.7, 134.4, 131.0, 129.3, 128.9, 128.8, 128.0, 126.7, 125.7, 124.6, 116.3, 84.3, 80.6, 55.2, 32.1, 28.0. HPLC [n-hexane-i-PrOH (90:10), 254 nm, 0.5 mL/min] Chiralcel OD-H column, t R = 18.8 min (major), t R = 23.9 (minor), 95% ee.