Synlett 2010(13): 2029-2032  
DOI: 10.1055/s-0030-1258483
CLUSTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Organocatalytic Enantioselective Michael Addition of Aldehydes to Vinyl Sulfones in Water

Jian Xiao, Yan-Ling Liu, Teck-Peng Loh*
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798, Singapore
Fax: +6567911961; e-Mail: teckpeng@ntu.edu.sg;
Further Information

Publication History

Received 13 May 2010
Publication Date:
09 July 2010 (online)

Abstract

The first organocatalytic enantioselective Michael addition of aldehydes to vinyl sulfones in water was achieved using our rationally designed organocatalyst. The rigid nature of the tricycle with an inherent chiral pocket provides a well-organized chiral environment, which together with the hydrophobic pocket, enabled this elusive reaction to proceed smoothly in water.

12

Typical Reaction Procedure
To a mixture of 1,1-bis(phenylsulfonyl)ethylene (31 mg, 0.1 mmol), catalyst I (2.8 mg, 0.01 mmol), and DMAP (1.2 mg, 0.01 mmol) in H2O (0.5 mL) was added isoveraldehyde (34.4 mg, 0.4 mmol) and stirred vigorously for 12 h at r.t. Then MeOH (1 mL) was added and the mixture was cooled to 0 ˚C before NaBH4 (8 mg, 0.2 mmol) was added. After stirring at 0 ˚C for 0.5 h, the mixture was extracted with EtOAc (3 × 5 mL). The combined organic layers were washed with brine (5 mL), dried over anhyd MgSO4, and concentrated under reduced pressure. The desired products were purified with silica gel column chromatography (EtOAc-hexanes = 1:2). The ee was determined by HPLC with Chiralpak AS-H column at 220 nm (2-PrOH-hexane = 20:80), 0.5 mL/min, t R(major) = 40.0 min, t R (minor) = 47.0 min; [α]D ²0 +3.1 (c 2.3, CHCl3, 589 nm); yellow light solid; R f  = 0.15 (EtOAc-hexane = 1:2). ¹H NMR (300 MHz, CDCl3): δ = 7.98-7.93 (m, 4 H), 7.72-7.67 (m, 2 H), 7.59-7.54 (m, 4 H), 5.22 (dd, J = 3.3, 7.2 Hz, 1 H), 3.73 (dd, J = 3.3, 11.0 Hz, 1 H), 3.51 (dd, J = 7.9, 11.0 Hz, 1 H), 2.37-2.13 (m, 2 H), 1.78-1.57 (m, 3 H), 0.85 (d, J = 3.4 Hz, 3 H), 0.82 (d, J = 3.4 Hz, 3 H). ¹³C NMR (75 Hz, CDCl3): δ = 138.0, 137.7, 134.5, 129.7, 129.5, 129.1, 129.0, 81.6, 64.7, 44.4, 29.8, 26.1, 19.4, 19.2. HRMS (ESI-TOF): m/z calcd for C19H25SO2: 333.1347 [M + H]+; found: 333.1342.