Conjugate addition of heteroatom nucleophiles to a,P-unsaturated sulfoxides

The first report of asymmetric heteroatom conjugate addition to a,P-unsaturated sulfoxides was made in 1971 [11,12], and has been followed by few studies in this area relative to the analogous asymmetric reactions with carbon nucleophiles. The addition of piperidine in methanol to (-)-(S)-cis-propenyl p-tolyl sulfoxide (133) 

Pyne and coworkers have studied both the inter- and intramolecular reaction between amines and optically active a,P-unsaturated sulfoxides, and have applied this methodology to synthesis of natural products [109,110,112-114]. 

The intermolecular conjugate addition of benzylamine to (i s)-10-isobornyl a,P-unsaturated sulfoxides has been studied [110]. The (Z)-isomer (137) underwent highly diastereoselective conjugate addition to give (139) as the major product 

The asymmetric intramolecular conjugate addition of amines to optically active a,p-unsaturated sulfoxides has been studied [111-115], For example, the (Rs)-(E)-a,P-unsaturated sulfoxide (141), upon basic hydrolysis with lithium hydroxide, gave a mixture of the diastereoisomeric isoquinolines (143) and (144) in the ratio 63 37, An enhanced diastereoselectivity was observed upon basic hydrolysis of the (i s)-(2)-a,P-unsaturated sulfoxide (142) with benzyltriethylammonium hydroxide, giving (143) and (144) in the ratio 16 84 (note that the major product 

P-Nitro-a,p-unsaturated sulfoxides have been shown to react with pyrrolidine to give the corresponding nitroenamine with loss of the sulfoxide functionality [116]. 

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