Studies on the diastereoselective allylation of aldehydes with enantiopure 2-sulfinylallyl building blocks
摘要:
A comparative study on the allylation of aldehydes with enantiopure (S-S)-2-(p-tolylsulfonyl)-prop-2-en-1-ol (S-S)-1a and the corresponding chloride (S-S)-1b under two different reaction systems is reported. In general, better yields were obtained from chloride (S-S)-1b, whereas higher diastereoinduction was observed from alcohol (S-S)-1a. The sense of diastereoinduction is the same in both systems and the stereochemistry of the major diastereomer has been determined. Moreover, the configurational stability of the sulfoxide group on the resulting sulfinyl homoallylic alcohols 3 has been proven in each reaction system. which demonstrates the efficiency of the sulfoxide group as chiral auxiliary in these allylation processes. Finally. as an example of the synthetic potential of the resulting adducts, a total synthesis of natural enantioenriched (S)-nicotine from sulfinylalcohol 3h is reported, (C) 2001 Elsevier Science Ltd. All rights reserved.
3-Chloro-2-(phenylsulfinyl)-1-propene and 3-chloro-2-(phenylsulfonyl)-1-propene: preparation and utility as reagents for .alpha.,.alpha.'-annelation of cyclic ketones
[reaction: see text] A simple, efficient, and diastereoselective zinc-promoted allylation of aldehydes with enantiopure (Ss)-3-chloro-2-(p-tolylsulfinyl)-1-propene [(Ss)-1] under aqueous Barbier conditions is described. The observed diastereoselectivity can be explained via an acyclic antiperiplanar transition state model.