Diastereoselective Addition of Allyltriphenylstannane to 3-Sulfinylfurfural Mediated by Titanium(IV) Tetrachloride and Tin(IV) Tetrachloride

The addition of allyltriphenylstannane to 3-sulfinylfurfural (3) in the presence of titanium(1V) tetrachloride proceeded with high diastereoselectivity to give the furyl alcohol (6).whereas the similar treatment with tin(lV) tetrachloride afforded the other diastereoisomeric alcohol (7), exclusively.Lewis acid-promoted allylation of aldehydes using allylmetal compounds such as allyltrialkylsilanes and allyltriarylstannanes has been widely studied.'From the view point of asymmetric reactions, there have been a number of reports which inchode thr use of allylmetal compounds bearing chiral l i g a n d ~, ~ chiral aldehydes3and chiral Lewis acid mediator^.^In the course of our studies on the asymmetric cycloaddition employing chiral sulfoxides,5 we were intrigued by the use of a chiral sulfinyl furfural for the reaction mediated by a Lewis acid.Despite of numerous efforts6 for asymmetric condensations using a-sulfinyl carbonyl compounds, little work has been done on the asymmetric addition to P-sulfinyl carbonyl compounds.This is presumably because of its low performance in chelation control.3aOur interest in Lewis acid-mediated reactions prompted us to investigate the possibility of asymmetric condensation of P-sulfinyl carbonyl compounds.Reported herein is a highly diastereoselective condensation of P-sulfinyl carbonyl compounds (i.e.3-sulfinyl furfural) with aliyltriphenylstannane in the presence of a Lewis acid.