1,5-Stereocontrol in reactions of 2,4-disubstituted alk-2-enylstannanes with aldehydes; an approach to the stereoselective synthesis of branched triols

2-(tert-Butyldimethylsilyloxymethyl)-4-(methoxymethoxy)pent-2-enyl(tributyl)stannane is transmetallated by tin(IV) chloride stereoselectively to give a pent-1-en-3-yltin trichloride that reacts with aldehydes with excellent (E)-1,5-syn-stereocontrol, e.g. (3E)-1,5-syn-3-(tert-butyldimethylsilyloxymethyl)-5-(methoxymethoxy)-1-phenylhex-3-en-1-ol was the dominant product with benzaldehyde. The products from these reactions were taken through to more complex 2-substituted alk-2-enyl(tributyl)stannanes but only very low yields of the expected products were obtained from tin(IV) chloride mediated reactions of these stannanes and aldehydes. Nevertheless a stereoselective synthesis of 2-substituted 4-[(E)-2-alkoxypropylidene]tetrahydrofurans was developed.