Dramatic change of regioselectivity in the addition of silylated organolithium reagents with oxazolidines induced by the presence of a titanium salt

Diastereoselective reactions between oxazolidines and organolithium reagents afford β-amino alcohols having chiral vinyl and alkynylsilane moieties. A meaningful change of regioselectivity, from the α- to the γ-position, occurred when these reactions were performed in the presence of titanium isopropoxide, since allyl and allenylsilane derivatives were thus produced.