Highly Stereoselective Synthesis of Trisubstituted cis-[3]Cumulenols from Alkynylated Oxatitanacycles in the Presence of Lewis acids

A highly efficient and stereoselective method for the synthesis of trisubstituted cis-[3]cumulenols via oxatitanacycles derived from titanium-mediated coupling of 1,3-butadiynes with aldehydes or ketones promoted by Lewis-acids is described.