Stereoselective synthesis of unsymmetrical conjugated dienes and trienes utilizing silacyclobutenes

Treatment of the different kinds of alkynyl-substituted dialkynyldiarylsilanes with zirconocene-ethylene complex Cp2Zr(CH2CH2) followed by acidification with 3 N HCl gave regio- and stereoselectively the corresponding silacyclobutenes in good yields. Desilylation of the silacyclobutenes with tetrabutylammonium fluoride afforded stereoselectively unsymmetrical conjugated (1E,3E)-dienes and -trienes (R1 or R2 = 1-cyclohexenyl) in excellent yields.