Abstract: The cycloaddition reactions of (Z)-J ,2-diphenyl-1, 3-butadiene were studied with a high regioselectivity. The products were identified by IR, NMRand MS. The regioselectivity in the Diels-Alder reactions of (Z)-1 ,2-diphenyl-1,3-butadiene can be rationalized by frontier orbital theory. The primary orbital interactions which have been used to predict the regioselectivity in the Diels-Alder reaction could not account for the regioselectivity observed with (Z)-1,2-diphenyl-1,3-butadiene. When the secondary orbital interactions were included in the theory, the preferred regioisomer was rationalized in every case. The frontier molecular orbitals of (Z)-1, 2-diphenyl-1, 3-butadiene and the dienophiles were determined by the CNDO/2 method.

Key words: Diene synthesis, Regioselectivity, Diphenylbutadiene, CNDO/2 method, Frontier molecular orbital theory