Abstract
Methyl propiolate undergoes Lewis acid catalyzed reactions with alkenes in high yield. Mono- and 1,2-disubstituted alkenes give mainly cyclobutenes. 1,1 -Disubstituted, trisubstituted, and tetrasubstituted alkenes give only ene adducts. Use of ethylaluminum dichloride as catalyst allows the isolation of pure products from acid-sensitive alkenes. Functionalized al- kenes containing nonbasic functional groups are suitable substrates. Alkenes containing more basic functional groups are suit- able if 2 equiv of catalyst is used.