Allene cycloadditions. Part IV. Reactions of tetramethylallene with unsymmetrically substituted olefins

Abstract

Cycloadditions between tetramethylallene and chlorotrifluoroethylene, 1,1-dichlorodifluoroethylene, and acrylonitrile occur in Pyrex vessels only after isomerisation of the hydrocarbon to 2,4-dimethylpenta-1,3-diene, and the adducts formed are a 47 : 53 mixture of cis- and trans-2-chloro-2,3,3-trifluoro-1 -methyl-1 -(2-methylprop-1-enyl)-cyclobutane. 2,2-dichloro-3,3-difluoro-1-methyl-1 -(2-methylprop-1-enyl)cyclobutane, and 4-cyano-1,3,3-trimethylcyclohexene, respectively. N.m.r. analysis indicates that the cyclobutanes are puckered, with a marked preference for their 2-methylprop-1-enyl groups to be situated equatorially.