Allene cycloadditions. Part V. Temperature dependence of product distribution in alkylallene–alkyne reactions

Abstract

3-Methylbuta-1,2-diene reacts with hexafluorobut-2-yne at 80° to give a 3:1 mixture of 3,3-dimethyl-4-methylene-1,2-bistrifluoromethylcyclobutene and 3-isopropylidene-1,2-bistrifluoromethylcyclobutene, the product ratio remaining constant up to 150°. (Z)-1,1,1-trifluoro-5-methyl-4-(prop-2-enyl)-2-trifluoromethylhexa-2,4-diene isomerises at 100–140° to give 3,3-dimethyl-2-(prop-2-enyl)-1,4-bistrifluoromethylcyclobutene. The temperature dependence of the product distribution in the reaction between hexafluorobut-2-yne and 2,4-dimethylpenta-2,3-di-ene is reported and discussed.