Jump rope rotation in trans-cycloalkenes

A series of 1,2-bis-methylenecycloalkane monoepoxides(2a-e)was prepared from the related 12-to 16-membered cyclic ketones. Reduction with lithium in ammonia afforded the corresponding trans-and cis-2-methylcycloalkenylmethanols (3a/4a-3e/4e) in ratios of 92:8-78:22. Sharpless epoxidation of these allylic alcohols with 0.6 equivalents of the reagent prepared from titanium isopropoxlde, (+)-diisopropyl tartrate, and t-butylhydroperoxide gave rise to a mixture of the epoxy alcohols 6a-e and recovered allylic alcohols. In the case of the 12- to 14-membered cycloalkenes the recovered alcohols 3a-c were optically active. The 15- and 16-membered cases 3d and e were racemic. Barriers to jump rope rotation were calculated by means of the Still Macro Model program.