The chemistry of terpenes. Part XIX. Reaction of (+)-3α,4α-epoxycarane with halogen acids and acetic acid

Abstract

The reaction of (+)-3α,4α-epoxycarane (2) with ethereal hydrogen chloride affords a mixture of (–)-3β-chlorocaran-4α-ol (1a; X = Cl) and (+)-4β-chlorocaran-3α-ol (4). The acetate of the former can be converted into (+)-4α-acetoxycaran-3α-ol (6a) by heating with 1,4-diazabicyclo[2.2.2]octane in dimethylformamide. Treatment of the epoxide (2) with hydrogen bromide in acetic acid yields p-cymene, (–)-3β-bromocaran-4α-ol (1a; X = Br), (–)-2β-bromo-p-menth-8-en-1α-ol (3b), and (–)-2β,8-dibromo-p-menthan-1α-ol (8). The reaction of (2) with hot acetic acid leads to (–)-4α-acetoxycaran-3β-ol (1c), (+)-8-acetoxy-p-mentha-1,5-diene (10a), and (–)-car-3(10)-en-4α-ol (11).