The chemistry of terpenes. Part IV. The hydroboronation of (+)-car-3-ene at elevated temperatures

Abstract

Hydroboronation of (+)-car-3-ene at 20° gives bis-(cis-caran-4-yl)borane from which (–)-cis-caran-trans-4-ol is exclusively obtained by oxidation. When, however, the bis-(cis-caran-4-yl)borane is heated at progressively higher temperatures and the products oxidised, (–)-cis-caran-trans-5-ol, (–)-cis-caran-trans-2-ol, (minus;)-cis-m-menth-4-ene-8-ol and finally the cis- and trans- caran-10-ols are formed in addition to (–)-cis-caran-trans-4-ol. Oxidation of the mixture of alcohols obtained from borane isomerisation at 100°, followed by reduction with lithium aluminium hydride, directly affords (+)-cis-caran-cis-5-ol.