Stereochemistry of an Ene Reaction Involving 1,7‐Dienes; Bicyclo[3.3.1]nonanes from (3‐Cyclohexenyl)diallylcarbinols

Abstract
(3‐Cyclohexenyl)diallylcarbinols undergo a thermal retro‐ene reaction to give crotonylcyclohexenes at ca. 200°. A side‐reaction is an ene reaction to give bicyclo[3.3.1]nonanes. These become the main products above 300°. The stereochemistry of 2‐allyl‐1,4,6‐trimethylbicyclo[3.3.1]‐6‐none‐2‐ols and related compounds is discussed, and a case is described in which the allyl group is not freely rotating.