The cis isomers of 1-allyl-2-phenylcyclohexane and 1-benzyl-2-vinylcyclohexane yield predominantly 1: 3 addition, while the trans isomers show a high selectivity for 2: 6 addition, which is explained by steric interactions. Introduction of a third substituent, OH or OCH3, on the alkenyl substituted carbon of the cyclohexane ring gives almost exclusively 1: 3 addition. This can mostly be explained in terms of more steric hindrance in the conformations ...