Stereoselective synthesis of cyclopropanes bearing adjacent stereocenters

Two approaches towards the stereoselective synthesis of cyclopropanes beari ng adjacent stereocenters have been investigated. On one hand, moderate to synthetically useful levels of stereoselectivity were observed in the cyclo propanation of allylic alcohols bearing a remote allylic stereocenter, and evidence has been put forward for the directing effect of a neighbouring ar omatic group in the Zn-promoted cyclopropanation of this class of substrate s. On the other hand, the hydroboration of isopropenylcyclopropanes was stu died and shown to proceed in a highly diastereoselective fashion in the cas e of the cis isomers.