Radical-mediated synthesis of bridgehead-substituted bicycloalkanes. A convenient route to the bicyclo(3.2.1)octyl system

A study of the behavior of the (3-methylenecyclohexyl)ethyl radical is presented. It is shown that cyclization of the radical to the isomeric 1-bicyclo(3.2.1)octylmethyl radical occurs with an activation energy of 11.6 kcal mol-1. This barrier tallies with the calculated value of 12.6 kcal mol-1. The ring closure behavior of the radical can be utilized for high-yield synthesis of bicyclo(3.2.1) ocanes with useful functionality at the bridgehead.