Addition of thiols to some 5-substituted norborn-2-enes

Abstract

Thiols react with 5-substituted norborn-2-ene derivatives to afford 2-exo- and 3-exo-sulphides by addition across the double bond. Product proportions appear to depend on the relative stability of the intermediate radicals formed by attack at positions 2 and 3 respectively, and, in additions of benzenethiol, also on the variation in the degree of reversibility of radical attack at positions 2 and 3. The addition of thiols to norborn-2-en-5-one forms 2-exo-, 3-exo-, and 7-anti-sulphides, the last having its origin either in the rearrangement of the intermediate formed by radical attack at position 2, or in the formation of a non-classical homoenolised radical by attack at position 2.