Free-radical addition reactions of some olefins related to bicyclo[2,2,2]octane

Abstract

The products of the addition of benzenethiol to bicyclo[2,2,2]oct-2-ene, 2-methylenebicyclo[2,2,2]octane, 5-methylenebicyclo[2,2,2]oct-2-ene, 2,3-dimethylenebicyclo[2,2,2]octane, 5,6-dimethylenebicyclo[2,2,2]oct-2-ene, and 8,9-dimethylenebicyclo[3,2,2]non-6-ene have been investigated. The additions of methanethiol to 2,3-dimethylenebicyclo[2,2,2]octane, of p-thiocresol to 5,6-dimethylenebicyclo[2,2,2]oct-2-ene, and of bromotrichloromethane and methylene dibromide to bicyclo[2,2,2]oct-2-ene have also been studied. In the additions to mono-olefins, products of 1,2-addition to the double bond result, whereas with conjugated dienes products of 1,4-addition to the diene systems are formed. Only a few per cent, at most, of products of homoconjugative addition were isolated in the addition of benzenethiol to 5-methylenebicyclo[2,2,2]oct-2-ene. No such product was detected in additions to 5,6-dimethylenebicyclo[2,2,2]oct-2-ene and 8,9-dimethylenebicyclo[3,2,2]non-6-ene. The double bonds and diene systems in these compounds react independently of each other to a large extent. The reactivities (relative to oct-1-ene) of the olefins and dienes in the bicyclo[2,2,2]octane series towards benzenethiol, and towards methyl thioglycollate have been obtained. Apart from the conjugated dienes, which have high reactivities, the olefins and non-conjugated diene are less reactive than the corresponding compounds related to norbornene. This may indicate the smaller degree of strain in olefins in the bicyclo[2,2,2]octane series.