Medium-ring 1,5-dienes. Part II. The radical and electrophile-induced cyclisation of germacra-1(10),4,7(11)-triene

The (E,E)-cyclodeca-1,5-diene derivative, germacra-1(10),4,7(11)-triene (1), has been cyclised to a variety of trans-decalin (selinane) derivatives by using the electrophilic reagents hypobromous acid, mercury(II) acetate, and sulphuric acid and radical-mediated reactions with benzenethiol, diphenyl disulphide, and carbon tetrachloride. A concerted mechanism in combination with a preferred reacting conformation is proposed to account for the high regio- and stereo-specificity of the reactions.