Elemental F2 with transannular dienes: regioselectivities and mechanisms.

Three reaction paths, namely, molecule-induced homolytic, free radical, and electrophilic, were modeled computationally at the MP2 level of ab initio theory and studied experimentally for the reaction of F2 with the terminal dienes of bicyclo[3.3.1]nonane series. The addition of fluorine is accompanied by transannular cyclization to the adamantane derivatives in which strong evidence for the electrophilic mechanism both in nucleophilic (acetonitrile) and non-nucleophilic (CFCl3 , CHCl3 ) solvents were found. The presence of KF in CFCl3 and CHCl3 facilitates the addition and substantially reduces the formation of tar products.