Reductive dechlorination and degradation of mirex and kepone with Vitamin B12

Vitamin B12s effects the reductive dechlorination of mirex (dechlorane) in protic solvent systems, under both catalytic and stoichiometric conditions, mainly to yield compounds of composition C10Cl12-nHn, with n = 1-8, in which the basic dihomocubane cage structure is retained; the formation of cage-opened, reductively dehalogenated derivatives of 4,7-methanoindene occurs only to a very minor extent. The corresponding reactions of kepone (chlordecone), in contrast, occur with predominant formation of indene derivatives. Under certain mild conditions, vitamin B12s induces a fragmentation of kepone leading to the destruction of the dihomocubane moiety and the formation of an isolable organocobalamin having a C3Cl3H2 residue attached to the cobalt atom. In strongly alkaline media, the reaction of kepone with vitamin B12s may in addition yield high-molecular-weight condensation products of unknown constitution. Reactions of this type are of interest as prototypes of soil-decontamination processes.