Alkene insertion reactivity of a -carboranyl-substituted 9-borafluorene.

The synthesis of 9-borafluorene with an electron-withdrawing -carboranyl substituent and its reactions with a series of alkenes are described. The -carboranyl substituent is bonded one of the cluster carbon atoms to the boron atom of the 9-borafluorene moiety. In all cases, the reactions afford partly saturated analogs of borepins ( 6,7-dihydroborepins) by unprecedented alkene insertion into the endocyclic B-C bond of the borole ring.