CONTROL OF REGIOSELECTIVITY BY CHELATING SUBSTRATES IN SOME RHODIUM(I) AND RHODIUM(III)-CATALYZED REACTIONS OF BUTADIENE

Rhodium(I) catalyses the addition of butadiene to chelating substrates such as N-allylamides of organic acids, or alkylamides of but-3-enoic or pent-4-enoic acids, under mild conditions, to give linear products exclusively. No reaction occurs in the absence of chelation. Rhodium(III) reacts in the same way with amides of butenoic acid, but gives branched products regioselectively with N-allylcarboxamides or sulfonamides. Rhodium(I) and rhodium(III) complexes with chelating amides have been isolated and their reactivity has been investigated. The chelation effect causing reactivity and regioselectivity changes in rhodium(I)- and rhodium(III)-catalysed reactions is discussed.