TRANSITION METAL-DIENE COMPLEXES IN ORGANIC-SYNTHESIS .30. ON THE MECHANISM OF THE OXIDATIVE CYCLIZATIONS OF TRICARBONYL(ETA(4)-CYCLOHEXADIENE)IRON COMPLEXES - UNEQUIVOCAL DETERMINATION OF THE REGIOSELECTIVITYAND THE STEREOSPECIFICITY OF THE CYCLIZATION PROCESS BY DEUTERIUM LABELING STUDIES

Oxidative cyclizations of tricarbonyliron-cyclohexadiene complexes are shown to proceed by stereospecific loss of the 6-syn hydrogen atom. T he regioselectivity of these reactions is dependent on the type of the oxidizing reagent. Two-electron oxidants effect a completely regiosel ective cyclization at C-4 of the cyclohexadiene ligand, while one-elec tron oxidants provide the product resulting from preferential attack a t C-6.