Synthesis and Enantioselective Diels−Alder Reactions of Optically Active Cobalt(III) Salen-1,3-butadien-2-yl Complexes

The syntheses of two optically active Co(salen)-1,3-butadien-2-yl complexes are reported. One of the dienyl complexes was characterized by X-ray crystallography. The dienyl complexes underwent Diels−Alder reactions with high enantioselectivity with dimethyl fumarate. A highlight of this chemistry is that Diels−Alder cycloadduct cobalt complexes were cleanly cleaved at the cobalt−carbon bond with concomitant optically active cobalt complex starting material and optically active cyclohexene cycloadduct recovery.