Optically Active Cationic Cobalt(III) Complexes: Highly Efficient Catalysts for Enantioselective Hetero Diels–Alder Reaction

Optically active β-ketoiminato cobalt(III) complexes were developed for use as effective catalysts of the enantioselective hetero Diels–Alder reaction of aryl and alkyl aldehydes with 1-methoxy-[3-(tert-butyldimethylsilyl)oxy]-1,3-butadiene. In the presence of 5 mol% cationic cobalt(III) triflate complexes derived from optically active 1,2-bis(3,5-dimethylphenyl)-1,2-ethylenediamine, the hetero Diels–Alder reaction of p-nitro- benzaldehyde proceeded in 94% yield with 94% ee.