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-nitrobenzaldehyde proceeded in 94% yield with 94% ee.