Abstract
A series of chiral vanadium complexes were prepared with amino acid and salicylaldehyde. These chiral complexes have been utilized in the studies of asymmetric coupling of 2-naphthols, chiral cyanohydrins and chiral aminonitriles syntheses. In asymmetric coupling of 2-naphthols, addition of trimethylsilyl chloride was necessary to promote the reaction rate when complex 13 was the catalyst. However, when using complex 19b as the catalyst to catalyze the enantioselective coupling of 2-naphthols, the BINOL products were obtained with up to 75% ee without additive. For the cyanohydrins syntheses, the complex 31 was able to catalyze trimethylsilyl cyanation of aldehyde in acetone. The chiral cyanohydrins were obtained in high yield with 72-90% ee. This catalyst was further studied in aminonitriles formation, but the enantioselectivity was not satisfactory. In the presence of 20 mol% complex 31, the chiral aminonitrile was synthesized in 34% ee.