Cinchonidinium acetate as a convenient catalyst for the asymmetric synthesis of cis-stilbenediamines

摘要

Inexpensive and readily available cinchonidinium acetate is an effective catalyst for the syn-selective aza-Henry reaction of arylnitromethanes and aryl imines. The resulting masked cis-stilbenediamine products are produced in excellent diastereoselectivity and good enantioselectivity, and enantiopure material can be achieved via recrystallization. The features of the cinchona catalyst needed for selectivity are discussed, with specific emphasis on formation of a kinetically controlled syn-product without epimerization of the highly acidic α-nitro stereocenter.