Dehydroabietyl squaramide incorporating chiral pyrrolidine for highly diastereo- and enantioselective Michael reaction between cyclohexanone and β-nitrostyrenes

Abstract

Through an efficient two-step synthetic strategy, we synthesized two novel dehydroabietyl pyrrolidin-2-yl squaramides, which were evaluated for their ability to catalyze the asymmetric Michael addition of cyclohexanone to β-nitrostyrenes. The (R)-pyrrolidin-2-yl substituted dehydroabietyl squaramide emerged as the superior catalyst, facilitating the asymmetric synthesis of the corresponding adducts with high yields (87–98%) and good to excellent stereoselectivity (up to >99 : 1 syn/anti ratio, 99% ee).