Amination of Nitroolefins Catalyzed by Chiral Bifunctional Ammonium Salt

Significance

An enantioselective conjugate ­addition of tert-butyl benzyloxycarbamate (1) to nitroalkenes 2 has been reported to proceed without the need for base additives in the presence of quaternary ammonium phase-transfer catalyst 3. Conjugate adducts 4 were obtained in high yields with high enantioselectivity. A catalyst loading of 0.05 mol% was routinely applied, and even 0.01 mol% of chiral ammonium bromide 3 was demonstrated to give similar enantioselectivity. Somewhat lower enantioselectivity was observed for ­nitroalkenes with aliphatic substituents. The reaction conditions were shown to be compatible with substrates containing base- and/or acid-sensitive functional groups. The resulting amination products 4 could be readily transformed into the corresponding 1,2-diamines.