Bifunctional Organocatalysts for the Asymmetric Addition of Malonate to Nitroalkenes

Significance

A new class of highly active and selective (thio)urea-substituted cinchona-alkaloid-based catalysts for the Michael addition of malo­nate to nitroalkenes is presented. The power of these catalysts is due to their bifunctionality: the quinuclidine ring generates the deprotonated ma­lonate nucleophile, whereas the (thio)urea moiety activates the nitroolefin electrophile through hydrogen-bonding interactions. Using the catalyst 9-epi-DHQT (see scheme) at low catalyst loading (only 0.5-5 mol%), the addition of malonate to a single face of the (thio)urea-bound nitroalkene provides Michael products in high yields and enantioselectivities. This organocatalytic reaction works well with both activated and unactivated nitroolefins.