Formation of Nitro Alcohols via Asymmetric Hydroxylation of Nitroolefins

Significance

The authors present an organocatalytic method to prepare nitroalcohols from nitro­olefins and oximes through a conjugate 1,4-addition. This reaction, which leads to the formal products of a Henry reaction, is useful for the preparation of aliphatic nitroalcohols, while corresponding asymmetric, organocatalytic Henry reactions work best with aromatic substrates. The reaction is catalyzed by a bifunctional catalyst combining the cinchona-alkaloid motif with a thiourea moiety. The catalyst is speculated to activate the oxime via hydrogen bonding towards the basic nitrogen and the nitroolefin through hydrogen bonding with the thiourea. The substrate scope is limited to aliphatic nitroolefins, but the yields are found to be good to very good, with high enan­tioselectivities.