Rational design of highly diastereoselective, organic base-catalyzed, room-temperature Michael addition reactions

Via the rational design of a single-preferred transition state, stabilized by electron donor-acceptor-type attractive interactions, structural and geometric requirements for the corresponding starting compounds have been determined. The Ni(II) complex of the Schiff base of glycine with o-[N-α-picolylamino]acetophenone, as a nucleophilic glycine equivalent, and N-(trans-enoyl)oxazolidin-2-ones, as derivatives of an α,β-unsaturated carboxylic acid, were found to be the substrates of choice featuring geometric/conformational homogeneity and high reactivity. The corresponding Michael addition reactions were found to proceed at room temperature in the presence of catalytic amounts of DBU to afford quantitatively the addition products with virtually complete diastereoselectivity. Acidic decomposition of the products followed by treatment of the reaction mixture with NH₄OH gave rise to the diastereomerically pure 3-substituted pyroglutamic acids.