Dual-reagent organocatalysis with a phosphine and electron-deficient alkene: application to the Henry reaction

Triphenylphosphine in combination with methyl acrylate was found to be able to catalyze the Henry (nitroaldol) reaction of various aldehydes and α-keto esters to give the corresponding β-nitroalkanols in good to excellent yields, and a catalytic cycle involving a zwitterionic phosphine–alkene adduct was proposed for this dual-reagent organocatalysis according to the deuterium-labeling experiments with CD3NO2.