Methylcarbonate and Bicarbonate Phosphonium Salts as Catalysts for the Nitroaldol (Henry) Reaction

Phosphonium ionic liquids exchanged with bicarbonate and methylcarbonate anions (CILs) exhibit catalytic performances comparable to those of sterically hindered (non nucleophilic) organosuperbases such as DBU. At 25-50 degrees C, under solventless conditions, CILs efficiently catalyze the Henry addition of different aldehydes and ketones to nitroalkanes: not only they allow the selective formation of nitroaldols but they unlock a novel high-yielding access to dinitromethyl derivatives of ketones.