Chiral Ammonium Aryloxides as Brønsted Base Catalysts for the Henry Reaction of Nitroalkanes to Aromatic and Aliphatic Aldehydes

Abstract : An enantioselective organocatalyzed Henry reaction was reported using chiral ammonium aryloxides as Brønsted base organocatalysts. A wide range of aliphatic and aromatic aldehydes along with several nitroalkanes are tolerated providing the corresponding enantioenriched β‐nitroalcohols with moderate to high diastereomeric ratios and up to 83 % ee. An inversion of the diastereoselectivity was observed when changing from aromatic to aliphatic aldehydes. Transition state models were proposed in order to account for this phenomenon.