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.