Amino-lndanol Catalyzed Enantioselective Reactions of 3-Hydroxy-2-Pyridones

摘要

The Diels-Alder reaction is one of the most important reactions for the synthesis of complex molecules, providing access to carbocyclic compounds containing up to four stereogenic centers in a single step. Asymmetric catalysis in a Diels-Alder reaction has mainly been realized using chiral Lewis acids. Recently, the use of organic Bronsted acids or Br0nsted bases has emerged as a viable alternative for catalytic Diels-Alder reactions. Cycloaddition of 2-pyrone and 2-pyridone dienes generates structurally and stereochemically rich bicyclooctenes. However, these dienes have some aromatic character and participate in Diels-Alder reactions less readily. Deng et al. reported that 3-hydroxy-2-pyrones, using a cinchona alkaloid derivative as a catalyst, can take part in Diels-Alder reactions with excellent ee's. Okamura et al. were the first to report that the Diels-Alder reactions of 3-hydroxy-2-pyridone can be catalyzed by Br0nsted bases. While preparing a glycosidase inhibitor, Vasella developed a methodology using quinine to promote the reaction between 3-hydroxy-2-pyridone and 8-phenylmenthyl acrylate, leading to a dr of 96%.