Catalyzed by p-toluenesulfonic acid in dry acetonitrile, oxirane-containing tertiaryenamides underwent efficient cyclization via intramolecularaddition to produce 3-hydroxy-3,4-dihydropyridin-2(1H)-one derivatives in moderate to good yields.
Reversal of Nucleophilicity of Enamides in Water: Control of Cyclization Pathways by Reaction Media for the Orthogonal Synthesis of Dihydropyridinone and Pyrrolidinone <i>Clausena</i> Alkaloids
作者:Luo Yang、Qi-Yu Zheng、De-Xian Wang、Zhi-Tang Huang、Mei-Xiang Wang
DOI:10.1021/ol800740h
日期:2008.6.1
A highly efficient, metal-free, and divergent method for the synthesis of 3,4-dihydropyridin-2-one and pyrrolidin-2-one Clausena alkaloids and their analogs is reported. While the oxirane-containing enamides underwent the TFA-mediated 6-endo-enamide-epoxide cyclization reaction in (BuOH)-O-t to produce homoclausenamides, an unprecedented nucleophilic reaction occurred at the alpha-carbon of enamides in water to yield 5-endo-enamide-epoxide cyclization products in excellent yields. The reversal of nucleophilicity of enamides in intramolecular cyclization is discussed in terms of steric and electronic effects of the oxirane-containing enamides.