DABCO-Mediated [4+2] Annulation of But-3-yn-2-one and Activated Ketones: Facile Preparation of 2,3-Dihydropyran-4-one
作者:Zhong Lian、Qian-Yi Zhao、Yin Wei、Min Shi
DOI:10.1002/ejoc.201200264
日期:2012.6
that nitrogen-containing Lewis base mediated [4+2] annulation of but-3-yn-2-one with activated ketones could proceed efficiently to give the corresponding 2,3-dihydropyran-4-ones in moderate to good yields under mild conditions. The substrate scope has been carefully examined. Moreover, a plausible reaction mechanism for the [4+2] annulation of but-3-yn-2-one with activated ketones mediated by DABCO has
Cycloadditions of 1-methoxy-3-trimethylsilyloxy-1,3-butadiene (1) with halogenated carbonyl compounds (2) yielded corresponding substituted tetrahydro- and/or dihydropyran-4-ones (3 and/or 4). Lewis acids were found to be effective as catalysts. Reactions with less reactive carbonyl compounds (2c,d) afforded p-hydroxyacetophenone (5) produced by cyclodimerization of 1. Stereochemistry of the adducts was deduced by H-1 nmr spectroscopy.