6-Endo-and 5-exo-digonal cyclizations of o-hydroxyphenyl ethynyl ketones: A key step for highly selective benzopyranone formation

K Nakatani, A Okamoto, I Saito

Index: Nakatani, Kazuhiko; Okamoto, Akimitsu; Saito, Isao Tetrahedron, 1996 , vol. 52, # 28 p. 9427 - 9446

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Citation Number: 29

Abstract

The cyclization of o-hydroxyphenyl ethynyl ketones was examined from theoretical and experimental standpoints in order to develop efficient synthetic methods for the construction of 2-substituted pyranones possessing significant biological activities. Ab initio studies at HF/6–31G∗ level on the cyclization indicated that both 6-endo-digonal and 5-exo-digonal cyclizations giving benzopyranones and benzofuranones, respectively, were endothermic ...