Organic letters

Metal-Catalyzed Chemoselective Cycloisomerization of cis-2, 4-Dien-1-als to 3-Cyclopentenones and 4-Alkylidene-3, 4-dihydro-2 H-pyrans

CY Lo, CC Lin, HM Cheng, RS Liu

Index: Lo, Ching-Yu; Lin, Chung-Chang; Cheng, Hsin-Mei; Liu, Rai-Shung Organic Letters, 2006 , vol. 8, # 14 p. 3153 - 3156

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Citation Number: 25

Abstract

PtCl2 (5 mol%) catalyst effected cycloisomerization of cis-2, 4-dien-1-al (1) to 3- cyclopentenone (3) efficiently in hot toluene. In the presence of p-TSA, this PtCl2 catalysis gave 2-cyclopentenone (5) exclusively because of the secondary isomerization reaction. Although the 1-2 equilibrium state greatly favors aldehyde (1), PdCl2 (PhCN) 2 (5 mol%) catalyzed cycloisomerization of aldehyde (1) to 4, 6, 7, 8-tetrahydro-3 H-isochromene (4) ...