Metal-Catalyzed Chemoselective Cycloisomerization of cis-2,4-Dien-1-als to 3-Cyclopentenones and 4-Alkylidene-3,4-dihydro-2H-pyrans
摘要:
[GRAPHICS]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-3H-isochromene (4) smoothly in hot toluene. A plausible mechanism is proposed on the basis of reaction observation and isotope-labeled experiment.
Metal-Catalyzed Cycloisomerization of Enyne Functionalities via a 1,3-Alkylidene Migration
作者:Ming-Yuan Lin、Arindam Das、Rai-Shung Liu
DOI:10.1021/ja062515h
日期:2006.7.1
We report a new metal-catalyzed 6-endo-dig cyclization of cis-4,6-dien-1-yn-3-ols, which produces substituted benzene and naphthalene derivatives with structural reorganization. In this process, we observe a 1,3-alkylidene migration via cleavage of the olefin double bond of the starting substrates. The ease and reliability of this cyclization are manifested by its compatibility with a wide array of diverse substrates and several pi-alkyne activators, including PtCl2, Zn(OTf)2, AuCl, and AuCl3.
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