Palladium-Catalyzed Intramolecular Oxidative Alkylation of Unactivated Olefins
Tao Pei, Xiang Wang and Ross A. Widenhoefer*
*Duke University, P. M. Gross Chemical Laboratory, Durham, North Carolina
27708-0346, Email: rwidenho
chem.duke.edu
T. Pei, X. Wang, R. A. Widenhoefer, J. Am. Chem. Soc., 2003, 125, 648-649.
DOI: 10.1021/ja026317b
Abstract
A mild, palladium-catalyzed intramolecular oxidative alkylation of various ζ-alkenyl β-diketones and ζ-alkenyl β-keto esters in the presence of CuCl2 at room temperature formed the corresponding 2-cyclohexenones in high yield.
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Details
The document discusses the development of a palladium(II)-catalyzed oxidative alkylation of unactivated olefins by Tao Pei, Xiang Wang, and Ross A. Widenhoefer from Duke University. Traditional oxidative alkylation via the Heck reaction has been challenging due to inefficient oxidative addition of alkyl halides and competitive β-hydride elimination. The authors report a novel method using Pd(II) complexes to catalyze the nucleophilic addition of carbon nucleophiles to olefins in the presence of an oxidant, avoiding the need for alkyl halides. They initially targeted β-diketones but found that hydroalkylation occurred instead. However, they successfully achieved oxidative alkylation with ω-alkenyl β-diketones, yielding cyclohexenone derivatives. The reaction tolerated various terminal acyl groups and allylic substitutions, and was applicable to spirobicyclic compounds and ω-alkenyl β-keto esters. The proposed mechanism involves the formation of a palladium cyclohexylmethyl species, followed by isomerization and olefin displacement. The study highlights the first effective transition metal-catalyzed protocol for oxidative alkylation of unactivated olefins, with ongoing efforts to expand substrate scope and understand the mechanism and selectivity factors. The research was supported by various foundations and Duke University.
Palladium-Catalyzed Intramolecular Addition of 1,3-Diones to Unactivated Olefins
T. Pei, R. A. Widenhoefer, J. Am. Chem. Soc., 2001, 123, 11290-11291.
Key Words
Cyclization, Active Methylenes, Cyclohexenones
ID: J48-Y2003-1300
