J. Am. Chem. Soc., 125 (37), 11176 -11177, 2003. 10.1021/ja036792p S0002-7863(03)06792-1
Web Release Date: August 21, 2003

Copyright © 2003 American Chemical Society

Palladium-Catalyzed -Arylation of Esters and Amides under More Neutral Conditions

Takuo Hama, Xiaoxiang Liu, Darcy A. Culkin, and John F. Hartwig*

Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107

John.Hartwig@yale.edu

Received June 19, 2003

Abstract:

Two procedures for the -arylation of carbonyl compounds under conditions that are more neutral than those of reactions of aryl halides with alkali metal enolates are reported. The first procedure rests upon the development of catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) and the highly reactive dimeric Pd(I) complex {P(t-Bu)3]PdBr}2. By this procedure, zinc enolates prepared from -bromo esters and amides react with aryl halides to form -aryl esters and amides in high yields under mild conditions with 1-2 mol % catalyst and with remarkable functional group tolerance. By the second procedure, silyl ketene and silyl ketimine acetals react with aryl bromides in the presence of substoichiometric zinc fluoride, 1 mol % Pd(dba)2, and 2 mol % P(t-Bu)3 in DMF solvent at 80 C. Reactions of zinc tert-butyl acetate and propionate enolates and trimethylsilyl ketene acetals of tert-butyl propionate and methyl isobutyrate with aryl bromides bearing electron-donating and potentially reactive, base-sensitive electron-withdrawing groups and with pyridyl bromides are reported. In addition, the diastereoselective coupling of phenyl bromide with an imide enolate bearing the Evans auxiliary is reported, and this study shows that racemization of base-sensitive stereocenters does not occur during the coupling process under these more neutral conditions.

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