Synthesis 2001(7): 1098-1109
DOI: 10.1055/s-2001-14576
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Efficient Palladium-Catalyzed Alkoxycarbonylation of N-Heteroaryl Chlorides - A Practical Synthesis of Building Blocks for Pharmaceuticals and Herbicides

Matthias Beller*a, Wolfgang Mägerleina, Adriano F. Indoleseb, Christine Fischera
a Institut für Organische Katalyseforschung (IfOK) an der Universität Rostock e. V., Buchbinderstr. 5-6, 18055 Rostock, Germany
Fax: +49-(381)-4669324; e-Mail: matthias.beller@ifok.uni-rostock.de;
b Solvias AG, WRO-1055.622, Klybeckstr. 191, CH-4002 Basel, Switzerland
Further Information

Publication History

Received 14 February 2001
Publication Date:
30 September 2004 (online)

Abstract

The alkoxycarbonylation of various N-heteroaryl chlorides was examined in detail. Studies of the butoxycarbonylation of 2- and 3-chloropyridine revealed the importance of selecting both the right phosphine ligand and ligand concentration in order to obtain efficient conversion and selectivity. Amongst the different ligands tested, 1,4-bis(diphenylphosphino)butane (dppb) and 1,1′-bis(diphenylphosphino)ferrocene (dppf) led to the most efficient palladium catalyst systems for the conversion of 2- and 4-chloropyridines and similar heteroaryl chlorides. The best catalytic systems for the alkoxycarbonylation of less activated substrates, such as 3-chloropyridines, were found to be those containing 1,4-bis(dicyclohexylphosphino)butane. Good to excellent yields of a number of N-heterocyclic carboxylic acid esters were realized by applying the appropriate ligand in the right concentration at low catalyst loadings (0.005-0.5 mol% Pd). For the first time catalyst turnover numbers (TON) of up to 13,000 were obtained for the carbonylation of a (hetero)aryl chloride.

10

Mägerlein, W.; Indolese, A.; Beller, M. Angew. Chem., Int. Ed. 2001, in press.

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2- and 3-Chloropyridine are a factor of 10-50 more expensive than 2- and 3-picoline.

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The respective n-butyl ethers are formed as side-products in 13-15% yield.

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For experiments at different temperatures, CO pressures, and catalyst concentrations, or with other ligands and bases, the conditions given in the respective tables were used.