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Most Requested Journal Articles 2Q02-Chemistry and Related

Following is one of the documents most requested by researchers using CAS electronic products.

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CAS indexed 30 chemical substances from this document. CAS subject entries for this document include: Vinylation catalysts; Coupling reaction; Crystal structure; and 4 additional concepts.

CAPLUS COPYRIGHT 2002 ACS

TITLE:	Palladium Complexes with Tridentate Pincer Bis-Carbene Ligands as Efficient Catalysts for C-C Coupling
AUTHOR(S):	Loch, Jennifer A.; Albrecht, Martin; Peris, Eduardo; Mata, Jose; Faller, Jack W.; Crabtree, Robert H.
CORPORATE SOURCE:	Department of Chemistry, Yale University, New Haven, CT, 06520-8107, USA
SOURCE:	Organometallics (2002), 21(4), 700-706 CODEN: ORGND7; ISSN: 0276-7333
PUBLISHER:	American Chemical Society
LANGUAGE:	English

ABSTRACT:
The synthesis and x-ray crystallog. characterization of a Pd carbene complex (3, shown as I) with a rigid C,N,C-tridentate pincer carbene ligand are described. A mixt. of 2,6-dibromopyridine and 1-butylimidazole was stirred at 150.degree. for 20 h. The mixt. was cooled and dissolved in CHCl3. Et2O was then added, giving pyridine deriv. 2 (shown as II) in 91% yield. Ligand 2 and [Pd(OAc)2] were then stirred in DMSO for 3 h at room temp. and then for 12 h at 50.degree.. Subsequently the reaction mixt. was heated to 155.degree. for 1 h and then cooled to room temp. The soln. was poured into CH2Cl2 and Et2O was added, giving 3 in 71% yield. At high temps. (165.degree.) 3 is an active and robust catalyst in the Heck reaction. Complex 3 gives some of the highest turnover nos. yet reported for coupling with aryl chlorides. Time dependence, reuse, and Heck reaction conditions are discussed for 3. Data with F- as base did not support Shaw's Heck mechanism. Suzuki and Sonogashira coupling reactions are also catalyzed by 3. The Pd carbene complex 5 (shown as III), contg. an analogous C,N-bidentate ligand, is compared to 3 in terms of stability, catalytic activity, and reaction profile in the Heck reaction. The x-ray crystal of 5 was also detd.

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