Bulky Alkylphosphines with Neopentyl Substituents as Ligands in the Amination of Aryl Bromides and Chlorides

Lensey L. Hill,† Lucas R. Moore,† Rongcai Huang,† Raluca Craciun,† Andrew J. Vincent,† David A. Dixon,*† Joe Chou,‡ Christopher J. Woltermann,‡ and Kevin H. Shaughnessy*†
Department of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, Alabama 35487-0336, and FMC Corporation, Lithium Division, Highway 161, Box 795, Bessemer City, North Carolina 28016-0795
J. Org. Chem., 2006, 71 (14), pp 5117–5125
DOI: 10.1021/jo060303x
Publication Date (Web): June 3, 2006
Copyright © 2006 American Chemical Society
†

 University of Alabama.

,
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

,
‡

 FMC Corporation.

, kshaughn@bama.ua.edu

Abstract

Abstract Image

Di(tert-butyl)neopentylphosphine (DTBNpP) in combination with palladium sources provided catalysts with comparable or better activity for the Hartwig−Buchwald amination of aryl bromides than tri(tert-butyl)phosphine (TTBP) under mild conditions. DTBNpP also provided effective catalysts for amination reactions of aryl chlorides at elevated temperatures. Further replacement of tert-butyl groups with neopentyl substituents resulted in less effective ligands for amination reactions. Computationally derived cone angles showed that replacement of a tert-butyl group with a neopentyl group significantly increased the cone angle of the phosphine. The larger cone angle of DTBNpP than TTBP appears to correlate with the higher activity of catalysts derived from DTBNpP in the amination of aryl bromides. TTBP is a stronger electron donor than DTBNpP, which may explain the higher activity for TTBP-derived catalysts toward aryl chlorides.

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History

  • Published In Issue July 07, 2006
  • Received February 14, 2006

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