Allylic Amines via Iridium-Catalyzed C−C Bond Forming Hydrogenation:  Imine Vinylation in the Absence of Stoichiometric Byproducts or Metallic Reagents

Andriy Barchuk, Ming-Yu Ngai, and Michael J. Krische*
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
J. Am. Chem. Soc., 2007, 129 (27), pp 8432–8433
DOI: 10.1021/ja073018j
Publication Date (Web): June 16, 2007
Copyright © 2007 American Chemical Society
*

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

, mkrische@mail.utexas.edu

Abstract

Abstract Image

Exposure of aromatic, heteroaromatic, and aliphatic N-arylsulfonyl aldimines 1a−12a in toluene solution at 60 °C to 2-butyne and hydrogen at ambient pressure in the presence of a cationic iridium(I) catalyst modified by BIPHEP enables formation of reductive coupling products, allylic amines 1b−12b, in good isolated yields as single geometrical isomers (>95:5, E:Z). The nonsymmetric alkynes 4-methyl-2-pentyne couple to imines 6a, 12a, and 13a under standard conditions with complete levels of regioselection. Hydrogenative coupling of 2-hexyne to imines 6a, 12a, and 13a delivers allylic amines 15b, 16b, and 18b in 10:1 regioisomeric ratios in each case. As revealed by 2H NMR analysis, reductive coupling of 2-butyne to imine 2a under an atmosphere of elemental deuterium provides deuterio-2b, which incorporates deuterium at the vinylic position (83% 2H) and at the allylic methyl groups (5% 2H). An equal distribution of deuterium at the allylic methyl groups suggests H−D exchange at the propargylic positions of 2-butyne in advance of C−C coupling.

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History

  • Published In Issue July 11, 2007
  • Received April 30, 2007

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