Cobalt-Catalyzed Highly Regio- and Stereoselective Intermolecular Reductive Coupling of Alkynes with Conjugated Alkenes

Chun-Chih Wang, Pao-Shun Lin, and Chien-Hong Cheng*
Department of Chemistry, Tsing Hua University, Hsinchu, Taiwan 300, China
J. Am. Chem. Soc., 2002, 124 (33), pp 9696–9697
DOI: 10.1021/ja026543l
Publication Date (Web): July 26, 2002
Copyright © 2002 American Chemical Society
*

 To whom correspondence should be addressed. E-mail:  chcheng@ faculty.nthu.edu.tw.

Abstract

Abstract Image

In the presence of Co(PPh3)2I2, PPh3, water, and zinc powder, the reaction of alkynes (R1CCR2:  R1 = Ph, R2 = Me (1a); R1 = Ph, R2 = Ph (1b); R1 = Et, R2 = Et (1c); R1 = Ph, R2 = (CH2)3OH (1d); R1 = CO2Et, R2 = Ph (1e); R1 = CO2Me, R2 = (CH2)4CH3 (1f); R1 = CO2Et, R2 = SiMe3 (1g)) with alkenes having an electron-withdrawing substituent (CH2CHR:  R = CO2Bu (2a), CN (2b), SO2Ph (2c) and CO2Me (2d)) proceeded smoothly in acetonitrile to give the corresponding reductive coupling products (R1HCCR2CH2CH2R, 3a−j) in fair to excellent yields. This reductive coupling is highly regio- and stereoselective; only one isomer was observed for each reaction. The results of an isotope-labeling experiment using D2O (99%) to replace normal water for the reductive coupling of vinyl phenyl sulfone 2c with alkyne 1a revealed that the product is E-Ph(D)CCMeCH2CH(D)SO2Ph deuterated at the olefinic proton and one of the protons of the α-methylene group in 84 and 96%, respectively. Possible mechanisms for this highly regio- and stereoselective ene−yne catalytic reaction are proposed.

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History

  • Published In Issue August 21, 2002
  • Received April 16, 2002

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