The Unprecedented Cobalt-Catalysed Oxidative Glaser Coupling under Reductive Conditions

Abstract

The cobalt-catalysed Glaser-type coupling of terminal alkynes was achieved utilising nitrobenzene as a stoichiometric oxidising agent under reductive conditions. The proposed electron transfer from zinc powder to a nitrobenzene coordinated to the cobalt centre initiates the coupling of the coordinated alkynes. Other aryl-, alkenyl-, alkyl-, and silylacetylenes besides phenylacetylene could also be coupled to generate the 1,3-diynes in moderate to very good yields.

alkyne - cobalt - Glaser coupling - oxidation - diynes

References

1a Glaser C. Ber. Dtsch Chem. Ges.  1869,  2:  422 

1b Eglinton G. Galbraith AR. J. Chem. Soc.  1959,  889 

1c Eglinton G. McCrae W. Adv. Org. Chem.  1963,  4:  225 

1d Hay AS. J. Org. Chem.  1962,  27:  3320 

1e Boldi AM. Anthony J. Knobler CB. Diederich F. Angew. Chem., Int. Ed. Engl  1992,  31:  1240 ; Angew. Chem. 1992, 104, 1270

1f Siemsen P. Livingston RC. Diederich F. Angew. Chem. Int. Ed.  2000,  39:  2632 ; Angew. Chem. 2000, 112, 2740

For recent examples, see:

2a Hilt G. Hengst C. Hess W. Eur. J. Org. Chem.  2008,  2293 

2b Hilt G. Hess W. Harms K. Synthesis  2008,  75 

2c Hilt G. Paul A. Harms K. J. Org. Chem.  2008,  73:  5187 

3a Hilt G. Hess W. Vogler T. Hengst C. J. Organomet. Chem.  2005,  690:  5170 

3b Hilt G. Vogler T. Hess W. Galbiati F. Chem. Commun.  2005,  1474 

4

The use of deuterated nitrobenzene led to the corresponding aniline and diazobenzene side products without loss of any deuterium labeling.

For the Cadiot-Chodkiewicz coupling, see:

5a Cadiot P. Chodkiewicz W. In Chemistry of Acetylenes   Viehe HG. Marcel Dekker; New York: 1969.  p.597 

5b Siemsen P. Felber B. In Handbook of C-H Transformations   Vol. 1:  Dyker G. 2005.  p.53-62  

5c Siemsen P. Felber B. In Handbook of C-H Transformations   Vol. 1:  Dyker G. 2005.  p.83-84  

5d Marino JP. Nguyen HN. J. Org. Chem.  2002,  67:  6841