Aromatic Carbonyl Compound Reduction and Pinacol Coupling Processes Mediated by Titanocene(III)/Zn in Water

Abstract

A novel procedure for the reduction and pinacol coupling of aromatic aldehydes and ketones mediated by titanocene(III)/Zn in water is described. The titanocene-catalyzed version in sea water proved to be especially convenient for the reduction of aryl ketones. Mechanistically, the reaction presumably proceeds via free-radical chemistry.

Key words

green-chemistry - radical reactions - titanium - water - zinc

References

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11

In the absence of Zn, the red-brown color of a Cp₂TiCl₂ solution in deoxygenated water became only yellow after ten hours stirring. When we added Zn, however, the color of the solution immediately changed to green and, after a couple of minutes, to blue.

16

Cp₂TiCl₂ is not too expensive (10 g = 28.50, Aldrich catalogue), but Zn dust is considerably cheaper (1 Kg = 21.70).

20

Mediterranean Sea water was taken from ‘Las Acacias’ beach, Málaga (Spain), in August 2004.