Synthesis 2005(15): 2619-2622  
DOI: 10.1055/s-2005-872163
SPECIALTOPIC
© Georg Thieme Verlag Stuttgart · New York

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

Juan L. Oller-López, Araceli G. Campaña, Juan M. Cuerva*, J. Enrique Oltra*
Department of Organic Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, 18071 Granada, Spain
Fax: +34(958)248437; e-Mail: joltra@ugr.es; e-Mail: jmcuerva@ugr.es;
Further Information

Publication History

Received 7 July 2005
Publication Date:
12 August 2005 (online)

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.

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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.