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Catalyst-free synthesis of symmetrical diaryl ketones from arylstannanes and oxalyl chloride
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1  INQUISUR, Departamento de Química, Universidad Nacional del Sur, Avda. Alem 1253, (8000) Bahía Blanca, Argentina

Abstract: Oxalyl chloride (1) has been known to be involved as C1 synthon for ketone synthesis,1 as an alternative route for carbonylation with CO gas. Given the importance of ketones in pharmaceutical and industrial applications,there is a permanent interest in finding new ways for their synthesis. Based on the exceptional leaving group ability of the trialkylstannyl group in EAS, we have recently proposed efficient catalyst-free and regioselective synthesis of unsymmetrical ketones using different acyl chlorides.2 Driven by these results we initiated studies on the reaction of arylstannanes with 1. Now, we describe a novel regioselective synthesis of symmetrical diaryl ketones using 1 as C1 carbonyl synthon, under catalyst-free conditions. These results are significant from the point of view of its simplicity, the wide range of synthetically3 or commercially available arylstannanes and the associated convenience in the utilization of 1 as carbonyl synthon, instead of specific acyl chlorides. All the reactions studied went, exclusively, through an ipso-substitution independently whether the directing influences of the aryl substituents and the trialkylstannyl group are either matched or mismatched. We suggest a mechanism by which 1 acts as C1 synthon on these reactions. In addition, a special work up is proposed in order to recover the trialkyltin chlorides generated. 1 Rao, M. L. N.; Venkatesh, V.; Dasgupta, P. Tetrahedron Lett. 2010, 51, 4975-4980. 2Lo Fiego, M. J.; Silbestri, G. F.; Lockhart, M. T.; Chopa, A. B. J. Org. Chem. 2011, 76, 1707-1714. 3 Silbestri, G. F.; Lo Fiego, M. J.; Lockhart, M. T.; Chopa, A. B. J. Organometal. Chem. 2010, 695, 2578-2585.
Keywords: Arylstannanes, Oxalyl chloride, Symmetrical diaryl ketones