Abstract
The activation of C–H bonds through catalytic reactions using transition metals is an important challenge in organic chemistry in which the intermediates are related to those produced in the classical cross-coupling reactions. As part of our research program devoted to the development of metal-catalyzed reactions using indium organometallics, a protocol for the C–H activation and C–C coupling of 2-arylpyridines with triorganoindium reagents under Rh(I) catalysis is reported. Under the optimized conditions, we found that Me3In and Ar3In reagents reacted with 2-arylpyridines and related compounds in the presence of Rh(PPh3)3Cl, in PhCl/THF (9:1), at 120 °C for 48 h, to afford the ortho-coupling products in moderate to good yields. The nitrogen atom in the pyridine ring acts as a directing group to assist the functionalization at the ortho position of the aryl group forming a new C–C bond at this position.
Highlights
Since our discovery [1,2], the palladium catalyzed cross-coupling reaction of indium(III)organometallics has been established as a useful tool in organic synthesis [3,4]
A heteroatom acts as directing group for the C–H activation through coordination with the metal center to form a metallacycle that reacts with the organometallic to afford the coupling product (Scheme 1) [20,21]
Our research started by testing the reaction of triorganoindium reagents with Our research started by testing the reaction of triorganoindium reagents with 2-(p-tolyl)pyridine
Summary
Since our discovery [1,2], the palladium catalyzed cross-coupling reaction of indium(III)organometallics has been established as a useful tool in organic synthesis [3,4]. A heteroatom acts as directing group for the C–H activation through coordination with the metal center to form a metallacycle that reacts with the organometallic to afford the coupling product (Scheme 1) [20,21]. In this field, Oi et al reported the Rh(I)-catalyzed ortho-arylation of 2-phenylpyridines with organotin compounds [22], a catalytic system used in related reactions using boronic acids [23]. Despite the novelty of this methodology, and to the best of our knowledge, organoindium compounds have not been applied as carbon nucleophiles
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