60021-28-5

A study of Pd-catalyzed arylation of arylboronic acids with triarylphosphines is presented. Various parameters of this transformation, such as the oxygen presence, choice of solvent, temperature, palladium source, bases and oxidants, were tested and the optimal conditions of the aryl transfer were determined. The effect of electron-withdrawing and electron-donating substituents on the aryl groups of both reactants was also investigated. The unusual transfer of the acetate group from Pd(OAc)2 to p-nitrophenylboronic acid in the presence of PAr3 is reported. A plausible mechanism of the Pd-catalyzed aryl group transfer from PAr3 to the arylboronic acid is proposed.

The palladium-catalysed direct heteroarylation of the pyridyl-containing substrates, 2-(5-bromothiophen-2-yl)pyridine and 8-bromoquinoline, proceeds in moderate to high yields with a variety of heteroarenes in the presence of 1-2 mol% of a palladium catalyst. This approach allows the access to polyheteroaromatics which are interesting building blocks as (NC)-chelate ligands. The reaction proceeds regioselectively at the C5 position of thiophenes, thiazoles, furans or pyrroles and tolerates various substituents such as formyl, acetyl, ester, nitrile or chloro on the heteroarene. Therefore, this method allows a straightforward modulation of the electron density distribution on such derivatives.

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