Direct Synthesis of Benzoylpyridines from Chloropyridines via a Palladium-Carbene Catalyzed Carbonylative Suzuki Cross-Coupling Reaction

Abstract

The use of N-heterocyclic carbene-type ligands with palladium catalysts allows the activation of chloropyridines and chloroquinoline towards carbonylative cross-coupling with phenylboronic acid for the synthesis of unsymmetrical biaryl ketones.

palladium - N-heterocyclic carbene ligand - pyridyl chloride

References

For reviews, see:

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<A NAME="RG13803ST-6">6</A> As our investigations neared completion, palladium-imidazolium carbonylative coupling of more actived aryl diazonium ions with aryl boronic acids was reported: Andrus MB. Ma Y. Zang Y. Song C. Tetrahedron Lett.  2002,  43:  9137 

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<A NAME="RG13803ST-9">9</A>

In a number of coupling reactions of aryl chlorides, it was found that a 1:1 Pd-ligand ratio (ligand = N-heterocyclic carbene, phosphine, …) led to optimum reaction rates (see ref. 2 and ref. 5b for N-heterocyclic carbene ligands).

<A NAME="RG13803ST-10">10</A>

TOF: turnover frequencies defined as the number of moles of substrate transformed per mole of catalyst and per hour calculated after one hour of reaction.