Alkoxy- and amidocarbonylation of functionalised aryl and heteroaryl halides catalysed by a Bedford palladacycle and dppf: a comparison with the primary Pd(ii) precursors (PhCN)2PdCl2 and Pd(OAc)2

Abstract

The versatility of a Bedford-type palladacycle 1, namely [{Pd(µ-Cl){κ²-P,C-P(OC₆H₂-2,4-^tBu₂)(OC₆H₃-2,4-tBu₂)₂}}₂], as a primary Pd source, in combination with the ligand bis-1,1′-(diphenylphosphino)ferrocene (dppf) has been established in carbonylation reactions of aryl and heteroaryl bromides with methanol, piperidine and related nucleophiles. Palladacycle 1 has been compared with other primary Pd sources, e.g. (PhCN)₂PdCl₂ and Pd(OAc)₂. The efficacy of the carbonylation processes appear to be linked to the [Pd] concentration, substrate : catalyst ratio, CO pressure and reaction temperature. In amidocarbonylation, double carbonylation is observed for certain organohalides. In the case of 2,5-dibromopyridine, regioselective amination (Hartwig–Buchwald type) also occurs as a side-reaction.