Palladium-Catalyzed Intermolecular α-Arylation of Zinc Amide Enolates under Mild Conditions.

The intermolecular α-arylation and vinylation of amides by palladium-catalyzed coupling of aryl\nbromides and vinyl bromides with zinc enolates of amides is reported. Reactions of three different types of\nzinc enolates have been developed. The reactions of aryl halides occur in high yields with isolated\nReformatsky reagents generated from α-bromo amides, with Reformatsky reagents generated in situ from\nα-bromo amides, and with zinc enolates generated by quenching lithium enolates of amides with zinc\nchloride. This use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of amide\narylation. The reactions occur at room temperature or 70 °C with bromoarenes containing cyano, nitro,\nester, keto, fluoro, hydroxyl, or amino functionality and with bromopyridines. Moreover, the reaction has\nbeen developed with morpholine amides, the products of which are precursors to ketones and aldehydes.\nThe arylation of zinc enolates of amides was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-<i>tert</i>-butylphosphine (Q-phos) or the highly reactive, dimeric, Pd(I) complex {[P(<i>t-</i>Bu)<sub>3</sub>]PdBr}<sub>2</sub>.