Highly Modular Synthesis of 1,2-Diketones via Multicomponent Coupling Reactions of Isocyanides as CO Equivalents

A one-pot, four-component Pd-catalyzed coupling has been developed for the synthesis of unsymmetrical 1,2-diketones from aryl halides and alkyl zincs employing tert-butyl isocyanide as a CO source. The intermediate 1,2-diketones have been elaborated to quinoxalines. Mechanistic studies help to rationalize the high selectivity for the bis- vs monoinsertion product.