Rh(III)-CatalyzedDecarboxylative Coupling of Acrylic Acids with Unsaturated Oxime Esters:Carboxylic Acids Serve as Traceless Activators

摘要

α,β-Unsaturated carboxylic acids undergo Rh(III)-catalyzed decarboxylative coupling with α,β-unsaturated O-pivaloyl oximes to provide substituted pyridines in good yield. The carboxylic acid, which is removed by decarboxylation, serves as a traceless activating group, giving 5-substituted pyridines with very high levels of regioselectivity. Mechanistic studies rule out a picolinic acid intermediate, and an isolable rhodium complex sheds further light on the reaction mechanism.