two: α‐Diazocarbonyl compounds display a diverse pattern of reactivity upon palladium‐catalyzed reaction with esters. Esters bearing an alkynyl group on the carbonyl carbon atom lead to two different CC bonds at the same carbon atom in a single operation through decarboxylation and migratory insertion, whereas aromatic and benzylic acid derivatives afford aromatic and benzylic esters bearing an O‐substituted
suggest that the reaction using a compact and basic mono-phosphorus complex proceeds by the Chalk–Harrod mechanism involving the reductive elimination from an (η3-allyl)(silyl)palladium(II). A poor electron-donating mono-phosphorus ligand such as P(OPh)3 destabilizes a Pd(II) species and promotes direct reductive elimination to give the 1,4-Z product. On the other hand, a compact and electron-donating phosphorus