Dual reactivity of O-α-allenyl esters under palladium(0) catalysis: From carbopalladation/allylic alkylation domino sequence to decarboxylative allenylation

In a mechanistically-oriented study, O-α-allenyl esters have been evaluated as potential substrates for Pd-catalyzed carbopalladation/allylic alkylation domino sequences and decarboxylative allenylation reactions. The domino sequence turned out to be feasible only with electron-deficient aryl iodides, thereby showing a narrower potential than that previously observed with the malonamide-based series. The decarboxylative allenylation of O-α-allenyl esters was also tested and turned out to be practicable with β-ketoester-based substrates and using specific basic conditions. Plausible reaction mechanisms are proposed to account for the observed reactivities.