Pd‐catalyzed anti‐Markovnikov Hydrocarboxylation of Vinylarenes with Formic Acid Free of Auxiliary Additive

Utilization of formic acid directly as a carboxylic reagent with pre-decomposition into CO and H2O was an attractive and promising protocol to scaffold carboxylic acids. Herein, with BINAP-modified Pd(OAc)2 catalytic system free of Ac2O or DCC, the hydrocarboxylation of styrene (and its derivatives) with FA predominantly following anti-Markovnikov’s rule was fulfilled successfully to afford the linear carboxylic acids in the isolated yields of 60~88%. The external CO in catalytic amount was introduced as a co-ligand to work together with BINAP to adjust the behavior of Pd-catalyst. The in situ FT-IR and 1H NMR analyses convince that this one-step hydrocarboxylation goes by palladium-hydride (PdII-H) mechanism.