Palladium-catalysed enantioselective hydroaryloxycarbonylation of styrenes by 4-substituted phenols

Palladium-catalysed hydroaryloxycarbonylation of a set of styrenes was performed under carbon monoxide atmosphere towards the corresponding propanoic acid aryl esters. The reaction conditions were optimized and several phosphine ligands (achiral mono- and bidentate, chiral (enantiopure) bidentate) were investigated in Pd-catalyst systems generated in situ. In general, the application of mono- and diphosphines favours the formation of branched and linear regioisomers, respectively. Carrying out the reaction in enantioselective fashion, the DIOP modified catalyst proved to be the most efficient one among the chiral ligands studied. The substituent effect on the regio- and enantioselectivity was also investigated regarding both the substrate (styrene) and the O-nucleophile (phenol) with Pd-DIOP system. Simultaneous modifications of substituents of the 'reactants' were also carried out. The preference of the linear ester regioisomer and low enantiomeric excesses were obtained. (C) 2017 Published by Elsevier B.V.