Selective arylation of 2-substituted indoles towards 1,2- and 2,3-functional indoles directed through the catalytic system

A simple palladium catalysed procedure for the synthesis of 1,2- and 2,3-disubstituted indoles is reported. It was found that the selectivity of the reaction, i.e. the N1- versus the C3-arylation of 2-functional indoles was mainly directed by electronic factors. Fine tuning of the reaction conditions and the right choice of the substrates allowed a full selective N1-(ArI, [Pd(OAc)2], PPh3) or C3 (ArBr, [Pd(OAc)2], AgBF4) arylation. Using only 1 mol% Pd-catalyst gave up to 92% isolated yield of expected compound.