Facile Buchwald–Hartwig coupling of sterically encumbered substrates effected by PNP ligands
The diphosphinoamine ligands [(Ph2P)2N(Ar); 1 (Ar = C6H5), 2 (Ar = 2,6-iPr2C6H3)] were effectively utilized in Buchwald–Hartwig coupling of a range of sterically demanding substrates. The reaction was carried out using conventional and microwave routes and the latter reduces the reaction time from 3 d to 15–30 min. A broad substrate scope was achieved in this protocol and most of the coupling products are isolated on a mutligram scale. DFT calculations were carried out to elucidate the reaction mechanism.