Regioselective coupling of benzyl chlorides with allyl and allenyl boronates catalysed by a bidentate phosphine ligand/palladium catalyst

Abstract

A palladium-catalysed aromative benzylic allylation and allenylation of benzyl chlorides with allyl and allenyl pinacolborates is described for the first time. The reactions proceed smoothly in the presence of a bidentate phosphine ligand to afford normal cross-coupling products in good yields. This novel synthetic procedure exhibits good tolerance for various electron-withdrawing and -donating functional groups linked to aromatic rings and is also well tolerant of sensitive functional groups such as NO₂, CF₃, CN, and COOMe. The utilisation of a bidentate ligand and heating are essential to transformation. The DFT calculation results reveal that wide-bite-angle bidentate ligands are beneficial to the formation of an η¹-benzyl-η¹-allylpalladium intermediate and that the normal coupling is thermodynamically favourable.