Resorcinarene-Based o-Biarylphosphines in Palladium-Catalysed Suzuki-Miyaura Cross-Coupling Reactions of Bulky Substrates

Two o-biarylphosphines, in which the arene ring remote from the phosphorus atom is part of a resorcin[4] arene cavitand, have been synthesised, characterised by X-ray diffraction and assessed in the cross-coupling reactions of bulky aryl chlorides with sterically hindered arylboronic acids. Only atropisomers with externally located P atoms were obtained. The resorcinarene ligand with the o-PCy2C6H4 substituent was found to be more efficient than the Buchwald analogue SPhos in catalysing coupling reactions, reacting around 1.4 times faster. Its superior performance has been attributed to the permanent exo positioning of the metal centre, which engenders steric interactions with two pentyl substituents and therefore facilitates the reductive elimination step.