A ubiquitous accelerating effect of chlorobenzene (PhCl) was observed unexpectedly in the Pd-catalyzed cascade Sonogashira–hydroarylation reaction. This new type of carbon–carbon bond forming cross-coupling reaction was efficiently catalysed by Pd2(dba)3 in the presence of a catalytic amount of PhCl, which provides a facile and direct approach to the synthesis of trisubstituted olefins.
