Influence of the catalytic conditions on the selectivity of the Pd-catalyzed Heck arylation of acrolein derivatives

The Heck arylation of acrolein with a variety of condensed aryl and heteroaryl halides is described. Depending on the substrate, up to 87% isolated yield to the expected aldehydes was achieved. When the reaction was run on diethylacetal acrolein, the choice of catalytic system dramatically affected the selectivity of the reaction: the catalyst system based on Herrmann's palladacycle complex gave mainly saturated esters 2, whereas Cacchi's conditions led to the formation of α,β-unsaturated aldehydes 1.