Diazadiene-stabilized palladacyclopent-2-enes and the catalytic addition of various allylic systems to dimethyl acetylenedicarboxylate

Article abstract of DOI:10.1016/0022-328X(91)86318-K

With diazadiene (dad = RN=CR'-CR'=NR) as co-ligand the palladacyclopent-2-enes 3 formed by direct coupling of a 1-alkene and an acetylenedicarboxylic acid ester can be trapped.With activated 1-alkenes such as allylic alcohols the reaction becomes catalytic, yielding linear addition-products 4-11 from two molecules of the alkene and one molecule of the alkyne; no simple reductive elimination occurs, but instead elimination of one mole of water takes place.Allylic esters react analogously but a cyclic 1:2-addition-product 15 (also formed by loss of the leaving group) is the main product.The elimination of the leaving group is probably the driving force of the reaction, since only β-H-transfer that make elimination possible are observed.