Vaska’s complex [IrCl(CO)(PPh3)2] efficiently catalyzes the intramolecular carbonylative [2+2+1] cycloaddition of allenynes. A dimethyl substituent on the allene terminus and a low partial pressure of carbon monoxide realize the selective engagement of the internal Ï-bond of allene.
Wilkinson’s catalyst [RhCl(PPh3)3] catalyzed a cycloisomerization of allenynes which possess geminal methyls on the allene terminus and an intramolecular ene-type reaction proceeded to give various cross-conjugated trienes. Thermal Diels-Alder reaction of the obtained triene was examined to give a bicyclic compound in a high yield.