Regioselective Palladium(II)-Catalyzed Synthesis of Five- or Seven-Membered Ring Lactones and Five-, Six- or Seven-Membered Ring Lactams by Cyclocarbonylation Methodology

Abstract

2-Allylphenols react with carbon monoxide and hydrogen in the presence of catalytic quantities of a cationic palladium(II) complex [(PCy3)2Pd(H)(H2O)]+BF4- or palladium acetate and 1,4-bis(diphenylphosphino)butane, affording five- or seven-membered ring lactones (bicyclic, tricyclic, and pentacyclic) as the principal products, often in excellent yields. Use of 2-aminostyrenes as reactants and catalytic quantities of palladium acetate and tricyclohexylphosphine, affords five-membered ring lactams in high yield and selectivity. Bicyclic and tricyclic heterocycles containing six-membered ring lactams can be synthesized from the reaction of 2-allylanilines with CO/H2 using the catalytic system Pd(OAc)2/PPh3, while use of 1,4-bis(diphenylphosphino)butane instead of PPh3 in the latter process results in the formation of the seven-membered lactams benzazepinones in good yield. The regiochemical control depends on the nature of the palladium catalyst, the relative pressures of the gases, and the solvent.