Microwave-assisted, regioselective, Petasis olefination of unsymmetrical oxalates. Formation of pyruvate-based enol ethers and enamines

The Petasis olefination of unsymmetrical oxalates and oxalate monoesters/monoamides (tert-BuO2CC(O)X, where X = OR, NR2) is highly regioselective and provides pyruvate-based enol ether and enamine derivatives. The olefination step occurs under conventional thermal conditions, but is dramatically improved––shorter reaction times and higher yields––when promoted by microwave irradiation.