An electrochemical alternative strategy to the synthesis of β-lactams - Part 3 [1]. Room-temperature ionic liquids vs molecular organic solvents

摘要

Electrochemically induced cyclization of bromoamides to β-lactams has been achieved in room-temperature ionic liquids (RTILs). The use of volatile, organic solvents (VOCs) and of supportingelectrolytes may be avoided. Proton exchange reaction between amide substrates and suitable electrogenerated bases gives rise to a C{sub}4 carbanion which undergoes cyclization to β-lactam via intramolecular nucleophilic substitution (C3-C4 bond formation). β-Lactams have been isolated in good to elevated yields. The "non innocent" nature of the RTILs (imidazolium-based salts) is considered. Proton exchange reaction between N-dialkylimidazolium cation and EGB yielding N-heterocyclic carbene is discussed.