Group VIII carbamoyl complexes as catalysts for alkyne hydrocarboxylation and electrochemical proton reduction

Abstract

A series of group VIII carbamoyl complexes, [M(2-NHC(O)C5H4N)(CO)2(2-SC5H4N)] [where M = Fe, Ru and Os], was found to be efficient and regioselective catalysts for the intramolecular hydroxycarboxylation of α,ω-alkynoic acids, yielding exocyclic enol lactones for ring sizes up to 7 atoms, and endocyclic enol lactones for ring sizes up to 12 atoms. They also catalysed the regioselective intermolecular hydroxycarboxylation reaction between propargylic alcohol and carboxylic acids to form β-oxo-esters. These complexes could also function as electrocatalysts in proton reduction, and evaluation of their redox potentials revealed that the iron complex was much more efficient than the ruthenium or osmium analogues.