Microwave-assisted ruthenium catalysed high-pressure synthesis of N-heterocyclic compounds

The four-component reaction of an alpha,beta-unsaturated aldehyde and a primary amine with carbon monoxide and ethylene in the presence of Ru-3(CO)(12) as a precatalyst yielding mixtures of chiral gamma-lactams and substituted pyrrole derivatives has, for the first time, been performed under microwave irradiation. It has also been possible to collect samples of the reaction mixture without releasing the applied pressure of the gas phase, and therefore, monitoring of substrates, intermediates, and products during the synthetic procedure became accessible. Compared to classical thermally induced reactions, microwave irradiation leads to a significant shortening of reaction times, and requires lower partial pressures of carbon monoxide and ethylene and a lower precatalyst loading. [GRAPHICS] .