Catalyst-free reactions under solvent-free conditions: microwave-assisted synthesis of heterocyclic hydrazones below the melting points of neat reactants

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones, 1-3, with a variety of aromatic and heteroaromatic hydrazines, 4, is remarkably accelerated upo n irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent thus providing an environmentally friendly route to several heterocyclic hydrazones.