Microwave irradiation as a green alternative to phase transfer catalysis: Solid-liquid phase alkylation of active methylene containing substrates under solvent-free conditions

An ecofriendly, microwave (MW) promoted and solventless method is described for the alkylation of diethyl malonate, ethyl acetoacetate and ethyl cyanoacetate by a variety of alkyl halides in the presence of K2CO3. In the solid-liquid phase alkylation of active methylene containing substrates, it seems to be of general value that the phase-transfer catalyst, that is an onium salt in the present case, can be omitted and substituted by MW irradiation promoting the formation of the potassium salt of the substrate and its transfer to the organic phase. In certain cases, the use of triethylbenzyl-ammonium chloride led to the formation of by-products under the conditions (similar to 160 degrees C/similar to 12 bar) applied.