Contribution of microwaves in organic synthesis:: statement of a methodology for the microwave-induced preparation of benzofuran-2(3H)-one and its comparison with classical heating

The intramolecular cyclisation of 2-hydroxyphenylacetic acid 1 into coumaran-2-one 2 was studied under both microwave irradiation and classical heating for comparison purposes. The use of a monomode oven allowed an accurate consideration of the temperature distribution in the microwave reaction vessel, which revealed a very strong and unexpected thermal heterogeneity. The reaction was facilitated by the presence of a trace of toluene-p-sulfonic acid, the catalytic role of which is demonstrated.