Ethyl 2-(Benzimidazol-2-yl)-3-(dimethylamino)acrylate ( 3 ) has been used as starting material to develop a mild, efficient solvent-free preparation of ethyl 1-oxo (or thioxo)-1,2dihydro-pyrimido[1,6-a ]benzimidazol-4-carboxylates 6 (X = O, S) from a variety of isocyanates 4b-d and isothiocyanates 4a , e,f , in yields ranging from 52 to 82%. The synthesis of the starting benzimidazole 3 (82% yield) without solvent, assisted by focused microwave irradiation, is also reported.
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