A facile, scalable preparation of 4-oxo-4,7-dihydrothieno[2,3-b]pyridine-5-carbonitriles

We report a new synthesis of thieno[2,3-b]pyridine-5-carbonitriles from 2-aminothiophene-3-carboxylate esters. The key step of the synthesis is a thermally promoted elimination/decarboxylation followed by nucleophilic cyclization to give 4-oxo-4,7-dihydrothieno[2,3-b]pyridine-5-carbonitriles. The reactions proceed in good yield and generally require no chromatographic purification. These compounds are easily transformed in two steps to 4-chloro-2-iodothieno[2,3-b]pyridine-5-carbonitriles which are key intermediates in the synthesis of various kinase inhibitors.