Ring switching tricomponent synthesis of pyrano[2,3-b]pyridine multifunctional derivatives

New 3-acylamino-7-hydroxy-5-methyl-2-oxo-2H-pyrano[2,3-b]pyridine-6-carbonitriles were synthesized via a tricomponent condensation of 3-cyano-4-methyl-1,2,5,6-tetrahydropyridine-2,6-dione, triethyl orthoformate and N-acylglycines under the Erlenmeyer–Plochl reaction conditions. According to X-ray data, in the solid phase they exist as hydroxypyridine tautomer form.