Synthesis of 5-Amino-2-(2-(1-(4-(1,3-dioxoisoindolin-2-yl)phenyl)ethylidene)-hydrazinyl)-7-substituted-7H-pyrano[2,3-d]thiazole-6-carbonitrile (15a, b) and 2-(2-(1-(4-(1,3-dioxoisoindolin-2-yl)phenyl)ethylidene)hydrazinyl)-5-oxo-7-substituted-4,5-dihydrothiazolo[4,5-b]pyridine-6-carbonitrile (16a, b)