Facile access to 6-substituted 1,4,5,7-tetrahydropyrrolo[3,4-b]-pyridines via hantzsch type dimethyl 4-aryl-2-formyl-6-methyl-1,4-dihydropyridine-3,5-dicarboxylates

Efficient assembly of 6‐substituted 4‐aryl‐5‐oxo‐1,4,5,7‐tetrahydropyrrolo[3,4‐b]pyridines (7a‐f) is described according to a Hantzsch type reaction from formyl‐ester 4 by imination, borohydride reduction and intramolecular thermal amino‐ester cyclization. The starting compound 4 was prepared in three steps from the readily available formyl derivative 1, methyl 4,4‐dimethoxy‐3‐oxobutanoate and methyl 3‐aminocrotonate.