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Synthesis of methyl 4-aryl-6-methyl-4,7-dihydro-1H-pyrazolo-[3,4-b]pyridine-5-carboxylates from methyl 4-aryl-6-methyl-2-oxo-1,2,3,4-tetrahydropyridine-5-carboxylates

1996; Issue: 9 Linguagem: Inglês

10.1039/p19960000947

2050-8255

Yamila Verdecia, Margarita Suárez, Alhmed Morales, Elena Rodríguez, Estael Ochoa, Leandro González, Nazario Martı́n, M. QUINTEIRO, Carlos Seoane, J. L. SOTO,

Phenothiazines and Benzothiazines Synthesis and Activities

Novel methyl 4,7-dihydro-1H-pyrazolo[3,4-b]pyridine-5-carboxylates 3a–e have been prepared in a two step procedure from the readily available 2-oxo-1,2,3,4-tetrahydropyridine-5-carboxylates 1a–e by treatment with the Vilsmeier–Haack reagent. Further treatment of the novel o-chloroformyl substituted methyl 1,4-dihydropyridine-5-carboxylates 2a–e with hydrazine affords the corresponding methyl pyrazolo[3,4-b]pyridine-5-carboxylates in good yields. Semiempirical calculations reveal a favoured geometry with a boat conformation in the dihydropyridine system and a planar pyrazole ring.