Kinetic study on the anelation of heterocycles.2.pyrido[2,3-b]pyrazine and pyrido[3,4-b]pyrazine derivatives synthesized by the hinsberg reaction

Autor: María Inés Abasolo, Fabián Atlasovich, Beatriz M. Fernández, Carlos H. Gaozza, D. E. Bianchi
Rok vydání: 1990
Předmět:
Zdroj: Journal of Heterocyclic Chemistry. 27:157-162
ISSN: 1943-5193
0022-152X
Popis: The regioselective synthesis of pyrido[2,3-b]- and [3,4-b]pyrazine derivatives II by the Hinsberg reaction is reported starting from 2,3 and 3,4-diaminopyridine and excess of pyruvic acid or ethyl pyruvate as reactants. Good yields (higher than 90%) were obtained for pyrido[2,3-b]pyrazine derivatives at room temperature using anhydrous methanol and chloroform as solvents which promote regioselective reactions to give 2-methylpyrido[2,3-b]pyrazin-3(4H)-one (3a) and 3-methylpyrido[2,3-b]pyrazin-2(1H)-one (4a) respectively. On the other hand, when the same procedure was applied to 3,4-diaminopyridine results were not so encouraging for the formation of 2-methylpyrido[3,4-b]pyrazin-3(4H)-one (3b) and 3-methylpyrido[3,4-b]-pyrazin-2(1H)one (4b). Kinetic studies were performed in aqueous buffers (pH -0.89 to 11.5) and different organic solvents trying to improve yields and achieve regioselectivity. The course of the reactions was followed by uv spectrophotometry being those with ethyl pyruvate 2 to 800 times faster than with pyruvic acid. This investigation involves the kinetics and mechanism of this reaction studying its factibility when π-deficient substrates are used and its regioselectivity according to the position of the pyridine nitrogen atom.
Databáze: OpenAIRE
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