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Reaction products of dialkyl acetylenedicarboxylates with 2,3‐diaminopyridine
Author(s) -
Seki Taketsugu,
Iwanami Yasuo
Publication year - 1995
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570320367
Subject(s) - chemistry , enamine , side chain , ring (chemistry) , derivative (finance) , condensation , medicinal chemistry , ethanol , chelation , stereochemistry , chain (unit) , organic chemistry , catalysis , physics , astronomy , financial economics , economics , thermodynamics , polymer
The condensation of dialkyl acetylenedicarboxylates 1 and 2 with 2,3‐diaminopyridine (3) or its 5‐bromo derivative 4 in ethanol gave pyrido[2,3‐ b ]pyrazinones with a common side chain ‐CH 2 ‐COOR at their 2‐position, 5–7 , but in the presence of sulfuric acid the reaction afforded their isomers with the same side chain at the 3‐position, 8–10 . All of the products were shown to exist in enamine form, in which a ring double bond has been displaced onto their side chain (CHCOOR) being facilitated by an internal chelation as demonstrated by their ir and 1 H nmr spectra.
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