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Bicyclic [ b ]‐heteroannulated pyridazine derivatives. 9 . cyclization reactions of 4,4‐dimethyl‐ and 4‐phenyltetrahydropyridazine‐3,6‐dione 3‐hydrazones with esters of keto dicarboxylic acids
Author(s) -
Wejroch Krystyna,
Lange Jerzy,
Kielak Anna,
KarolakWojciechowska Janina,
Sośnicki Jacek,
Jagodziński Tadeusz
Publication year - 2001
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.5570380411
Subject(s) - chemistry , tautomer , bicyclic molecule , yield (engineering) , medicinal chemistry , solvent , imine , molecule , enamine , organic chemistry , stereochemistry , catalysis , materials science , metallurgy
Bis(ethoxycarbonyl)alkylidene derivatives 4 and 5 of the respective title hydrazones were obtained in the reactions with diethyl oxomalonate, diethyl oxosuccinate, diethyl 2‐oxoglutarate, and diethyl oxalo‐propionate as mixtures of geometric isomers with high predominance of one of them. On heating at 160‐200° without any solvent or on refluxing in ethanol 4 cyclized to yield the corresponding pyri‐dazino[6, 1‐ c ]triazines 6 , whereas heating of 5 gave, depending on the chain length, the corresponding pyra‐zolylpyridazines 8b and 8d or the pyridazinylpyridazine 8c . X‐ray analysis was used to determine the structures of 6 and 8 ; the unit cell of 6c was found to accommodate 16 molecules representing four conforma‐tional varieties. The different behavior of 4 and 5 in the cyclization reactions was interpreted in terms of the tautomeric equilibrium which was shifted towards the enamine form in 4 , and towards the imine form, in 5 . Transmission of a long‐range chirality effect in 4d and 5a‐d manifested itself in the 1 H nmr spectra as the magnetic non‐equivalence of the CH 2 protons in one or both ester ethyl groups.