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Tautomeric structure of 1‐methyldihydropyridazino‐[3,4‐ b ]quinoxalines in solution
Author(s) -
Kurasawa Yoshihisa,
Takada Atsushi,
Kim Ho Sik,
Okamoto Yoshihisa
Publication year - 1993
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.5570300633
Subject(s) - chemistry , quinoxaline , tautomer , trifluoroacetic acid , dimethyl sulfoxide , sulfoxide , medicinal chemistry , base (topology) , organic chemistry , mathematical analysis , mathematics
The reaction of 6‐chloro‐2‐(1‐methylhydrazino)quinoxaline 4‐oxide 1 with ethyl 2‐ethoxymethylene‐2‐cyano‐acetate or ethoxymethylenemalononitrile gave 6‐chloro‐2‐[2‐(2‐cyano‐2‐ethoxycarbonylvinyl)‐1‐methylhy‐drazino]quinoxaline 4‐oxide 3a or 6‐chloro‐2‐[2‐(2,2‐dicyanovinyl)‐1‐methylhydrazino]quinoxaline 3b , respectively. The reaction of 3a with a base afforded 7‐chloro‐1‐methyl‐1,5‐dihydropyridazino[3,4‐ b ]quinoxaline 4 . From the NOE spectral data, the 1‐methyldihydropyridazino[3,4‐ b ]quinoxalines 2a, 2b and 4 were found to exist as the 1,5‐dihydro form in a dimethyl sulfoxide or trifluoroacetic acid/dimethyl sulfoxide solution.