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A Divergent Synthesis of Spiropyrazole Derivatives Containing Iminolactone and/or Cyclic Imide Moiety
Author(s) -
Masumoto Eiichi,
Maruoka Hiroshi,
Okabe Fumi,
Fujioka Toshihiro,
Yamagata Kenji
Publication year - 2015
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.1946
Subject(s) - chemistry , moiety , acetic acid , pyrazole , acetic anhydride , imide , sodium hydride , chloroform , derivative (finance) , medicinal chemistry , solvent , hydrolysis , organic chemistry , catalysis , financial economics , economics
An approach to spiropyrazole derivatives containing iminolactone and/or cyclic imide moiety starting from 1 H ‐pyrazole‐4‐acetic acid derivative is described. Hydrolysis of C ‐cyanomethylated 1 H ‐pyrazole‐4‐acetic acid methyl ester ( 1 ), which was easily prepared from 1 H ‐pyrazole‐4‐acetic acid derivative by a C ‐cyanomethylation, led to the C ‐cyanomethylated 1 H ‐pyrazole‐4‐acetic acid ( 2 ). Compound 2 was reacted with ethanol in the presence of tin(IV) chloride in refluxing chloroform to give the key intermediate ethyl imidate ( 3 ). Sodium hydride‐assisted lactonization of 3 in N,N ‐dimethylformamide afforded the spiropyrazole derivative containing iminolactone moiety ( 4 ). On the other hand, thermal treatment of 3 with sodium acetate in the absence of solvent caused another intramolecular cyclization to yield the spiropyrazole derivative containing cyclic imide moiety ( 6 ).