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Synthesis and properties of iso viagra . A 2‐methyl‐2 H ‐pyrazolo[4,3‐ d ]pyrirnidin‐7‐one isomer of viagra ®
Author(s) -
ElAbadelah Mustafa M.,
Sabri Salim S.,
Khanfar Monther A.,
Yasin Hani A.,
Voelter Wolfgang
Publication year - 2002
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.5570390532
Subject(s) - chemistry , synthon , nitration , methylhydrazine , derivative (finance) , amide , medicinal chemistry , stereochemistry , organic chemistry , financial economics , economics , phenylhydrazine
The synthesis and spectral properties (ir, ms, nmr) of a substituted 2‐methyl‐2 H ‐pyrazolo[4,3‐ d ]‐pyrimidin‐7‐one ( 3 ), an isomer of Viagra ® , are described. The key synthon, 4‐amino‐1‐methyl‐5‐propyl‐3‐pyrazolecarboxamide ( 7 ), is prepared via the reaction of ethyl 2,4‐dioxoheptanoate with methylhydrazine, followed by cyclization, nitration, amidation, and nitro group reduction. Interaction of 7 with 2‐ethoxyben‐zoyl chloride yielded the respective bis‐amide ( 8 ) which was cyclized in polyphosphoric acid to the corresponding pyrazolo[4,3‐ d ]pyrimidin‐7‐one derivative 9 . Chlorosulfonylation of 9 , and subsequent treatment with 1‐methylpiperazine furnished iso Viagra ( 3 ).