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A convenient synthesis of pyrazolidine and 3‐amino‐6,7‐dihydro‐1H,5H‐pyrazolo[1,2‐a] pyrazol‐1‐one
Author(s) -
Boros Eric E.,
Bouvier Frédéric,
Randhawa Sab,
Rabinowitz Michael H.
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.5570380310
Subject(s) - chemistry , hydrochloride , yield (engineering) , ring (chemistry) , distillation , chromatography , combinatorial chemistry , organic chemistry , materials science , metallurgy
A convenient four‐step synthesis of the aminobicyclopyrazolone hydrochloride 1 ·HC1 was achieved starting from di‐ tert ‐butyl hydrazodiformate (8) . The route entails cyclization of 8 with 1,3‐dibromopropane under phase transfer conditions followed by deprotection of 1,2‐di‐ tert ‐butoxycarbonylpyrazolidine (9) to give pyrazolidine hydrochloride ( 2 ·HC1). Cyanoacetylation of the latter and ring closure of the resulting cyanoacetyl pyrazolidine (7) gave 1·HC1. This novel synthesis circumvents distillation of pyrazolidine (2) and flash chromatography to provide the hydrochloride of 1 in 35–46% overall yields compared to 6% yield for the patent procedure.