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A convenient synthesis of pyrazolidine and 3-amino-6,7-dihydro-1H,5H-pyrazolo[1,2-a] pyrazol-1-one

✍ Scribed by Eric E. Boros; Frédéric Bouvier; Sab Randhawa; Michael H. Rabinowitz

Publisher
Journal of Heterocyclic Chemistry
Year
2001
Tongue
English
Weight
36 KB
Volume
38
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

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.

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Synthesis of 6-(2-hydroxybenzoyl)pyrazol
Synthesis of 6-(2-hydroxybenzoyl)pyrazolo[1,5-a]pyrimidines by reaction of 5-amino-1h-pyrazoles and 3-formylchromone
✍ Jairo Quiroga; Diana Mejía; Braulio Insuasty; Rodrigo Abonía; Manuel Nogueras; A 📂 Article 📅 2002 🏛 Journal of Heterocyclic Chemistry 🌐 English ⚖ 41 KB

## Abstract Reaction of 3‐formylchromone (**1**) with 5‐amino‐1__H__‐pyrazoles (**2**) in ethanol, afforded 6‐(2‐hydroxy‐benzoyl)pyrazolo[1,5‐__a__]pyrimidines (**3a‐g**) in good yields. The structures and the regiospecificity of the reaction were established by nmr measurements and X‐ray analysis,