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Synthesis of 1-acyl-1,2-dihydro-3H-pyrazol-3-ones VIA lewis acid-mediated rearrangement of 3-acyloxypyrazoles

✍ Scribed by Hiroshi Maruoka; Kenji Yamagata; Fumi Okabe; Yukihiko Tomioka

Publisher
Journal of Heterocyclic Chemistry
Year
2006
Tongue
English
Weight
140 KB
Volume
43
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

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The unusual formation of 1‐acyl‐1,2‐dihydro‐3__H__‐pyrazol‐3‐ones starting from 3‐acyloxypyrazoles by Fries‐type rearrangement is described. Under normal conditions, acylation of 2,4‐dihydro‐3__H__‐pyrazol‐3‐ones 1 and 2 with acid chlorides or anhydrides in the presence of triethylamine gave the corresponding 3‐acyloxypyrazoles 3a‐f and 4a‐f. Treatment of 3a‐c and 4a‐f with Lewis acid, e.g. titanium(IV) chloride and tin(IV) chloride, caused migration of acyl groups to afford the corresponding 1‐acyl‐1,2‐dihydro‐3__H__‐pyrazol‐3‐ones 5a‐c and 6a‐f. Interestingly, the reactions of 3‐acyloxypyrazoles 3e and 3f with tin(IV) chloride provided the corresponding tin(IV) complexes 8e and 8f.

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Synthesis of 1-methyl-, 4-nitro-, 4-amin
Synthesis of 1-methyl-, 4-nitro-, 4-amino-and 4-iodo-1,2-dihydro-3H-pyrazol-3-ones
✍ Y. C. Fiamegos; G. A. Pilidis; G. Varvounis 📂 Article 📅 2001 🏛 Journal of Heterocyclic Chemistry 🌐 English ⚖ 44 KB

## Abstract 4‐Aminopyrazole‐3‐ones **4b, e, f** were prepared from pyrazole‐3‐ones **1b‐d** in a four‐step reaction sequence. Reaction of the latter with methyl __p__‐toluenesulfonate gave 1‐methylpyrazol‐3‐ones **2b‐d**. Compounds **2b‐d** were treated with aqueous nitric acid to give 4‐nitropyraz