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A divergent synthesis of dihydropyridazinones, N-substituted dihydropyrazoles, and O-substituted pyrazoles

✍ Scribed by Eiichi Masumoto; Hiroshi Maruoka; Fumi Okabe; Sho Nishida; Yuki Yoshimura; Toshihiro Fujioka; Kenji Yamagata

Publisher
Journal of Heterocyclic Chemistry
Year
2010
Tongue
English
Weight
168 KB
Volume
48
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

Dihydropyridazinones 4a, 4b, N‐substituted dihydropyrazoles 5b, 5c, 5d, and O‐substituted pyrazoles 6a, 6b, 6c, 6d have been synthesized starting from spirocyclopropanepyrazole derivative 2. Treatment of 2 with α‐chloro esters, e.g., methyl chloroacetate, ethyl chloroacetate, isopropyl chloroacetate, and tert‐butyl chloroacetate, in potassium carbonate/sodium iodide system caused ring opening and subsequent C‐ or N‐attack nucleophilic substitution to give the corresponding dihydropyridazinones 4a, 4b and N‐substituted dihydropyrazoles 5b, 5c, 5d. On the other hand, in the absence of sodium iodide, O‐substituted pyrazoles 6a, 6b, 6c, 6d were obtained from 2 via an O‐attack nucleophilic substitution. J. Heterocyclic Chem., 2011.

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