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Ring transformation of spirocyclopropanepyrazoles into pyrano[2,3-c]pyrazoles

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

Publisher
Journal of Heterocyclic Chemistry
Year
2009
Tongue
English
Weight
109 KB
Volume
46
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

magnified image

An approach to pyrano[2,3‐c]pyrazoles starting from spirocyclopropanepyrazoles via a ring‐opening/cyanomethylation and intramolecular cyclization is described. Reactions of spirocyclopropanepyrazoles 1a, 1b, 1c, 1d with chloroacetonitrile in the presence of sodium hydride gave the corresponding cyanomethoxypyrazoles 4a, 4b, 4c, 4d. Treatment of 4a, 4b, 4c, 4d with sodium hydride at room temperature caused intramolecular Michael addition reaction to afford the corresponding pyrano[2,3‐c]pyrazoles 5a, 5b, 5c, 5d. J. Heterocyclic Chem., (2009).

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