Ring Transformation of Spirocyclopropanepyrazoles into Pyrano[2,3-c]pyrazoles

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

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