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).