The Reaction of Huisgen Zwitterion with Diaryl-1,2-diones and Ketones: An Efficient Protocol for Carbon-Nitrogen Bond Formation

Abstract

The reaction of Huisgen zwitterion, derived from triphenylphosphine and dialkyl azodicarboxylate, with diaryl-1,2-diones afforded N,N-dicarboalkoxy monohydrazones via a mechanistically novel rearrangement. Cyclic and acyclic ketones furnished vinyl hydrazinedicarboxylates under similar conditions.

betaines - diazo compounds - hydrazones - ketones - rearrangements

References

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2b

The reaction of PPh₃ and DEAD with dimethyl acetylenedicarboxylate affording pyrazoles is mentioned; rationalization of this reaction as occurring via the zwitterion 3 was provided by Huisgen (Ref. 3a).

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12

It may be mentioned that the mechanism presented herein is identical to that suggested by Liu and Lee (references 6 and 9, respectively).