SYNTHESES OF 2-DIAZO-4-CYCLOPENTENE-1,3-DIONE AND 2-DIAZO-4,6-CYCLOHEPTADIENE-1,3-DIONE. A MARKED DIFFERENCE IN THE DEGREE OF RESONANCE CONTRIBUTION OF THE CANONICAL FORMS

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Abstract
2-Diazo-4-cyclopentene-1,3-dione 1 and 2-diazo-4,6-cycloheptadiene-1,3-dione 2 are synthesized. The spectral data of these compounds indicate that there are considerable difference between them in the degree of resonance contribution of the canonical forms: the contribution of the enolate canonical form 1b to the resonance hybrid cf 1 is less important than the corresponding form of usual 2-diazo-1,3-diones, while the enolate form 2b to 2 is very important.