The N -Electrophilicity of Aliphatic Diazo Compounds

The mesomeric structure 9.35a is related to cyclic diazo ketones based on this structure, 1,2-benzoquinone diazide may be called 2-diazocyclohexa-3,5-dien-l-one 

9 Miscellaneous Reactions Involving Diazo and Related Compounds 

After Huisgen s explanatory review, there was still silence on this reaction in the scientific community for some years until it was realized by Carboni and Lindsey (1962) that substituted 1,2,4,5-tetrazines are very reactive towards simple alkenes. Sauer et al. (1965), working in the same department as Huisgen at the University of Munich, evaluated such reactions in more detail, including alkynes in addition to alkenes. In the 1970 s, dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate (9.38) became much in demand as a synthon. It is obtained easily by esterification of 9.36, followed by treatment with nitrous gases (9-22 Organic Syntheses, Boger et al., 1992). 

As the development from the first report of Curtius (1884), one year after the discovery of diazoacetate, to the present widespread use of 1,2,4,5-tetrazines in 

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