Propene, 3-diazo cycloaddition reactions

An exceptionally interesting example of an intramolecular [3 + 2] cycloaddition, in which the diazo dipole and the olefinic C=C bond are separated by only one carbon atom, is outlined in Scheme 8.65. The thermal decomposition of the allenic tosylhydrazone sodium salt 267 produced 1,4-dihydropyridazine 269 (57). It is assumed that diazabicyclohexene 268 is a short lived reaction intermediate. This suggestion is supported by the observation that the generation of the diazocumulene l-diazo-2-methyl-l-propene in the presence of 3,3-dimethylcyclopropene also leads to 269. 

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