Diazoethene and its Derivatives

The diazo transfer from diazoalkanes to alkynes has also been applied to diphenyl-alkynylphosphine oxides. Low regiospecificity with unsymmetrically substituted alkynes was also observed here (Heydt and Regitz, 1977, 1978). 

Diazoethene (2.239) is a remarkable molecule because it is highly cumulative and isoelectronic with propadienone (2.240). Unsubstituted diazoethene has not, however, been isolated or experimentally characterized directly, but difluorodiazoethene has (see below). 

We will discuss theoretical investigations on diazoethene in Section 5.3. Those studies verified the bent structure, as indicated in 2.239 and 2.240. 

2 Methods for the Preparation of Alkane, Athene, and Alkyne Diazo Compounds 

Lahti and Berson (1981) trapped the carbene 2.245 with 3,3-dimethylcyclopropene and isolated the allene 2.246, as well as the corresponding allenes, with 1,3,3-tri-methylcyclopropene. These products are expected, if carbene 2.245 is a transient intermediate (2-96). 

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