Oxidations and Reductions of Diazo Compounds

As mentioned in the introduction to Section 9.3, we will discuss reactions with oxidation and reduction chemicals in this section. We will concentrate mainly on reagents that oxidize or reduce the diazo function and only marginally on reactions that involve reactions with other sites of diazo compounds. 

Diazoalkanes are fairly stable toward oxidation reagents. This is evident from one of the major reactions for their synthesis, the hydrazone dehydrogenation (see Subsect. 2.5.1). The diazoalkanes formed are stable against attack by the transition-metal oxides used as dehydrogenation reagents. 

Diazo compounds are also not attacked by atmospheric oxygen at ambient temperature, although they react with ozone and in photosensitized oxygenations. 

Bailey et al. (1965) found that in a-diazocarbonyl compounds with a terminal diazo group (-CH=N2) the diazo function is replaced by an O-atom, i.e., a glyoxal derivative is formed primarily, but the final products result from CH bond cleavage. In other cases, however, the a,yff-dicarbonyl compound is stable. An example, described by Ursini et al. (1992), is the oxo-de-diazoniation (9-35) of various 6-diazopenicillanates (9.70, R = 4-NO2C6H4CH2 and other alkyl groups). The a-diketone is obtained at -15 to -10°C in dichloromethane with ozone in 86-97% yield. 

With increasing knowledge and experience on the reactivity of singlet and triplet carbenes (see Sect. 8.1), and of singlet and triplet dioxygen (see Sect. 8.5) in the 1960 s and 1970 s, it seemed to be feasible to consider that a 02-molecule, as a highly electrophilic reagent, may attack the nucleophilic C (a)-atom of diazoalkanes 

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