Ketene Ketone photolysis, cyclic

In this chapter, we discuss the rate coefficients and the mechanisms of oxidation of ketones. The classes covered include alkanones, hydroxyketones, diketones, unsaturated ketones, ketenes, cyclic ketones, ketones derived from biogenic compounds, and halogen-substituted ketones. Photolysis is a major atmospheric process for many ketones, and will be discussed in chapter IX. The major bimolecular reactions removing ketones from the atmosphere are with OH. Although less important than the OH... 

The photolysis of cyclic diazo ketones in hydroxylic solvents leads to ring contracted carboxylic acid derivatives via this ketocarbene -> ketene rearrangement. Examples of such reactions are given in (2.24)239) and (2.25) 240). In this last example a photoequilibrium between the diazo ketone and its valence isomer, a diazirine, has been observed, both products then eliminating nitrogen to afford the cyclobutane carboxylic acid. 

Photolysis of the cyclic vinyl ketone 5,5-dimethyl-3-azido-2-cyclo-hexene-l-one (61) in aqueous tetrahydrofuran resulted in ring enlargement to the azepine (62). Irradiation of the same azide in benzene did not however lead to photodecomposition. A reaction path involving a cyclic ketene-imine was put forward. 

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