Cyclopropanones photochemical reactions

Sustituted l-azolin-5-ones have been described thus, 2-ethoxy-1-azolin-5-one (24) is a stable compound that has been prepared from succinimide [80OS(59) 132]. 2-Ethoxy-l-azolin-5-one undergoes a photochemical ring contraction giving cyclopropanone derivatives. The photochemical reaction of (24) in /< r/-butylalcohol as solvent yield tert-butyl A-(l-ethoxy-cyclopropyl)cabamate (25). 

The cyclopropyl enone 31 was photoisomerized to the cyclopropanone 32 at liquid nitrogen temperatures.34) The unstable 32 was characterized on the basis of ir spectra and thermal and photochemical reactions (see Section 4.1.5). When 31 was irradiated at room temperature in 45% acetic acid, the phenol 33 was produced, most probably through 32 and the spiro dienone intermediate 34 (Scheme 5).35>... 

Photochemical Reactions.—The structural and geometrical isomerizations of 1,2-diphenylcyclopropane have been subjected to detailed analysis and the photochemical (and thermal) decomposition of cyclopropanone has been examined in the vapour phase. ... 

Carbon monoxide may be eliminated from cyclopropanones either by thermal or photochemical processes (Table 12). In fact, decarbonylation is sometimes an undesirable side reaction in the synthesis of cyclopropanones. For example, the reaction of dimethylketene and ethyl diazoacetate affords carbon monoxide and ethyl acrylate 115 rather than the desired ketone. 2°)... 

A recent photochemical study of cyclopropanone has demonstrated that two reactions take place at certain wavelengths. 75) Although the quantum yield for decomposition of 2 ( Cp) is approximately unity over the range A =2920—3650 A, the quantum yield for ethylene formation... 

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