Ketenes reactions with singlet oxygen

Bis-silyl ketene acetals devoid of -protons undergo a clean silatropic ene reaction with singlet oxygen (see Sections 2.3.2.1,3.ii and 2.3.2.4.3.H) to generate the a-silylperoxy silyl ester quantitatively. Treatment with methanol affords the a-hydroperoxy acid, also quantitatively (Scheme 23). Hytkogenation over platinum reveals the a-hydroxy acid, once again, quantitatively. Despite diis encouragement the substrate limitation is severe. 

D. Silylation - Ketene bis(trimethylsilyl)acetals result from treatment of acid dianions with chlorotrimethylsilane.58 59 Esters behave analogously.60 Silylated ketene acetals can react like acid dianion equivalents. For example, reaction with singlet oxygen was used to produce the first operoxylactone.61,62... 

Dioxetan-ones appear to be intermediates in the chemiluminescent reaction of singlet oxygen with ketenes, in the presence of fluorescers 81> ... 

Several ketenes have been converted into l,2-dioxetan-3-ones by reaction with triphenyl phosphite ozonide (77JA5836), and ketenimines form cyclic iminoperoxides with photochemi-cally generated singlet oxygen (Scheme 97) <79AG(E)788,80CC898). 

These compounds have also been prepared more simply by reaction of triphenyl phosphite ozonide with the more readily available ketenes (equation II). The ozonide is known to generate singlet oxygen, which reacts with the ketene to form an intermediate that collapses to the a-peroxylactone. ... 

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