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The compound described as ‘cholestane-3,4,6-trione’ by Windaus and Kuhr has been shown to be the 3-ethyl ether of the corresponding dienol. Although relatively stable to acid, the enol ether may be hydrolysed to yield the triketone, a mixture of two stable tautomers, which may be separated readily by fractional crystallisation. Structures have been assigned to the two tautomers on spectroscopic evidence.

A detailed study of the photochemistry of a number of α-nitrostilbenes is reported. The previously described intramolecular cyclization of (1) which resulted in cleavage of the double bond was not found to occur to any extent in the other compounds examined. The majority of the compounds were found to yield significant amounts of aldehydes and nitriles, which result from a new fragmentation pathway arising from initial photochemical nitro-nitrite isomerization.

The photochemistry of cyclohexylidenenitromethane (6), 3-ethyl-2-nitropent-2-ene (7), (Z)-α-methyl-α- nitrostilbene (12), (E)-3-methyl- 1-nitro-1-phenylbut-1-ene (15) and 4,4-dimethyl-3-nitro-5α-cholest-2- ene (27) has been examined to determine the structural features required for deconjugation to the β, γ-unsaturated isomer. The mechanism of the light-induced formation of the corresponding α, β- unsaturated ketone , which may accompany deconjugation , has also been examined. Support for a scheme involving γ-hydrogen abstraction to give an unsaturated nitronic acid, followed by N- hydroxyoxaziridine formation and collapse to the ketone, is provided in the photochemistry of the stable nitronic acids, 4-t-butyl-aci-nitrocyclohexane (17) and 9-aci-nitrofluorene (18). Syntheses of the nitro olefins (6), (7), (12), (15) and (27), and the nitronic acid (17) are also reported.