Homoconjugated ketones with extended unsaturation: Wavelength‐selective, regioselective, diastereoselective, and enantiospecific photochemical transformations of methyl 7‐oxospiro[5.5]undeca‐1,3‐and ‐2,4,‐diene‐2‐carboxylate

The title molecules were shown to photorearrange with remarkable selectivity. Wavelength variation steers the rearrangement modes, of which the [1,2]‐acyl shift was found to be largely regioselective, diastereoselective, and enantiospecific. Chemical intercorrelation of products and mechanistic studies were carried out all along. The potential significance of these photochemical processes in selective synthetic schemes is discussed.