ABSTRACT
The main focus in the area of ß,γ-enone photochemistry has clearly concentrated on the oxadi-π-methane (ODPM) rearrangement, a reaction the merits of which have also been recognized by synthetic chemists. For synthetic purposes the reaction can be readily controlled by the use of appropriate triplet sensitizers and selection of the wavelength. The ODPM transformation of bridged ß, γ-unsaturated ketones is, as expected on mechanistic grounds, enantiospecific. Generally excellent ODPM substrates are encountered in the classes of mono-, bi- and spirocyclic as well as bridged a,ß-unsaturated ketones. The rearrangement of the 1-methoxy-substituted bicycle octenones follows a mechanistic variant of the ODPM reaction, which includes two consecutive single-step phototransformations, i.e. the ODPM path to, again triplet-sensitized, and the conversion to the final 1,4-diketones. In summary of phototransformation has the essential characteristics of a general synthetic method permitting easy and safe handling and has the potential to be employed in large scale applications, at least, on a multigram to kilogram scale.
