DeMayo cycloaddition

The isodaucane sesquiterpene (+)-aphanamol I was synthesized in the laboratory of B. Wickberg using the DeMayo cycloaddition as the key step. The required starting material 3(S)-isopropyl-1-methylcyclopentene was prepared by the Tsuji-Wilkinson decarbonylation of the corresponding a,p-unsaturated aldehyde. 

DeMayo cycloaddition Photochemical [2+2] cycloaddition of enones and alkenes to give substituted cyclobutanes. 132... 

In a careful study of cyclopentenone photocycloaddition reaction, DeMayo and coworkers215 have noted that ketone sensitizers of triplet energy less than 71.2 kcal did not sensitize cycloaddition to cyclohexene. Triphenylene (Et = 66.6 kcal) and acenaphthene (ET = 59.3 kcal) were exceptional since they resulted in quantum yields of 0.10 and 0.21, respectively. This behavior, as well as the fact that 0.1 M cyclopentenone quenched acenaphthene fluorescence by 90% in an EPA (ether-isopentane-alcohol) glass at 77°K strongly implicate singlet energy transfer. 

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