Bicyclo octanediones

The photochemical addition of ethene at 0°C in methylene chloride to the enedione (77) affords a high yield of the adduct (78). This was converted to the monochloro derivative (79) which also undergoes photoaddition of ethene to yield the Z> adduct (80). This on elimination of HCl yielded the quinol (81) which can be oxidised to the quinone (82). Cycloaddition of alkenes (cyclopentene, cyclohexene, and cycloheptene) has been carried out to the same enedione (77) to yield the adducts (83). lyoda et al. have also described a convenient synthesis of the bicyclo-octanediones(84) by a photochemical addition of alkenes to the enedione (77). The adducts (84) can be reduced by zinc in acetic acid to the desired products. Cycloaddition of ethyne to the same enedione followed by reduction affords the bicyclooctanes (85). The photoaddition of alkenes to the dibromo-enedione (86) is also effective and yields, after reduction, the adducts (87). 

Exercise 17-45 2,6-Bicyclo[2.2.2]octanedione, 16, exhibits no enolic properties. Explain. 

An interesting effect of light intensity has been observed in the reaction of bicyclo[2.2.2]octanedione 170) with aromatic aldehydes 140). These reactions produced esters of a-ketols 171) and labile a-aroyl-a-hydroxyketones 172). At first... 

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