Acenaphthylene photocycloaddition

Acenaphthylene undergoes photocycloaddition to cyclopentadiene(87> and acrylonitrile<68) to yield the following products ... 

The photocycloaddition of maleic anhydride to acenaphthylene has been studied by Hartmann and Heine.(107a> Irradiation of acenaphthylene in the presence of maleic anhydride in light-atom solvents (dioxane, acetone, or acetonitrile) yields only dimers or copolymers of acenaphthylene. In heavy-atom solvents (dichloromethane, dibromomethane, or iodomethane), however, dimerization is suppressed and cycloaddition with maleic anhydride predominates ... 

Table 10.9. Heavy-Atom Effect on the Photocycloaddition of Acenaphthylene to Cyclopentadiene

A heavy-atom effect on the photocycloaddition of acenaphthylene to acrylonitrile has also been observed.<68) The effect of heavy atoms in this case is seen as an apparent increase in the quantum yield of product formation in heavy-atom solvents as opposed to cyclohexane (the time to achieve about 42% reaction in cyclohexane is greater than that required to produce the same conversion in dibromoethane by a factor of ten). An increase in the rate of acenaphthylene intersystem crossing due to heavy-atom perturbation was proposed to explain this increase in reaction rate. 

The photocycloaddition of acrylonitrile to acenaphthylene is found to be competitive with photodimerization in the non-ionic detergent Nippol PBC-34, while... 

Photocycloadditions are also exploited in the synthesis of fused polycyclic compounds. Tetracyclic (4-hetera)cyclopent[, c]acenaphthylenes can be synthesized by light-induced cycloaddition of 4-alk-l-ynylcoumarins to 2,3-dimethylbut-2-enes (Scheme 6.33). Addition of triplet-excited 4-alk-l-ynylcoumarin to the alkene affords the triplet biradical, which undergoes 1,5-cyclization to cyclopentenylcar-bene. The latter undergoes electrocyclic ring closure and [1,9]-H shift to yield the product [37]. 

Shirota, Y, Nagata, J., and Mikawa, H., The photocycloaddition of acenaphthylene with tetracyanoethylene, Chem. Lett., 49, 1972. 

Photodimerization of acenaphthylene in aqueous solution is inhibited by /1-CD, but leads to a quantitative conversion in the presence of y-CD, giving 42a and 42b in a ratio of 99 1 (Scheme 16) [85]. The photocycloaddition of acrylonitrile to acenaphthylene included in fi-CD affords only the dv-crossadduct 42c. 

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