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Both direct and sensitized irradiations of the endo title compound lead to a decarbony-lation product,4-isopropylbiphenyl,via Norrish Type 1 reaction,while the exo isomer gives a carbeneintermediate and subsequently formaldehyde 2-biphenylyl isopropyl hemiacetal,which in turngradually decomposes to dimethyl phenylbenzyl alcohol at room temperature.The triplet pathwaydominates the photoreaction of the exo isomer.The singlet and triplet lifetimes of the reactant arefound to be 0.29 ns and 5.4μs,respectively.~3(n,π~*),~1(n,π~*),~3(π,π~*)electronic configurationsof the exo isomer and ~3(π,π~*)of the endo isomer are photochemically active,but ~1(π,π~*)of the endoisomer shows indirect photoreactivity.
Both direct and sensitized irradiations of the endo title compound lead to a decarbonylation product, 4-isopropylbiphenyl, via Norrish Type 1 reaction, while the exo isomer gives a carbene intermediate and following formaldehyde 2-biphenylyl isopropylhemiacetal, which in turngradually decomposes to dimethyl phenylbenzyl alcohol at room temperature.The triplet pathwaydominates the photoreaction of the exo isomer.The singlet and triplet lifetimes of the reactant arefound to be 0.29 ns and 5.4 μs, respectively. ~ 3 (n, π ~ *), ~ 1 (n, π ~ *), ~ 3 (π, π ~ *) electronic configurations of the exo isomer and ~ 3 (π, π ~ *) of the endo isomers are photochemically active, but ~ 1 shows indirect photoreactivity.