Photochemistry of endo and exo electronic configurations of biphenylyl methyl propanal

AbstractBoth 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 subsequently formaldehyde 2‐biphenylyl isopropyl hemiacetal, which in turn gradually decomposes to dimethyl phenylbenzyl alcohol at room temperature. The triplet pathway dominates the photoreaction of the exo isomer. The singlet and triplet lifetimes of the reactant are found to be 0.29 ns and 5.4 μs, respectively, 3(n, x*), 1(n, x*), 3(x, x*) electronic configurations of the exo isomer and 3(x, x*) of the endo isomer are photochemically active, but 1(x, x*) of the endo isomer shows indirect photoreactivity.