Photolytic Cleavage of Remote Functional Groups in Polyfunctional Molecules. Photolysis of exo- and endo-Benzobicycloocten-2-yl Chloride

Article abstract of DOI:10.1021/jo00367a020

The aryl-induced photolytic cleavage of a remote C-Cl bond, earlier reported for the 2-position in the benzonorbornenyl series, is extended to the 2-position of the title compounds (exo-BBCl and endo-BBCl).Cleavage with 254-nm excitation is an efficient reaction (ψ_dis = 0.45 and 0.005, exo and endo, respectively), involving the aryl singlet excited state.Radical and carbocation derived products are observed (eq.3), with the latter including an olefin (8), a cyclopropane (9), and rearranged ethers (10 and 13) attributed to "hot" cation intermediates.The rate constants for C-Cl cleavage sre as follows: exo <2.2.1> 1.1*10⁹ s^-1; exo 2.2.2>, 3.8*10⁸ s^-1; endo <2.2.1>, 1.7*10⁶ s^-1; endo <2.2.2>, 2.7*10⁵ s^-1.These rates are discussed within the context of previously proposed mechanisms.