Photolytic Cleavage of Remote Functional Groups in Polyfunctional Molecules. Activation of a γ C-Cl Bond in the endo- and exo-Benzobicycloocten-3-yl Chlorides

Article abstract of DOI:10.1021/jo00374a033

The aryl-induced photolytic cleavage of a distal C-Cl bond, earlier reported for a β-substituent benzobicyclo<2.2.1> (eq 1) and -<2.2.2> (eq 2) substrates, has been extended to the γ position in the title compounds (endo-BBOC and exo-BBOC).Photolyses of these compounds in methanolic solution using 254-nm light primarily lead to products derived from carbocation intermediates (eq 4 and 5) with quantum efficiencies for loss of starting material φ_dis = 8.1 * 10^-2 and 7.6 * 10^-3 (endo and exo, respectively).The greater reactivity of the endo isomer contrasts with that observed in the <2.2.1> and <2.2.2> series where large exo/endo rate ratios are the rule (Table III).This inverted reactivity pattern is attributed to the favorable aryl/chlorine relationship in the endo isomer (Figure 1), which compensates for the increased Ar-C3 separation otherwise characteristic of these γ functionalities.