Abstract:

Diimide, generated from azodicarboxylic acid at 25°, was used to reduce a series of cycloalkenes and cycloalkadienes (C5-C8, C12). In agreement with redns. with diimide conducted at 80°C by Garbisch, Schildcrout, Patterson, and Sprecher (1965), the relative reactivity of the monoenes fall in the order norbornen »C8(cis) \textgreater C5 \textgreater C7 \textgreater C6; however, the spread in rates is greater in the present study. Compared to cyclohexene, the relative reactivity of C8(trans) and norbornene are 2200 and 700, resp., at 25°. 1,3-Cyclohexadiene is more reactive than cyclohexene; however, the cyclo-C5, cyclo-C7, and cyclo-C8-1,3-dienes are less reactive than the monoene each forms on redn. Although conjugation tends to lower the reactivity of a diene, torsional strain, which serves here as a driving force, may reduce the planarity of a conjugated system, as in 1,3-cyclohexadiene, and thus the conjugative interaction as well. [on SciFinder(R)]