The synthesis of two rigid bichromophoric systems in which the chromophores are separated by relays of nine and thirteen σ-bonds: two useful models for further exploring the distance dependence of long-range intramolecular electron transfer

Abstract

This paper describes the synthesis of two novel rigid bichromophoric systems, (6) and (7), in which the dimethoxynapthalene donor and the dicyanoethylene acceptor groups are separated, by relays of nine and thirteen σ-bonds. Treatment of 1,4-naphthoquinone (8) with quadricyclane (9) gave the [2 + 2 + 2] adduct (10) which, upon treatment with sodium hydride and methyl iodide, gave the methanobenzo[b]biphenylene compound (11). Thermal reaction of (11) with dimethyl acetylenedicarboxylate and RuH₂CO(PPh₃)₃ gave the adduct (12) which readily underwent [2 + 2 + 2] cycloaddition with quadricyclane to give (13a), and finally (13d), after a series of simple transformations. Treatment of (13d) with 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene gave the adduct (16) which was easily converted into the ketone (6a), and finally into the dicyanomethylene derivative (6b) by a Knoevenagel condensation. Subjecting (13d) to the same series of reactions that were applied to (11) led to the formation of the ketone (7a) and the dicyanomethylene derivative (7b), via(15a)–(15d) and (17).