Selective access to p-dialkyl-carbo-benzenes from a [6]pericyclynedione: the n-butyl nucleophile model for a metal switch study

Abstract

The synthesis, spectroscopic properties, comparative electrochemical behavior in CHCl3 vs CH2Cl2, and X-ray crystal structure of p-di-n-butyl-tetraphenyl-carbo-benzene are described. The selectivity of preparation of the ultimate [6]pericyclynediol precursor has been examined by comparing the reactivity of the [6]pericyclynedione substrate with four n-Bu-MXn nucleophiles involving more or less halogenated metal centers MXn (0 ≤ n ≤ 2): Li, MgBr, MgCl, CeCl2/LiCl. The cerium reagent is found to be the most efficient, giving approximately twice the yield given by Grignard reagents in the target diadduct (90% vs 51%–53%). The dibutyl-carbo-benzene product happens to be soluble in both CHCl3 and CH2Cl2: cyclic voltammograms of either solution exhibit almost identical peak potentials with reduced reversibility of the redox processes in CHCl3.