Studies on nucleophilic substitution reactions with cyclopentadienyliron complexes of some chloroarenes and nitroarenes and syntheses of substituted arenes by demetallation of the substitution products

Abstract

Nucleophilic substitution reactions with the cyclopentadienyliron (CpFe) complex of m- or p-dichlorobenzene with carbanion nucleophiles derived from ethyl acetoacetate (EAA), dibenzoylmethane (DBM) or diacetylmethane (DAM) were found to give only monosubstitution as previously observed for the CpFe complex of o-dichlorobenzene. Reaction of the CpFe complex of 2,6-dimethylchlorobenzene (XIVa) or 2,6-dimethylnitrobenzene (XIVb) with nucleophiles derived from ammonia, dimethylamine, n-butylamine, pyrrolidine, ethanol, phenol, o-thiocresol and EAA all gave S NAr products, without significant steric hindrance. However, no reaction was observed in the treatment of XIVa or XIVb with DBM, suggesting that only with a bulky nucleophile such as that derived from DBM were steric hindrance effects sufficiently large to prevent an S NAr reaction with XIV, a or XIVb. Pyrolytic sublimation of the various S NAr products was found to cause decomposition in some cases, but in most instances, demetallation took place giving rise to substituted arenes. New substituted arenes prepared in this way in the present work included RC 6H 4CH(COC 6H 5) 2, with R = p-CH 3, o-Cl, m-Cl or p-Cl, and 2,6-(CH 3) 2C 6H 3Y, with Y = CH 3(CH 2) 3NH, C 2H 5O or o-CH 3C 6H 4S.