Oxidative coupling-type mechanism of N,N-dialkylanilines in solvent-free conditions forming crystal violet derivatives. A clay-mediated and microwave-promoted approach

Abstract

In the clay-mediated reaction of N,N-disubstituted anilines using microwave radiation as an energy source in the absence of solvent, crystal violet and derivatives, diphenylmethanes, and biphenyls were isolated along with intermediates supporting an oxidative coupling-type mechanism.Key words: clay, dyes, microwave radiation, solvent-free reactions.

A Bentonitic Clay Assisted Method for the Preparation of 2-(R-Anilino)-1, 4-Naphthoquinones

“…Based on the chemical composition of the clay, with Fe 3+ sites, the last step of the Scheme 2 Reaction of 1,4-naphthoquinone with aniline without a catalyst mechanism is proposed to involve an oxidation-reduction reaction. It is worth mentioning that bentonite's oxidation properties, due to a redox reaction Fe 3+ /Fe +2 , have been previously reported in other organic reactions [41].…”

“…The vast majority of clay catalysts used in organic synthetic chemistry are based on the naturally occurring smectite clays, montmorillonites, also known as bentonites [41]. Since these clay catalysts have been shown to contain both, Brönsted and Lewis acid sites and a large surface area, a bentonitic clay was considered as the catalyst of choice for the present study.…”

An Efficient Solvent‐free Synthetic Technique of 4,4′‐Diaminotriarylmethane Leuco Materials

“…1 H and 13 C NMR spectra were obtained using a Bruker (DRX-500 Avance) NMR spectrometer at ambient temperature, with 1 H NMR spectra referenced to tetramethylsilane and 13 C NMR spectra to the solvent central peak (for example, δ 77.23 for CDCl 3 ). IR spectra were taken as thin films for liquid compounds and as KBr pellets for solids on an ABB Bomem MB-100 FTIR spectrophotometer.…”

“…Accordingly, different methods for the preparation of the aforementioned compounds have been described such as those from arene nucleophiles and triethyl orthoformate, or benzhydrol in the presence of acid catalysts, 9 from condensation of amines and anilines using acids 10 or zeolites 11 and also by reaction of aniline derivatives with metal catalysts such as Pd(OAc) 2 12 or clay-mediated oxidative coupling of disubstituted anilines using microwave radiation, in which DTM derivatives were obtained in low to moderate yields. 13 One of the most useful methods for the synthesis of DTM is the reaction of arylaldehydes with N,N-dimethylaniline in the presence of an acid such as sulfuric acid, HCl, p-TSA, zeolites or montmorillonite K-10.…”

CuBr/H2O2-Mediated Oxidative Coupling ofN,N-Dialkylarylamines in ­Water: A Practical Synthesis of Benzidine Derivatives

“…5 A number of methods for the coupling reaction have been reported. [6][7][8][9][10][11] Among them, oxidative coupling of aniline derivatives provided an efficient access to benzidine derivatives. Recently, TiCl 4 10 and 1,8-bis(diphenylmethylium)naphthalenediyl dications 11 were both reported to be effective oxidants for such coupling reactions, although the large excess of anilines (in the former) and the relatively hard-to-obtain dications (in the latter) retarded their acceptance as practical approaches.…”