4-Alkylnitrobenzenes effectively undergo coupling with aryl bromides at their benzylic position in the presence of a palladium catalyst and a base to give the corresponding mono- and/or di-arylated products in good yields. (C) 1998 Elsevier Science Ltd, All rights reserved.
First General Synthesis of (<i>p</i>-Nitroaryl)diarylmethanes <i>via</i> Vicarious Nucleophilic Substitution of Hydrogen
作者:Alan R. Katritzky、Dorin Toader
DOI:10.1021/jo9624197
日期:1997.6.13
A general regiospecific method for the synthesis of (p-nitroaryl)diarylmethanes has been developed starting from diarylmethanols and 2- and/or 3-substituted nitrobenzenes. This utilizes the quantitative condensation between benzotriazole and diarylmethanols under acidic catalysis and in the presence of perfluorocarbon fluids, followed by vicarious nucleophilic substitution of the resulting diarylmethylbenzotriazoles upon nitrobenzenes in moderate to high yield. Oxidative nucleophilic substitution of hydrogen is observed as a side process. These vicarious nucleophilic substitutions complement Friedel-Crafts reactions for the synthesis of triarylmethanes.
Synthesis of (p-Nitroaryl)diarylmethanes via Vicarious Nucleophilic Substitution of Hydrogen
作者:M. Ma˛kosza、M. Surowiec、S. Voskresensky
DOI:10.1055/s-2000-6411
日期:——
(p-Nitroaryl)diarylmethanes are readily prepared via vicarious nucleophilic substitution of hydrogen in nitroarenes with carbanions of diarylmethyl p-chlorophenyl sulfide. These carbanions are efficient for introduction of diarylmethyl substituents in the para position of nitroarenes via the VNS reaction. The reaction does not proceed ortho to the nitro group due to steric hindrances on the addition step.
Oxidation of Nitrobenzylic Carbanions with Dimethyldioxirane. New Synthesis of Quinomethanes and Nitrobenzylic Carbinols. First Examples of Methylation of Carbanions with Dimethyldioxirane
The reaction of nitrobenzylic carbanions with dimethyldioxirane (DMD) results in oxidation at the carbanion center or at the nitronate center to give nitrobenzylic carbinols or quinomethanes, respectively. Minor amounts of the methylation products are also formed. Both of these processes were observed for carbanions of (p-nitroaryl)diarylmethanes. The outcome of the oxidation process is very sensitive