Change of mechanism with a change of substituents for a Zincke reaction

The reaction between N-(2,4-dinitrophenyl)-4-(4-pyridyl)pyridinium chloride and 4-aminothiophenol led to an unexpected displacement of the 2,4-dinitrophenyl group, in contrast with the normal Zincke product formed with other nucleophilic 4-substituted anilines. Evidence for a SET process was obtained from EPR spectra of the reaction mixture.     

Synthesis of biphenyl anilines using iodo phenylformamides via a one-pot Suzuki coupling reaction

We have developed a novel and economical synthesis of biphenyl anilines via a one-pot Suzuki coupling reaction with iodo phenylformamides. This literature is an unprecedented approach to biphenyl anilines replacing costly aminophenylboronic acids with economical iodo anilines for the preparation of biphenyl anilines. It also provides a viable synthesis toward substituted biphenyl anilines where the required aminophenylboronic acids are not readily available.     

Selective N-monomethylation of primary anilines with dimethyl carbonate in continuous flow

Selective N-monomethylation of anilines has been achieved under continuous flow conditions using dimethyl carbonate as a green methylating agent in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene. Our methodology takes advantage of the expanded process windows available in the continuous flow regime to safely induce monomethylation in superheated solvents at high pressure. We propose selective N-monomethylation is achieved via an in situ protection-deprotection pathway, which is supported by the observed reactivities of several putative reaction intermediates. The robust and scalable method was applicable to a broad range of primary aniline substrates including ortho-, meta-, and para-substituted anilines, as well as electron-rich and electron-deficient anilines. The synthetic precursor of diazepam, 5-chloro-2-(methylamino)benzophenone, was selectively synthesized under our optimized conditions.     

An unusual behaviour of N-(tert-butoxycarbonyl)- and N-pivaloyl-(methylthio)anilines in metallation reactions

The metallation reaction of N-Boc-and N-Piv-(methylthio)anilines are here described. The results show that N-Boc derivatives are metallated only by superbases to give products substituted at the thiomethylic group. N-Piv derivatives show a different behaviour: ortho-derivative is metallated by both butyllithium and superbase at the thiomethylic carbon atom, while para-derivative is metallated in ortho to the N-Piv group by butyllithium and at the thiomethylic carbon atom by superbase. The meta-derivative is metallated only by superbase at the thiomethylic carbon atom.     

Reaction between isoprene and aniline on complex palladium catalysts

Isoprene and aniline have been reacted on the catalytic system Pd(acac)₂-Ph₃P to form a mixture of isomeric telomers: N-(dimethyloctadien-2,7-yl-1)anilines and N-(dimethyloctadien-1,7-yl-3)anilines but on the catalytic system Pd(acac)₂-Ph₃P-CF₃COOH the main product is a mixture of N-(methylbuten-2-yl)aniline adducts. The reaction between N-methylaniline and isoprene on the latter catalyst also gives a mixture of N-methyl and N-(methylbuten-2-yl)aniline adducts.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1794–1798, August, 1992.     

Green and Efficient Protocol for the Synthesis of N-(2-Hydroxyethyl)anilines by the Alkylation Reaction in Ionic Liquid

A green and efficient protocol for the synthesis of N-(2-hydroxyethyl)anilines by the selective alkylation reaction in ionic liquid [BMIM]BF₄ (1-butyl-3-methylimidazolium tetrafluoroborate) has been developed, eliminating the need for toxic and expensive catalysts and volatile organic solvents. The effects of the amount of ionic liquid, temperature, time, and substrate structure on the reaction were investigated. The conversion and selectivity of N-(2-hydroxyethyl)anilines obtained in ionic liquid [BMIM]BF₄ are significantly increased in comparison to those traditional methods. Furthermore, the ionic liquid could be easily separated and reused at least five times. It provided a simple and efficient alternative way for the industrial synthesis of N-(2-hydroxyethyl)anilines.     

A green one-pot multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications using silica nanoparticles as reusable catalyst

A one-pot practical, efficient, and environmentally benign multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications has been developed using a very mild, neutral, and reusable silica nanoparticles as catalyst. The 4H-pyran derivatives were synthesized by a three component reaction of an aldehyde, malononitrile, and 5,5-dimethyl-1,3-cyclohexanedione or ethyl acetoacetate at room temperature or refluxing in ethanol. Alternatively, polysubstituted anilines were synthesized via a four component reaction of an aldehyde, a ketone, and two equivalents of malononitrile in ethanol.     

A new variant of Knorr''''s pyrrole synthesis

The reaction between ethyl 3-bromopyruvate and p-substituted anilines was found to involve the unexpected participation of acetone (solvent) forming N-aryl-5-methyl-pyrrole-3-carboxylates.The influence of p-substituents of aniline and the feasibility with other ketones were studied.N-aryl-indole-3-carboxylate (17) was synthesized successfully with this method.The unique character of p-methoxy-aniline in this reaction was discussed.     

Electrochemical Synthesis of Benzazoles from Alcohols and o‐Substituted Anilines with a Catalytic Amount of CoII Salt

An electrochemical synthesis of benzazoles directly from alcohols and o‐substituted anilines has been developed. The reaction conditions have been optimized by varying the composition of the electrolyte and the metal salt used as catalyst. The cyclization proceeds smoothly with a catalytic amount of a cobalt salt under air at room temperature to afford 2‐substituted benzimidazoles, benzothiazoles, and benzoxazoles in good to excellent yields with a wide substrate scope.     

Selective Reduction of Nitroarenes with Molybdenum Disulfide

Commercial MoS₂ was found to be a highly selective catalyst for the reduction of nitrobenzenes to the corresponding anilines with hydrazine under mild conditions. MoS₂ is not only much cheaper, but also more selective than noble metal catalysts for the reduction of functional nitrobenzenes to the corresponding anilines. Nitrobenzenes with halides (F, Cl, Br and I) were reduced selectively, and the corresponding anilines were obtained in excellent yields, and no dehalogenation was detected. Functional groups such as NH₂, OH, alkene groups were tolerated during the reduction of the nitro compounds. The reduction of p‐chloronitrobenzene was studied over MoS₂ and Pd/C respectively with hydrazine. The yield of p‐chloroaniline was much higher with MoS₂ than that with Pd/C at full conversion.     

Reaction of the carbonate radical with substituted anilines

Rate constants for the reaction of carbonate radical with aniline and some parasubstituted anilines have been determined by the flash photolysis technique. Using σ⁺ para values the rate constants at pH 8.5 correlate very well with the Hammett equation yielding ρ= − 1. The carbonate radical oxidises aniline giving the anilino radical. The products so formed have been identified through studies under conditions of continuous irradiation.     

Solvent-free reductive amination of aromatic aldehydes catalyzed by CeCl3·7H2O

Abstract

CeCl₃·7H₂O is found to be an efficient catalyst in the one-pot reductive amination of aromatic aldehydes under solvent-free conditions. Selectivity is observed in the reaction of cinnamaldehyde with aromatic amines, providing an alternative green route to the synthesis of N-cinnamyl anilines. The reaction conditions are mild and the desired product is obtained in good yields.     

Sterically Congested 2,6‐Disubstituted Anilines from Direct C−N Bond Formation at an Iodine(III) Center

2,6‐Disubstituted anilines are readily prepared from the direct reaction between amides and diaryliodonium salts. As demonstrated for 24 different examples, the reaction is of unusually broad scope with respect to the sterically congested arene and the nitrogen source, occurs without the requirement for any additional promoter, and proceeds through a direct reductive elimination at the iodine(III) center. The efficiency of the coupling procedure is further demonstrated within the short synthesis of a chemerin binding inhibitor.     

Brønsted acid-mediated cascade cyclization of 2-propynolphenols/anilines leading to 4-halo-2H-chromenes and 1,2-dihydroquinolines

A convenient strategy is present for easy construction of a series of 4-halo-2H-chromenes and 1,2-dihydroquinolines through Brønsted acid-mediated cascade cyclization of readily accessible 2-propynolphenols/anilines. Our developed approaches prove have good functional-group applicabilities and could be enlarged to gram quantities in high yields. Moreover, the resulting halides could be further exploited in subsequent palladium-catalyzed coupling reactions.     

Copper‐Catalyzed Mild Nitration of Protected Anilines

A practical copper‐catalyzed direct nitration of protected anilines, by using one equivalent of nitric acid as the nitrating agent, has been developed. This procedure features mild reaction conditions, wide structural scope (with regard to both N‐protecting group and arene substitution), and high functional‐group tolerance. Dinitration with two equivalents of nitric acid is also feasible.     

Metal-based Heterogeneous Catalysts for One-Pot Synthesis of Secondary Anilines from Nitroarenes and Aldehydes

Recently, N-substituted anilines have been the object of increasing research interest in the field of organic chemistry due to their role as key intermediates for the synthesis of important compounds such as polymers, dyes, drugs, agrochemicals and pharmaceutical products. Among the various methods reported in literature for the formation of C–N bonds to access secondary anilines, the one-pot reductive amination of aldehydes with nitroarenes is the most interesting procedure, because it allows to obtain diverse N-substituted aryl amines by simple reduction of nitro compounds followed by condensation with aldehydes and subsequent reduction of the imine intermediates. These kinds of tandem reactions are generally catalyzed by transition metal-based catalysts, mainly potentially reusable metal nanoparticles. The rapid growth in the last years in the field of metal-based heterogeneous catalysts for the one-pot reductive amination of aldehydes with nitroarenes demands for a review on the state of the art with a special emphasis on the different kinds of metals used as catalysts and their recyclability features.     

Restricted rotation of the amino group and ring inversion in highly substituted anilines. A dynamic NMR and computational study

The reaction of cyclic ylidene malononitriles with acetylene (di)carboxylic acid esters led to the production of nine bicyclic systems incorporating highly substituted (5/6) anilines. The free energy of activation (ΔG^#) for the restricted rotation about the aniline-NH₂ bond was experimentally measured in each case and a correlation was evident between the increase in steric strain in the ground state, the electron withdrawing capabilities of the ring substituents, and a reduction in the rotational barrier. For four of the compounds, the slow ring interconversion (chair?chair) for the annelated saturated seven-membered ring that formed part of the bicyclic system was also evident. In these four compounds, both dynamic processes were also studied theoretically using ab initio methods whilst the ring interconversion was additionally studied using molecular dynamic simulations. The interconversion between the two stable chair forms was deemed to occur via a conformation series consisting of chair?boat?twist-boat?boat?chair.     

One‐Pot Preparation of Fluorinated α‐Aminoalkyl Phosphonates under Microwave Irradiation and Solvent‐Free Conditions

A facile one‐pot method has been developed for the synthesis of fluorine‐containing α‐amino phosphonates in good yields by a three‐component reaction of fluorinated aromatic aldehydes, anilines, and diethyl phosphate in the presence of a silica‐gel support under microwave irradiation within 10 min. All new compounds are fully characterized by spectral methods and elemental analysis.     

Effective metal-free electrooxidative thiocyanation of anilines

An original anodic C–H thiocyanation of anilines with NH₄SCN has been developed, allowing to obtain the products in 88–98% yields under potentiostatic diaphragm electrolysis on glassy carbon electrodes at E_anode = 0.60 V and moderate consumption of electricity. The preliminary voltammetric analysis included the assessment of the changes in the thiocyanate ion curve after the addition of aniline, as well as the measurements of the potentials of the reagents and products, which gave insight into mechanisms of the process (formation of thiocyanate radical and thiocyanogen) and was necessary for its optimization.     

Synthesis and cytotoxic activity of new hexaazadibenzotetracenes derived from trans-1,2-diaminocyclohexane

A one-pot synthesis of N,N'-disubstituted (3bR*,7aR*,10bR*,14aR*)-octadecahydro-1H ,8H-2,3a,7b,9,10a,14b-hexaazadibenzo[fg, op]tetracenes via the catalytic heterocyclization of trans-1,6,7,12-tetraaza-perhydrotetracene with formaldehyde or CH₂(NMe₂)₂ and anilines has been accomplished. Preliminary screening of thus obtained perhydro hexaazadibenzotetracenes for cytotoxic activity has been performed.