Synthetic applications of electrochemically produced α-methoxyamides. Part 2. Oxidation of hydroxyproline derivatives

The electrochemical methoxylation of N-acetyl-4-hydroxyproline esters has been investigated. Both the free alcohol 3 and the corresponding 4-acetoxy derivative 4 as well as the cis-4-acetoxyproline 17 are methoxylated anodically preferentially at C(5), giving a mixture of stereoisomeric methoxy compounds. These mixtures can be used for further substitution as exemplified by the allylation of the methoxylated 4-acetoxy derivatives, giving substitution products preferentially trans to the acetoxy group although with low selectivity. The low selectivity is discussed in terms of kinetic vs. thermodynamic control.     

Facile and regioselective synthesis of novel 2,4-disubstituted-5-fluoropyrimidines as potential kinase inhibitors

2,4-Disubstituted-5-fluoropyrimidine is a biologically active molecular core seen in various anticancer agents such as 5-fluorouracil (5-FU). As part of a programme aimed at discovering kinase inhibitors, routes to two series of novel compounds (5-fluoropyrimidine-2-carboxamides and 5-fluoropyrimidine-4-carboxamides) were successfully executed. For the first series, regioselective substitution at the 4-position of the pyrimidine with an amine (HNR¹R²) was achieved, followed by preparation of the amide at the 2-position. The route to the second series involved introduction of the methoxy protecting group at the 4-position, which allowed subsequent amine substitution to occur at the 2-position. The 4-amide substituent was finally introduced by direct conversion of the 4-methoxy into a 4-chloro group followed by transformation into an amide by palladium catalysis.     

Photochromic properties of thienylpyrrole azo dyes in solution

The photochromic behaviour of thienylpyrrole azo dyes in THF solutions was studied for the first time. The photochromic properties are strongly dependent on the substitution pattern on the dyes. Nitro-substituted thienylpyrrole azo dyes are particularly interesting since they exhibit very fast colouration/decolouration processes. The activation energies of these compounds are among the lowest values reported for heterocyclic azo dyes. These compounds show aggregation phenomena in freshly prepared solutions of THF, which lead to variable photochromic behaviours. Only after 1-5 h the solutions reach equilibrium and then reproducible photochromic behaviour can be observed.     

Diazo compounds of the heterocyclic series. 4. Some peculiarities of the diazo coupling of benzimidazole-2-diazonium salts with phenols and their ethers

The corresponding hydroxy (methoxy)-substituted azobenzimidazoles were obtained by diazo coupling of benzimidazole-2-diazonium salts with phenols and their complete and incomplete ethers in strongly acidic media; in the case of phenol ethers the process is complicated by dealkylation of the methoxy group in the ortho position relative to the azo bridge.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 637–642, May, 1990.     

Heterocyclic diazo compounds. 5. Reaction of benzimidazole-2-diazonium salts with naphthols and their ethers

The principal pathways for the reaction of benzimidazole-2-diazonium ion salts with naphthols and their methyl ethers in a mixture of phosphoric acid annd acetic acid have been elucidated. In concentrated acidic media, in addition to substitution at the 4-position in naphthol and its ether, azo coupling at the 8-positin is also possible. It has been found that a 2-methoxy group in naphtylazobenzimidazole exhibits anomalously high reactivity with respect to hydrolytic cleavage, which explains the observed ease of dealkylation of the azo compound during the course of the azo coupling sequence.For Communication No. 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 67–72, January, 1992.     

One step synthesis of azo compounds from nitroaromatics and anilines

A general and efficient method for synthesis of both symmetric and asymmetric aromatic azo compounds in one single step has been developed. The nitro compounds were reduced and the substituted anilines were oxidized by each other without any metal in the base condition. Various azo compounds with halogen, methyl and methoxy functional group were obtained by using available, cheap nitro compounds and substituted anilines. In addition, the electronic effect and substituent effect of the compounds have been discussed.     

Investigations of the Vicarious C‐Aminations of 5,7‐Dinitrobenzotriazole and 4,6‐Dinitrobenzotriazol‐3‐ium‐1‐oxide and Their Energetic Properties

This combined experimental and theoretical study details the vicarious nucleophilic substitution by amination of 5,7‐dinitrobenzotriazol ( 1 ) and 4,6‐dinitrobenzotriazole‐3‐ium‐1‐oxide ( 4 ) with trimethylhydrazinium iodide to afford the new corresponding one‐ and two‐time aminated compounds and investigations of its mechanism by EPR spectroscopy. The preferred position for the first amination is computed by spin density population and verified by X‐ray crystallography. The zwitterionic structure of 4 is investigated in solution by ¹H NMR spectroscopy and in solid state by X‐ray diffraction. Furthermore, the crystal structure of 1 is presented. The energetic behavior of the aminated products as well as the starting materials 1 and 4 was investigated, regarding sensitivities and performance.     

吡啶基三唑功能化罗丹明化合物的合成

以2-溴甲基吡啶氢溴酸盐和叠氮化钠为原料,合成中间体2-叠氮甲基吡啶（1）;对羟基苯甲醛和溴丙炔经取代反应合成中间体4-（丙-2-炔基丙氧基）苯甲醛（2）; 2与1经点击反应制得关键中间体BPT（3）; 3与罗丹明B酰肼经还原胺化反应得罗丹明类荧光探针,其结构经¹H NMR, IR和元素分析表征。     

Synthesis of orthogonally protected 2-deoxystreptamine stereoisomers

Enantiomerically pure 4,6-diaminocyclohexenols are obtained from carbohydrate derived 1,7-dienes by ring-closing metathesis and palladium catalyzed allylic amination using o-nitrobenzenesulfonylamides as nucleophiles. In the latter reaction the use of a cyclic carbonate as a leaving group proved to be essential to facilitate a smooth substitution. The obtained compounds were converted into orthogonally protected diaminocyclitols, which are stereoisomers of the naturally occurring 2-deoxystreptamine, a constituent of aminoglycoside antibiotics.     

Imidazole derivatives that contain potentially labile groupings attached to the N atom. 7. Synthesis of 1-substituted 2-aminobenzimidazoles by ammonolysis of 1-R-3-methoxybenzimidazolium salts

A new method for the synthesis of 1-substituted 2-aminobenzimidazoles, which are difficult or impossible to obtain by direct amination with sodium amide, is proposed. The method consists in the action of liquid ammonia on 1-R-3-methoxybenzimidazolium salts. The reaction is accompanied by the addition of the amide ion in the 2 position and elimination of a methoxy group.See [1] for Communication 6.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1086–1088, August, 1982.     

N,2-二芳基二氮亚烯甲酰胺合成的新方法

偶氮化合物可用作非线性光学材料、激光盘信息存贮材料和现代科技中的油溶性染料［１］．传统偶氮化合物的制备有重氮盐偶合和取代肼氧化等许多方法［２～４］,其偶氮基两端一般联有烃基或芳环,而联有羰基的偶氮类化合物用通常方法难以制备．本文首次用Ｎ－溴代丁二酰亚...     

Lead-Catalyzed Synthesis of Azo Compounds by Ammonium Acetate Reduction of Aromatic Nitro Compounds

Abstract

Lead/ammonium acetate is a convenient reagent for the reduction of aromatic nitro compounds to the corresponding symmetrically substituted azo compounds. Various azo compounds containing additional reducible substituents such as halogen, nitrile, acid, phenol, ester, methoxy, etc., functions have been synthesized in a single step by the use of this reagent. The conversion is reasonably fast, clean, high yielding and occurs at room temperature in methanol.     

Azulene‐1‐azo‐2′‐thiazoles. Synthesis and properties

Several derivatives belonging to a new compound class, namely azulene‐1‐azo‐2′‐thiazoles, were prepared by the diazotization of 2‐aminothiazoles in the presence of HNO₃/H₃PO₄ followed by the coupling of diazonium salts with azulenes in buffered medium. The reactions proved to be general for this class, the yields are, however, considerably influenced by the substituents at thiazole moiety. For the first time a N‐oxide provided from an amino substituted five‐member nitrogenous heterocycle was diazotized and coupled. The structure of the obtained compounds was assigned and their physico‐chemical properties were discussed. The new azulene azo derivatives exhibit a strong bathochromic shift in UV‐Vis due to the intense push‐pull effect of aromatic system and to the intrinsic properties of thiazole moiety.     

Bisindoles. 15. Acidic condensation of bis(2-ethoxycarbonyl-5-indolyl) oxide and bis(2-ethoxycarbonyl-5-indolyl)methane with aromatic aldehydes

The acidic condensation of bis (2-ethoxycarbonyl-5-indolyl) oxide and bis(2-ethoxycarbonyl-5-indolyl)methane with aromatic aldehydes was studied. Bis(3-chloro) compounds with labile chlorine atoms, by nucleophilic substitution of which the corresponding dimethylamino, hydroxy, methoxy, acetoxy, cyano, and mercapto derivatives were obtained, were isolated.See [1] for communication 14.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 365–368, March, 1983.     

Chemoselective amination of 5-bromo-2-chloro-3-fluoropyridine

The chemoselective functionalization of 5-bromo-2-chloro-3-fluoropyridine (1c) is described. Catalytic amination conditions (Pd2dba3, Xantphos, base) afford exclusively the bromide substitution product (2) for both secondary amines and primary anilines. A reversal in chemoselectivity is observed under neat conditions in the absence of palladium catalysis, with substitution at the 2-chloro position preferred to generate 3. Last, selective substitution of the 3-fluoro group is achieved under SNAr conditions to afford the dihalo adduct (4).     

Nucleophilic Amination of Methoxy Arenes Promoted by a Sodium Hydride/Iodide Composite

A method for the nucleophilic amination of methoxy arenes was established by using sodium hydride (NaH) in the presence of lithium iodide (LiI). This method offers an efficient route to benzannulated nitrogen heterocycles. Mechanistic studies showed that the reaction proceeds through an unusual concerted nucleophilic aromatic substitution.     

Über den Verteilungssatz der Auxochrome bei Azokörpern IV Azokörper mit zueinander p-ständigen Auxochromen

In azo compounds with CH₃O groups in o-position to the azo groups the introduction of the weak auxochromes CH₃– and CH₃O– into the p-position to the methoxy group (m-position to the chromophor) causes relatively strong bathochromic effects, in conformity with the rule of repartition.     

Exploration of antioxidant activity of newly synthesized azo flavones and its correlation with electrochemical parameters along with the study of their redox behaviour

A series of 7-hydroxy-2-aryl-3-(2-aryldiazenyl)-4H-chromen-4-one derivatives was synthesized in quantitative yields. Herein, we demonstrate the antioxidant potential of the synthesized substituted azo flavones using 1,1-diphenyl-2-picryl-hydrazyl assay method along with the evaluation of their redox behaviour by cyclic voltammetry. The synthesized compounds manifested good antioxidant potential as compared to standard antioxidant ascorbic acid, which especially pertains to the compounds having methoxy and hydroxyl groups. A good correlation between minimum inhibitory concentration (IC₅₀) and deduced electrochemical parameter, i.e., half peak oxidation potential (E _p/2) values, was established.     

Pyridazines with heteroatom substituents in position 3 and 5. 2. Regioselective introduction of mercapto groups in pyridazines

The nucleophilic substitution of halogen in 3,5-dichloro-6-phenylpyridazine 1 , 5-chloro-2-methyl-6-phenylpyridazin-3(2H)-one 13 as well as in 3-chloro-2-methyl-6-phenylpyridazin-5(2H)-one 14 with methoxy, ethoxy and the 2-methyl-2-propanethiolate anion is described. In the last type of compounds the t-butylthio groups can be eliminated regioselectively with Lewis acids, resulting in the formation of monomercapto and mono-thiopyridazines.     

Colour and constitution of azo compounds derived from diaminoazines

Visible absorption spectra have been recorded for azo compounds derived from 2,5-dichlorosulphanilic acid azo-coupled with $\text{N}$,$\text{N}$-diethyl-m-phenylenediamine, and with azine analogues. The effects of the ring-aza substituents as well as cyano on the spectra indicate a surprising difference in sensitivity of the two ring positions meta to the azo group. M.O. calculations show chat the amino group ortho to the azo linkage introduces asymmetry into the HOMO, and this is responsible for the differing effects of substitution.