苯炔参与的去芳构化反应研究进展

去芳构化反应是有机化学热点研究领域之一,可从二维平面分子出发构筑高官能团化的三维立体分子.近年来,苯炔作为一类高活性中间体被有机化学家们广泛用于去芳构化反应研究中,并取得了一系列创新成果.从含氮芳杂环同苯炔的去芳构化反应、苯炔与双烯体的[4+2]环加成去芳构化反应以及苯炔以其它途径参与的去芳构化反应三个方面,对机理进行...     

Transition-Metal-Free α-Arylation of β-Keto Amides via an Interrupted Insertion Reaction of Arynes

Direct α-arylation reactions of secondary β-keto amides with arynes, generated by fluoride-induced elimination of ortho-silyl aryltriflates, are described. The transformation proceeds via an interrupted insertion reaction of arynes and leads to densely functionalized aromatic compounds exhibiting a chiral 'all carbon' quaternary center under transition-metal-free conditions. An organocatalytic asymmetric version of the reaction also proved possible, affording the proof of concept that arynes can be involved in enantioselective transformations.     

Peculiarities of the reactions of autohydrogenolysis of organosulfur compounds in the presence of MAlCl4

The reactions of hydrogenolysis of representatives of various classes of organosulfur compounds (hexyl mercaptan, dihexyl sulfide, dihexyl disulfide, thiophene, and concentrates of sulfides isolated from diesel fuel) in the presence of MAlCl₄ (M= Li, Na, K) was studied. High degrees of conversion of sulfur-containing compounds in hydrogenolysis reactions are achieved at substantially low temperatures (150–250°C). The reactions of elimination of sulfur from organosulfur compounds with the formation of H₂S occur with the participation of hydride ions, formed in the process; in this case the solvent performs the function of a proton donor. In liquid conversion products the presence of aromatic hydrocarbons is detected. The scheme of occurrence of the coupled reactions occurring in the presence of MAlCl₄ is cited.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 135–140, January, 1991.     

Catalytic Carbonylation and Carboxylation of Organosulfur Compounds via C−S Cleavage

Transition‐metal‐catalyzed carbonylation with CO gas occupies a privileged position in organic synthesis for the synthesis of carbonyl compounds. Although this attractive and useful chemistry has led many researchers to investigate carbonylative transformations of various organic (pseudo)halides, C?S‐cleaving carbonylation of organosulfur compounds has been fairly limited. Recently, a broad spectrum of C?S‐cleaving transformations has been emerging in the field of cross‐coupling. In light of the importance of carbonyl compounds as well as considerable advancement for employing organosulfur compounds as competent surrogates of (pseudo)halides, carbonylative transformations of C?S bonds should be of high value. This Minireview focuses on catalytic C?S carbonylation of organosulfur compounds with CO or its equivalents. In addition, reductive carboxylation of C?S bonds with CO₂ is described.     

Self-assembled monolayers on electrode surfaces: a probe for redox kinetics

The formation and characterization of self-assembled monolayers of organosulfur compounds like alkanethiols and dialkyl (di)sulfides on metal surfaces such as gold are areas of current research interest. The presence of an aromatic ring in a thiol molecule can enhance the binding between Au and the thiol, resulting in the formation of compact and impervious self-assembled monolayers. The formation of a monolayer of 2-mercaptobenzothiazole (MBT), containing an aromatic group with a fused thiazole ring but no long alkyl chain, is achieved on a gold electrode surface. Voltammetric investigations of ferro/ferricyanide and ferrous/ferric redox systems carried out on this Au|MBT electrode are reported. Further, the possibility of using such an Au|MBT electrode to distinguish between inner and outer sphere electron transfer reactions is indicated. Received: 2 January 1998 / Accepted: 14 May 1998     

Synthesis of azobenzenes: the coloured pieces of molecular materials

Azobenzenes are ubiquitous motifs very important in many areas of science. Azo compounds display crucial properties for important applications, mainly for the chemical industry. Because of their discovery, the main application of aromatic azo compounds has been their use as dyes. These compounds are excellent candidates to function as molecular switches because of their efficient cis-trans isomerization in the presence of appropriate radiation. The classical methods for the synthesis of azo compounds are the azo coupling reaction (coupling of diazonium salts with activated aromatic compounds), the Mills reaction (reaction between aromatic nitroso derivatives and anilines) and the Wallach reaction (transformation of azoxybenzenes into 4-hydroxy substituted azoderivatives in acid media). More recently, other preparative methods have been reported. This critical review covers the various synthetic methods reported on azo compounds with special emphasis on the more recent ones and their mechanistic aspects (170 references).     

A new class of cathode materials for rechargeable magnesium batteries: Organosulfur compounds based on sulfur–sulfur bonds

A class of energy storage materials, organosulfur compounds with S–S bonds, has been proposed as novel cathode materials for rechargeable magnesium batteries. The cleavage and recombination of S–S bonds formed during discharge and charge process are the key components for the capacity. The cathode performance of three organosulfur materials, i.e. 2,5-dimercapto-1,3,4-thiadiazole (DMcT), poly-2,2′dithiodianiline (PDTDA) and a conductive sulfur-containing material (CMS) were characterized here. Among them, DMcT compounded with polyaniline (PAn) can provide a relatively flat discharge potential at about 1.4 V vs. Mg/Mg²⁺. PDTDA exhibits better kinetics and electrical conductivity based on the intramolecular electrocatalytic effect of the aniline moiety on thiolate anions. CMS compounded with PAn produces stable backbones to provide electrically conducting channels and higher disulfide bond content; it exhibits nearly 120 mAh/g initial discharge capacity and good capacity retention. We expect that further improvements to the capacity and cyclability will make organosulfur compounds potential cathode materials for magnesium batteries.     

Highly efficient route to fused polycyclic aromatics via palladium-catalyzed aryne annulation by aryl halides

Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

Sulfonimidamides and Imidosulfuric Diamides: Compounds from an Underexplored Part of Biologically Relevant Chemical Space

Two novel solid reagents—1-sulfonimidoyl- and 1-sulfamimidoyl-3-methylimidazolium derivatives—for the synthesis of sulfonimidamides and imidosulfuric diamides, respectively, were developed. It is shown that these reagents are very effective in substitution reactions with various N- and O-nucleophiles; therefore, they significantly extend the accessibility to the chemical space covered by organosulfur(VI) compounds with S=N bonds. In addition, previously unknown imidosulfuric diamides with free imino nitrogen groups were prepared, and their physical and chemical properties were characterized (including molecular geometry, pK_a, Log P, microsomal stability, and reactivity towards typical electrophiles). Similar to other organosulfur(VI) derivatives with S=N bonds, these compounds can be considered as promising bioisosteres of amides, ureas, or sulfonamides.     

One century of aryne chemistry

Arynes, which are formally derived from aromatic rings by abstraction of two hydrogen atoms, have been a focus of organic chemistry for 100 years. In contrast to ortho-benzyne, which is mentioned in almost every introductory textbook on organic reaction mechanisms as a reactive intermediate of nucleophilic aromatic substitution, the meta and para isomers were regarded as rather exotic until recently. This situation has changed dramatically with the discovery of the enediyne antibiotics, a promising new class of antitumor drugs, and has aroused the interest of research groups from all branches of chemistry. Nowadays, arynes and related compounds are among the most intensively studied systems in chemistry. However, many aspects of the chemistry of these reactive intermediates are not well understood yet. In this review we outline the historical developement with an emphasis on recent progress in this challenging field of research.     

Aryne insertion into α-cyanocarbonyl compounds: direct introduction of carbonyl and cyanomethyl moieties into the aromatic skeletons

Two different carbon functional groups can be introduced simultaneously into 1,2-positions of aromatic skeletons based upon a novel insertion reaction of arynes into a carbonyl-cyanomethyl σ-bond of α-cyanocarbonyl compounds.     

Facile insertion reaction of arynes into carbon-carbon sigma-bonds

The carbon-carbon sigma-bond of various beta-dicarbonyl compounds was found to add to the triple bond of arynes under extremely mild conditions, leading to direct introduction of different carbon functional groups into the aromatic skeletons.     

Determination of polycyclic aromatic sulfur heterocycles in diesel particulate matter and diesel fuel by gas chromatography with atomic emission detection

The sulfur content of diesel fuel is of environmental concern because sulfur can facilitate the formation of diesel particulate matter (DPM) and sulfur dioxide (SO2) in the exhaust can poison catalytic converters. The US Environmental Protection Agency (EPA) has established more stringent regulations to reduce the sulfur content of diesel fuels in the near future. In this study, various types of organosulfur compounds in DPM extracts and the corresponding fuels have been determined by gas chromatography with atomic emission detection. The diesel fuels used have sulfur contents of 2284 and 433 ppm, respectively, and are labeled as high-sulfur and low-sulfur diesel fuels. The compounds identified are mainly polycyclic aromatic sulfur heterocycles (PASHs). In the fuels tested, trimethylbenzothiophenes (TMBTs), dibenzothiophenes (DBTs), and 4-methyldibenzothiophene (4-MDBT) were the most abundant sulfur compounds, while larger PASH compounds were more abundant in DPM extracts. The high-sulfur diesel fuel contained a larger proportion of PASHs with one or two rings (lighter PASHs). In DPM, the concentrations of total organic sulfur and individual PASHs are higher for the high-sulfur diesel fuel, and the relative percentage of one or two-ring PASHs is higher as well. The influence of engine load on the DPM composition was also examined. With increasing load, the PASH concentration in DPM decreased for lighter PASHs, increased for heavier PASHs, and had a bell-shaped distribution for PASHs in between.     

Recent advances in the application of sulfinic acids for the construction of sulfur-containing compounds

Sulfur-containing organic compounds display wide applications in the field of materials science, synthetic chemistry, and pharmaceutical industry. Thus, numerous synthetic strategies have been developed for the synthesis of sulfur-containing compounds in synthetic chemistry. In recent years, the utilization of sulfinic acids as versatile synthons has emerged as attractive and powerful approach to access various organosulfur compounds through sulfonylation, sulfinylation or sulfenylation reaction...     

Cyclotrimerization reactions of arynes and strained cycloalkynes

The use of arynes and related species as substrates in metal-catalyzed cycloaddition reactions leads to structurally interesting products. Palladium-catalyzed cyclotrimerization of arynes provides a new method for the synthesis of polycyclic aromatic hydrocarbons. For instance, the chemoselective formal [2 + 2 + 2] cocycloaddition of 2,3-triphenylynes with alkynes affords extended triphenylenes, which are good candidates to behave as liquid crystals. Cotrimerization of benzyne and electron-deficient alkenes selectively affords dihydrophenanthrenes or ortho-olefinated biaryls depending on the catalytic system employed. The use of 2,2'-bis(diphenylphosphino)-1,1'-binophythyl (BINAP)-based palladium(0) catalysts in the cocyclotrimerization of 7-methoxynaphthalyne and dimethyl acetylenedicarboxylate affords an enantiomerically enriched tetrasubstituted pentahelicene, the first example of a metal-catalyzed enantioselective reaction involving arynes. Strained cyclic alkynes can also participate in the palladium-catalyzed cyclotrimerization reactions, which again lead to structurally interesting products.     

Generation, structure and reactivity of arynes: A theoretical study

The semiempirical AM1 SCF-MO method is used to study the benzyne mechanism for aromatic nucleophilic substitution of various m-substituted chlorobenzenes and 3-chloropyridine. The calculations predict that most of the fixed substituents studied here would induce the formation of 2,3-arynes through their electron-withdrawing resonance or inductive effects. The geometry and electronic structure of the 2,3- and 3,4-arynes investigated here, confirm the generally acceptedo-benzyne structure postulated for arynes. The sites of nucleophilic addition to arynes as predicted here are in fair agreement with expectation and experimental findings.     

Direct C-arylation of beta-enamino esters and ketones with arynes

An efficient, mild, and general method for the C-arylation of beta-enamino esters and ketones with arynes has been developed. This methodology provides a facile and direct access to a variety of substituted aromatic beta-enamino compounds in moderate to excellent yield. [reaction: see text]     

Selective palladium-catalyzed cocyclotrimerization of arynes with dimethyl acetylenedicarboxylate: A versatile method for the synthesis of polycyclic aromatic hydrocarbons

Benzyne (1a) and the substituted derivatives 4,5-difluorobenzyne (1b) and 3-methoxybenzyne (2) undergo chemoselective palladium-catalyzed [2 + 2 + 2]-cocyclotrimerization with dimethyl acetylenedicarboxylate (DMAD) to afford the corresponding phenanthrenes and/or naphthalenes. The major products are phenanthrenes if Pd(PPh(3))(4) is used as the catalyst, naphthalenes if Pd(2)(dba)(3) is used. When the method is applied to polycyclic arynes 3-6, which are generated from the corresponding o-trimethylsilylaryl triflates, the same reactivity pattern is observed: the reaction can be selectively directed either toward the cocyclization of one molecule of aryne and two molecules of alkyne or to the reaction of two molecules of aryne with one molecule of alkyne, by appropriate choice of the palladium catalyst. The synthesis of polycyclic aromatic compounds 33-39 using this methodology is reported.     

Simple molecule-based fluorescent sensors for vapor detection of TNT

1,4-Diarylpentiptycenes (1a-e) were synthesized from 1,4-dichloro- or 1,4-difluoro-2,5-diarylbenzene derivatives by double base-promoted dehydrohalogenation to give corresponding arynes, which in the presence of anthracene undergo cycloaddition providing 1,4-diarylpentiptycenes in moderate overall yields. The resulting 1,4-diarylpentiptycenes show fluorescence modulated by the 1,4-aryl residues. The fluorescence is quenched in the presence of vapors of nitroaromatic compounds suggesting potential application in sensing of explosives.     

Evaluation of desulfurization procedures for the elimination of sulfur interferences in the organotin analysis of sediments

Different clean-up and desulfurization procedures were compared in order to check their efficiency in eliminating elemental sulfur and organosulfur compounds from sediment extracts. Adsorption column chromatography cannot remove elemental sulfur or organosulfur compounds. Treatment with activated copper powder only removes elemental sulfur, but organosulfur compounds remain in the extract, and phenyltins are partially lost (up to 50%). Ligand exchange chromatography with AgNO₃-coated silica gel as adsorbent effectively removes elemental sulfur and interfering organosulfur compounds from the sediment extract allowing the quantitation of butyltins with recoveries >80%. Since the phenyltin compounds do not survive the desulfurization step, they should be measured in the untreated extract.