Selective synthesis of oxazoles and pyrazines from α-bromo-1-phenylethanone using a by-product-promoted strategy

Oxazoles and pyrazines are fundamental heterocycles that widely found in natural products or drugs. In this work, a selective strategy for oxazoles and pyrazines synthesis using α-bromo-1-phenylethanone and ammonium acetate as starting materials was reported. This methodology features mild reaction conditions, readily accessible starting materials and good chemoselectivity. Mechanistic study indicates that this reaction involves a by-product-promoted (BPP) process for the formation of oxazole, that is, the in-situ formed hydrogen bromide (HBr) during the reaction promotes the whole tandem process.     

Catalytic metallonitrene/alkyne metathesis: a powerful cascade process for the synthesis of nitrogen-containing molecules

A conceptually novel metallonitrene/alkyne metathesis cascade reaction has been developed for the construction of nitrogen-containing compounds from simple alkyne starting materials. Rhodium(II) tetracarboxylate salts are efficient catalysts for this reaction, in which an electrophilic rhodium nitrene is trapped by an alkyne, resulting in the formation of a new C-N bond and the generation of a reactive metallocarbene for cascade reaction. The reaction is tolerant of both alkyl and aryl substituents on the alkyne, and proceeds at room temperature in a variety of common solvents. The modular nature of the reaction allows for the rapid construction of congested bicyclic systems from remarkably simple alkyne starting materials.     

Temperature-controlled Cascade Reaction of Phloroglucinoltribenzyl Ether Promoted by Trifluoroacetic Anhydride and Trifluoroacetic Acid

We report the first trifluoroacetic anhydride-and trifluoroacetic acid-promoted cascade reaction with phloroglucinoltribenzyl ether and carboxylic acid as starting materials. By simply varying the temperature of systems containing the same starting materials, different products were produced in high yields. A three-step consecutive reaction process was also proposed.     

A Complete Switch of the Directional Selectivity in the Annulation of 2‐Hydroxybenzaldehydes with Alkynes

Controlling reaction selectivity is an eternal pursuit for chemists working in chemical synthesis. As part of this endeavor, our group has been exploring the possibility of constructing different natural product skeletons from the same simple starting materials by using different catalytic systems. In our previous work, an isoflavanone skeleton was obtained from the annulation of a salicylaldehyde and an alkyne when a gold catalyst was employed. In this paper, it is shown that a coumarin skeleton can be efficiently obtained through an annulation reaction with the same starting materials, that is, terminal alkynes and salicylaldehydes, by simply switching to a rhodium catalyst. A plausible reaction mechanism is proposed for this new annulation based on isotopic substitution experiments.     

Concise synthesis of isoquinoline via the Ugi and Heck reactions

[reaction: see text] Two types of isoquinoline scaffolds were successfully constructed in a combinatorial format via the Ugi four-component reaction and the Pd-catalyzed intramolecular Heck reaction, starting from readily available starting materials.     

Domino "Staudinger/semi-aza-Wittig/fragmentation" reactions of gamma-azido-beta-hydroxyketones

Treatment of gamma-azido-beta-hydroxyketones with triphenylphosphine resulted, depending on the structural features of the starting materials, in a domino "Staudinger/semi-aza-Wittig/fragmentation" reaction rather than a normal aza-Wittig reaction. 2-Azido-1-hydroxy-1-(2,4-dioxoalkyl)cyclopentanes, readily available by condensation of 1,3-dicarbonyl dianions with 2-azidocyclopentanone, proved to be optimal starting materials for these reactions which afforded 1-(1,3-dioxoalkyl)amino-2-(alkylidene)cyclopentanes.     

Study of kinetics of reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw materials with sulphuric acid has been studied in a non-isothermal-non-adiabatic type calorimeter. The influence of different starting conditions, temperature and ilmenite particle-size distribution on the thermo-kinetics of the reaction was investigated. A kinetic model is presented for this heterogeneous system for a specified ilmenite particle-size distribution and starting temperature. On the basis of this model and experimentally determined parameters it it possible to analyse by simulation the autothermic reaction of digestion of different titanium ores with sulphuric acid.     

A Cu (I) catalyzed large scale synthesis of an antipsychotic drug substance Clozapine with new precursor 2-chloro benzoic acid

Development of an economic and commercial manufacturing process for an anti-psychotic drug substance clozapine with an alternative key starting material (2-chloro benzoic acid) in the place of literature reported key starting material Anthranilic acid. To avoid narcotic key starting materials usage in drug substances the author invented a commercially available raw material 2-chlorobenzoic acid, which reacts with another key starting material 4-chloro-1, 2-diamino benzene. This reaction proceeds through Ullman reaction to produce multi scale level Clozapine which quality meets the ICH requirements.     

Efficient access to azaindoles and indoles

[Structure: see text] An expedient, catalytic method for the synthesis of diverse azaindoles and indoles, starting from readily available and inexpensive starting materials, is described. Conditions were developed for effective reductive alkylation of electron-deficient o-chloroarylamines, substrates previously viewed as poor partners in this reaction. The derived N-alkylated o-chloroarylamines were elaborated to N-alkylazaindoles and N-alkylindoles via a novel one-pot process comprising copper-free Sonogashira alkynylation and a base-mediated indolization reaction.     

3-亚甲基异吲哚酮的合成新方法

亚甲基异吲哚酮衍生物2是一类重要的药物合成中间体, 近来又被用作新型有机金属染料合成的配体。文献报道化合物2的主要合成方法是采用苯基锂衍生物的分子内反应, 或以有机钛为主要原料合成目标产物, 但以上方法原料难得, 反应条件苛刻, 产率不理想, 难以大规模合成。我们首次发现以苯基环缩醛为原料一步法合成亚甲基异吲哚酮2的新方法, 原料易得, 条件温和, 操作简便, 产率良好, 为苯甲醛作起始原料合成化合物2提供了一条新途径。     

Heteroatom as a promotor: synthesis of polyfunctionalized benzenes and naphthalenes

Construction of a new benzene via the electrocyclization of diene-allene is an efficient protocol to access polysubstituted benzenes from simple, readily available starting materials. In this paper, we present a comprehensive study of a heteroatom-promoted propargyl-allenyl isomerization and electrocyclization for the facile and efficient synthesis of polyfunctionalized benzenes and naphthalenes. As a result of the readily accessible starting materials, simple operation, and mild conditions, this reaction should be an appealing strategy in organic synthesis.     

A simple and convenient procedure for the synthesis of 1-aminophosphonates from aromatic aldehydes

A simple, efficient, possible industrial process has been developed for the synthesis of 1-aminophosphonic acids from simple starting materials. As described below, treatment of aromatic aldehydes with ammonia and reaction with diethyl phosphite gives diethyl N-(arylmethylene)-1-aminoaryl methylphosphonates, which can be easily hydrolyzed to diethyl 1-aminoarylmethylphosphonates. This method is easy, rapid, and good yielding for the synthesis of 1-aminoalkylphosphonates from simple starting materials.     

Organocatalytic synthesis of dipyrromethanes by the addition of N-methylpyrrole to aldehydes

The reaction of aldehydes with N-methylpyrrole carried out in the presence of catalytic pyrrolidinium tetrafluoroborate at room temperature affords the corresponding dipyrromethanes and minor amounts of tripyrranes. This new, mild, and convenient process represents the first organocatalytic synthesis of dipyrromethanes. The products are obtained in chemical yields similar to those obtained with existing methods, which, however, require either a much larger excess of heterocycle (when aldehydes are employed as starting materials), or more drastic reaction conditions (when aldehyde equivalents are used as starting materials) than those employed here. A mechanism is proposed to explain the course of this reaction.     

New light on an old story: facile and efficient synthesis of 1,3-diaryl-5-spirohexahydropyrimidines via a six-molecule, three-component mannich-type reaction

A facile and efficient synthesis of 1,3-diaryl-5-spirohexahydropyrimidines via a one-pot condensation of anilines, formaldehyde, and cyclohexanones is reported. In this one-pot, three-component reaction, six molecules of reactants are involved and six new covalent bonds are generated. Bicyclic products are obtained from the starting materials in one pot using readily available starting materials and catalysts.     

3-亚甲基异吲哚酮的合成新方法(英文)

亚甲基异吲哚酮衍生物2是一类重要的药物合成中间体,近来又被用作新型有机金属染料合成的配体。文献报道化合物2的主要合成方法是采用苯基锂衍生物的分子内反应,或以有机钛为主要原料合成目标产物,但以上方法原料难得,反应条件苛刻,产率不理想,难以大规模合成。我们首次发现以苯基环缩醛为原料一步法合成亚甲基异吲哚酮2的新方法,原料易得,条件温和,操作简便,产率良好,为本甲醛作起始原料合成化合物2提供了一条新途径。     

Sequential MCR/Fisher indolization strategy for the construction of polycyclic carbazole derivatives

A one-pot method for the synthesis of novel polycyclic carbazole derivatives from readily available starting materials using a sequential multicomponent reaction/Fisher indolization strategy is described.     

Generation of indeno[1,2-c]pyrroles via a Pd-catalyzed reaction of 2-alkynylbromobenzene with propargylic sulfonamide

A novel route for the efficient assembly of indeno[1,2-c]pyrrole derivatives via a palladium-catalyzed tandem reaction of 2-alkynylbromobenzene with propargylic sulfonamide is reported. The starting materials are easily available, and the reaction proceeds smoothly with good functional group tolerance.     

Lithiation directed by amino alkoxides. Application to the synthesis of new disubstituted dihydrodipyridopyrazines

The synthesis of new 4,6-disubstituted dihydrodipyridopyrazines starting from corresponding carboxaldehydes via lithiation directed by alpha-amino alkoxides is described. The N,N,N'-trimethylethylenediamine was used as amine component for in situ formation of the alpha-amino alkoxides. After optimization, this reaction allowed easy access to new interesting starting materials for further applications by palladium-catalyzed reactions.     

Cyclisierungen unter beteiligung von fluoridionen, 3. Mittell. [1,2] teilfluorierte 1.3- und 1.4-dioxane

Cyclization of 2-(2-chloroethoxy)-perfluorocarboxylic acid halides 3 with alkali metal fluoride gives 2.3-perfluoro- 1.4-dioxanes 6 with yields up to 84 %. This reaction is also used for the preparation of 4.5.6-perfluoro-1.3- dioxanes 12 starting from 3-chloromethoxyperfluorocarbonyl compounds 11. — The preparation of starting materials is described.     

Osmium‐Mediated Oxidative Cyclizations: A Study into the Range of Initiators That Facilitate Cyclization

A general route to prepare substituted, saturated five‐membered heterocycles has been developed. The application of a wide range of starting materials to the osmium‐catalyzed oxidative cyclization reaction is described. Diols, hydroxy‐amides, hydroxy‐sulfonamides, and carbamates all cyclize in moderate to excellent yields to give cis‐tetrahydrofurans and pyrrolidines, depending upon the position of the heteroatoms in the starting materials. These cyclizations all proceed with near total selectivity for the cis‐heterocycles, and with stereospecific introduction of a hydroxy group adjacent to the ring. Moreover, routes to enantiopure starting materials are described, which give enantiopure products upon cyclization. Catalyst loadings of as low as one mol percent have been successfully employed for this transformation.