Utilization of bromination reactions for the determination of carbamazepine using bromate–bromide mixture as a green brominating agent

One titrimetric and two spectrophotometric procedures have been developed for the assay of carbamazepine (CBZ) in bulk drug, formulations and spiked human urine. The methods are based on the bromination of CBZ by the bromine generated in situ by the action of the acid on the bromate–bromide mixture. The twin advantages of avoiding liquid bromine and analysis in a cost-effective manner are realized. In titrimetry, the drug was treated with a known excess of bromate–bromide mixture in hydrochloric acid medium followed by the determination of unreacted bromine iodometrically. Spectrophotometry involves the addition of a measured excess of bromate–bromide reagent in acid medium to CBZ, and after the reaction is ensured to be complete, the residual bromine was determined by reacting with a fixed amount of either methyl orange and measuring the absorbance at 510 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B). Titrimetric procedure is applicable over the range of 1.00–7.50 mg CBZ, and the calculations are based on a 1:1 reaction stoichiometry (CBZ:KBrO₃). In spectrophotometric methods, Beer’s law is valid within concentration ranges of 0.25–1.50 and 0.50–6.00 μg ml⁻¹ CBZ for methods A and B, respectively. The proposed methods were successfully applied to the determination of CBZ in tablets and syrup, in addition to spiked human urine by the spectrophotometric methods, with mean recoveries of 95.50–104.0% and the results were statistically compared with those of an official method by applying Student’s t-test and F-test.     

Facile aerobic photo-oxidative synthesis of α-diketones from alkynes

We report a useful method for facile aerobic photo-oxidative synthesis of α-diketones from alkynes with MgBr₂·OEt₂. This procedure provides a practical synthetic method of α-diketones using easily handled bromine sources, harmless visible light, and molecular oxygen as terminal oxidant.     

Facile,efficient and diastereoselective synthesis of α-hydrazine tetrazoles through a novel one-pot four-component reaction

A novel and efficient method for the diastereoselective synthesis of α-hydrazine tetrazoles via an isocyanide-based multicomponent reaction is reported in good yields. The α-hydrazine tetrazoles were obtained by a facile azide Ugi four-component reaction (U-4CR) using cyclic ketones, trimethylsilyl azide, hydrazides, and corresponding isocyanide without any catalyst and with high bond forming efficiency at room temperature.     

Solvent-free synthesis of δ-carbolines/carbazoles from 3-nitro-2-phenylpyridines/2-nitrobiphenyl derivatives using DPPE as a reducing agent

A green and efficient preparation of functionalized δ-carbolines/carbazoles via reductive ring closure by 1,2-bis(dipenylphosphino)ethane under solvent-free conditions is described. The starting materials 3-nitro-2-phenylpyridines/2-nitrobiphenyl derivatives are readily prepared through Suzuki-Miyaura cross-coupling reaction from commercially available compounds. And the polar by-product ethane-1,2-diylbis(diphenylphosphine oxide) is easily removed from the relatively polar reaction mixture. Various substituted δ-carbolines/carbazoles are obtained in acceptable yields. It is particularly worth mentioning that substrates with electron-withdrawing groups (EWG) also give the desired products in good yield.     

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions has been developed.In the presence of PhI(OAc)₂ as promoter and under ambient conditions,the reactions of styrenes and triiodomethane undergo the transformation smoothly to deliver the corresponding a-iodoketones without additional photocatalyst in good yields under sunlight irradiation.Mea nwhile,the reactions of styrenes with tribromomethane and trichloromethane generate the desiredα-bromoketones and a-chloroketones in high yields by using Ru(bpy)₃Cl₂ as a photocatalyst under blue LED(450-455 nm) irradiation.     

Facile synthesis of α-hydroxy carboxylic acids from the corresponding α-amino acids

An effective and improved procedure is developed for the synthesis of α-hydroxy carboxylic acids by treatment of the corresponding protonated α-amino acid with tert-butyl nitrite in 1,4-dioxane–water. The amino moiety must be protonated and located α to a carboxylic acid function in order to undergo initial diazotization and successive hydroxylation, since neither β-amino acids nor acid derivatives such as esters and amides undergo hydroxylations. The method is successfully applied for the synthesis of 18 proteinogenic amino acids.     

Highly efficient one-pot synthesis of α-aminophosphonates using nanoporous AlSBA-15 catalyst in a three-component system

Research on Chemical Intermediates - Nanoporous AlSBA-15 catalysts with different nSi/nAl ratios (41, 129, and 210) were synthesized using a hydrothermal method. These catalysts were characterized...     

Hydrotalcite-bound ruthenium as a multifunctional heterogeneous catalyst for one-pot synthesis of α-alkylated nitriles and quinolines

This article reviews our recent progress in one-pot syntheses of α-alkylated nitriles and quinolines by heterogeneous catalysis with hydrotalcite-bound ruthenium based on cooperative action between cationic Ru species and the base sites of the hydrotalcite surface.     

A convenient one-pot synthesis of 4-amino-3-arylpyrazoles from α-phthaloylaminoacetophenones

Condensation of α-phthaloylaminoacetophenones 1a-c with N,N-dimethylformamide dimethyl acetal afforded the novel enamines 3a-c. Cyclization of 3 with hydrazine, alkylhydrazine or phenylhydrazine salts (4a-d) gave 4-phthaloylamino-3-arylpyrazoles 7–9 in high yields. Deprotection of 7–9 was accomplished with hydrazine to provide 4-amino-3-arylpyrazoles 5 in good yields.     

Concise synthesis of α-trisubstituted amines from ketones using N-methoxyamines

Three-component allylation and cyanation utilizing a ketone and an N-methoxyamine are reported. The high nucleophilicity of the N-methoxyamine and high electrophilicity of the corresponding iminium ion enable the concise synthesis of α-trisubstituted amines in a single step.     

Facile synthesis of cyclic α-perfluoroalkyl-α-aminophosphonates

Addition of diethylphosphite to cyclic α-perfluoalkyl substituted imines in the presence of boron trifluoride etherate as a catalyst presents an efficient route for racemic saturated cyclic α-perfluoroalkyl-α-aminophosphonates. Hydrolysis of latter compounds gives the corresponding α-aminoalkanephosphonic acids existing as the corresponding zwitterions according IR and X-ray data.     

Facile one-pot synthesis of 5-amino-1H-pyrazole-4-carbonitriles using alumina–silica-supported MnO2 as recyclable catalyst in water

Research on Chemical Intermediates - A novel, facile, one-pot, multicomponent protocol for the synthesis of 5-amino-1H-pyrazole-4-carbonitrile derivatives has been developed using...     

Facile one-pot synthesis of unprecedented β,β'-linked porphyrin-chlorin heterodimers

A type of porphyrin-chlorin heterodimers have been synthesized in a one-pot reaction, and their porphyrin and chlorin moieties are directly β,β'-linked through an sp(3) carbon. These species have been characterized by mass spectroscopy, (1)H NMR, X-ray crystallography, cyclic voltammetry, UV-vis and fluorescence spectroscopy.     

An efficient synthesis of β-acylureas via a three-component, one-pot synthesis using TCS/ZnCl2

A simple and efficient one-pot, three-component synthesis of new trisubstituted ureas containing diastereotopic protons is achieved via the reaction of aromatic aldehydes, aromatic ketones, and dimethyl cyanamide using a TCS/ZnCl₂ reagent mixture at room temperature.     

Efficient synthesis of α-tertiary α-silylamines from aryl sulfonylimidates via one-pot, sequential C-Si/C-C bond formations

An efficient and flexible route for the synthesis of α-tertiary (α,α-dibranched) α-silylamines via sequential reactions of sulfonylimidates using readily available phenyldimethylsilyllithium and Grignard reagents is described. The procedure allows successive formation of C-Si/C-C bonds in a single flask.     

Regio- and stereoselective synthesis of multisubstituted olefins and conjugate dienes by using α-oxo ketene dithioacetals as the building blocks

An efficient palladium(0)-catalyzed, Cu(I)-mediated synthetic route to trisubstituted olefins and conjugate dienes has been developed via oxo directing Liebeskind-Srogl cross-coupling reactions of gem-dihaloolefin-type α-oxo ketene dithioacetals with aryl and alkenylboronic acids. The synthetic protocol has demonstrated rare examples of transition-metal-promoted transformations of ketene dithioacetals, providing a novel route to highly functionalized conjugate dienes.     

Distereoselective one-pot synthesis of pyrimidopyrimidines using sulfated tin oxide as a reusable catalyst： An extension of Biginelli-type reaction

The Biginelli-type compounds 4,5,8a-triarylhexahydropyrimido[4,5-d]pyrimidine-2,7（1H,3H）-diones were synthesized by a one-pot three-component reaction using sulfated tin oxide as a reusable catalyst. This method has the advantages of high yields, short reaction time, simple starting materials and reusability of catalyst for several times.     

Cyclic chlorophosphites as scaffolds for the one-pot synthesis of α-aminophosphonates under solvent-free conditions

New α-aminophosphonates of the type (OCH₂CMe₂CH₂O)P(O)CH(NHCO₂R)(R′) [6a-i, 7a-e, and 8a-c] have been synthesized in high yields by a three-component reaction using (OCH₂CMe₂CH₂O)PCl (3), benzamide (or urethane or benzyl carbamate), and an aldehyde without using any catalyst under solvent-free conditions. This route can be readily adapted for bis-aminophosphonates as well as optically active binaphthoxy α-aminophosphonates; it also tolerates the phenolic -OH group as shown by the synthesis of hydroxy functionalized aminophosphonates. Partial hydrolysis of compounds 7a-d leads to products in which the phosphorinane ring is cleaved first. Compounds (OCH₂CMe₂CH₂O)P(O)CH[NHC(O)Ph](9-anthryl) (6f) and optically pure (R,S)-(−)-(C₂₀H₁₂O₂)P(O)CH(NHCO₂Et)(Ph) (14a) were characterized by X-ray crystallography.     

Facile and efficient aerobic one-pot synthesis of benzimidazoles using Ce(NO3)3·6H2O as promoter

A series of 2-substituted benzimidazoles was synthesized under aerobic conditions, by simply heating 1,2-diaminobenzene and aldehydes in DMF at 80 °C, employing Ce(NO₃)₃·6H₂O as promoter and atmospheric air as an efficient oxidant. The procedure afforded the products from good to excellent yields. Furthermore, this new economic and eco-friendly protocol avoids the use of toxic metal catalysts, as well as additional bases and oxidants.     

Facile one-pot synthesis of tetrahydroisoquinolines from amino acids via hypochlorite-mediated decarboxylation and Pictet–Spengler condensation

A convenient method for oxidative decarboxylation of α-amino acids is presented. The aldehyde products may be isolated or converted to tetrahydroisoquinolines by addition of dopamine via Pictet–Spengler reaction. Racemic products are generated by phosphate buffer >300 mM to maximize regioselectivity. (S)-Enantiomer products are generated by norcoclaurine synthase reaction in maleic acid buffer to minimize chemical background reaction.