Use of Di‐tert‐butyl‐dicarbonate Both as a Protecting and Activating Group in the Synthesis of Dipeptides

Amide formation from amino acids was achieved in an easy and convenient one‐pot procedure using di‐tert‐butyl dicarbonate both as a protecting and an activating agent. A number of dipeptides have been synthesized in good yields.     

Application of the PMC Protecting Group in the Efficient Synthesis of 4,4‐Disubstituted Piperidines

Abstract

An efficient synthesis of the 4,4‐disubstituted piperidine scaffold 1 was accomplished by treating the PMC N‐protected α,β‐unsaturated ethyl cyanoacetate 9 with various Grignard reagents (R₁MgX). Subsequent heating at 190°C in a strong base provided carboxylic acids 12–20b in good yield. The PMC group was easily removed at room temperature with 33% HBr in acetic acid.     

Facile Synthesis of Isoquinolines, β‐Carbolines,and 3‐Deazapurines

Isoquinoline, β‐carbolines, and 3‐deazapurines were prepared in 52–81% yields via oxidative decarboxylation of cyclic α‐amino acids using ammonium persulfate as an oxidant in the presence of catalytic silver.     

Selective Removal of the Isopropylidene Group in 4-O-Protected 1,6-Anhydro-2,3-O-Isopropylidene-β-D-Mannopyranose and the Conformational Impact of it

Abstract

Pyridinium p-toluenesulfonate (PPTS) is a reagent of choice for the selective removal of an O-isopropylidene group in a 1,6-anhydro-β-d-aldohexopyranose, where the remaining OH-group is protected.     

Simple and Efficient Synthesis of 4,7‐Dimethoxy‐1(H)‐indene

Stirring 4,7‐dimethoxy‐1‐indanol in chloroform at room temperature in the presence of a catalytic amount of p‐toluenesulfonic acid gave 4,7‐dimethoxy‐1(H)‐indene in quantitative yield. Other solvents, including benzene, which was the most frequently used one for this reaction, gave mostly polymeric materials. The new method was also effective for dehydration of other electron‐rich benzylic alcohols.     

Solid‐Solid Phase and Solvent‐Free Oxidative Removal of N‐(4‐Alkoxyphenyl) Groups of Monocyclic β‐Lactams with Ceric Ammonium Nitrate as a Cheap,Simple, and Efficient Method

Five N‐(4‐methoxyphenyl)‐ and five N‐(4‐ethoxyphenyl)‐β‐lactams were prepared by ketene‐imine [2+2] cycloaddition (Staudinger reaction). Then these 2‐azetidinones were N‐dearylated by grinding together with ceric ammonium nitrate without hazardous solvents in good to excellent yields. The solid‐solid phase N‐dearylation is easier, simpler, and more efficient than the general method in solution. The pure N‐unsubstituted β‐lactams obtained by a nontedious workup and without further purification.     

Simple and Convenient Synthesis of 4‐Unsubstituted‐3‐(3‐Oxoalkyl)isocoumarins

A simple transformation of 2‐alkylfurans and 2‐formylbenzoic acids into 4‐unsubstituted 3‐(3‐oxoalkyl)isocoumarins is described. It is based on the synthesis of 2‐(2‐carboxybenzyl)furans followed by their acid‐catalyzed recyclization to the target isocoumarins.     

The Preparation and Application of Bismuth (III) Ion‐Selective Electrode Based on Nanoparticles of Bismuth Sulfide

Abstract

Nanoparticles of bismuth sulfide were prepared in the organic phase and the optimum synthesis conditions for the nanoparticles were studied in detail. Transmission electron microscope (TEM) results indicated that the size distribution of the nanoparticles was proportional with an average diameter of 46.4 nm. A novel bismuth ion‐selective electrode (ISE) was prepared by dispersing the bismuth sulfide nanoparticles in polyvinylchloride (PVC) membrane. The linear range was 1.00×10^?8～1.00×10^?4 mol L^?1 and the detection limit was 8.10×10^?9 mol L^?1. The response of the electrode was fast with quite reasonable reproducibility and stability. It was used to determine bismuth in three kinds of stomach medicines and the results were in good agreement with the flame atomic absorption spectrometry (FAAS) method.     

A New Route of Synthesis of 5‐(N‐Phenethylamino)salicylic Acid Derivatives by Rapid and Selective Reduction of the Amide Group with NaBH4/Acetic Acid

A good yield of 5‐(N‐phenethylamino)salicylic acid derivatives was successfully obtained from the corresponding methyl 2‐acetoxy‐5‐(N‐phenethylamino)benzoate esters by rapid and selective reduction of the amide group in the acyl protected salicylic acid with NaBH₄/acetic acid in dioxane followed by hydrolysis of the ester group.     

(Sodium Alginate/Acrylamide) Semi‐Interpenetrating Polymer Networks and their Usability on Removal of Lead,Cadmium, Nickel Ions

In this study, (sodium alginate (NaAlg)/acrylamide (AAm)) interpenetrating polymer networks (IPN) have been prepared at three different compositions, where the sodium alginate composition varies 1, 2, and 3% (w/v) in 50% (w/v) acrylamide solutions. These solutions have been irradiated with a ⁶⁰Co‐γ source at different doses. The percent conversion was determined gravimetrically and 100% gelation was achieved at the 10.0 kGy dose. The swelling results at pH 7.0 and 9.0 indicated that (NaAlg/AAm)3IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water, with swelling increasing in the order of Ni²⁺>Cd²⁺>Pb²⁺. Diffusion in aqueous solutions of metal ions within (NaAlg/AAm)IPN hydrogels was found to be Fickian character. Diffusion coefficients of (NaAlg/AAm)IPN hydrogels in water and aqueous solutions of metal ions were calculated. The maximum weight loss temperature and half life temperature for NaAlg, PAAm, (NaAlg/AAm)IPN and (NaAlg/AAm)IPN‐metal ion systems were found from thermal analysis studies. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb nickel, cadmium and lead ions from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of metal ion at pH 7.0. Adsorption isotherms were constructed for the (NaAlg/AAm)IPN‐metal ion systems. S type adsorption in the Giles classification system was found.     

4,5‐Dihydrothiazoline—A New Protecting and Activating Group for Generation of α‐Aminocarbanions of Secondary Amines

4,5‐Dihydrothiazoline has been successfully used as a protecting and activating group for synthesis of various 1‐substituted 1,2,3,4‐tetrahydroisoquinolines via a lithiation–electrophillic substitution reaction sequence.     

Synthesis of (R)‐Japonilure and (4R,9Z)‐9‐Octadecen‐4‐olide,Pheromones of the Japanese Beetle and Currant Stem Girdler

Asymmetric total synthesis of the sex pheromones of Japanese beetle and currant stem girdler, (R)‐japonilure (1) and (4R,9Z)‐9‐octadecen‐4‐olide (2), has been achieved.     

Studies on the Selective Reduction of the Amide Link of Acyclic and Macrocyclic Amidoketals: Unexpected Cleavage and trans‐Acetalization with Red‐Al®

Selective reduction of the amide moiety of acyclic and macrocyclic amidoketals was studied in presence of various reagents (BH₃ · Me₂S, iBuAlH₂, Red‐Al^®, LiAlH₄). The best results were obtained with lithium aluminium hydride in the presence of triethylamine traces, whereas borane dimethyl sulfide gave rise to a partial ketal reduction of the acyclic compound and Red‐Al^® to a cleavage of the macrocyclic molecule accompanied by an unexpected trans‐acetalization.     

Simple,Efficient, and Stereoselective Oxidation of Triphenylfurans to cis‐But‐2‐ene‐1,4‐diones

Triphenylfurans are stereoselctively oxidized to cis‐but‐2‐ene‐1,4‐diones, suitable precursors of 3(2H)‐furanones, in very good yields using ammonium nitrate or potassium nitrate in 80% aqueous acetic acid.     

An Efficient,Simple, and Eco‐Friendly Method for the Synthesis of Sydnone‐Containing Thiazoles Under Solvent‐Free Conditions

Abstract

Novel 4‐substituted‐3‐(3‐substituted sydnolydine‐4‐hydrazono)thiazoles 3a‐l have been synthesized under solvent free conditions by grinding the reactants in a mortar with a pestle.     

Synthesis of Some New N‐Substituted Pyrroles,Pyrrolo[1,2‐a]quinazoline,and Diaza‐as‐indacene Derivatives

2‐Phenyl‐1,1,3‐tricyano‐3‐bromopropene 1 reacts with the aromatic amines 2a–f and 6a–c to afford the N‐substituted pyrroles 4a–d, the pyrrolo[1,2‐a]quinazoline derivatives 5a, b, and the diaza‐as‐indacene derivatives 7a–c and 8a–c, presumably via elimination of hydrogen bromide followed by cyclization of the formed acyclic intermediates. All structures are confirmed by analytical and spectral data.     

Selective Reductions of C‐(4,6‐O‐Benzylidene‐β‐d‐glucopyranosyl) Nitromethane

Abstract

The nitromethyl group of C‐(4,6‐O‐benzylidene‐β‐d‐glucopyranosyl) nitromethane was manipulated by various reduction and oxidation methods and further functionalizations into –CH₂NHOH, –CH?NOH, –CN, –CH?O, and –CH₂NHCONH₂, all with retention of the 4,6‐O‐benzylidene group. Certain reduction methods gave rise to a novel secondary amine via an unusual dimeric aminal.     

Preparation of a Cu(II)‐Immobilized Co‐polymer(CIC) for Effective Removal of Urea

The study describes the preparation of Cu(II)‐immobilized copolymer(CIC) under optimum conditions for the effective removal of urea. The copolymeric hydrogels, synthesized by free‐radical aqueous copolymerization of monomers acrylamide and sodium acrylate, have been analyzed for their Cu(II) uptake behavior. The sorption of Cu(II) into polymer follows a Langmuir–type pattern and amount sorbed depends upon the composition of copolymeric gels, presence of other co‐ions in the solution, pH of the solution, initial concentration of sorbate, degree of crosslinking of the copolymeric hydrogel, temperature of the solution etc. In the preliminary study, the Cu(II) immobilized co‐polymer(CIC) sorbent demonstrated a fair tendency to remove urea from aqueous solutions.     

Simple,Mild, and Efficient Method for the Reduction of 1,4‐Benzoquinones to Hydroquinones by the Action of NaN3

A simple, mild, and efficient method is presented for the reduction of 1,4‐benzoquinones to hydroquinones by the action of NaN₃ under neutral conditions in the presence of water.