Efficient and Mild Procedure for Reductive Methylation of Amines Using N‐Methylpiperidine Zinc Borohydride

A simple and efficient procedure for reductive methylation of primary and secondary amines using N‐methylpiperidine zinc borohydride (ZBNMPP), giving tertiary amines, is described. The reaction is carried out in methanol at room temperature under neutral conditions.     

Molybdatophosphoric Acid/NaNO2/Wet SiO2 as an Efficient System for the Aromatization of 1,2‐Dihydroquinolines under Mild and Heterogeneous Conditions

A combination of molybdatophosphoric acid and NaNO₂ in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of 1,2‐dihydroquinolines to their corresponding quinoline derivatives in dichlomethane at room temperature with excellent yields.     

An Efficient One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2‐ones Catalyzed by Methanesulfonic Acid

Abstract

An efficient synthesis of 3,4‐dihydropyrimidin‐2‐ones (DHPMs) from the aldehydes, β‐ketoesters, and urea in ethanol using methanesulfonic acid (CH₃SO₃H) as the catalyst is described. Compared with the classical Biginelli reaction conditions, this method has the advantage of excellent yields and short reaction time.     

Perchloric Acid–Doped Polyaniline as an Efficient and Reusable Catalyst for the Synthesis of 2-Substituted Benzothiazoles

2-Substituted benzothiazoles have been efficiently synthesized in good yields by the condensation reaction of o-aminothiophenol with aldehydes in the presence of a catalytic amount of perchloric acid–doped polyaniline (HClO₄/PANI). The low cost, simple recovery, and efficient reusability are remarkable characteristics of this catalyst.     

Convenient,Cost‐Effective,and Mild Method for the N‐Acetylation of Anilines and Secondary Amines

Abstract

An efficient, cost‐effective, and mild method for the N‐acetylation of anilines and secondary amines with ammonium acetate in acetic acid media at reflux temperature in good yield is described.     

Trichloroisocyanuric Acid–KF as an Efficient Reagent for One-Pot Synthesis of Dialkylfluorophosphates from Dialkylphosphites

Trichloroisocyanuric acid–KF afforded dialkylfluorophosphates from dialkylphosphites at room temperature through a facile electrophilic–nucleophilic metathesis.     

Acid‐Promoted Thioacetalization in Water using 2‐(1,3‐Dithian‐2‐ylidene)malonic Acid as an Odorless and Efficient Thioacetalization Reagent

Thioacetalization using 2‐(1,3‐dithian‐2‐ylidene)malonic acid 1 as a nonthiolic, odorless 1,3‐propanedithiol equivalent promoted by p‐dodecylbenzenesulfonic acid in water has been achieved. A range of selected carbonyl compounds 2 was converted into the corresponding dithioacetals 3 in high yields. Moreover, the thioacetalization showed high chemoselectivity between aldehydes and ketones.     

Efficient Procedure for the Preparation of Oligomer-Free N α -Fmoc Amino Acids

A two-step method is presented for the peptide-free, high-purity, and high-yield synthesis of N^α-Fmoc amino acids. The first step involves the preparation of stable dicyclohexylammonium–amino acid ionic adduct in acetone. Subsequently, the ionic adducts, on reaction with Fmoc-Nosu under mild alkaline conditions, give dipeptide-free N^α-Fmoc amino acids. The positive charge of the dicyclohexylammonium counterion in the ionic salt has a longer radius, moderating the nucleophilicity of the carboxylate ion of the amino acid and preventing by-products by arresting the formation of mixed anhydrides, the precursors of oligopeptide impurities.     

Efficient and Convenient Procedure for Preparation of N‐Sulfonylimines Catalyzed by Montmorillonite K‐10

A general and practical chemical route to the synthesis of N‐sulfonylimines using montmorillonite K‐10 as the catalyst is described. This method provides several advantages such as operational simplicity, short reaction time, using of inexpensive materials, noncorrosivity, lack of pollution, and high yields.     

Novel,Water‐Based Procedure for the Mono Iodination of Aromatic Amines and Phenols

A mixture of potassium chlorate and potassium iodide was found to be a good iodinating agent for various aromatic amines and phenols with excellent yields in the presence of mineral acid in aqueous medium.     

Glycerol as an Efficient Medium for the Petasis Borono–Mannich Reaction

The multicomponent Petasis borono–Mannich (PBM) reaction is a useful tool for the preparation of complex molecules in a single step from boronic acids, aldehydes/ketones, and amines. Here, we describe the use of glycerol in the PBM reaction of salicylaldehydes or 2-pyridinecarbaldehyde with several boronic acids and secondary amines. From these readily available starting materials, alkylaminophenols, 2-substituted pyridines, and 2H-chromenes were prepared in reasonable to good yields. Glycerol was compared with other solvents, and in some cases, it provided the reaction product in higher yield. Crude glycerol, as generated by the biodiesel industry, was evaluated and found to be a suitable solvent for the PBM reaction, successfully expanding the potential use of this industry by-product. Based on density functional theory (DFT) calculations and the obtained experimental results, the involvement of glycerol-derived boronic esters in the reaction mechanism is suggested to be competitive with the free boronic acid pathway. Similar Gibbs free energies for the aryl migration from the boronate species to the iminium were determined for both mechanisms.     

New One‐Pot Procedure for the Synthesis of 2‐Substituted Benzimidazoles

A highly selective synthesis of 2‐substituted benzimidazole derivatives from the reaction of o‐phenylendiamine derivatives and aromatic aldehydes in the presence of an organic salt, NH₄OAc, in absolute ethanol is presented. The products were obtained by evaporating the solvent followed by a simple recrystallization with excellent yields.     

ZrOCl2 · 8H2O as an Efficient Reagent for the Solvent‐Free Synthesis of 3,4‐Dihydropyrimidin‐2‐(1H)‐ones

ZrOCl₂ · 8H₂O, a commercially available reagent, can be used for the promotion of the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones under solvent‐free reaction conditions. All reactions were performed at 90°C in good to high yields.     

A Mild and Efficient Procedure for the Preparation of Chromone-2-carboxylates

Chromone-2-carboxylates are widely used for the pharmacological activity of several of its derivatives1. The general synthesis of such chromone derivates includes two steps (Scheme 1): a Claison condensation of dialkyl oxalate with 2-hydroxyacetophenones to achieve alkyl 3-(2-hydroxyphenyl)-3-oxopropanoates in the presence of NaH, NaOEt, or NaOMe; cyclodehydration of the alkyl 3-(2-hydroxyaryl)-3-oxopropanoates to obtain chromones under acid condition. The total yield of the two steps is q…     

γ-Al2O3-Supported 12-Tungstosilicic Acid as an Efficient Heterogeneous Catalyst for the Synthesis of α-Aminonitrile

The multicomponent Strecker reaction using trimethylsilyle cyanide was performed in very short reaction times, and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of alumina-supported tungstosilicic acid.     

Mild and Efficient Procedure for the Synthesis of 1,5‐Benzodiazepines Catalyzed by Magnesium Perchlorate

A convenient and efficient method for the synthesis of 1,5‐benzodiazepines by the reaction of o‐phenylenediamines (OPDA) and ketones with hydrogens at the α‐position has been developed. The reaction is carried out at room in the presence of a catalytic amount of magnesium perchlorate under solvent‐free conditions.     

Triton B–Mediated Mild,Convenient, and Efficient Method for the Selective Alkylation of Cyclic Secondary Amines and Thiols

Alkylation of cyclic secondary amines, thiols, and pyridazinones has been demonstrated with alkyl halides using Triton B as base and reaction medium.     

Scandium(III) Triflate as an Efficient and Reusable Catalyst for Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones

Sc(III) triflate efficiently catalyzes the three‐component condensation reaction of an aldehyde, a β‐ketoester, and urea in refluxing acetonitrile to afford the corresponding 3,4‐dihydropyrimidin‐2(1H)‐ones in excellent yields. The catalyst can be recovered and reused, making this method friendly and environmentally acceptable.     

Efficient Synthesis of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines

A general method for the preparation of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines is described. These heterocycles can be synthesized from their respective anilines with 2‐chloro‐2‐imidazoline or 2‐chloro‐1,4,5,6‐tetrahydropyrimidine, generated in situ from imidazolidin‐2‐one and tetrahydropyrimidin‐2(1H)‐one activated by dimethyl chlorophosphate, in good to excellent yields.     

Development of NaNO2–O2 system as an oxidant at uranium leaching processes

A process of ferrous ion oxidation by sodium nitrite in sulfate uranium in situ leaching solutions was investigated. Kinetic, spectrophotometric, and heat effect studies have been made in order to investigate the chemistry of the oxidation process. As a result the method of ferrous ion oxidation in uranium in situ leaching solution was developed that makes possible to decrease sodium nitrite consumption by 20?C30 times comparing with traditional oxidation technique. It was founded also that process of ferrous ion oxidation can be conducted with partial sodium nitrite recirculation.