InCl3 as an Efficient Catalyst for Cyclotrimerization of Aldehydes: Synthesis of 1,3,5‐Trioxane Under Solvent‐Free Conditions

1,3,5‐Trioxanes derived from aldehydes were synthesized using indium trichloride as a catalyst. Cyclotrimerization of the aldehydes gave excellent yields under neat conditions within a short span of time.     

Synthesis of Novel Pyrazolines via 1,3‐Dipolar Cycloadditions of Heterocyclic Isopropenes

An efficient and practical synthesis of novel pyrazoline structures has been achieved through 1,3‐dipolar cycloaddition of the corresponding heterocyclic isopropenes and diazo precursors.     

Microwave‐Assisted Efficient Synthesis of Dihydropyrimidines in Solvent‐Free Condition

Abstract

An efficient synthesis of 3,4‐dihydropyrimidinones from an aldehyde, a ketoester, and a urea or thiourea using a catalytic amount of ferric chloride hexahydrate is described. Microwave irradiation has been used to accelerate the synthesis of the Biginelli compounds under solvent‐free conditions and in a short reaction time and with good yield.     

PEG‐SO3H as Catalyst for 3,4‐Dihydropyrimidones via Biginelli Reaction Under Microwave and Solvent‐Free Conditions

An efficient and environmentally friendly process for the synthesis of 3,4‐dihydropyrimidones via the Biginelli‐type condensation reaction using poly(ethylene glycol)‐bound sulfonic acid as catalyst irradiated by microwave has been developed. The functionalized poly(ethylene glycol) acted simultaneously as catalyst and as solvent in the condensation. The workup was easy, and the products were obtained in good to excellent yields and high purities.     

Efficient Synthesis of 3‐Pyrrolylquinolines via an 1,3‐Dipolar Cycloaddition/Oxidation Sequence

The synthesis of some new functionalized quinolyl derivatives relies on the 1,3‐dipolar cycloaddition of an azomethine ylide, generated from sarcosine and paraformaldehyde, to quinolyl α,β‐unsaturated esters, followed by oxidation of the pyrrolidinyl moiety to pyrrole with activated MnO₂.     

Facile Preparation of Benzylic Iodides Under Solvent‐Free Conditions Using Microwave Irradiation

Abstract

Benzylic alcohols are rapidly converted to the corresponding benzylic iodides using combination of p‐toluenesulfonic acid (PTSA) and potassium iodide under solvent‐free microwave irradiation conditions.     

One‐Pot Synthesis of Iminoimidazolines under Microwave Irradiation in Solvent‐Free Conditions

Substituted iminoimidazolines were synthesized from a one‐pot reaction of aromatic or hetero‐aromatic amines with imidazolidine‐2‐thione under solvent‐free conditions using microwave irradiation with good to excellent yields.     

Synthesis of 2‐Substituted 4,5‐Diphenyloxazoles under Solvent‐Free Microwave Irradiation Conditions

A novel method for the direct conversion of deoxybenzoin into 2‐alkyl‐4,5‐diphenyloxazoles and 2‐aryl‐4,5‐diphenyloxazoles has been developed using treatment of HTIB and nitriles under solvent‐free microwave irradiation conditions.     

PEG‐Supported Sulfonic Acid as an Efficient and Recyclable Catalyst for the Synthesis of 1,1‐Diacetates under Solvent‐Free Conditions

An operationally simple, efficient, and environmentally benign synthesis of 1,1‐diacetates in good yields by reaction of different aldehydes with acetic anhydride in the presence of PEG‐supported sulfonic acid under solvent‐free conditions is described.     

Synthesis of Substituted 1,4‐Dihydropyridines in Water Using Phase‐Transfer Catalyst Under Microwave Irradiation

Abstract

The synthesis of various substituted 1,4‐dihydropyridines has been achieved by the reaction of aldehydes, ethyl/methyl acetoacetates, and ammonium acetate in water using phase‐transfer catalyst under microwave irradiation. Compared to the classical Hantzsch's reaction conditions, this new method consistently has the advantage of good yields and short reaction times. Bifunctional compounds containing two units have been synthesized using dialdehyde as precursor in good yields.     

Facile Synthesis of Pyrano[2,3‐c]pyrazol‐6‐one Derivatives Under Microwave Irradiation in Solvent‐Free Conditions

A series of substituted 1H,6H‐pyrano[2,3‐c]pyrazol‐6‐one derivatives were synthesized from one‐pot cyclocondensation of hydrazine derivatives or 1H‐pyrazol‐5‐one derivatives with various β‐keto esters under solvent‐free conditions using microwave irradiation in short time with good to excellent yields.     

Efficient Synthesis of Phosphono‐ and Phosphinoxidomethylated N‐Heterocycles under Solvent‐Free Microwave Conditions

Simple N‐heterocycles were converted to N‐phosphono‐ and phosphinoxidomethyl derivatives by a solvent‐free microwave‐assisted condensation of the heterocycle, paraformaldehyde, and diethylphosphite or diphenylphosphine oxide in a convenient and, in most cases, efficient way. In contrast to an earlier report, imidazole proved to be unreactive in this type of phospha‐Mannich reaction.     

Efficient Synthesis of tert‐Butyl Ethers under Solvent‐Free Conditions

A simple and efficient synthesis of tert‐butyl ethers from various alcohols and substituted phenols using tert‐butyl bromide in the presence of basic lead carbonate as a catalyst. The catalyst is easily recovered via filtration and can be reused up to three times without appreciable loss of activity.     

Microwave‐Assisted Protection of Phenols as tert‐Butyldimethylsilyl (TBDMS) Ethers Under Solvent‐Free Conditions

Abstract

A facile, time‐saving procedure to protect phenols with tert‐butyldimethylsilyl chloride using imidazole as catalyst under solvent‐free conditions is described. Several phenolic compounds with different substitution patterns can be silylated in high yield with substantially reduced generation of residues, a present goal in organic synthesis.     

One‐Step Synthesis of 2‐Aryl‐4,5‐diphenylimidazoles Under Microwave Irradiation

Abstract

A series of 2‐aryl‐4,5‐diphenylimidazoles were synthesized by a one‐step condensation reaction of benzil, aromatic aldehyde, and ammonium acetate in acetic acid under microwave irradiation. The reactions were completed in 4–11 min with good yields and easy workup.     

Microwave‐Enhanced Ferrier Reaction: A Facile Synthesis of 2,3‐Unsaturated‐O‐Glycosides Under Solvent‐Free Conditions

A variety of 2,3‐unsaturated‐O‐glycosides have been prepared by the Ferrier rearrangement of acetyl protected glycals under microwave irradiation using silica gel as an acid catalyst. Environmental friendliness, high yields, and short reaction times are the key features of this method. Furthermore, the method was applicable not only to the Ferrier reaction of 3,4,6‐tri‐O‐acetyl glucal and 3,4,6‐tri‐O‐acetyl galactal but also to the Ferrier reaction of 3,4‐di‐O‐acetyl arabinal.     

Microwave‐Assisted Solvent‐Free Regiospecific Synthesis of 5‐Alkylidene and 5‐Arylidenehydantoins

Hydantoins have become a well‐known class of structures that have found significant applications as agrochemicals and therapeutics. This structural motif is of interest in the synthesis of small building blocks suitable for the preparation of potentially bioactive molecules. In this sense, 5‐alkylidene and 5‐arylidenehydantoins constitute nice examples of precursors of synthetic α‐amino acids. The microwave‐assisted synthesis of these compounds under green chemistry conditions is reported in this article. The method has proved to afford yields of 74–96%.     

Efficient One‐Pot Synthesis of 2‐Amino‐4,6‐diarylbenzene‐1,3‐dicarbonitrile under Solvent‐Free Conditions

A facile parallel synthesis of 2‐amino‐4,6‐diarylbenzene‐1,3‐dicarbonitrile derivatives via a one‐pot reaction of aromatic aldehydes, aromatic ketone, and malononitrile under solvent‐free conditions has been developed. This new protocol has the advantages of shorter time, higher yields, lower cost, and environmental friendliness.     

Synthesis of Interglycosidically S‐Linked 1‐Thio‐Oligosaccharides Under Microwave Irradiation*

Microwave irradiation (MWI) has accelerated the synthesis of S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)thiouronium bromide (2a), whose reaction with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide (1a) in the presence of Et₃N afforded stereoselectively the acetylated β,β‐1‐thiotrehalose 4a. Similarly, the respective D‐galactopyranosyl 4b and 2‐acetylamino‐2‐deoxy‐D‐glucopyranosyl 4c analog as well as 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl) 4d and 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl) 4e derivatives of 2,2′,3,3′,6,6′‐hexa‐O‐acetyl β,β‐1‐thiotrehalose were prepared.     

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.