Solvent‐Free Passerini Reactions

The influence of the substrate structure and concentration on the yield of the Passerini reaction was studied. A new, solvent‐free methodology for a convenient preparation of α‐acyloxyamides 4 was established and compared to the classical methodology. A higher reaction yield was obtained in shorter time, especially in the case of aromatic aldehydes.     

Dioxane Dibromide–Mediated Solvent‐Free Synthesis of Vicinal Dibromides

Structurally varied vicinal dibromides have been synthesized in high yield and good purity through highly stereoselective anti‐addition of bromine across the olefinic linkages using dioxane dibromide (DD) under solvent‐free conditions.     

Solvent‐Free Rapid Deprotection of Ketone and Aldehyde Oximes using Periodic Acid

Abstract

Ketone and aldehyde oximes can be readily converted to the corresponding carbonyl compounds in high yields under solvent‐free conditions when treated with periodic acid. Oximes bearing aliphatic C?C bonds can be selectively deoximated. The advantages of this protocol include a rapid reaction rate and a simple workup procedure. No volatile organic solvents are required in the reaction processes.     

Iodine‐Catalyzed Conversion of β‐Dicarbonyl Compounds into β‐Enaminones Within a Minute Under Solvent‐Free Conditions

Synthesis of β‐enaminones from β‐dicarbonyl compounds has been achieved in high yields within a minute using primary and aromatic amines and catalytic amounts of iodine under solvent‐free conditions at room temperature.     

Mild and Efficient Solvent‐Free Friedel–Crafts Acylation of Reserpine

The first mild, efficient, solvent‐free Friedel–Crafts acylation of reserpine has been developed, which resulted in the synthesis of 10‐ and 12‐acylated homologues in high overall yields.     

Solvent‐Free Thermal Dehydration of Pentitols on Zeolites

Abstract

Dehydration of D‐arabinitol, ribitol, and xylitol at high temperature in the presence of molecular sieves without solvent in an argon atmosphere is described. Products arising after the dehydration–cyclization (cyclodehydration) reaction with retention or inversion of the configuration of asymmetric carbon atoms, were observed. Complete analytical separations of exhaustively O‐acetylated reaction products were achieved by means of GC. The chemical structures of the compounds obtained were assigned using co‐injection with standards.     

Microwave‐Assisted Ring Opening of Epoxides in Solvent‐Free Conditions

The reaction of aryloxymethyl epoxide with anilines under solvent‐free conditions and microwave irradiation affords high yields of 1‐arylamino‐3‐aryloxypropan‐2‐ols. The reaction was rapid and completely regioselective.     

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.     

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.     

Solvent‐Free Synthesis of Benzothiazolines in the Presence of Alumina

o‐Aminothiophenol reacted with ketones and β‐keto esters in the presence of alumina under mild and solvent‐free conditions to afford the corresponding benzothiazolines in high yields. Alumina can be reused for subsequent reactions without any loss of the activity.     

Improved Solvent‐Free Dakin Oxidation Protocol

A solvent‐free Dakin reaction with mCPBA was accomplished with various aromatic aldehydes, resulting in an easy and improved methodology for the preparation of corresponding phenols. 3,4‐Methylenedioxyphenol, 3,4‐dimethoxyphenol, 4‐methoxyphenol, 4‐chlorophenol, and other functionalized phenols were obtained in high yields from the corresponding aromatic aldehydes in a few minutes. This new methodology represents an efficient alternative for this important synthetic conversion.     

Convenient and Regioselective One‐Pot Solvent‐Free Synthesis of ß‐Hydroxyphosphonates

A simple, efficient, regioselective, and solvent‐free method has been developed for the synthesis of β‐hydroxyphosphonates from epoxides and triethyl phosphite using ZnCl₂ in high yields under mild conditions.     

Solvent‐Free,Palladium‐Catalyzed Suzuki–Miyaura Cross‐Couplings of Aryl Chlorides with Arylboronic Acids

Pd(MeCN)₂Cl₂/PCy₃ was found to be an efficient catalytic system for the Suzuki–Miyaura cross‐couplings of aryl chlorides with arylboronic acids under solvent‐free conditions. Furthermore, the presence of the conventional solvents had deleterious effect on the reaction. In the presence of Pd(MeCN)₂Cl₂, PCy₃, and TBAF (tetra‐n‐butylammonium fluoride), a number of aryl chlorides including heteroaryl chlorides were coupled with arylboronic acids or heteroarylboronic acids smoothly to afford the corresponding products in moderate to excellent yields.     

Solvent‐Free Claisen Condensation of Isophorone and Verbenone with para‐Hydroxyethylaminobenzaldehydes

A solvent‐free Claisen condensation between isophorone or verbenone on two para‐hydroxyethylaminobenzaldehydes is described. The method provides the condensation products quickly and, in most cases, without chromatography.     

Solvent‐Free Synthesis of Arylamides and Arylimides,Analogues of Acetylcholine

Abstract

Several arylamides and arylimides, novel inhibitors of acetylcholinesterase, were obtained under solventless conditions; the target molecules were produced with a good overall yield and short reaction times.     

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%.     

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.     

Synthesis of Bis(indolyl)methanes using a Catalytic Amount of ZnO under Solvent‐Free Conditions

Efficient electrophilic substitution reactions of indoles with various aromatic aldehydes were carried out using a catalytic amount of ZnO under solvent‐free conditions to afford the corresponding bis(indolyl)methanes in excellent yields. Among the various methods published for the synthesis of bis(indolyl)methane, ZnO is a very cheap, environmentally friendly, and reusable catalyst that can be used for synthesis of a new range of bis(indolyl)methane derivatives.     

One‐Pot Solvent‐Free Preparation of 2‐Phenyl‐1,3,2‐aryldioxaborins on Acidic Alumina

One‐pot, solvent‐free, microwave‐promoted preparation of 1,3,2‐aryldioxaborines on the surface of acidic alumina is described.     

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.