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.     

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.     

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.     

D,L‐Proline‐Catalyzed One‐Pot Synthesis of Pyrans and Pyrano[2,3‐c]pyrazole Derivatives by a Grinding Method under Solvent‐Free Conditions

D,L‐Proline was found to efficiently catalyze the one‐pot condensation of aromatic aldehydes, malononitrile, and dimedone (1,3‐cyclohexanedione or 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one) 2‐Amino‐3‐cycano‐4‐aryl‐7,7‐dimethyl‐5,6,7,8‐tetrahydrobenzo[b]pyrans and 6‐amino‐5‐cyano‐4‐aryl‐1,4‐dihydropyrano[2,3‐c]pyrazoles were synthesized by a grinding method under solvent‐free conditions. The reaction proceeded cleanly at room temperature to afford the products in good yields.     

Green Synthesis of Pyrano[2,3‐d]‐pyrimidine Derivatives in Ionic Liquids

Pyrano[2,3‐d]pyrimidine derivatives were synthesized in high yields by a condensation reaction between arylmethylidenemalononitrile and barbituric acid using room‐temperature ionic liquids such as 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm]BF₄) or 1‐butylpyridinium tetrafluoroborate ([BPy]BF₄) as solvents under neutral conditions.     

Solvent‐Free,One‐Pot Synthesis of Pyrano[2,3‐c]pyrazole Derivatives in the Presence of KF·2H2O by Grinding

Abstract

A solvent‐free, one‐pot process for the preparation of 4H‐pyrans in the presence of KF?·?2H₂O by grinding was achieved. Its advantages are easy workup, mild reaction conditions, high yields, and environmental friendliness.     

Facile Synthesis of 5‐Benzylidene Rhodamine Derivatives under Microwave Irradiation

A series of 5‐benzylidenerhodamine derivatives were synthesized by the cross‐aldol condensation of an aromatic aldehyde with rhodamine or rhodamine acetic acid in sodium acetate/acetic acid under microwave irradiation. The reaction was completed in 8–20 min with 63–94% yields and was environmentally benign with easy workup.     

Facile Ionic Liquids-Promoted One-Pot Synthesis of Polyhydroquinoline Derivatives under Solvent Free Conditions

In recent years, much attention has been directed towards the syntheses of 1,4-dihydropyridyl compounds due to the fact that 1,4-dihydropyridyl compounds possess a variety of biological activities.[1] In view of the importance of polyhydroquinoline derivatives, many classical methods for the synthesis of polyhydroquinoline derivatives were reported[2] by conventional heating and refluxing approaches in the presence of organic solvent. These methods, however, involve long reaction time, harsh reaction conditions, the use of a large quantity of organic solvent and unsatisfactory yields. Therefore,improvements in such syntheses have been sought continuously.     

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.     

Facile Deprotection of Aromatic tert‐Butyl and Allylic Esters Under Microwave Irradiation Conditions

Abstract

A simple and efficient method for the deprotection of tert‐butyl and allylic esters is described, which occurs under microwave irradiation with p‐toluenesulfonic acid in solvent‐free conditions.     

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.     

Facile Synthesis of 1, 2-Diazepine Derivatives under Microwave Irradiation

An efficient and convenient synthesis of 3, 5, 7-triaryl-4H-1, 2-diazepine from 2, 4,6-triarylpyrylium salts and hydrazine in water under microwave irradiation is reported. The same reaction can be conducted using 2, 4, 6-triarylthiopyrylium salts and hydrazine.     

One‐Pot Preparation of Fluorinated α‐Aminoalkyl Phosphonates under Microwave Irradiation and Solvent‐Free Conditions

A facile one‐pot method has been developed for the synthesis of fluorine‐containing α‐amino phosphonates in good yields by a three‐component reaction of fluorinated aromatic aldehydes, anilines, and diethyl phosphate in the presence of a silica‐gel support under microwave irradiation within 10 min. All new compounds are fully characterized by spectral methods and elemental analysis.     

Microwave‐Assisted Synthesis of Amide under Solvent‐free Conditions

An efficient and environmentally friendly synthetic method for the synthesis of primary amides under microwave irradiation was described, in which the primary amine was directly reacted with acid without any catalytic agents. The reaction took place in 8–12 min, which was much shorter than the traditional synthetic methods, with almost quantitative yields. The influential factor of the reaction was discussed. The tautomerization between the carboxylic acid group and the H atom in α‐carbon of L‐amino acid was observed, presumably a dehydrated intermediate forming from this tautomerized isomer.     

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.     

Facile Synthesis of Pyrazolo[3,4‐d]pyrimidines and Pyrimido[4,5‐d]pyrimidin‐4‐one Derivatives

Pyrazolopyrimidine and pyrimidopyrimidine derivatives have shown a wide range of biological activities such as acting as A₁ adenosine receptors, kinase insert domain receptor (KDR), Rous sarcoma oncogene (Src), epidermal growth factor receptor (EGFR), antiproliferative, dihydrofolate reductase (DHFR), antimicrobial, antifungal, and lipid peroxidation. Because of this wide range of activities, we have synthesized pyrazolo[3,4‐d]pyrimidines and pyrimido[4,5‐d]pyrimidin‐4‐one derivatives.     

Efficient Synthesis of Tetrahydrobenzo[b]pyrans under Solvent‐Free Conditions at Room Temperature

A range of tetrahydrobenzo[b]pyrans have been synthesized in very good yields under solvent‐free conditions by grinding α‐cyanocinnamonitrils or β‐cyano‐β‐carbethoxy styrene and 5,5‐dimethyl‐1,3‐cyclohexanedione in the presence of TEBA as catalyst. The short reaction time, cleaner reaction, and easy workup make this protocol practical and economically attractive.     

Porous Calcium Hydroxyapatite as an Efficient Catalyst for Synthesis of Pyrazolines via 1,3‐Dipolar Cycoloaddition Under Solvent‐Free Microwave Irradiation

Adsorbed on porous calcium hydroxyapatite, 1,3‐dipolar cycloaddition of diphenylnitrilimine on olefins is readily catalyzed under solvent‐free microwaves irradiation. The pyrazolines are obtained in few minutes with high yields. Specific surface of porous calcium hydroxyapatite and microwaves effects are discussed.     

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.