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.     

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.     

Ferric Perchlorate–Catalyzed One‐Pot Synthesis of α‐Aminonitriles using Trimethylsilylcyanide

A simple and efficient one‐pot method has been developed for the synthesis of α‐aminonitriles from aldehydes, amines, and trimethylsilyl cyanide in the presence of a catalytic amount of ferric perchlorate.     

Synthesis of N‐Substituted 4,6‐Dimethyl‐3‐cyano‐2‐pyridones Under Microwave Irradiation

N‐substituted 4,6‐dimethyl‐3‐cyano‐2‐pyridones have been prepared from acetylacetone, N‐substituted cyanoacetamide, and pyperidine as catalyst under microwave irradiation without solvent. The rapid and simple method produced pure products in high yields.     

KF‐Alumina Catalyzed One‐Pot Synthesis of Pyrido[2,3‐d]Pyrimidine Derivatives

Abstract

A series of pyrido[2,3‐d]pyrimidine derivatives was synthesized by the reaction of arylaldehyde, malononitrile, and 4‐amino‐2,6‐dihydroxylpyrimidine in ethyl alcohol at 80°C catalyzed by KF‐Al₂O₃. Compared with other synthetic methods, this new method has the advantage of easier workup, milder reaction conditions, and good yields.     

Facile One‐Pot Synthesis of 3‐{2‐[5‐Hydroxy‐4‐(2‐hydroxy‐ethyl)‐3‐methyl‐pyrazol‐1‐yl]‐thiazol‐4‐yl}‐chromen‐2‐ones via a Three‐Component Reaction

Reaction of 3‐(2‐bromo‐acetyl)‐chromen‐2‐one with thiosemicarbazide and 2‐acetylbutyro lactone in anhydrous ethanol gave 3‐{2‐[5‐hydroxy‐4‐(2‐hydroxy‐ethyl)‐3‐methyl‐pyrazol‐1‐yl]‐thiazol‐4‐yl}‐chromen‐2‐one in good yields.     

KHSO4 · H2O/SiO2‐Catalyzed,One‐Pot,Solvent‐Free Synthesis of Pyrazolines,Tetrahydrocarbozoles and Indoles using Microwave Irradiation

A new high‐yielding, operationally simple, solvent‐free, and mild method for preparation of pyrazolines, tetrahydrocarbazoles, and indoles has been developed using KHSO₄ · H₂O impregnated on SiO₂. The reactions have been probed under microwave irradiation (MWI), and ultrasonic and thermal conditions, employing different solid supports. The data revealed that KHSO₄ · H₂O impregnated on SiO₂ under MWI provides the best yields in a shorter time under solvent‐free reaction conditions.     

P2O5/SiO2‐Catalyzed One‐Pot Synthesis of Amides from Ketones via Schmidt Reaction under Microwave Irradiation in Dry Media

A facile and efficient method for the preparation of amides from ketones by the Schmidt reaction is described for the first time using P₂O₅/SiO₂ and sodium azide under solvent‐free microwave irradiation. Advantages of this procedure are selectivity, good yields, a simple operation, short reaction time, and solvent‐free conditions.     

SbCl3‐Al2O3–Catalyzed,Solvent‐Free,One‐Pot Synthesis of Benzo[b]1,4‐diazepines

This article explores the use of antimony(III) chloride adsorbed on neutral alumina as an efficient catalyst for the one‐pot synthesis of benzo[b]1,4‐diazepines (83–94%) under solvent‐free conditions. The process is easy, efficient, ecofriendly, and economical.     

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.     

Three‐Component,One‐Pot Synthesis of Pyrido[2,3‐d]pyrimidine Derivatives Catalyzed by KF‐alumina

Abstract

A series of pyrido[2,3‐d]pyrimidine derivatives were synthesized by the three‐component reaction of arylaldehyde, cyanoacetate, and 4‐amino‐2,6‐dihydroxylpyrimidine in ethyl alcohol at 80°C catalyzed by KF‐Al₂O₃. It was interesting that further aromatization took place automatically. Compared with other synthetic methods, this new method has the advantage of easier workup, milder reaction conditions, and good yields.     

Sulfamic Acid–Catalyzed,Three-Component,One-Pot Synthesis of [1,2,4]Triazolo/Benzimidazolo Quinazolinone Derivatives

An efficient and convenient approach is reported for three-component, one-pot synthesis of the [1,2,4]triazolo/benzimidazolo quinazolinones by condensation of 2-amino benzimidazole or 3-amino-1,2,4-triazole as amine sources with dimedone and different aldehydes in the presence of sulfamic acid as a reusable, green catalyst in acetonitrile and under heating conditions.     

Regioselective Synthesis of 2H‐Benzothiopyrano[3,2‐c]quinolin‐7(8H)‐ones by Tri‐n‐butyltinhydride–Mediated Radical Cyclization

A number of hitherto unreported 2H‐benzothiopyrano[3,2‐c]quinolin‐7(8H)‐ones have been regioselectively synthesized in 90–96% yield by tri‐n‐butyltinhydride–AIBN–mediated radical cyclization from 4‐(2′‐bromothioarylmethyl)‐1‐methylquinolin‐2(1H)‐ones and their corresponding sulfones. 4‐(2′‐Bromothioarylmethyl)quinolin‐2(1H)‐ones were in turn prepared from 4‐bromomethylquinolin‐2(1H)‐one and o‐bromothiophenols by refluxing in acetone in the presence of anhydrous K₂CO₃. These were converted to the corresponding sulfones by oxidation with two equivalents of m‐CPBA in refluxing dichloromethane for 1 h.     

Three‐Component One‐Pot Synthesis of 1,4‐Dihydropyrano[2,3‐c]pyrazole Derivatives in Aqueous Media

Abstract

6‐Amino‐5‐cyano‐4‐aryl‐1,4‐dihydropyrano[2,3‐c]pyrazoles were synthesized by three‐component reaction of aromatic aldehydes, malononitrile, and 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one using triethylbenzylammonium chloride (TEBA) as catalyst in aqueous media. The reaction has the advantages of good yield, less pollution, ease of separation, and of being environment friendly.     

Convenient One‐Pot Heterogeneous Catalytic Method for the Preparation of 3,4‐Dihydropyrimidin‐2(1H)‐ones

A new, simple, environmentally friendly synthesis of dihydropyrimidinones from aromatic and aliphatic aldehydes, ethyl acetoacetate, and urea or thiourea using a small‐pore‐size zeolite as catalyst is described. Compared with the classical Biginelli reaction conditions, this method has the advantage of high yield, shorter reaction time, and recyclable and reusable catalyst.     

Triphenyl Phosphonium Perchlorate–Catalyzed Imino Diels–Alder Synthesis of Azabicyclo[2.2.2]octan‐5‐ones

Abstract

A facile synthesis of azabicyclo[2.2.2]octan‐5‐ones by triphenyl phosphonium perchlorate–catalyzed imino Diels–Alder reaction of Schiff bases with cyclohex‐2‐enone.     

One‐Pot Synthesis of 2‐(1‐Alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐quinoxaline Derivatives using Molecular Iodine

The title compound (5) has been prepared in one pot by refluxing 1‐(1‐alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐ethanone (1) with substituted o‐phenylenediamine (2) in ethanol in the presence of iodine. Alternatively, 5 could also be prepared by treating 2‐bromo‐1‐(1‐ alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐ethanone (3A) with 2 in refluxing ethanol. The formation of 5 from 1 and 2 probably occurs through the intermediacy of 3B (i.e., 3, X=I) and 4.     

Novel Method for the Synthesis of [1,2,4]Triazino[4,3‐c]quinazoline System

4‐Hydrazinoquinazoline was found to form new 2‐(3,4‐dihydro‐3oxo‐2H‐[1,2,4]triazino[4,3‐c]quinazolin‐4‐yl)acetic acid with maleic anhydride in on‐step sequence. Proposed heterocyclization includes, probably, acylation reaction followed by intramolecular uncleophilic addition.     

A Neat and Rapid Synthesis of 2‐Aryloxymethylene‐6‐Arylimidazo[2,1‐b]‐1,3,4‐Thiadiazole Under Microwave Irradiation

A neat and rapid procedure is reported for the synthesis of a variety of 2‐aryloxymethylene‐6‐arylimidazo[2,1‐b]‐1,3,4‐thiadiazole (3a–3r) by condensation reaction of 2‐amino‐5‐aryloxymethylene‐1,3,4‐thiadiazole (1a–1f) with ω‐bromoacetophenone (2a–2c) in ethanol solvent under microwave irradiation, which yielded a series of novel compounds. The yields are good to excellent. The procedure is simple and does not need any added catalyst or dehydrating reagent. Moreover, the crystals do not require further purification to give the products.     

One‐Pot Synthesis of 2‐Amino‐4‐aryl‐3‐carbalkoxy‐7,7‐dimethyl‐5,6,7,8‐tetrahydrobenzo[b]pyran Derivatives Catalyzed by KF/Basic Al2O3 Under Ultrasound Irradiation

Abstract

Synthesis of 2‐amino‐4‐aryl‐3‐carbalkoxy‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tertrahydrobenzo[b]pyran derivatives was carried out in 81–98% yields by one‐pot condensation of aromatic aldehydes with cyanoacetic esters and 5,5‐dimethyl‐1,3‐cyclohexanedione catalyzed by KF/basic Al₂O₃ at room temperature under ultrasound irradiation.