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.     

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.     

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.     

Facile One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐one Catalyzed by Zn(NH2SO3)2

An efficient synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones (DHPMS) from aromatic aldehydes, β‐keto ester, and urea (or thiourea) in refluxing ethanol using zinc sulfamate as a catalyst is first described here. Compared to the classical Biginelli reaction, this new method consistently has the advantages of good yields (76–96%), short reaction time (2–5 h), no corrosion of equipment, ease of manipulation, and low‐cost catalyst.     

One‐Pot Synthesis of 5‐Alkylfuran‐2(5H)‐ones

5‐Alkylfuran‐2(5H)‐ones can be efficiently obtained using a one‐pot approach, starting from methyl 3‐nitropropanoate and aldehydes, in ethyl acetate, with Amberlyst A‐21 as catalyst, in 60–90% overall yield.     

Solvent‐Free Approach to 3,4‐Dihydropyrimidin‐2(1H)‐(thio)ones: Biginelli Reaction Catalyzed by a Wells–Dawson Reusable Heteropolyacid

The Biginelli reaction is performed in an efficient, simple, solvent‐free procedure, using a small amount of H₆P₂W₁₈O₆₂ · 24H₂O, a reusable heteropolyacid catalyst with Wells–Dawson structure. Both aromatic and aliphatic aldehydes, and different β‐dicarbonyl compounds and urea or thiourea, were used as starting materials. Seventeen examples of dihydropyrimidinones and dihydropyrimidinethiones were prepared by heating the reactants either in refluxing acetonitrile or in the absence of solvent. Operational simplicity, the use of a noncorrosive, reusable catalyst in solventless conditions, short reaction times, and very good to excellent yields in most of the selected examples are the main advantages of the method.     

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.     

Practical One‐Pot Procedure for the Synthesis of 1,2,3,4‐Tetrahydroquinolines by the Imino‐Diels‐Alder Reaction

A novel‐one‐pot procedure for the synthesis of tetrahydroquinolines via the imino‐Diels‐Alder reaction is described. This procedure gives better yields and exhibits better versatility for alkene substrates than the existing hemi‐aminal based methodologies.     

Lewis Acid–Doped Natural Phosphate: New Catalysts for the One‐Pot Synthesis of 3,4‐Dihydropyrimdin‐2(1H)‐one

Inexpensive and readily available natural phosphate doped with metal halides is used to efficiently catalyze the three‐component condensation reaction of an aldehyde, a beta‐keto ester, and urea to afford the corresponding dihydropyrimidin‐2(1H)‐ones in high 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.     

Brønsted Acidic Ionic Liquid: An Efficient and Reusable Catalyst for the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones

A novel ionic liquid, 3‐carboxymethyl‐1‐methylimidazolium bisulfate (CMImHSO₄), was synthesized and used as a recyclable catalyst for the Biginelli reaction under solvent‐free conditions. High yields of various substituted 3,4‐dihydropyrimidin‐2(1H)‐ones (or thiones) were obtained. The ionic liquid can be recovered and recycled easily without loss of activity.     

Expeditious One‐Pot and Solvent‐Free Synthesis of Dihydroquinazolin‐4(1H)‐ones in the Presence of Microwaves

Dihydroquinazolin‐4(1H)‐ones were synthesized for the first time by a novel three‐component condensation of isatoic anhydride, a primary amine, and an aldehyde catalyzed by Amberlyst‐15 in the presence of microwaves under neat conditions. The catalyst is reusable, thus making the process more environmentally friendly.     

Facile One‐Pot Synthesis of Oxazolidin‐2‐ones from Phenyl 2‐Hydroxyalkyl Selenides

A novel, convenient, efficient, three‐step, one‐pot synthesis of 2‐oxazolidinones from phenyl 2‐hydroxyalkyl selenides was developed. Using this methodology, 2‐oxazolidinones are obtained in good yields (76–85%) by reaction of phenyl 2‐hydroxyalkyl selenides with benzoyl isocyanate and subsequent oxidation/cyclization, followed by hydrolysis with hydrochloric acid solution.     

Microwave‐Assisted One‐Pot Synthesis of 2‐(Substituted phenyl)‐1H‐benzimidazole Derivatives

A series of 2‐(substituted phenyl)‐1H‐benzimidazole derivatives with various 5‐and 6‐position substituents (‐H, ‐CH₃, ‐CF₃) were synthesized via microwave irradiation using a short synthetic route and Na₂S₂O₅ as oxidant. This simple, fast, and efficient preparation of benzimidazole derivatives has been developed using readily available and inexpensive reagents (aldehydes and 1,2‐phenylenediamines) under solvent‐free conditions.     

Efficient Green Procedure for the Synthesis of Coumarin Derivatives by a One‐Pot,Three‐Component Reaction under Solvent‐Free Conditions

A simple, efficient, and general method has been developed for the synthesis of coumarin derivatives through a one‐pot reaction of aromatic aldehydes, 2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione and 5,5‐dimethyl‐1,3‐cyclohexanedione, in the presence of TEBA under solvent‐free conditions using grinding methods. The mild reaction conditions, simple protocol, high yields, and cleaner reaction make this protocol practical and economically attractive.     

Simple Protocol for the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Using SnCl2 · 2H2O–LiCl as an Inexpensive Catalyst System

Abstract

A one‐pot synthesis of the 3,4‐dihydropyrimidin‐2(1H)‐ones catalyzed by tin chloride–lithium chloride combination catalyst system involving three component heteroannular cyclization is reported.     

One‐Pot Synthesis of Tetrahydro‐2‐Methylidenefurans

Abstract

Tetrahydro‐2‐methylidenefurans were prepared by the ring‐opening/recyclization reaction of 2‐(disubstituted amino)‐4,5‐dihydro‐3‐furancarbonitriles with dichloroacetyl chloride in the presence of potassium carbonate.     

Convergent One‐Pot Synthesis of 3‐Substituted Quinazolin‐4(3H)‐ones under Solvent‐Free Conditions

A convenient method for the synthesis of 3‐substituted quinazolin‐4(3H)‐ones using the convergent reactions of formic acid, a primary amine, and isatoic anhydride under solvent‐free conditions and with brief microwave irradiation is described.     

Simple and Efficient Procedure for the One‐Pot Synthesis of β‐Acetamido‐β‐aryl‐propiophenones by Molecular Iodine–Catalyzed Tandem Reaction

Molecular iodine efficiently catalyzes the four‐component tandem reaction of araldehydes, arylmethyl ketones, acetyl chloride, and acetonitrile to afford the corresponding β‐acetamido‐β‐aryl‐propiophenones. The new protocol gives high yields of the products, and the reactions go to completion within 10–15 min on a hot plate at 80–85°C.     

One‐Pot Synthesis of Pyrazole‐5(3)‐carboxyamides

Abstract

A convenient one‐pot synthesis of eight pyrazole‐5(3)‐carboxyamides from the reaction of the 5(3)‐trichloromethylpyrazoles with amines, in good yield, is reported. These reactions show that the trichloromethyl group is a convenient precursor to carboxyamide groups.