Synthesis of N‐Aryl‐2‐substituted Tetrahydrobenzimidazoles via Direct N‐Arylation

A series of novel N‐aryl‐2‐substituted tetrahydrobenzimidazoles has been synthesized via direct N‐arylation of 2‐substituted tetrahydrobenzimidazoles, which was accomplished by a medium aryl electrophile, 4‐methylsulfonylfluorobenze, in the presence of 37% KF/Al₂O₃ and 18‐crown‐6 in fair yields under mild reaction conditions. Meanwhile, the hydrogenation of 2‐phenylbenzimidazole was studied.     

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.     

Stereoselective Synthesis of cis‐1‐Aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes in Water

The highly stereoselective preparation of cis‐1‐aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes with arsonium salt and olefin in water is described. It is simple, efficient, and environmentally benign.     

Thallium(III) Nitrate Mediated Ring Contraction of 2‐Aryl‐1,2,3,4‐tetrahydro‐4‐quinolones: Stereoselective Synthesis of trans Methyl 2‐Aryl‐2,3‐dihydroindol‐3‐carboxylates

The ring contraction of N‐acetyl‐2‐aryl‐1,2,3,4‐tetrahydro‐4‐quinolones 1a–d with thallium(III) nitrate in trimethyl orthoformate afforded stereoselectively trans methyl N‐acetyl‐2‐aryl‐2,3‐dihydroindol‐3‐carboxylates 5a–d by oxidative rearrangement of aryl ring A.     

Efficient Transformation of Aldoximes to Nitriles Using 2‐Chloro‐1‐methylpyridinium Iodide Under Mild Conditions

Abstract

Various (aliphatic, aromatic, and heterocyclic aromatic) types of aldoximes were converted into the corresponding nitriles in good to excellent yields using 2‐chloro‐1‐methylpyridinium iodide (CMPI) as a dehydrating agent under mild conditions.     

Expeditious One‐Step Method to 5‐Aryl‐2‐furoyl Substituted Thioureas and Thiosemicarbazides in Aqueous Media

An expeditious and green approach to 5‐aryl‐2‐furoyl substituted thioureas and thiosemicarbazides in aqueous media via a one‐step procedure is described.     

Convenient Synthesis of 5‐Aryl Uracils

A convenient one‐step synthesis of 5‐aryl uracils has been developed. The procedure involves heating ethyl 3‐hydroxy‐2‐arylpropenate with urea at 130°C, followed by base‐catalyzed cyclization. The method is simple and high yielding.     

Suzuki–Miyaura Reaction of Unactivated Aryl Chlorides Using Benzimidazol‐2‐Ylidene Ligands

Abstract

Four functionalized bis(benzimidazolium) salts (2a–d) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. A highly effective, easy to handle, and environmentally bengin process for palladium‐mediated Suzuki cross‐coupling was developed. The in situ prepared three‐component system Pd(OAc)₂/bis(benzimidazolium) bromides (2a–d) and Cs₂CO₃ catalyzes quantitatively the Suzuki cross‐coupling of deactivated aryl chloride in aqueous media.     

Novel Procedure for Highly Stereoselective Synthesis of Bicyclic Cyclopropane‐lactam with cis‐2‐Aryl‐1‐benzoyl‐3,3‐dicyanocyclopropane and 2‐Cyanomethyl‐1,3‐benzothiazole in Water

The novel procedure for synthesis of cyclopropyl lactams incorporating benzothiazole structure units from cis‐2‐aryl‐1‐benzoyl‐3,3‐dicynocyclopropane and 2‐cyanomethyl‐1,3‐benzothiazole has been achieved. This method is highly stereoselective and environmentally friendly.     

Synthesis of 3‐Aryl‐5‐methyl 4‐Substituted [1,2,4]Triazoles

Treatment of N‐substituted acetamides with oxalyl chloride generates imidoyl chlorides, which react readily with aryl hydrazides. Following cyclization, triazoles can easily be obtained in moderate to good yields. 5‐Methyl triazoles can be further functionalized through α‐lithiation and subsequent reaction with an electrophile.     

ZnBr2‐Catalyzed Efficient Oxidative Homo Coupling of Aryl Magnesium Bromides

Oxidative homo coupling of various arylmagnesium bromides in the presence of ZnBr₂ gave the corresponding symmetrical biaryls in moderate to good yields at room temperature. An efficient method under mild conditions without the use of reoxidant is described.     

Lanthanum Trifluoromethane-sulfonate‐Catalyzed Facile Synthesis of Per‐O‐acetylated Sugars and Their One‐Pot Conversion to S‐Aryl and O‐Alkyl/Aryl Glycosides†

Lanthanum trifluoromethanesulfonate‐catalyzed solvent‐free per‐O‐acetylation with stoichiometric acetic anhydride proceeds in high yield (95%–99%) to afford exclusively pyranose products as anomeric mixtures. Subsequent anomeric substitution employing borontrifluoride etherate and thiols or alcohols furnished the corresponding 1,2‐trans‐linked thioglycosides and O‐glycosides, respectively, in good to excellent overall yield (75%–85%). Alternatively, reaction of free sugars in neat alcohol employing the same catalyst at elevated temperature gives the corresponding 1,2‐cis‐linked O‐glycosides (along with 1,2‐trans‐linked glycosides as minor product) in good yield (73%–80%). Anomeric mixtures of compounds thus produced were characterized as their per‐O‐acetylated derivatives.      

Synthesis of 3‐Aryl‐5‐t‐butylsalicylaldehydes and their Chiral Schiff Base Compounds

Six meta‐substituted salicylaldehyde compounds have been prepared in 68–90% yields by the Suzuki–Miyaura coupling reaction using 3‐bromo‐5‐t‐butylsalicylaldehyde (1a) and arylboronic acids (2a–f) as reactants. Among the obtained products, 3‐(4‐fluorophenyl)‐5‐t‐butylsalicylaldehyde (3b), 3‐(4‐methylphenyl)‐5‐t‐butylsalicylaldehyde (3d), 3‐(1‐naphthyl)‐5‐t‐butylsalicylaldehyde (3e), and 3‐(2‐naphthyl)‐5‐t‐butylsalicylaldehyde (3f) have not been reported so far. A series of new Schiff base ligands (L1–L10) were obtained in 51–89% yields from these salicylaldehyde derivatives.     

New Approach to 3‐Aminothiophene‐ 2‐carboxylic Acid Derivatives: Access to 5‐Aryl‐4‐(ethylsulfanyl) Compounds

Treatment of DMSO/water solutions of β‐bromo‐α‐(ethylsulfanyl)cinnamonitriles with sodium sulphide and α‐halo acetic acids derivatives followed by cyclization in a potassium carbonate/acetone/DMSO mixture gave the expected 3‐amino‐5‐aryl‐4‐(ethylsulfanyl)thiophene‐2‐carboxylic acids derivatives in fair yields.     

Synthesis,Structures, and Properties of Novel N‐Aryl‐phenanthren‐o‐iminoquinones

The interaction of 9,10‐phenanthrenquinone with primary amines has been studied. Use of sterically hindered anilines gave the phenanthren‐o‐iminoquinones in good yields. These compounds are structural analogues of o‐benzoquinones. Using single‐electron reduction, o‐iminoquinones may synthesize metal's free‐radical complexes.     

PMA‐SiO2: A Heterogenous Catalyst for O‐, S‐, and N‐Nucleophilic Substitution Reactions of Aryl Propargyl Alcohols

Aryl‐propargylic alcohols undergo O‐, S‐, and N‐nucleophilic substitution reactions in the presence of a catalytic amount of PMA‐SiO₂.     

Hypervalent Iodine‐Mediated Synthesis of 1‐Aryl‐4‐methyl‐1,2,4‐triazolo[4,3‐a]quinoxalines by Oxidative Cyclization of Arene Carbaldehyde‐3‐methylquinoxalin‐2‐yl Hydrazones

Arene carbaldehyde‐3‐methylquinoxalin‐2‐yl hydrazones (2) obtained by the condensation of 2‐hydrazino‐3‐methylquinoxaline (1) with various aromatic aldehydes, on treatment with iodobenzene diacetate (IBD) in dichloromethane, undergo oxidative cyclization to exclusively afford 1‐aryl‐4‐methyl‐1,2,4‐triazolo[4,3‐a]quinoxalines (5) in excellent yield.     

Synthesis and Characterization of Alkyl and Aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines: X‐Ray Structures of Ethyl and Cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine

Abstract

We have synthesized and characterized a series of alkyl and aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines through a high‐yield, three‐step procedure starting from 4‐methylquinolin‐2‐ol. Nitration using concentrated nitric/sulfuric acids, followed by chlorination in phosphorus oxychloride, yielded 2‐chloro‐4‐methyl‐6‐nitro‐quinoline. All of the intermediates and aminated products have been characterized by multinuclear (¹H and ¹³C) NMR spectroscopy, elemental analysis, and, in the case of the two title compounds (ethyl and cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine), a single crystal X‐ray structure was obtained to verify the nature of the new materials.     

Exclusive Formation of 1‐Aryl‐3‐(5‐nitro‐2‐furyl)‐4‐aroylpyrazoles via Regiospecific 1,3‐Dipolar Cycloaddition of 3‐Arylsydnones with α,β‐Acetylenic Ketones

1,3‐Dipolar cycloaddition of 3‐arylsydnones with α,β‐acetylenic ketones containing nitrofuran moiety has been studied, and it was observed that the dipolar cycloaddition is regiospecific, forming 1‐aryl‐3‐(5‐nitro‐2‐furyl)‐4‐aroylpyrazoles exclusively.     

Transformation of Aryl Acyloin O‐Alkyl and O‐Phenyl Derivatives to Ketones

The treatment of aryl acyloin (α‐hydroxyketone) O‐alkyl and O‐phenyl derivatives with 2–3 equiv of Zn and 1–2 equiv of NH₄Cl in ethanol, refluxing for 20–120 min, gave the corresponding ketones with excellent yields. Further, α,β‐epoxy ketones can be efficiently transformed to β‐hydroxy ketones, and 2,2‐dialkoxy‐1‐phenyl ketone also can be dealkoxylated to 1‐phenyl ketone.