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.     

Catalytic Enantioselective Direct Aldol Addition of Aryl Ketones to α-Fluorinated Ketones

The catalytic enantioselective synthesis of α-fluorinated chiral tertiary alcohols from (hetero)aryl methyl ketones is described. The use of a bifunctional iminophosphorane (BIMP) superbase was found to facilitate direct aldol addition by providing the strong Brønsted basicity required for rapid aryl enolate formation. The new synthetic protocol is easy to perform and tolerates a broad range of functionalities and heterocycles with high enantioselectivity (up to >99:1 e.r.). Multi-gram scalability has been demonstrated along with catalyst recovery and recycling. ¹H NMR studies identified a 1400-fold rate enhancement under BIMP catalysis, compared to the prior state-of-the-art catalytic system. The utility of the aldol products has been highlighted with the synthesis of various enantioenriched building blocks and heterocycles, including 1,3-aminoalcohol, 1,3-diol, oxetane, and isoxazoline derivatives.     

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.     

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.     

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.     

One‐Pot Synthesis of α‐Formyloxy Ketones from Enolizable Ketones

One‐pot synthesis of α‐formyloxy tones as well as α‐acetoxy ketones from enolizable ketones and [hydroxy(tosyloxy) iodo] benzene (HTIB)/polymer supported [hydroxy(tosyloxy) iodo] benzene (PSHTIB) in N,N–dimethylformamide (DMF)/N, N–dimethylacetamide (DMA) in high yields is described.     

Facile One‐Pot Synthesis of 2‐Aryl‐substituted Nitriles and 2‐Aryl‐3‐keto Nitriles via Benzyne Reaction

2‐Aryl‐substituted nitriles were prepared in good to excellent yields in a one‐pot reaction by the reaction of benzyne, generated using neutral conditions from (phenyl)[o‐(trimethylsilyl)‐phenyl]iodonium triflate, and 2‐lithionitriles. 3‐Keto nitriles substituted at the 2‐position were obtained in good yields when these reactions were trapped with acid chlorides. The mechanism of the benzyne reaction in terms of a N‐lithiobenzocyclobutanimine intermediate is discussed.     

Transformations of Aryl Ketones via Ligand-Promoted C−C Bond Activation

The coupling of aromatic electrophiles (aryl halides, aryl ethers, aryl acids, aryl nitriles etc.) with nucleophiles is a core methodology for the synthesis of aryl compounds. Transformations of aryl ketones in an analogous manner via carbon–carbon bond activation could greatly expand the toolbox for the synthesis of aryl compounds due to the abundance of aryl ketones. An exploratory study of this approach is typically based on carbon–carbon cleavage triggered by ring-strain release and chelation assistance, and the products are also limited to a specific structural motif. Here we report a ligand-promoted β-carbon elimination strategy to activate the carbon–carbon bonds, which results in a range of transformations of aryl ketones, leading to useful aryl borates, and also to biaryls, aryl nitriles, and aryl alkenes. The use of a pyridine-oxazoline ligand is crucial for this catalytic transformation. A gram-scale borylation reaction of an aryl ketone via a simple one-pot operation is reported. The potential utility of this strategy is also demonstrated by the late-stage diversification of drug molecules probenecid, adapalene, and desoxyestrone, the fragrance tonalid as well as the natural product apocynin.     

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.     

Convenient Electrochemical Method for the Synthesis of α-Bromo Alkyl Aryl Ketones

An electrochemical procedure for the effective α-bromination of alkyl aryl ketones in excellent yield has been reported. The simple experimental procedure, catalyst-free conversion, and excellent yield of monobrominated products are the advantages of this method.     

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.     

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.     

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.     

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.     

Concise Synthesis of α-(Hydroxymethyl) Alkyl and Aryl Vinyl Ketones

2,4-Diketoesters 2 have first been reported as starting materials for the synthesis of a new class of α-hydroxymethyl-α,β-unsaturated ketones 3. Thus, under heterogeneous liquid–liquid medium in the presence of concentrated aqueous potassium carbonate as a base, both aliphatic and aromatic 2,4-dioxoalkanoates 2 react with aqueous formaldehyde to afford the corresponding ketones 3 in fair to good yields.     

General Synthesis of 1‐Substituted 2‐Methylbenzimidazoles from Ketones and 2‐Aminoacetanilide

A novel method for preparation of 1‐substituted benzimidazoles via reductive amination of ketones with N‐differentiated 1,2‐diaminobenzenes is described. The method appears to be general in application to acyclic and cyclic ketones, as well as heteroatom‐substituted cyclic ketones.     

Solid‐Phase Synthesis of N‐Aryl‐N′‐Carboalkoxy Guanidines by the Mitsunobu Reaction of Fmoc‐Guanidines

Abstract

A new method for the solid‐phase synthesis of N‐aryl‐N′‐carboalkoxy guanidines is described. Aromatic amines were reacted with Fmoc‐isothiocyanate to provide Fmoc‐thioureas, which were coupled with Rink amide resin to provide the corresponding resin‐bound Fmoc‐guanidines. Subsequent Mitsunobu alkylation with a variety of alcohols delivered N‐aryl‐N′ carboalkoxy guanidines in good to high purity after resin cleavage.