Synthesis Of Benzoxazoles Research Articles

Synthesis of Benzoxazoles Catalyzed by MCM-41, a Green and Reusable Catalyst

Benzoxazoles can be rapidly and efficiently synthesized from acyl chloride with 2-aminophenols in one simple step, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds.

Synthesis of Benzoxazole via the Beckmann Rearrangement of Salicylaldoxime on Protonated Zeolites: A Green Continuous Process

Benzoxazole was prepared through the Beckmann rearrangement of salicylaldoxime using a series of H-zeolites, K-10 montmorillonite clay, and some common oxide catalysts under well-optimized reaction conditions of temperature, weight hourly space velocity, and catalyst amount. Salicylaldoxime underwent a facile 1,2-o-hydroxyphenyl shift followed by an intramolecular cyclization to yield benzoxazole. Syn-anti isomerization of the oxime on acid catalysts is a key step in the reaction. o-Hydroxybenzonitrile, o-hydroxybenzamide, and salicylaldehyde were the main byproduct. We have observed definite correlations between acid sites distribution of the catalysts and different products formed during the reaction. Catalysts were susceptible for deactivation and the decrease in the percentage conversion of oxime with time is associated with a corresponding increase in the acid hydrolysis producing salicylaldehyde at later stages of the reaction. However, the deactivated catalysts can be regenerated without considerab...

Silica sulfuric acid catalyzed synthesis of benzoxazoles, benzimidazoles and oxazolo[4,5-b]pyridines under heterogeneous and solvent-free conditions

A simple, rapid and efficient method for the preparation of benzoxazoles, benzimidazoles and oxazolo[4,5-b]pyridines from the reaction of orthoesters with o-aminophenols, o-phenylenediamine and 2-amino-3-hydroxypyridine in the presence of silica sulfuric acid under heterogeneous and solvent-free conditions is reported. The significant features of this method are short reaction times, high yields of the products, mild reaction conditions, solvent free reaction, cheapness, non-toxicity and reusability of the catalyst.

ChemInform Abstract: Copper‐Catalyzed Domino Annulation Approaches to the Synthesis of Benzoxazoles under Microwave‐Accelerated and Conventional Thermal Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Iron-Catalyzed Intramolecular O-Arylation: Synthesis of 2-Aryl Benzoxazoles

A practical iron-catalyzed intramolecular O-arylation reaction and its application in the synthesis of benzoxazole derivatives, starting from the readily available 2-haloanilines, is presented. The key cyclization step involves the use of a combination of the cheap and environmentally friendly FeCl(3) and 2,2,6,6-tetramethyl-3,5 heptanedione (TMHD) as the catalyst system.

Oxazolidin-2-one-Promoted CuI-Catalyzed Amidation of Aryl Halides and Cyclization of o-Halobenzanilides

Oxazolidin-2-one was found to be a versatile and efficient ligand for the CuI-catalyzed amidation of aryl halides and the cyclization of ortho-halobenzanilides. Notably, the less active halides could also be applied successfully in the synthesis of benzoxazoles and benzothiazoles.

Copper-Catalyzed Domino Annulation Approaches to the Synthesis of Benzoxazoles under Microwave-Accelerated and Conventional Thermal Conditions

Two domino annulation approaches for benzoxazole synthesis have been developed. In the first approach, copper-catalyzed intermolecular cross-coupling of 1,2-dihaloarenes with primary amides initially forms the Ar-N bond of the benzoxazole ring, followed by copper-catalyzed intramolecular cyclization to form the Ar-O bond. Benzoxazoles were formed in good yields for the reaction of 1,2-dibromobenzene, but the reaction was not regioselective for the reaction of 3,4-dibromotoluene. Furthermore, the method is limited by the availability of 1,2-dihaloarenes. As a result of these limitations, an alternative more versatile one-pot domino annulation strategy was developed involving reaction of 2-bromoanilines with acyl chlorides in the presence of Cs2CO3, catalytic CuI, and the non-acylatable ligand 1,10-phenanthroline. Under these conditions initial acylation of the aniline is followed by copper-catalyzed intramolecular cyclization of the resultant 2-haloanilide to form the Ar-O bond of the benzoxazole ring. Optimized conditions using microwave irradiation achieved much shorter reaction times than conventional heating (i.e., 210 degrees C for 15 min versus 95 degrees C for 24 h) and were applied to the synthesis of a small library of benzoxazoles. These copper-catalyzed approaches complement existing strategies for benzoxazole synthesis, which typically utilize 2-aminopheonls as precursors.

ChemInform Abstract: Diversity‐Oriented Synthesis of Benzoxazoles and Benzothiazoles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

銅触媒を用いた位置選択的C–H活性化/C–O結合形成によるベンゾオキサゾール環形成反応

銅触媒を用いた位置選択的C–H活性化/C–O結合形成によるベンゾオキサゾール環形成反応

Diversity oriented synthesis of benzoxazoles and benzothiazoles

A combinatorial synthetic route yielding benzoxazoles and benzothiazoles is described. The use of o-halophenylisocyanides in the Ugi reaction (U-4CR) followed by a copper-catalyzed cyclization affords the benzoxazole as well as the benzothiazole moiety in good yield and high diversity.

Mild and Efficient Synthesis of Benzoxazoles, Benzothiazoles, Benzimidazoles, and Oxazolo[4,5‐b]pyridines Catalyzed by Bi(III) Salts under Solvent‐Free Conditions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Iodine-mediated cyclisation of thiobenzamides to produce benzothiazoles and benzoxazoles

Synthesis of benzothiazoles by reaction of iodine with thiobenzamides, which do not possess an ortho alkoxy or ester group, is described. The unlikely synthesis of benzoxazoles from reaction of 2-alkoxythiobenzamides with iodine is also reported.

Mild and Efficient Synthesis of Benzoxazoles, Benzothiazoles, Benzimidazoles, and Oxazolo[4,5-b]pyridines Catalyzed by Bi(III) Salts Under Solvent-Free Conditions

A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3-hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)3, Bi(OTf)3, and BiOClO4 · xH2O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts.

ZrOCl2·8H2O as an efficient, environmentally friendly and reusable catalyst for synthesis of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines under solvent-free conditions

Abstract A new and efficient method for the preparation of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5- b ]pyridines from reactions of orthoesters with o -substituted aminoaromatics and 2-amino-3-hydroxypyridine in the presence of catalytic amounts of the moisture stable, inexpensive ZrOCl 2 ·8H 2 O under solvent-free conditions is presented. This new protocol has the advantages of easy availability, easy handling, stability, reusability and eco-friendly of the catalyst, high yields, very short reaction times, solvent-free reaction conditions, simple experimental and work-up procedure.

Facile and Efficient One‐Pot Protocol for the Synthesis of Benzoxazole and Benzothiazole Derivatives Using Molecular Iodine as Catalyst.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Facile and Efficient One‐Pot Protocol for the Synthesis of Benzoxazole and Benzothiazole Derivatives using Molecular Iodine as Catalyst

Rapid and efficient condensation reactions of 2‐aminothiophenol and 2‐aminophenol with various aldehydes were carried out using I2 in solvent‐free conditions with or without microwave irradiation to afford the corresponding 2‐substituted benzothiazole and benzoxazole derivatives in good to excellent yields.

Rare-earth (Ce 3+, La 3+, Sm 3+, and RE 3+) exchanged Na-Y zeolites and K-10 clay as solid acid catalysts for the synthesis of benzoxazole via Beckmann rearrangement of salicylaldoxime

Rare-earth exchanged (Ce 3+, La 3+, Sm 3+, and RE 3+) Na-Y zeolites, K-10 montmorillonite clay and amorphous silica–alumina have been employed as solid acid catalysts for the vapor phase Beckmann rearrangement of salicylaldoxime to benzoxazole. Rare-earth exchanged Na-Y zeolites were prepared by simple ion-exchange methods. These systems were characterized by energy dispersed X-ray analysis, 27Al and 29Si MAS NMR, FTIR spectroscopy, temperature programmed desorption and surface area and pore volume measurements. The catalysts show both Brönsted and Lewis acidity. Definite correlation between Brönsted acid sites amount obtained from thermodesorption of 2,6-dimethylpyridine and benzoxazole formation in the reaction were observed. Hydrolysis of salicylaldoxime to salicylaldehyde is correlated with Lewis acidity as obtained from hydrocracking of cumene.

A simple and efficient one step synthesis of benzoxazoles and benzimidazoles from carboxylic acids

Benzoxazoles or benzimidazoles can be rapidly and efficiently synthesized from a variety of carboxylic acids with 2-aminophenols or 1,2-phenylenediamines in one simple step, respectively. The use of commercially available PS-PPh 3 resin combined with microwave heating delivered a variety of benzoxazoles and benzimidazoles in high yields and purities.

Novel Synthesis of Benzoxazoles from O‐Nitrophenols and Amines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Ortho Lithiation of N‐Pivaloylfluoroanilines as a Useful Tool for Either Selective Methylation or Benzoxazole Synthesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.