Amberlyst-15–Catalyzed Synthesis of 2-Substituted 1,3-Benzazoles in Water under Ultrasound

Rambabu, D.; Murthi, P. Radha Krishna; Dulla, Balakrishna; Rao, Mandava V. Basaveswara; Pal, Manojit

doi:10.1080/00397911.2013.769605

Cited by 31 publications

(10 citation statements)

References 32 publications

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“…On the other hand, we predict that the overall transformation occurs with the initial C-alkenylation through CÀH activation (Fujiwara-Moritani reaction) followed by an acid catalyzed annulation. In line with the reported literature, [21,22] the catalytic cycle is presented in Scheme 4. We presumed that electronically more deficient and more reactive Pd-catalyst (Pd(OCOCF 3 ) 2 ) is forming initially from the reaction of Pd(OAc) 2 and CF 3 COOH.…”

Section: Resultssupporting

confidence: 84%

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Synthesis of 4‐Alkenyl Benzoxazoles via Pd‐catalyzed ortho C−H Functionalization of 2‐Amidophenols

Panda

Sahoo

2018

Adv Synth Catal

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A one-pot direct transformation to remotely CÀH alkene functionalized 2-aryl benzoxazoles from the reaction of amidophenol and electronically deficient olefin was reported. Control experiments confirm that the Pd-catalyzed regioselective CÀH activation/alkenylation occurs at the first step by leading to ortho-alkenylated amidophenol; which subsequently underwent tandem intramolecular annulation to afford C4-alkenylated 2arylbenzoxazole derivatives.

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Section: Resultssupporting

confidence: 84%

“…In the presence of terminal oxidant (i. e., Ag 2 O), the newly generated Pd(0) oxidizes to Pd(II) for the next catalytic cycle. Finally, the cross‐coupled hydroxy anilide 3 aa′ undergoes acid‐catalyzed annulation to afford the desired benzoxazole 3 aa .…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 4‐Alkenyl Benzoxazoles via Pd‐catalyzed ortho C−H Functionalization of 2‐Amidophenols

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Sahoo

2018

Adv Synth Catal

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“…Among the methods utilized for the formation of benzoxazole rings, the synthesis of a 2‐substituted derivative from 2‐aminophenol as starting material stands out. Many studies in the literature point out to obtain a high yield benzoxazole ring (Scheme 1A) [15–27] . In addition to the necessity in improving the reaction conditions, it is also essential to place the carbonyl group in the C‐2 position of the oxazole ring instead of the aryl ring substitution, which will not allow much further derivatizations easily.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Benzoxazole‐2‐carboxylate Derivatives: Electronic‐ and Position‐effect of Functional Groups and Computational Modeling of the Selectivity for Oxazole Ring

et al. 2021

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In this study, Mitsunobu reagent, DEAD (diethyl azodicarboxylate) and PPh3, and ethyl‐oxalamide derivatives of 2‐aminophenol were reacted under mild reaction conditions. As a result of the cyclization reaction, benzoxazole derivatives bearing an ester group in the C‐2 position were obtained in a one‐pot protocol. It was observed that the electron‐donating groups at the C‐5 position and the electron‐withdrawing groups at the C‐6 position of the benzene ring increased the yield of the cyclic product. It was found that the cyclization does not occur when the carboxylic acid group is substituted in the benzene ring. The cyclization reaction we performed preferred the 5‐endo‐trig reaction instead of the 6‐exo‐trig. This experimental result was examined in detail with density functional theory (DFT) calculations as well. A computational exploration is presented herein that elucidates the detailed mechanism for Huisgen zwitterion‘s reaction with ethyl‐oxalamide derivatives of 2‐aminophenol. Potential alternative mechanisms were modeled with DFT calculations via CPCM/M06‐2X/6‐311++G(d,p)//B3LYP/6‐31+G(d,p) level method in tetrahydrofuran to understand shed light on the mechanism. Our computational results are in good agreement with experimental findings that benzoxazole derivatives are the sole products in this reaction.

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“…A method for the synthesis of a series of 2-substitutedBTs 104 in 82-92% yields was developed involving the condensation of ATP with a series of carboxylic acids using Amberlyst-15 as a recyclable catalyst under ultrasound irradiation in water (Scheme 85). This methodology does not use hazardous organic solvents and is carried out in an inert or anhydrous atmosphere [195].…”

Section: Condensation Under Microwave Irradiation (Mwi)mentioning

confidence: 99%

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

et al. 2021

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Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO2) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review.

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Amberlyst-15–Catalyzed Synthesis of 2-Substituted 1,3-Benzazoles in Water under Ultrasound

Cited by 31 publications

References 32 publications

Synthesis of 4‐Alkenyl Benzoxazoles via Pd‐catalyzed ortho C−H Functionalization of 2‐Amidophenols

Synthesis of 4‐Alkenyl Benzoxazoles via Pd‐catalyzed ortho C−H Functionalization of 2‐Amidophenols

Synthesis of Benzoxazole‐2‐carboxylate Derivatives: Electronic‐ and Position‐effect of Functional Groups and Computational Modeling of the Selectivity for Oxazole Ring

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

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