Highly efficient water-mediated approach to access benzazoles: metal catalyst and base-free synthesis of 2-substituted benzimidazoles, benzoxazoles, and benzothiazoles

Bala, Manju; Verma, Praveen Kumar; Sharma, Deepika; Kumar, Neeraj; Singh, Bikram

doi:10.1007/s11030-015-9572-8

Cited by 26 publications

(19 citation statements)

References 64 publications

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“…This is clearly an alternative to the transition-metal-based synthesis of benzoxazoles. 71 In the same year, Maleki et al studied the synthesis of benzoxazole derivatives 3 from o-aminophenol 2 and several aromatic aldehydes, orthoesters, carboxylic acids, amides, or acyl chlorides through a one-pot condensation in water at room temperature by using Ag@TiO 2 nanocom-posites as the catalyst. 72 As shown in Scheme 42, this method is simple, cost effective, and follows a green pathway for the synthesis of this privileged moiety.…”

Section: Account Syn Lettmentioning

confidence: 99%

A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry

Rajasekhar

Maiti

Chanda

2017

Synlett

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In 2014, more than 80% of the marketed drugs in the US contained heterocyclic compounds, which play a major role in the drugdiscovery process, as one of the primary components. Benzoxazole, consisting of an oxazole ring fused with a benzene ring, has shown profound impact in drug discovery research owing to its important bioactivity. This moiety has also shown important properties in material science. The synthesis of this privileged scaffold from readily available chemicals remains a primary focus for the synthetic chemistry community. In this review, efforts have been made to focus on the latest information available on the different synthetic strategies such as solution phase, multicomponent, green and solid phase chemistry and applications of different benzoxazole derivatives. Furthermore, the updated synthetic information incorporated in this review article will help to improve future synthesis of this scaffold. Conclusion and Outlook

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Section: Account Syn Lettmentioning

confidence: 99%

A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry

Rajasekhar

Maiti

Chanda

2017

Synlett

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“…4), confirming the role of K 2 S 2 O 8 is important in initial step (oxidation of benzylamine) as well as in final step (cyclization and oxidation of imine to final product). However, the final oxidation can not be ruled out to proceed either by atmospheric oxygen or sole oxygen dissolved in the water used as reaction solvent . K 2 S 2 O 8 is strong oxidizing agent and catalyze the oxidation of benzylamine to benzaldehyde, and also, reaction at room temperature, excludes the free radical pathway.…”

Section: Resultsmentioning

confidence: 99%

Transition Metal-free Single Step Approach for Arylated Pyrazolopyrimidinones and Quinazolinones Using Benzylamines/Benzylalcohols/Benzaldehydes

et al. 2017

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A transition metal-free, one step approach has been developed for the synthesis of pyrazolopyrimidinones using in-situ condensation of benzylamines, benzylalcohol and benzaldehyde with 4-amino-2-methyl-5-propyl-2H-pyrazole-3-carboxylic acid amide promoted by K 2 S 2 O 8 and water at room temperature. Present protocol tolerated various functional groups such as halides (Cl, F, Br), methoxy, ethoxy, hydroxyl, nitro, trifluromethyl, trifluoromethoxy and was also applicable to heterocyclic moieties. Different arylated pyrazolopyrimidinones were prepared in good to excellent yields. In the present reaction, K 2 S 2 O 8 is catalyzing the formation of imine as well helping in the cyclization to the desired product. We also reduced the industrially used synthesis steps for sildenafil analogues and prepared in three steps using present method. Arylquinazolinones were also synthesized in high yields using anthranilamide and benzylamines by this methodology.

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“…Bala et al reported water‐promoted synthesis of 2‐substituted benzothiazoles/benzoxazoles/benzimidazoles in a tandem manner [Eq. (17)].…”

Section: Condensation Of 2‐aminothiophenols With Various Cyclizatimentioning

confidence: 99%

A Review on Domino Condensation/Cyclization Reactions for the Synthesis of 2‐Substituted 1,3‐Benzothiazole Derivatives

Liu

Dong

2020

Eur J Org Chem

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Highly efficient water-mediated approach to access benzazoles: metal catalyst and base-free synthesis of 2-substituted benzimidazoles, benzoxazoles, and benzothiazoles

Cited by 26 publications

References 64 publications

A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry

A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry

Transition Metal-free Single Step Approach for Arylated Pyrazolopyrimidinones and Quinazolinones Using Benzylamines/Benzylalcohols/Benzaldehydes

A Review on Domino Condensation/Cyclization Reactions for the Synthesis of 2‐Substituted 1,3‐Benzothiazole Derivatives

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Highly efficient water-mediated approach to access benzazoles: metal catalyst and base-free synthesis of 2-substituted benzimidazoles, benzoxazoles, and benzothiazoles

Cited by 26 publications

References 64 publications

A Decade Update on Benzoxazoles, a Privileged Scaffold in ­Synthetic Organic Chemistry

A Decade Update on Benzoxazoles, a Privileged Scaffold in ­Synthetic Organic Chemistry

Transition Metal-free Single Step Approach for Arylated Pyrazolopyrimidinones and Quinazolinones Using Benzylamines/Benzylalcohols/Benzaldehydes

A Review on Domino Condensation/Cyclization Reactions for the Synthesis of 2‐Substituted 1,3‐Benzothiazole Derivatives

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A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry

A Decade Update on Benzoxazoles, a Privileged Scaffold in Synthetic Organic Chemistry