Browsing by Author "Narhe, Bharat D."

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A concise synthesis of 2-(2-aminothiophene)-benzimidazoles by one-pot multicomponent reaction
(2013)
Chen, Li-Hsun
;
Chuang, Ying-Sheng
;
Narhe, Bharat D.
;
Sun, Chung-Ming
;
應用化學系
A one-pot synthesis of 2-aminothiophene linked benzimidazoles was achieved by utilizing 2-cyanomethyl benzimidazoles in a modified Gewald multicomponent reaction. The synthetic strategy of the reaction involved treatment of 2-(cyanomethyl)-benzimdazole with aldehydes containing an active methylene group and sulfur powder under refluxing conditions. The multicomponent reaction proceeded via Knoevenagel condensation of 2-(cyanomethyl)-benzimdazole with aldehyde to generate an alpha,beta-unsaturated nitrile followed by cyclization with molecular sulfur under basic conditions to give biologically relevant 2-(2-aminothiophene)-benzimidazoles in good yields.
A Novel Mechanistic Study on Ultrasound-Assisted, One-Pot Synthesis of Functionalized Benzimidazo[2,1-b]quinazolin-1(1H)-ones
(2016-03)
Chen, Li-Hsun
;
Chung, Tsai-Wen
;
Narhe, Bharat D.
;
Sun, Chung-Ming
;
應用化學系
Ultrasound-assisted synthesis of benzimidazo[2,1-b]quinazolin-1(1H)-ones was achieved via piperidine-catalyzed three-component reaction of 2-aminobenzimidazoles, an aromatic aldehyde, and 1,3-dione in aqueous isopropanol. This mechanism was first suspected following our identification of unusual reaction intermediates in a one-pot reaction. An unprecedented coupling reaction, it involved a nucleophilic attack by 2-aminobenzimidazole on in situ generated Michael adduct, followed by electrocyclic ring formation reaction. In contrast to the commonly accepted mechanism, that the direct reaction of 2-amino benzimidazole with a Knoevenagel adduct cannot deliver target compounds.
Multicomponent Synthesis of Functionalized Tetrahydroacridinones: Insights into a Mechanistic Route
(2015-11-06)
Chung, Tsai-Wen
;
Narhe, Bharat D.
;
Lin, Chun-Cheng
;
Sun, Chung-Ming
;
應用化學系
A mechanistic study of three-component reactions of various aromatic amines with a number of aldehydes and 1,3-diones was achieved. The unprecedented reaction involved a nucleophilic attack of an aromatic amine on the in situ generated Michael adduct intermediate followed by six-electron ring cyclizations. It is contrary to the common belief that advocates involvement of coupling reactions between a Knoevenagel adduct and an aromatic amine to deliver substituted tetrahydroacridinones.
One-Pot, Two-Step Synthesis of Imidazo[1,2-a]benzimidazoles via A Multicomponent [4+1] Cycloaddition Reaction
(2013-10-01)
Hsiao, Ya-Shan
;
Narhe, Bharat D.
;
Chang, Ying-Sheng
;
Sun, Chung-Ming
;
應用化學系
A one-pot, two-step synthesis of imidazo[1,2-a]benzimidazoles has been achieved by a three-component reaction of 2-aminobenzimidazoles with an aromatic aldehyde and an isocyanide. The reaction involving condensation of 2-aminobenzimidazole with an aldehyde is run under microwave activation to generate an imine intermediate under basic conditions which then undergoes [4 + 1] cycloaddition with an isocyanide.
Rapid Two-Step Synthesis of Benzimidazo[1 ',2 ':1,5]-pyrrolo[2,3-c]isoquinolines by a Three-Component Coupling Reaction
(2014-08-01)
Narhe, Bharat D.
;
Tsai, Min-Huan
;
Sun, Chung-Ming
;
應用化學系
;
Department of Applied Chemistry
A two-step, three-component coupling reaction on ionic liquid supported 2-cyanomethylbenzimidazoles, methyl 2-formylbenzoate, and isocyanides under microwave activation is explored. Knoevenagel condensation of 2-cyanomethylbenzimidazole with methyl-2-formylbenzoate in the presence of piperidine catalyst is followed by [4 + 1] cycloaddition with an isocyanide in the next step. Consequent intramolecular delta-lactam formation allows rapid construction of novel aza-pentacycles, benzimidazo [1',2':1,5]pyrrolo [2,3-c]isoquinolines.
Rapid Two-Step Synthesis of Benzimidazo[1 \',2 \':1,5]-pyrrolo[2,3-c]isoquinolines by a Three-Component Coupling Reaction
(2014-08-01)
Narhe, Bharat D.
;
Tsai, Min-Huan
;
Sun, Chung-Ming
;
應用化學系
;
Department of Applied Chemistry
A two-step, three-component coupling reaction on ionic liquid supported 2-cyanomethylbenzimidazoles, methyl 2-formylbenzoate, and isocyanides under microwave activation is explored. Knoevenagel condensation of 2-cyanomethylbenzimidazole with methyl-2-formylbenzoate in the presence of piperidine catalyst is followed by [4 + 1] cycloaddition with an isocyanide in the next step. Consequent intramolecular delta-lactam formation allows rapid construction of novel aza-pentacycles, benzimidazo [1\',2\':1,5]pyrrolo [2,3-c]isoquinolines.