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Cross-coupling of Aromatic Aldehydes with N-(Amidobenzyl)benzotriazoles: An Alternative Route to α-Amidoketones

[ Vol. 15 , Issue. 10 ]

Author(s):

Wijitra Waengdongbung, Mongkol Nontakitticharoen* and Viwat Hahnvajanawong   Pages 838 - 844 ( 7 )

Abstract:


Background: Several transition-metal-catalyzed reactions have been used to synthesize biologically active α-amidoketones. These approaches involve inconvenient conditions or expensive catalysts. Alternative attempts based on transition-metal-free catalysts have also been reported including cross-coupling reaction of aldehydes with acylimines in the presence of thiazolium salt as an organic catalyst. We report herein the use of N,N-dimethylbenzimidazolium iodide which is a safe and recyclable organic pre-catalyst, along with N-(amidobenzyl)benzotriazoles as activated N-acylimines for this cross-coupling reaction.

Method: N-(Amidobenzyl)benzotriazoles (9a-c) were prepared from benzamide, aromatic aldehydes and benzotriazole. N,N-Dimethylbenzimidazolium iodide (11) was easily prepared via the methylation reaction of benzimidazole. Cross-coupling reactions were carried out in refluxing THF in the presence of DBU and organo-catalyst 11 for 5 hours.

Results: N,N-Dimethylbenzimidazolium-catalyzed cross-coupling reactions of various aromatic aldehydes (10a-f) with N-(amidobenzyl)benzotriazoles (9a-c) afforded α-amidoketones (12a-r) in good yields.

Conclusion: An alternative approach for the synthesis of α-amidoketones based on organo-catalytic cross-coupling reaction of aromatic aldehydes with acylimines have been accomplished in high yields.

Keywords:

α-Amidoketones, N-(amidobenzyl)benzotriazoles, masked N-acylimines, N, N-dimethylbenzimidazolium iodide, organic catalyst, aldehyde.

Affiliation:

Natural Products Research Unit, Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Natural Products Research Unit, Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Natural Products Research Unit, Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002



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