2,4,6-Trihydroxybenzoic Acid-Catalyzed Oxidative Ugi Reactions with Molecular Oxygen via Homo- and Cross-Coupling of
Chun-Ping Dong1, Akinori Uematsu1, Shun Kumazawa1
1Department of Applied Chemistry, Graduate School of Engineering , Osaka Prefecture University , 1-1 Gakuen-cho , Nakaku, Sakai , Osaka 599-8531 , Japan.
Abstract:
Metal-free, oxidative four-component Ugi reactions (U-4CRs) were conducted to synthesize dipeptides from two different amines, isocyanides, and carboxylic acids using 2,4,6-trihydroxybenzoic acid catalyst in O2 atmosphere. The organocatalytic U-4CRs proceed via oxidative cross-coupling of benzylamines with other aliphatic or aromatic amines to form imines, followed by condensation with isocyanides and carboxylic acids. The U-4CRs via cross-coupling of amines are rare, and the simple, metal-free procedures are advantageous for further applications in drug and heterocycle syntheses.
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