The DDQ-mediated Metal-free Cross-dehydrogenative-coupling Reaction

Cross-Dehydrogenative-Coupling(CDC)reaction is an useful approach to construct C-C and C-X bond by using unfunctionalized starting materials under oxidative conditions.It has some advantages such as higher atom efficiency and shorter reaction route.In order to obviate the drawbacks of high toxicity,cost and residual metal impurities associated with metal catalysts,much effort has been dedicated to the metal-free CDC reactions.2,3-Dichloro-5,6-dicyano-1,4-benzoquinone(DDQ)has been proved to be an effective candidate in this area due to its high oxidant potential.This dissertation focuses on the metal-free CDC reactions to construct C(sp3)-C(sp2)bonds using DDQ as an oxidant.The content is mainly divided into two parts as following:1)DDQ-mediated the coupling and cyclization of 1,3-diarylpropenes with 2-substituted-1,4-naphthoquinones and 4-hydroxycoumarins.The coupling reaction was performed in 1,2-dichloroethane at room temperature for 0.5 hour.When the amount of DDQ was 1.2 equiv,the coupling products were obtained in good yields.Add more 1.0 equiv DDQ into the solution after the coupling reaction,the coupling products transformed to the corresponding cyclized products in moderate yields.4-Hydroxycoumarins were proved to be available for both the coupling reaction and cyclization.A series of 2-substituted-3-alkyl-1,4-naphthoquinones,3-alkyl-4-hydroxycoumarins,pyranonaphthoquinones and pyranocoumarins which have potential pharmaceutical applications were obtained.2)DDQ-mediated the CDC reaction of 1,3-diphenylpropenes and ?-oxo ketene dithioacetals.The ratio of ?-oxo ketene dithioacetals and 1,3-diphenylpropenes was 1:2,the reaction was performed in ether acetate for 1 hour at room temperature,the desired products were obtained in excellent yields.A versatile synthesis strategy was suitable for ?-benzoyl,acetyl,ester and acylamino substituted ketene dithioacetals.All of the product were identified by NMR and MS.The thesis provides easy and available methods for the synthesis of the corresponding products.