Study On The Oxidative Coupling Reaction Mediated By Manganese Dioxide/Boron Trifluoride Ethyl Ether

Recently, Manganese dioxide has been extensively used in synthetic organic chemistry. It has attracted considerable attentions of the general organic workers for its extremely mild reaction conditions required and its economical, environmentally friendly etc. In this paper, taking the use of the good oxidation, we explored a new oxidation coupling system: manganese dioxide / boron trifluoride ethyl ether oxidation coupling system, and explored the possibility and applicability of the system in the intramolecular and intermolecular oxidative coupling reactions.The research work in this paper was introduced as followes: at the beginning of the thesis, a simple summary of two kinds of oxidative coupling reaction type and several aryl oxidative coupling systems was made. On the basis of summarizing the literature, this paper proposed the design idea: initially, the intramolecular oxidative coupling of 1,4-diarylbutane 1a was selected as the model to test the possibility of manganese dioxide / boron trifluoride ethyl ether oxidative coupling system in promoting intramolecular oxidative coupling reaction. Then we optimized the reaction conditions. The optimized conditions we got were: MnO2(6.00 eq) and BF3· OEt2(0.30 eq) in DCM(1.00 mL).With the optimized reaction conditions in hand, we selected different substituents of diphenyl butane, diphenyl acrylic, dibenzyl ether and other substrates to react under the conditions, as a result, they can be well adapted to the conditions and a good yield rate of intramolecular oxidative coupling products was obtained. In light of the above results,the reaction system was applied to intermolecular oxidative coupling of simple aromatics and also obtained the satisfactory results.In the latter part of the experiment, we proposed mechanism for the reaction, thought that it involved an initial electron transfer from the aryl ring 1a to MnO2 activated by BF3· OEt2 to give a radical cation intermediate11. Then substitution reaction at the neutral second aryl delivered intermediate12, which was finally converted to the biaryl 1b. Of course, a bis-radical cation intermediate 13 might also be involved in the oxidative coupling. Then electron transfered to form a new bond, and finally removed two hydrogen protons to give the biaryl 1b.