Efficient Synthesis Of Vinyl Sulfones Via Manganese-catalyzed Decarboxylative Coupling Of Cinnamic Acids

Vinyl sulfones (?,?-unsaturated sulfones) are important organic molecules and they are crucial structure scaffolds in many biological active compounds or drugs, such as inhibitors of many types of cysteine proteases, inhibitor of SrtA(sortase A). In addition, they are also widely used as Michael acceptor in organic chemistry. Because of their synthetic utilities and potential biological activities, the synthesis of vinyl sulfones has attracted a large number of organic chemist's attention. Reported the synthesis of aryl vinyl sulfones involved about a dozen different reaction method, according to these methods, we put forward this topic, cinnamic acid and benzene sulfonic acid sodium as raw material to synthesize aryl vinyl sulfones, made the following experiment explored:Firstly, this paper introduced the development process of the coupling reaction and gave a brief overview on some reported methods for the synthesis of aryl vinyl groups.Secondly, through the screening of catalyst, solvent type, reaction temperature and environment, explores a series of experiments, the optimal reaction conditions were 5mol% Mn(OAc)2,1.0 equiv cinnamic acids,3.0 equiv sodium benzene sulfonate salts,2.0 mL DMSO at 110? for 12 h in the air.Thirdly, with the optimized protocol in hand, we explored the substrate scope of the decarboxylation reaction. We found the reaction worked very well for a wide variety of substituted cinnamic acids, and the products were isolated in yields ranging from 57% to 80%. Substrates with electron-donating group or electron-withdrawing group such as methyl, fluoro, chloro, bromo, methoxy and nitro group on the phenyl ring of the cinnamic acids all provided the desired vinyl sulfones in good yields. The experimental results show that ortho-, meta- and para-nitro substituted cinnamic acids afforded little difference on the product yields. Additionally, we found methyl and bromo-substituted phenyl sulfinic acid sodium salts worked satisfactorily to afford the desired vinyl sulfones in 53-76% yield. Unfortunately the reaction was quite messy when sodium methanesulfinate, an alkyl sulfinic acid sodium salt, was used as the reactant. According to some phenomena generated by the reaction, some reasonable analysis and explanation are given. Finally, according to the results of the experiment and the relevant literature analysis, the possible reaction mechanism is proposed.