Research On Ring Opening And Ring Expansion Reactions Involving Multi-substituted Cyclopropane Derivatives

In recent years,substitued cyclopropanes,especially donor and acceptor cyclopropanes(D-A cyclopropanes)as a valuable intermediate of organic synthesis has attracted the attention of synthetic chemists.The substituted cyclopropanes are essentially reactive molecules.On the one hand,because of its thermodynamic properties,the internal ring strain is easy to initiate ring-opening reaction.On the other hand,the important reason is that it has special electronic structure.Based on the research of our group on the preparation of substituted cyclopropanes and their application in the synthesis of heterocyclic compounds.In this paper,synthesis of chalcone derivatives,furan derivatives,fully substituted anilines from substituted ethyl 1-cyano-l-cyclopropane-l-carboxylates and substited 1,1-dicyanocyclopropanes has been developed.The first part:A new synthessis of chalcone derivatives was developed by using ethyl 1-cyano-1-cyclopropane-1-carboxylates as starting materials.Chalcone derivatives were providing in 72-96%yield.Twenty-six desired products were obtained under the optimising reaction conditions.All products were characterized by NMR,IR,and LC-MS spectroscopies.The single crystal structures of four desired products were confirmed by X-ray diffraction method.The second part:Different furan derivatives were synthesized by substituted cyclopropanes.A strategy to construct 3-oxabicyclo[3.1.0]hexane cores was developed from 2-aroylcyclopropane-1-carboxylates via synergistic NaBH4 reduction/cyclization.Under the optimising reaction conditions,nineteen 3-oxabicyclo[3.1.0]hexane derivatives were obtained in 92-96%yield.A straightforward synthetic protocol was developed for the synthesis of highly functionalized cyclopenta[b]furan derivatives via DBU-mediated reaction between 2-aroyl-3-nitroaryl cyclopropane-1,1-dicarbonitrile and 3-aryl-2-cyanoacrylates.Cyclopenta[b]furan derivatives were obtained in 83-90%yield.Sixteen desired products were synthesized under the optimising reaction conditions.All products were characterized by NMR,IR,and LC-MS spectroscopies.The single crystal structures of six desired products were confirmed by X-ray diffraction method.The third part:A convenient method to synthesize fully substituted anilines was developed from donor-acceptor cyclopropanes and 3-ary 1-2-cyanoacrylates via DBU-mediated[4+2]annulations.Under the optimising reaction conditions,twenty-five desired products were afforded in 84-93%yield.All products were characterized by NMR,IR,and LC-MS spectroscopies.The single crystal structures of two desired products were confirmed by X-ray diffraction method.