Study On The Reactivity Of Methylenecyclopropanes (MCPs)

This dissertation is mainly focused on the reactivity of methylenecyclopropanes (MCPs) and comprises six parts. 1) The reactions of methylenecyclopropanes with phenylsulfenyl chloride, phenylselenyl chloride and diphenyl diselenide; 2) The coupling reactions of the ring-opening products derivated from methylenecyclopropanes; 3) The palladium-catalyzed ring-enlargement of mono-aryl group substituted methylenecyclopropanes to cyclobutenes. 4) The gold(I)-catalyzed domino ring-opening and ring-closing hydroamination of methylenecyclopropanes with sulfonamides; 5) The Lewis acid-catalyzed reactions of mono-aryl group substituted methylenecyclopropanes with diethyl ketomalonate in the presence of water; 6) The iodobenzene diacetate mediated novel 1,3-dipolar cycloaddition of methylenecyclopropanes, vinylidenecyclopropanes, and methylenecyclobutane with phthalhydrazine.Chapter 1: The reactions of methylenecyclopropanes with phenylsulfenyl chloride or phenylselenyl chloride give cyclobutene derivatives along with ring-opened products in good total yields at 0 °C in various solvents. The reactions of methylenecyclopropanes with diphenyl diselenide give the di-phenylselenyl substituted ring-opening products which can be transformed to 2,5-dihydrofuran derivatives under the oxidation with hydrogen peroxide at room temperature. Plausible mechanisms have been proposed.Chapter 2: The reactions of methylenecyclopropanes with iodine give ring-opened products, which can be transformed to2-iodo-4-phenylchalcogenyl-1-butenes without being separated under mild conditions. Compounds 2-iodo-4-phenylchalcogenyl-1-butenes can be applied to some palladium-catalyzed cross-coupling reactions such as Sonogashira reaction, Heck reaction, Kumada reaction, Suzuki reaction and Negishi reaction under mild conditions to give the corresponding coupling products in good yields. These reactions proceeded smoothly at room temperature (20 °C) in most cases without any phosphine ligand and additive. The phenylchalcogenyl group plays an important role in the reactions and plausible reaction mechanisms have been proposed.Chapter 3: Mono-aryl group substituted methylenecyclopropanes can be converted to the corresponding cyclobutenes under the catalysis of palladium in 1,2-dichloroethane under mild conditions. A plausible reaction mechanism has been proposed on the basis of deuterium labeling experiment.Chapter 4: The reactions of methylenecyclopropanes with sulfonamides produce the corresponding pyrrolidine derivatives in moderate to good yields under the catalysis of Au(I) via a domino ring-opening and ring-closing intramolecular hydroamination process.Chapter 5: Mono-aryl group substituted methylenecyclopropanes react with diethyl ketomalonate, an activated ketone, give the corresponding 7-hydroxy-5-oxa-spiro[2,4]heptan-6-one derivatives with syn-configuration in moderate yields. The reactions proceeded in the presence of water under the catalysis of Lewis acids such as Sc(OTf)₃, Yb(OTf)₃ or In(OTf)₃ at room temperature. The reaction mechanism has been discussed on the basis of an ¹⁸O-labeling experiment.Chapter 6: Iodobenzene diacetate-mediated reactions of methylenecyclopropanes, vinylidenecyclopropanes and a methylenecyclobutane with phthalhydrazine give the corresponding [3+2] cycloaddition products in good yields under mild conditions. In these reactions, phthalhydrazine was transformed to a 1,3-dipole intermediate in the presence of iodobenzene diacetate. A plausible reaction mechanism has been proposed.