Pd-catalyzed Dearomatizing Transformations Of Furans

Metal carbene is an important intermediate in many catalytic reactions, which canundergo diverse transformations. Transition-metal-catalyzed cross-coupling reactionsinvolving a carbene migratory insertion process have been developed extensively. Such a typeof coupling reactions provides useful methodologies for the construction of carbon-carbonand carbon-heteroatom bonds.Dearomatization of furan ring has been attracted a high interest from organic chemists.Various methods and applications involving dearomatization of furan ring have been reported.We reported in this thesis a facile Pd-catalyzed coupling of furfural hydrazones with arylhalides, which proceeds via2-furylmethylenepalladium halides intermediates provideefficient access to spiroacetal enol ethers. This is the first report on the formation of2-furylmethylenepalladium halides from stable furfural hydrazones instead of from unstable2-furylmethyl halides. The2-furylmethylenepalladium halides can undergo intramolecularnucleophilic dearomatization, and this protocol greatly expands the synthetic applications offuran derivatives.Indole is one of the most abundant and important class of heterocycles found in naturalproducts, pharmaceuticals, and other functional molecules. Consequently, the synthesis andfuntionalization of indoles has continued to attract much attention. In our following work, aother pathway for the transformation of2-furylmethylenepalladium halides via Pd-catalyzedcoupling of furfural hydrazones with N-ethyl-2-iodoanilines has been found. The2-furylmethylenepalladium halides were disclosed to be able to undergo β-heteroatomelimination/furan ring-opening process, and polysubstituted and functionalized indoles havebeen obtained in an efficient simple and practical fashion.