Spirooxindole Synthesis Via Palladium-Catalyzed Arvlative Dearomatization Reaction Of 2-Substituted Indoles

Indoles or indolines are important hereocyclic aromatic compounds,numerous strategies have been developed to synthesize these heterocyclic compounds,among them,the palladium-catalyzed dearomatization of indoles provides efficient access to polycyclic or spiro structures bearing indoline scanfold.In this dissertation,we have developed Palladium-catalyzed intramolecular dearomative reductive-Heck reaction and dearomative arylcyanation reaction of C2-substituted indoles to afford structurally diverse 3,2’-spiropyrrolidine oxindoles.1.The reductive-Heck arylative dearomatization of C2-subsitued indole to construct 3,2’-spiropyrrolidine oxindoles by using hydride source as trapping reagent was studied.We found optimum reaction conditions by screening different ligands、solvents and hydride sources.With Pd(OAc)2 as catalyst,PtBu3·HBF4 as ligand,HCOONa as hydride source,the reaction proceeds efficiently in MeOH at 100 oC,giving the corresponding spiro compounds in 94% yield.Further investigation of substrate scope revealed that a lot of funcional groups were all well-tolerated under the optimal reaction conditions,and the palladium-catalyzed dearomatization of C2-substituted benzofurans was also reailzed.Noteworthy,by changing HCO2 Na to AcONa,direct C3-arylation product [2,3-b]quinolinones via indole C-H bond activation can be obtained in good yields.The pyrrole C-H bond acivation can also be realized in this conditions.2.The palladium catalyzed arylcyanation dearomatization of C2-subsitued indole to construct 3,2’-spiropyrrolidine oxindoles by using zinc cyanide Zn(CN)2 as trapping reagent was studied.We found optimum reaction conditions by screening different ligands,solvents,bases.With Pd(OAc)2 as catalyst,PCy3·HBF4 as ligand,K2CO3 as base,the reaction proceeds smoothly in Dioxane at 140 oC,giving the arylcyanation products in moderate yields(60-66%)and almost 1:3 d.r.value.