Pd/NBE Catalyzed Ortho Acylation Of Aryl Halides And Nickel-Catalyzed Domino/Heck Cyclization Reaction

The transition-metal catalyzed domino reaction is well known as cascade or tandem reaction,which offers a straightforward route towards the synthesis of valuable synthetic intermediates,new pharmaceuticals,and/or unique polymeric materials.Among various types of domino reactions,palladium-catalyzed Catellani reaction and the nickel-catalyzed domino/Heck cyclization coupling reaction are of particular interest,because of their high synthetic efficiency and selectivity.How to construct new chemical bonds efficiently by domino reaction strategy has always been a hot topic in synthetic chemistry.In this paper,practical palladium/norbornene catalyzed ortho-acylation of aryl iodides and nickel-catalyzed domino/Heck cyclization coupling reactions were successfully realized,affording a vouriety of aryl ketones and oxindoles.The research contents mainly include the following three parts:(1)Palladium/norbornene catalyzed ortho-acylation of aryl iodides enabled by moisture-insensitive activative estersWe developed a novel and efficient palladium/norbornene protocol of aryl iodides by using triazine ester as ortho-acylation electrophile.This ortho-acylation exhibits high tolerance of moisture and can even proceeds smoothly in water in contrast to previous methodologies.An array of aryl ketones were obtained in moderate to excellent yields.Primary mechanism study showed high activity of triazine ester might stem from the synergistic effect of strong electron-withdrawing ability and unique coordination chemistry of the triazine ring.(2)Nickel-catalyzed Domino/Heck cyclization thiocarbonylation reactionA nickel-catalyzed reductive aryl thiocarbonylation of alkenes via thioester group transfer strategy by using simple and readily available thioesters was realized.In contrast to traditional activation of weaker C(acyl)–S bond,the C(acyl)–C bond of thioester was selectively cleaved to enable this reaction under mild condition.This approach features operational simplicity and broad substrate scope,providing a complementary and practical route for thioester synthesis without requiring toxic thiol or CO gas.The preliminary mechanistic investigations revealed a Ni(I)/Ni(III)process might be involved in the mechanism,and CO migratory insertion might proceed in this transformation.(3)Nickel-catalyzed Domino/Heck cyclization cyanation reactionWe achieved the nickel-catalyzed two-component reductive arylcyanation of aryl(pseudo)halide tethered alkenes using benzylthiocyanate as cyanide source via C–S bond activation.A wide range of aryl iodides with substituents at different positions were found to be amenable to this nickel-catalyzed reductive alkene difunctionalization process,leading to the introduction of nitrile group to a wide range of 3,3′-disubstituted oxindole structural motif.This transformation uses a less toxic organic cyanide reagent to replace the more toxic zinc cyanide in the traditional method,and provides a more environmentally friendly route for the synthesis of cyanoindole.According to the primary mechanism study,this transformation was achieved by oxidation addition and reduction coupling pathway.