Synthesis Of 2-Arylindoles Through Pd (?)-Catalyzed Cyclization Of Anilines With Vinyl Azides

Indole is not only widely found in natural products,but also key structural unit in many synthetic drugs.Among them,2-arylindoles are the important moiety of natural products as well as drug components.Consequently,chemists have been pursuing the efficient methods for the regioselective synthesis of 2-arylindoles,such as the traditional Fischer and Larock indole syntheses.However,these methods usually possess poor chemoselectivity with unsymmetrical carbonyl compounds and alkyne substrates.In the past decades,transition-metal-catalyzed direct C–H bond activations have proved to be one of the most powerful protocols in the syntheses of 2-arylindoles,such as the direct 2-arylation reactions of indoles,intramolecular cyclization of ortho-Nsubstituted styrene derivatives,oxidative cyclization of N-aryl enamines as well as the direct intermolecular dehydrogenation coupling of anilines with alkenes.In despite of a number of methodologies in expending the diversities of 2-arylindoles,the synthetic utility has been limited to some extent because of the requirement of an excess amount of prefunctionalized substrates,difficulty in controlling chemo-and/or regioselectivities as well as relatively harsh conditions.Therefore,it would be highly desirable to explore more efficient and regioselective protocols.Vinly azides feature as electrophile,nucleophile and radical acceptor in synthetic chemistry,which have emerged as rapid and versatile synthon in the preparation of Nheterocyclic systems.Base on the transition-metal-catalyzed C–H bond functionalisations,in this thesis we disclosed an efficient strategy for the synthesis of 2-arylindoles via Pd(II)-catalyzed cyclization of anilines with vinyl azides(Scheme 1).This protocol features good functional group tolerance and mild reaction conditions.Moreover,the thermal decomposition of vinyl azides to 2H-azirines ensured an inducing migratory insertion process,which promised the 2-arylindoles with excellent regioselectivities.(?)Scheme 1 Synthesis of 2-arylindoles through Pd(II)-catalyzed cyclization of anilines with vinyl azides...