Palladium-Catalyzed Reactions in the Synthesis of 3- and 4-Substituted Indoles

Article abstract of DOI:10.1021/jo00278a029

4-Bromo-1-tosylindole (1) was converted to tricyclic indole enone 11, a potential intermediate in the synthesis of tetracyclic ergot alkaloids, by a series of palladium-catalyzed processes.Attempts to construct the ergot D ring by the hetero-Diels-Alder reaction of enone 11 and 1-azabutadiene 12 produced not the expected <4+2> adduct 13 but the benzindoline derivative 14 resulting from attack of the aza diene at the indole 2-position.The thermodynamic stability of the naphthol nucleus makes enone 11 generally susceptible to attack at the indole 2-position,as evidenced by the attack of hydride and methyl cuprate nucleophiles at this position forming indolines 16 and 17, respectively.