Anionic Indole N-carbamoyl N --> C translocation. A directed remote metalation route to 2-Aryl- and 2-heteroarylindoles. synthesis of benz[a]carbazoles and Indeno[1,2-b]indoles

A new LDA-induced anionic N-C carbamoyl migration of 2-arylindoles (7) is reported. Treatment of N-carbamoylindoles 10 and 13, readily available by direct and ipso-borodesilylative Suzuki-Miyaura cross-coupling routes from 8 and 12, respectively, provides a general route to functionalized 2-arylindoles 11 and 14, respectively (Tables 1 and 2). The reaction has been applied to the synthesis of benzo a]carbazoles 16 and indeno1,2- b]indoles 18, and its intramolecularity has been established by a crossover experiment (Scheme 4).