Regioselective Synthesis of Elusive 4,9-Dihydro-1H-Carbazoles by Gold-Catalyzed Cycloisomerization of 3-Allenylmethylindoles
摘要:
A general and efficient synthesis of 4,9-dihydro-1H-carbazoles from 3-allenylmethylindoles is reported. The process, catalyzed by a cationic gold(I) complex, involves a formal C2-H bond activation of the indole unit by reaction with the allene. The nature of the substituents at the allylic and terminal positions of the allene moiety has a crucial effect on the regioselectivity of the cyclization, which is also influenced by the catalyst and the solvent employed. Moreover, some evidence of the contribution of different reaction routes is provided, which led us to propose a plausible multipathway mechanism consistent with all of the results described.
Synthesis of 2-Indol-3-ylbenzofulvenes through a Tandem Reaction Catalyzed by Cationic Gold(I) Complexes
摘要:
A new access to benzofulvenes bearing an indol-3-yl substituent at C-2 has been developed. Treatment of 3-propargylindoles possessing an additional hydroxy group at the other propargylic position with a cationic gold(I) complex triggers a tandem 1,2-indole migration/aura-iso-Nazarov cyclization/elimination sequence that takes place under mild conditions.
Regioselective Synthesis of Elusive 4,9-Dihydro-1<i>H</i>-Carbazoles by Gold-Catalyzed Cycloisomerization of 3-Allenylmethylindoles
作者:Estela Álvarez、Patricia García-García、Manuel A. Fernández-Rodríguez、Roberto Sanz
DOI:10.1021/jo401388b
日期:2013.10.4
A general and efficient synthesis of 4,9-dihydro-1H-carbazoles from 3-allenylmethylindoles is reported. The process, catalyzed by a cationic gold(I) complex, involves a formal C2-H bond activation of the indole unit by reaction with the allene. The nature of the substituents at the allylic and terminal positions of the allene moiety has a crucial effect on the regioselectivity of the cyclization, which is also influenced by the catalyst and the solvent employed. Moreover, some evidence of the contribution of different reaction routes is provided, which led us to propose a plausible multipathway mechanism consistent with all of the results described.
Synthesis of 2-Indol-3-ylbenzofulvenes through a Tandem Reaction Catalyzed by Cationic Gold(I) Complexes
A new access to benzofulvenes bearing an indol-3-yl substituent at C-2 has been developed. Treatment of 3-propargylindoles possessing an additional hydroxy group at the other propargylic position with a cationic gold(I) complex triggers a tandem 1,2-indole migration/aura-iso-Nazarov cyclization/elimination sequence that takes place under mild conditions.