A novel and efficient procedure for the generation of the reactive indole-2,3-quinodimethane intermediates from the allenylanilines is described. The indole-2,3-quinodimethane intermediates were captured by several dienophiles to afford the corresponding tetrahydro- and dihydrocarbazole derivatives. This method is significantly different from the previously reported ones, which involve the 1,4-elimination or its related reactions of the indole derivatives that possess suitable substituents at both the C-2 and C-3 positions.
The two conditions for the preparation of the reactive N-(tert-butoxycarbonyl)indolo-2,3-quinodimethane intermediate were developed by the reaction of the N-(tert-butoxycarbonyl)-2-(1-ethoxycarbonyloxymethylallenyl)aniline with K2CO3 or Pd2(dba)3 in refluxing toluene. The resulting N-(tert-butoxycarbonyl)indolo-2,3-quinodimethane was captured by several alkenyl and alkynyl dienophiles to provide the
A novel and efficient procedure for the generation of the reactive indole-2,3-quinodimethane intermediates from the allenylanilines is described. The indole-2,3-quinodimethane intermediates were captured by several dienophiles to afford the corresponding tetrahydro- and dihydrocarbazole derivatives. This method is significantly different from the previously reported ones, which involve the 1,4-elimination or its related reactions of the indole derivatives that possess suitable substituents at both the C-2 and C-3 positions.