抄録
In our continuing study of the reactivity and synthetic application of indolylborate as a versatile synthetic intermediate, we found that the use of indolylborate in palladium-catalyzed cross-coupling reaction is highly effective for the synthesis of indole derivatives. The present account deals with the results concerning a novel approach to indole alkaloids based on the use of the palladium-catalyzed cross-coupling. Dimeric indole alkaloid, yuechuke, was synthesized through the palladium-catalyzed carbonylative cross-coupling reaction. Pyridocarbazole alkaloids (ellipticine, olivacine, and their related alkaloids), and indolophenanthridine alkaloid (calothrixins A and B) were obtained by the use of cyclization/cross-coupling domino reaction. In addition, (CuOTf)2·toluene complex was demonstrated to catalyze 6π-electrocyclization of hexatrienes, leading to pyrido [4,3-b] carbazoles.
