Directed ortho metalation approach to C-7-substituted indoles. Suzuki-Miyaura cross coupling and the synthesis of pyrrolophenanthridone alkaloids.
[reaction: see text] Although the indole N-phosphinoyl derivative 4 undergoes n-BuLi deprotonation/electrophile quench to afford C-7-substituted products, its deprotection requires harsh conditions. On the other hand, the N-amide 12, upon sequential or one-pot C-2 metalation, silylation, C-7 metalation, and electrophile treatment, furnishes indoles 7 in good overall yields. In combination with the Suzuki-Miyaura protocol, C-7 aryl (heteroaryl)-substituted indoles 14 and 16 are obtained, including hippadine and pratosine, members of the pyrrolophenanthridone alkaloid family.
Hartung
Christian G
CG
Department of Chemistry, Queen's University, Kingston, ON, K7L 3N6, Canada.
Fecher
Anja
A
Chapell
Brian
B
Snieckus
Victor
V