Photochemical Synthesis of Indolocarbazoles through Tandem Indolization/Dimerization/Mannich Cyclization from Allenes

By: Jiaying Tang, Linlin Ren, Jianwei Li, Yonggong Wang, Dongyan Hu, Xiaogang Tong*, and Chengfeng Xia*

ORGANIC LETTERS 24（19）：3582-3587

DOI：https://doi.org/10.1021/acs.orglett.2c01371

Published：MAY 20 2022

Abstract

Indolocarbazole alkaloids and their derivatives were discovered to have potent protein kinase and topoisomerase I inhibitory activities. Disclosed herein is the photochemical synthesis of the indolocarbazole ring system from N-allenyl-2-iodoanilines. The tandem protocol included visible-light-mediated 5-exo-trig radical cyclization and subsequent radical dimerization, followed by acid-promoted deprotection and intramolecular Mannich cyclization. This strategy showed exceptional functional group tolerance and was successfully applied in the concise synthesis of natural products tjipanazoles B and D.