Radical cascade cyclization for the green and simple synthesis of silylated indolo[2,1-a ]isoquinoline derivatives via visible light-me diate d Si-H bonds activation

Photocatalytic and photoinduced silyl radicals cascade cyclization procedures for the green and simple preparation of fused tetracyclic skeleton silylated indolo[2,1- a ]isoquinoline-6(5 H )-ones from 2-arylN -acryloyl indoles with hydrosilanes are developed. The photocatalytic reaction is carried out with 9,10dicyanoanthracene (DCA) as an organophotocatalyst and 3-acetoxyquinuclidine as hydrogen atom transfer (HAT) catalyst at room temperature under metal- and oxidant-free conditions. The keys to the success of photoredox-catalytic conversion include (1) the reductive quenching of DCA * [ E 1/2 ( *P/P -) = + 1.97 V vs. SCE in MeCN] by 3-acetoxyquinuclidine ( E p = + 1.22 V vs. SCE in MeCN), and (2) the thermodynamic feasibility of hydrogen atom abstraction from hydridic Si-H bond by electrophilic N + center dot . Particularly, the simple photoinduced cascade cyclization using (TMS) 3 SiH with 2-aryl- N -acryloyl indoles was exploited via an electron -donor -acceptor (EDA) complex under visible light irradiation.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.