Radical relay strategy for the construction of alkylsulfonated indolo[2,1-a]isoquinoline-6(5H)-ones via SO2 insertion/Smiles rearrangement

Abstract

A new radical relay approach for the efficient construction of alkylsulfonated indolo[2,1-a]isoquinoline-6(5H)-ones in moderate to good yields under mild conditions via SO₂ insertion/Smiles rearrangement/intramolecular cyclization is developed. This approach utilizes 4-alkyl substituted Hantzsch esters as alkyl radical sources and further undergoes in situ SO₂ insertion to obtain alkylsulfonyl radical species, which avoids the use of unstable alkyl sulfonyl chlorides and highly toxic sulfonyl hydrazides. Additionally, this method for the direct assembly of alkylsulfonated polycyclic molecule skeletons displays high chemical selectivity, broad substrate scope, and step-economy.