Visible‐Light‐Driven Sulfonylation/Cyclization to Access Sulfonylated Benzo[4,5]imidazo[2,1‐a]isoquinolin‐6(5H)‐ones

Abstract

Visible‐light‐driven sulfonylation/cyclization of N‐methacryloyl‐2‐phenylbenzoimidazoles has been successfully developed. Using commercially available sulfonyl chloride as sulfonylation reagent, a wide range of sulfonylated benzo[4,5]imidazo[2,1‐a]isoquinolin‐6(5H)‐ones with potential antitumor activity were provided in acceptable to excellent yields. This method has the advantages of mild reaction conditions and outstanding functional group tolerance, and provides a new strategy for the development of potential antitumor lead compounds.

Transition‐Metal‐Free Radical Cyclization of 2‐Arylbenzoimidazoles with Unactivated AlkanesviaC(sp3)−H Functionalizations in Aqueous Media

“…Under heating conditions, DTBP produced the tert ‐butoxy radical, which abstracted hydrogen from 2 or 4 to obtain C ‐centered radical [12a–b] . Following that, the addition of C ‐centered radical to the C=C bond of 1 a delivered intermediate A , which produced the aryl radical intermediate B via intramolecular radical cyclization [4d–f,12c–d] . Then, B was oxidized to produce cation C , which underwent rapid deprotonation to give the final product 3 or 5 [4d–f,12c–d] …”

Visible-Light-Mediated Three-Component Cascade Sulfonylative Annulation

“… 47 Gao and coworkers demonstrated visible-light-mediated sulfonylation using sulfonyl chlorides ( Scheme 1 b). 14 Sodium metabisulfite has also been explored as a SO 2 surrogate. 48 − 50 Xie and coworkers recently incorporated SO 2 (using K 2 S 2 O 5 ) into N -propargylindoles toward the assembly of 9 H -pyrrolo[1,2- a ]indoles.…”

“…Sulfonylated molecules are ubiquitous in a large selection of pharmaceuticals, agrochemicals, and synthetic intermediates. − Traditional routes for sulfonylation rely on sulfinic acids and their salts, − sulfonylhydrazides, − tosyl chloride, − or the oxidation of sulfides and sulfoxides . Typically, sulfonylation processes require harsh oxidizing conditions, high temperatures, and/or equivalent amounts of additives, leading to issues of scalability and limited substrate scope.…”

“…have employed sulfonylhydrazides as a SO 2 surrogate (Scheme a), and Li and coworkers demonstrated sulfonylation as well as carbamoylation under transition-metal-free conditions . Gao and coworkers demonstrated visible-light-mediated sulfonylation using sulfonyl chlorides (Scheme b) . Sodium metabisulfite has also been explored as a SO 2 surrogate. − Xie and coworkers recently incorporated SO 2 (using K 2 S 2 O 5 ) into N -propargylindoles toward the assembly of 9 H -pyrrolo­[1,2- a ]­indoles .…”

Metal-free synthesis of sulfonylated indolo[2,1-a]isoquinolines from sulfur dioxide

“…Additionally, Gao and co-workers reported a visible light driven sulfonylation/cyclization to access sulfonylated indolo[2,1- a ]isoquinoline derivatives (Scheme 1b). 15 Despite these achievements, development of convenient and metal-free methods for the preparation of sulfonylated indolo[2,1- a ]isoquinoline derivatives is of significance and highly desired. 16…”