Structurally Diverse Synthesis of Five-, Six-, and Seven-Membered Benzosultams through Electrochemical Cyclization

Abstract

We have developed a metal- and oxidant-free approach to structurally diverse synthesis of benzosultams from aryl sulfonamides through an electrochemical cyclization. Upon variation of the ortho substituent on aryl sulfonamides, five-, six-, and seven-membered benzosultams were efficiently assembled in an atom- and resource-economic manner. The generality of the process is demonstrated by the formation of five- to seven-membered cyclic products from 42 substrates bearing substituents with different electronic effects and steric hindrance.

The advent of electrophilic hydroxylamine-derived reagents for the direct preparation of unprotected amines

“…157 The groups of Zhang, Chai, and Zhang developed the electrochemical cyclization of aryl sulfonamides to benzosultams via intramolecular aromatic C-H amination. 158 In our recent publication on the Fe-mediated N-methylamination of arenes, we also reported the synthesis of electron-poor tetrahydroquinolines in the presence of trifluoroacetic acid in HFIP (Scheme 11F). 133 This procedure unlocks the functionalization of electron-poor arenes in a more costeffective fashion compared to methods relying on the less abundant rhodium metal.…”

Synthesis of Six‐Membered N‐Heterocycle Frameworks Based on Intramolecular Metal‐Free N‐Centered Radical Chemistry

“…[24] Very recently, electrochemical cyclization of aryl sulfonamides was also applied to the synthesis of benzosultams. [25] There is no doubt that metal-free intramolecular CÀ H amination is an efficient method as it avoids the occurrence of residual metal contamination. In 2014, Wu and co-workers firstly reported the synthesis of benzosultams through I 2 /PhI (OAc) 2 -mediated intramolecular CÀ H amination in CH 2 Cl 2 (Scheme 9).…”

Intramolecular Arylation of 2‐Bromobenzenesulfonamides Using DMSO/HCOONa ⋅ 2H2O System: An Access To Dibenzosultams

“…Among preparative methods for dibenzosultams, the intramolecular cyclization is the most efficient approach from a practical viewpoint, as it requires only simple experimental manipulations. Previously established intramolecular cyclizations for dibenzosultams involve metal-catalyzed oxidative CÀ C coupling of N-arylbenzenesulfonamides or metal-catalyzed oxidative decarboxylative CÀ C coupling of 2phenylsulfamoylbenzoic acid (Scheme 1, a); [6,7] PhI(OAc) 2 -I 2 mediated oxidative CÀ H amination or electrochemical cyclization of o-arylbenzenesulfonamides (Scheme 1, b); [8,9] photo-induced, metal-catalyzed or radical initiator-promoted cyclization of N-(ohaloaryl)benzenesulfonamides or N-aryl-o-halobenzenesulfonamides (Scheme 1, c); [10,11] diazotization-induced cyclization of N-aryl-o-aminobenzenesulfonamides (Scheme 1, d). [3][4][5]12] Despite the above-mentioned protocols have been proved to be synthetically useful, they suffer from their own limitations.…”