Sodium Sulfite-Involved Photocatalytic Radical Cascade Cyclization of 2-Isocyanoaryl Thioethers: Access to 2-CF₂/CF₃-Containing Benzothiazoles

Abstract

A visible-light-induced radical cascade cyclization of 2-isocyanoaryl thioethers for the synthesis of 2-CF2/CF3-containing benzothiazoles has been developed. Sodium sulfite can participate in the photocatalytic cycle as a reductant that efficiently transforms Ir4+ into Ir3+ to promote the fluoroalkylation under mild reaction conditions.

Mn(III)‐Mediated Regioselective 6‐endo‐trig Radical Cyclization of o‐Vinylaryl Isocyanides to Access 2‐Functionalized Quinolines

“…In 2012, Chatani and coworkers disclosed that with the oxidation of Mn(III) salts arylboronic acids could generate aryl radical for the synthesis of phenanthridines. [9][10]24] We initiated this study by establishing optimal experiment conditions using the model reaction of 1-isocyano-2-(1-phenylvinyl)benzene 1 a with phenylboronic acid 2 a in the presence of manganese (III) salts. [9][10]24] We initiated this study by establishing optimal experiment conditions using the model reaction of 1-isocyano-2-(1-phenylvinyl)benzene 1 a with phenylboronic acid 2 a in the presence of manganese (III) salts.…”

“…[26] In light of the significance of these compounds, the development of efficient methods for CÀ P bond construction attracts continuous interests. [9][10]28] To further expand the application of this protocol, the reactions of o-vinyl arylisocyanides 1 with diaryl phosphine oxides 4 in the presence of Mn(III)-salt were conducted. [9][10]28] To further expand the application of this protocol, the reactions of o-vinyl arylisocyanides 1 with diaryl phosphine oxides 4 in the presence of Mn(III)-salt were conducted.…”

“…[23] Afterward, the generation of aryl radical form arylboronic acids to initiate cascade cyclization of isocyanides for the synthesis of functionalized heterocycles has also been reported. [9][10]24] We initiated this study by establishing optimal experiment conditions using the model reaction of 1-isocyano-2-(1-phenylvinyl)benzene 1 a with phenylboronic acid 2 a in the presence of manganese (III) salts. After extensive screening of various reaction parameters including catalyst loadings, solvents, temperature, etc., the optimized reaction conditions were established as follows: 1 a (0.2 mmol), 2 a (2.0 equiv.…”

“…[4] Notably, ortho-functionalized aromatic isocyanides have been applied as valuable synthons in radical cascade reactions for the synthesis of N-heterocycle scaffolds, due to their capability to incorporate various substituents simultaneously with the construction of ring systems, showing remarkable operational simplicity and atom-/stepeconomy. )-or carbon (aryl or alkyl)-centered radicals to generate corresponding imidoyl radicals, which subsequently undergo intramolecular cyclization after addition to their adjacent functionalities to eventually afford various N-heterocycles, including phenanthridines, [6] quinolines, [7] quinoxalines, [8] benzimidazoles, [9] benzothiazoles, [10] benzoselenazoles, [11] etc ( Figure 1). )-or carbon (aryl or alkyl)-centered radicals to generate corresponding imidoyl radicals, which subsequently undergo intramolecular cyclization after addition to their adjacent functionalities to eventually afford various N-heterocycles, including phenanthridines, [6] quinolines, [7] quinoxalines, [8] benzimidazoles, [9] benzothiazoles, [10] benzoselenazoles, [11] etc ( Figure 1).…”

“…[5] For instance, a number of ortho-functionalized aromatic isocyanides have been employed as radical acceptors reacting with heteroatom (P, S, Si, etc. )-or carbon (aryl or alkyl)-centered radicals to generate corresponding imidoyl radicals, which subsequently undergo intramolecular cyclization after addition to their adjacent functionalities to eventually afford various N-heterocycles, including phenanthridines, [6] quinolines, [7] quinoxalines, [8] benzimidazoles, [9] benzothiazoles, [10] benzoselenazoles, [11] etc (Figure 1).…”