Novel Route to 2,3-Substituted Benzo[b]thiophenes via Intramolecular Radical Cyclization

Abstract

A novel route to 2,3-substituted benzo[b]thiophenes by intramolecular radical cyclization of polarized ketene dithioacetals derived from o-bromoarylacetonitriles or the corresponding 3-(methylthio)-3-alkyl/aryl/heteroaryl analogues has been reported.

Chemoselective Ullmann coupling at room temperature: a facile access to 2-aminobenzo[b]thiophenes

“…IR (as film in CCl4): ν (cm -1 ) = 3274, 2923,2365,2340,2247,2190,1605,1509,1467,1439,1405, 1300, 1249, 1027, 832, 752. 1 H NMR (700 MHz, DMSO-D6) δ 12.18 (s, 1H), 7.71 (d, J = 8.0 Hz, 1H), 7.70 -7.67 (m, 3H), 7.53 (t, J = 7.6 Hz, 1H), 7.36 (td, J = 7.8, 1.4 Hz, 1H), 7.03 -6.98 (m, 2H), 3.77 (s, 3H).…”

“…Rf: 0.30 in 25% ethyl acetate in hexane IR (as film in CCl4): ν (cm -1 ) = 3285, 3057, 2973,2933,2250,2186,1523,1458,1438,1367,1165,1126,1075,1027, 751, 736. 1 H NMR (400 MHz, CDCl3) δ = 7.68 (dd, J = 8.0, 1.6 Hz, 1H), 7.63 (dd, J = 8.0, 0.8 Hz, 1H), 7.43 (td, J = 7.6, 1.2 Hz, 1H), 7.39 (s, 1H), 7.29 (td, J = 7.8, 1.6 Hz, 1H), 5.49 (s, 1H), 4.61 -4.53 (m, 1H), 1.27 (d, J = 6.8 Hz, 3H), 1.22 (d, J = 6.8 Hz, 3H). 3448, 3242, 2931, 2869, 2819, 2372, 2345, 2251, 1521, 1458, 1389, 1294, 1276, 1223, 1129, 1113, 1068, 1017, 852, 819, 800, 757. 1 H NMR (400 MHz, CDCl3) δ = 8.30 (s, 1H), 7.75 (dd, J = 8.0, 1.6 Hz, 1H), 7.66 (dd, J = 8.0, 0.8 Hz, 1H), 7.47 (td, J = 7.6, 0.8 Hz, 1H), 7.33 (td, J = 7.6, 1.6 Hz, 1H), 5.60 (s, 1H), 3.67 - [M+H]: 370.0406, Found: 370.0412.…”

Recent developments in synthetic methods for benzo[b]heteroles

“…Ila and coworkers reported a benzothiophene synthesis through cyclization of a bifunctional substrate bearing aryl-Br and alkenyl-SMe moieties using catalytic Bu 3 SnCl and AIBN along with NaCNBH 3 (Scheme 39). 88 The reaction most likely involves the formation of an aryl radical and its attack on the sulfur atom, and has proved effective for the preparation of 3-cyanobenzothiophene derivatives bearing various 2-substituents.…”

Diversity‐Oriented Synthesis of Substituted Benzo[b]thiophenes and Their Hetero‐Fused Analogues through Palladium‐Catalyzed Oxidative CH Functionalization/Intramolecular Arylthiolation

“…Substituted benzo[ b ]thiophenes represent an important class of heterocyclic compounds because they exhibit a broad range of biological activities and provide useful properties in material science 1a. b, 2 The benzo[ b ]thiophene ring system and its derivatives are the core structures of numerous drug molecules,1a, b such as clinically used raloxifene,3a–c arzoxifene,3d and zileuton 3e–f. Consequently, the synthesis of this privileged structure has attracted much attention in recent years and many efficient methods have been developed 1.…”