Catalyst-free sulfenylation of indoles with sulfinic esters in ethanol

Abstract

A novel catalyst-free method for the synthesis of structurally diverse indole thioethers in moderate to excellent yields.

Iodine-Mediated Sulfenylation of Imidazo[1,2-a]pyridines with Ethyl Arylsulfinates

“…To identify the best reaction conditions, ethyl 4methylbenzenesulfinate (1a) and 2-phenylimidazo[1,2a]pyridine (2a) were initially used as the model substrates (Table 2). Literature method of catalyst free sulfenylation of indoles in ethanol using sulfinic esters 17 was unsuccessful in our case, and the utilization of hydrazine hydrate 18 as reducing agent could not improve the situation (Table 2, entries 1-2). Further literature survey revealed that anhydrides are efficient reagents 19 for the deoxygenation of arylsulfoxides to the corresponding sulfides.…”

Sulfenylation of Arenes with Ethyl Arylsulfinates in Water

“…A similar disproportionate reaction of sodium benzenesulfinate to a thiosulfonate has just been observed by Wang et al 86 Then, this intermediate 8a as an electrophile reacted with 1a to form the desired product 3a . 87 , 88 Subsequently, the benzenesulfinic acid generated can be converted into 8a in the presence of TBAI. 89 , 90 Finally, a sulfenylation cycle was established.…”

Iodine(III) Enabled Dehydrogenative Aryl C−S Coupling by in situ Generated Sulfenium Ion

“…3‐(phenylthio)‐1H‐indole (3 mb) : R f =0.35 (5% ethyl acetate/hexane); off white solid; mp 155–157 °C; yield 41% (54 mg); 1 H NMR (400 MHz, CDCl 3 ) δ 8.42 (s, 1H), 7.62 (d, J =8.0 Hz, 1H), 7.49 (d, J =2.0 Hz, 1H), 7.45 (d, J =8.0 Hz, 1H), 7.30–7.26 (m, 1H), 7.20–7.14 (m, 3H), 7.13–7.09 (m, 2H), 7.05 (t, J =7.2 Hz, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 139.4, 136.6, 130.8, 129.3, 128.8, 126.0, 124.9, 123.2, 121.0, 119.8, 111.7, 103.0.…”