A metal‐free aerobicoxidative C–H sulfenylation of aryl‐fused cyclic amines with various thiols was developed with excellent functional compatibility. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3‐sulfenylindoles, flavin II enabled transformations resulting in substitution at the position para to the N atom on the aryl ring to obtain 6‐sulfenylquinolines.
A method which avoids metal and halogen for the synthesis of 3-arylthioindoles from indoles and diaryl disulfides using ammonium persulfate in methanol has been presented. Moreover, double C–H sulfenylation of indoles at 2 and 3-positions has also been achieved using iodine and ammonium persulfate.
Flavin–iodine coupled organocatalysis for the aerobic oxidative direct sulfenylation of indoles with thiols under mild conditions
作者:Ryoma Ohkado、Tatsuro Ishikawa、Hiroki Iida
DOI:10.1039/c8gc00117k
日期:——
A unique coupled redox organocatalysis system using flavin and iodine catalysts efficiently promoted the metal-free aerobic oxidative direct sulfenylation of indoles with thiols at ambient temperature without any sacrificial reagents, except environmentally benign molecular oxygen. Biomimetic flavin catalysis plays multiple roles in aerobic oxidative transformations, not only regenerating I2 from in
The C-3 sulfenylation reaction of indoles has been achieved under mild reaction conditions by simply employing NaOH as promoter and thiols as thiolating reagents. This simple method allows for easy and rapid synthesis of various 3-sulfenylated indoles with generally good to excellent yields. Primary attempts in scale-up synthesis give satisfactory result.
3-(Alkylsulfanyl)- and 3-(arylsulfanyl)indoles were efficiently prepared by the reaction of indoles with sodium sulfinates mediated by iodineâPPh3 in ethanol. The salient features of the present protocol are simplicity, high efficiency, non-anhydrous conditions, environmentally friendly reagents and solvent, and short reaction time.