Visible-light-induced and iron-catalyzed methylation of N-arylacrylamides with dimethyl sulphoxide: a convenient access to 3-ethyl-3-methyl oxindoles

Abstract

A visible-light-induced and iron-catalyzed methylation of arylacrylamides by dimethyl sulphoxide (DMSO) is achieved, leading to 3-ethyl-3-methyl indolin-2-ones in high yields. This reaction tolerates a series of functional groups, such as methoxy, trifluoromethyl, cyano, nitro, acetyl and ethyloxy carbonyl groups. The visible-light promoted radical methylation and arylation of the alkenyl group are involved in this reaction.

The Deuterated “Magic Methyl” Group: A Guide to Site‐Selective Trideuteromethyl Incorporation and Labeling by Using CD3Reagents

“…The Wang group also achieved the transformation of methyl‐ N ‐aryl‐methacrylamides to trideuteromethylated oxindole derivates with [D 6 ]DMSO. Unlike Antonchick, they performed the reaction under visible‐light promoted conditions, and no TFA was required [78] . The exact role of light is unclear.…”

Light Runs Across Iron Catalysts in Organic Transformations

“…In 2017, Wang and co‐workers developed a novel visible‐light‐induced iron‐catalyzed methylation of N ‐arylacrylamides with dimethyl sulfoxide (DMSO) to synthesize 3‐ethyl‐3‐methyl oxindoles (Scheme 11). [24] This method showed synthetic advantages owing to its good functional group tolerance. Although the exact role of light is still unclear, the authors attributed the increased efficiency to the facile photoreduction of Fe 3+ and more hydroxyl radicals produced during the Fenton process.…”

Dimethyl Sulfoxide: Yesterday's Solvent, Today's Reagent

“…In a similar work in the same year, derivatives of oxindole 12 were synthesized by Wang et al . in the presence of Fenton's reagent (ferrous sulfate heptahydrate as catalyst and H 2 O 2 as oxidant) under white LED irradiation (Scheme ).…”