An efficient acid-mediated oxythiolation of o-vinylanilides has been accomplished, employing N-(arylthio)succinimide as an electrophilic arylthiolating reagent for the synthesis of various arylthio tethered benzoxazine derivatives in good to excellent yield. The important features of this method include wide functional group tolerance, quick reaction time, absence of metal or additive, and excellent substrates scope. The developed method was also successfully extended to the oxyselenation of o-vinylanilides in the absence of acid promoter. © 2018 American Chemical Society.