Electroorganic synthesis using a fluoride ion mediator under ultrasonic irradiation: synthesis of oxindole and 3-oxotetrahydroisoquinoline derivatives.

[reaction: see text] Anodic intramolecular cyclization of alpha-(phenylthio)acetamides using a fluoride ion mediator was realized. Under ultrasonic irradiation, cyclization was accelerated markedly to give desired cyclized products in moderate to good yields. The local heating effect of ultrasonic irradiation seems to be more advantageous than usual heating.