Diethylphosphine oxide (DEPO): high-yielding and facile preparation of indolones in water

Indolones are prepared in excellent yield at 80 °C in water by radical reaction (aryl radical formation, hydrogen atom abstraction, cyclization, and rearomatization) mediated by the reagent diethylphosphine oxide (DEPO). The reaction features V-501 as a water-soluble initiator; no other additives are needed. The process proceeds at a much lower temperature than is required for efficient reaction with toxic tributyltin hydride in benzene and permits significantly higher isolated yields than the corresponding reaction mediated by ethylpiperidine hypophosphite (EPHP)