Synthesis of α1-oxindole-α-hydroxyphosphonates under catalyst-free conditions using polyethylene glycol (PEG-400) as an efficient and recyclable reaction medium

A simple, efficient, eco-friendly, and cost-effective method has been developed for the synthesis of α1-oxindole-α-hydroxyphosphonate derivatives (3a–o) by a one-pot reaction of isatins (1a–o) with trialkyl phosphites (2a–o) under catalyst-free-conditions using inexpensive, non-toxic polyethylene glycol (PEG-400) in excellent yields (82–92%). The present methodology offers an environmental acceptability; low cost, high yields, and recyclability of the PEG-400 are the important features of this protocol.