Catalyst-free synthesis of α 1 -oxindole-α-hydroxyphosphonates via phospha-aldol reaction of isatins employing N-heterocyclic phosphine (NHP)-thiourea.

A highly efficient phospha-aldol reaction for the synthesis of α1 -oxindole-α-hydroxyphosphonates is developed utilizing N-heterocyclic phosphine (NHP)-thiourea as a phosphonylation reagent under catalyst, additive free conditions. This methodology encompasses a variety of isatin derivatives to provide α1 -oxindole- α-hydroxyphosphonates up to 99% yield.