Benign chlorine-free approaches to organophosphorus compounds

Organophosphorus compounds have widespread use throughout the world, as agricultural chemicals, medicinal agents, flame retardants, plasticizing and stabilizing agents, selective extractants for metal salts from ores, additives for petroleum products and corrosion inhibitors. Moreover, they are also endowed with metal binding properties, for this reason they have a paramount role in catalysis, being able to direct the activity and selectivity of a metal. Currently, organophosphorus compounds are produced on industrial scale using white phosphorus and chlorine, through an environmentally harmful process which generates equimolar amount of chlorinated waste. In the quest for alternative environmentally benign technology, several routes have been envisaged starting either from elemental phosphorus or from one of its direct low-valent derivative as hypophosphite. In this contribution, we summarize the latest findings on "green" synthetic approaches towards organophosphorus derivatives. Reactions of elemental phosphorus with organic molecules by means of photochemical irradiation, through a radical mechanism, by electrophilic / nucleophilic addition, mediated by a transition metal or by electrochemical means, will be described. Moreover, a synthetic strategy which uses hypophosphorus acid and its alkali salts as phosphorilating agents towards organic molecules will be as well depicted.