Nucleophilic reactivity of organophosphorus compounds. Part I. The reaction of phosphonic and thiophosphonic acids with diethylmethyl-keten ketal

Abstract

Diethylmethylketen ketal reacts with alkyl hydrogen alkylphosphonates or alkyl hydrogen alkylphosphonothionates in benzene solution to give ethyl propionate and alkyl ethyl alkylphosphonate or alkyl ethyl alkylphosphonothiolate in yields in excess of 90%. A mechanism is suggested involving the addition of the phosphonic or thiophosphonic acid to the double bond of the ketal via the nucleophilic oxygen atom of either acid, followed by rearrangement of the resultant intermediate through a six-membered cyclic transition state to give the products. Intermolecular hydrogen bonding between alkyl hydrogen alkylphosphonothionates and alkyl ethyl alkylphosphonothiolates is also reported and discussed.