The isomerization/chlorination of 0,0-dialkyl methylthiophosphonates with phosphorus oxychloride—a new convenient synthesis of S-alkyl methylthiophosphonic acid derivatives

A new method for the synthesis of S-alkyl methylthiophosphonic acid derivatives is reported. The chlorination of 0,0-dialkyl methylthiophosphonates 8 with phosphorus oxychloride proceeds with isomerization of the P=S to the P–S bond to give S-alkyl methylthiophosphonochloridates 9 , which react further with various nucleophiles in the presence of triethylamine to afford S-alkyl methylthiophosphonic acid derivatives 10 . Among them, several compounds 10 show excellent fungicidal or insecticidal activities. © 1995 John Wiley & Sons, Inc.