A Convenient Method for α‐Chlorination of 1,3‐Diketones and β‐Keto Esters with DMSO or Ph2SO/(COCl)2

Abstract It has been found that the monochlorination of most of 1,3‐diketones and β‐ketoesters under investigation can be achieved using DMSO or Ph 2 SO/(COCl) 2 at −20∼0 °C in moderate to high yields. The 1,3‐diketones, which enol forms are stabilized by an intramolecular hydrogen bond, bulky β‐ketoesters, and α‐monoalkylated 1,3‐dicarbonyls undergo chlorination well with DMSO/(COCl) 2 , whereas the chlorination of the less bulky β‐ketoesters needs Ph 2 SO/(COCl) 2 instead. The chlorodimethylsulfonium salt or chlorodiphenylsulfonium salt generated by the reaction of DMSO or Ph 2 SO with (COCl) 2 is proposed as a Cl + source for chlorination, which provides a convenient access to the monochlorination of 1,3‐dicarbonyls.