Synthesis of 14c‐labeled 2,2‐dichloropropionic acid

A widely used herbicide, 2,2‐dichloropropionic acid (dalapon), was synthesized with 14C‐labeling in the C‐1 or C‐2 positions. The carboxyl labeled material was prepared in 55% yield by carbonation of 1,1‐dichloro‐ethyllithium at approximately −104°. Starting with trichloroacetic acid, the C‐2 labeled product was prepared in an overall yield of 39% by means of a 4‐step reaction sequence which involved the removal of a chlorine atom and the addition of a methyl group.