pyridine-catalyzed reaction between a number of propanedioic acid derivatives 1 and thionylchloride has been investigated in detail. Contrary to popular belief the straightforward formation of the corresponding α-chloro sulfenyl chlorides 2 is the exception rather than the rule. The propanediamide 2e, not available by the “standard” reaction of 1e with thionylchloride, is surprisingly formed by reaction of 1e