Properties and reactions of substituted 1,2‐thiazetidine 1,1‐dioxides: Synthesis of 1,2‐thiazetidine‐2,3‐diacetic acid derivatives and their rearrangement to 1,2‐thiazinan‐3‐ones

β‐Sultam‐3‐acetic acid ester 3 prepared from rac‐S ‐benzyl‐β‐homocysteine is alkylated with bromoacetates yielding diacetates 9 which are transformed into the phenylthio esters 11 . The thiazinanone derivatives 12 are obtained from 11 by rearrangement with lithium bis(trimethylsilyl)amide in excellent yields, and the syntheses of the derivatives 13, 14 , and 15 are described. The stereochemistry of all products is elucidated by spectroscopic methods, and a reaction pathway is proposed. It is supported by the synthesis of the isomeric β‐sultam‐2,3‐diacetate 20 , which does not rearrange to a thiazinanone derivative. Some side reactions are described.