Properties and Reactions of Substituted 1,2-Thiazetidine 1,1-Dioxides: 3-Acetoxy-1,2-thiazetidine 1,1-Dioxide, Synthesis and Reactions with C-Nucleophiles

N‐Silylated 3‐acetoxy‐1,2‐thiazetidine 1,1‐dioxide (5) is prepared from L‐cystine. Reactions of 5 with silyl enol ethers yield C‐3‐substituted β‐sultams 6, 12 and 15. Desilylation of 6 affords 7, which undergoes photochemical cyclization to give the bicyclic β‐sultam 10. In the course of such reactions, a portion of the C‐3‐substituted β‐sultam is consumed in a retro‐Michael‐type reaction, leading to the open‐chained sulfonamides 8 and 13 as side products. In the case of reactions between 5 and silyl enol ethers of cyclic ketones 16, only such open‐chained products, 17, are isolated. Reactions of 5 with substituted malonates yield the β‐sultams 19 and 20. Structures and stereochemistry are elucidated by spectroscopic methods.