Synthesis of Isolable Thiirane 1-Imides and Their Stereospecific Ring-enlargement to 1,2-Thiazetidines

The isolation of thiirane 1-imides was achieved via imination of anti- and syn-9,9′-bibenzonorbornenylidene sulfides by Chloramine T at room temperature, followed by crystallization of the reaction mixture at −18 °C. Allowing CD2Cl2 solutions of the thiirane 1-imides stand at room temperature or heating their crystals to around 120 °C led to the formation of the corresponding 1,2-thiazetidines with retention of the configuration of the thiirane 1-imides.