The chemistry of small ring compounds. Part 45 Thermolysis and photolysis of l‐(alkylthio)cyclopropyl azides

Abstract 1‐(Alkylthio)cyclopropyl azides ‐ readily accessible from the corresponding chlorides and bromides ‐ are smoothly decomposed at 70°C with nitrogen evolution. The main process is a ring enlargement to 2‐(alkylthio)azetines 2, accompanied by cleavage to thiocyanate and alkene. Reaction parameters for the thioazetine formation suggest a two‐step mechanism involving an intermediate cyclopropylnitrene. Ring enlargement can be averted if the alkylthio group contains a double bond. Thus, the allylthiocyclopropyl azide 8 gives a nitrene that can interact not only with the three‐membered ring but also with the double bond, leading to spirocyclic products (15 and 16 in Scheme 1). The photolysis (300 nm) of these azides gives exclusively the fragmentation products thiocyanate and olefin.