Probing the chemistry of rare sulfur allotropes: S-9, S-12 and S-20

Sulfur allotropes S-9, S-12 and S-20 were prepared to examine their sulfur-transfer properties in reactions with various alkenes and dienes. All three molecules underwent decomposition and were successfully trapped. The S-12 and S-20 molecules delivered similar products in respectable yields. With dienes, an S-2 fragment was preferentially secured with the cyclic tetrasulfide being a minor product. S-20 was trapped by norbornene to give the tri- and pentasulfides in good yield. In the case of S-9, yields of the trapped products were not as high as with the larger allotropes, although S-9 with norbornene delivered the corresponding episulfide. Overall, these three allotropes are not as effective as S-10 as sulfurating agents.