ZnSO4.7H2O Supported Thiourea: an Efficient Reagent for Synthesis of Thiiranes from Epoxides

Thiirane is found in naturally occurring compounds, herbicides, pesticides, polymeric compounds, pharmaceuticals, and in many other manmade chemicals [1]. Transformation of epoxides to thiiranes by an oxygen–sulfur exchange reaction is a useful reaction and has been achieved with various methods using sulfur transfer agents [2-3]. ZnSO4.7H2O is inexpensive, efficient, readily available, and mild catalyst, which has surface properties, and suggests very rich organic chemistry. Zinc sulfate is the inorganic_compound with the formula ZnSO4 as well as any of three hydrates . It was historically known as "white vitriol". It is a colorless solid that is a common source of soluble zinc ions [4]. Herein, we wish to introduce a simple and efficient method for conversion of oxiranes to their corresponding thiiranes using thiourea supported on ZnSO4.7H2O under nonaqueous conditions in refluxing acetonitrile. The capability of this synthetic protocol was investigated by the reaction of activated, deactivated, and cyclic epoxides with thiourea/ ZnSO4.7H2O system under the optimized conditions. The epoxides were converted to the corresponding thiiranes in exellent yields within short times (Scheme 1).

Thiirane; Epoxides; ZincSulfate-heptahydrate(ZnSO4.7H2O)