A simple and efficient route to A-ring fused steroidal isothiazoles was developed. The key step involves C-S bond formation via substitution of a vinyl triflate at c-3. Prostate cancer is a common malignancy in the worldwide male population. Although hormonal therapies are commonly used, antiandrogens have shown to be as effective and less toxic. 1 Several pharmaceutical companies2 are now focusing on the biological evaluation of synthetic steroidal antiandrogens. In this sense, the Food and Drug Administration has recently approved one of them (Proscar, Merck & Co.) to be used. However many steroidal and nonsteroidal antiandrogens have other properties (compensatory increase in hormonal levels, progestational activity, inhibition of fertility)4 that reduce their use for clinical therapies. It was known that the electronic character of the heterocyclic ring is critical in the binding affinity5 and responsible for the biological activity6 of several heterocyclic fused steroids. Semiempirical and ab initio level calculations performed on a series of heterocycles indicated the requirement for a partial negative charge at the heteroatom attached to C-3 of the steroid nucleus to attain androgen receptor affinity. Synthesis and testing of some A-Ring fused steroids supported this hypothesis. In view of this, we decided to synthesize the isothiazol derivative I. Examination of the literature showed that a few methods have been developed for the preparation of mononuclear and aromatic isothiazoles7 but no steroidal til~~~~~~~~ provide a convenient approach.