Silver-mediated thio-acetoxylation and TFA triggered cyclization of amino disulfides with unactivated alkenes: synthesis of 3-aryl/alkyl-1,4-benzothiazines†
A convenient strategy for the synthesis of 3-aryl/alkyl-1,4-benzothiazines has been developed. This reaction proceeds via 1,2-thioacetoxylation of an alkene with silver acetate and acetic acid as an additive, followed by cyclization using TFA. The addition of alkene took place in a regioselective manner, forming exclusively one regioisomer, which was confirmed by a single crystal X-ray study. Various differently substituted alkenes, such as aromatic and aliphatic olefins, were coupled with amino disulfides to form a library of benzothiazine derivatives.