Iodine-mediated cyclisation of thiobenzamides to produce benzothiazoles and benzoxazoles

NIS-promoted guanylation of amines

“…4,8,11 Although the precise reaction mechanism has not been clarified yet, we assume that a carbodiimide is the key intermediate, which is trapped by the amine affording the expected protected guanidine along with triethylamine iodide and succinimide derivatives. 20 In conclusion, we demonstrated the ability of the thiophilic NIS to promote the conversion of amines into protected guanidines. This reaction was shown to easily tolerate a diversity of substitution patterns on the amines.…”

Switching Regioselectivity of β‐Ketothioamides by Means of Iodine Catalysis: Synthesis of Thiazolylidenes and 1,4‐Dithiines

“…Firstly, KTAs 1 are mediated by DABCO to deprotonate, thus forming intermediate A, which reacts with I 2 to generate intermediate B. [12] When R = aryl and the amount of I 2 is 0.5 equivalents, intermediate A reacts with B by means of nucleophilic substitution to give intermediate C. Finally, C undergoes an intramolecular cyclization reaction to give D, which loses a molecule of H 2 S to lead to the formation of the thiazolylidenes 2. Clearly, the present reaction mechanism is very different from that reported in the literature.…”

Regioselective Transition‐Metal‐Free Synthesis of Diverse Benzothiazoles by Thermally Induced Cyclization of ortho‐Halobenzanilides

“…Accordingly, oxidative intramolecular cyclization using various oxidants, including Jacobson's and Hugershoff's method, has been widely used in the synthesis of substituted‐benzothiazoles. However, they also have some disadvantages such as using stoichiometric or excess amount of toxic reagents,,,, incompatible with certain functional groups, and generating a mixture of regioisomeric products . Specially, thiobenzanilides bearing ortho ‐alkoxy group were seriously limited on the regioselectivity based on electron density on the primary ring and stability of the reaction intermediates ,,.…”

“…However, they also have some disadvantages such as using stoichiometric or excess amount of toxic reagents,,,, incompatible with certain functional groups, and generating a mixture of regioisomeric products . Specially, thiobenzanilides bearing ortho ‐alkoxy group were seriously limited on the regioselectivity based on electron density on the primary ring and stability of the reaction intermediates ,,. Transition‐metal catalyzed intramolecular cyclization of either o ‐halothiobenzanilides or the C−H cyclization of thiobenzanilides to construct a C−S bond was provided as a complementary approach to the synthesis of substituted‐benzothiazoles .…”