A general procedure for the synthesis of 2-substituted tetrahydro-1,3-thiazepines is presented, by MW-assisted cyclization of 4-thioamidobutanols. The acyclic precursors were prepared in high overall yields by an expeditious three step diacylation/thionation/deprotection sequence from 4-aminobutanol. Microwave assisted ring closure of 4-thioamidoalcohols promoted by trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of several hitherto unreported seven-membered iminothioethers bearing 2-aryl, alkenyl, aralkyl and alkyl substituents. The cyclodehydration reaction is likely to involve a SN2-type displacement and affords good to excellent yields of the desired heterocycles in very short reaction times.
Keywords: medium-size heterocycles; tetrahydrothiazepines; cyclodehydration; microwaves; PPSE
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Mollo, M. C.; Kilimciler, N. B.; Bisceglia, J. A.; Orelli, L. R. Beilstein Arch. 2019, 2019135. doi:10.3762/bxiv.2019.135.v1
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