Reactivity of curcumin and curcuminoid β-diketones with o-aminothiophenol: synthesis of 1,5-benzothiazepines

Four new 1,5-benzothiazepines were synthesized by reaction of o-aminothiophenol with curcumin and curcuminoid β-diketones, in methanol acetic acid. The mechanism involves a Michael addition on the CC double bond affording benzothiazepine two pendant groups, an aryl group adjacent to sulfur atom 1-phenylethanone NH seven membered ring. 1D 2D multinuclear NMR (1H, 13C, 15N, 119F) solution 13C 15N solid state proved be essential elucidate structures these benzothiazepines, particular their tautomerism. A secondary product has been identified that structure benzothiazole. Keywords: curcumin; β-diketones; aminothiophenol;