Investigation of the reaction between 3-benzisothiazolones, an isoindole isoster and activated acetylenes: synthesis of novel heterocyclic backbones for building bioactive molecules

Investigation of the reaction between benzo[d]isothiazol-3-one, 2-aminobenzo[d]isothiazol-3-one, its isoster 2-aminoisoindolin-1-one, and activated acetylenes, in the presence of triphenylphosphine, led us to synthesize novel heterocyclic compounds that could be attractive for the building of biologically active molecules. A one-pot PPh3-promoted tandem reaction, with acetylene dicarboxylates and dibenzoylacetylene, afforded new tricyclic pyrazolo-fused benzisothiazoles. The PPh3-promoted reaction between benzisothiazolones and methyl propiolate afforded 1,4-benzothiazepine-5-one derivatives, via an isothiazole ring expansion. These studies are providing additional insights in benzisothiazolone chemistry and describe simple and original synthetic accesses to novel derivatives.