Useful access to uncommon thiazolo[3,2-a]indoles

A practical and environmentally benign protocol for the assembly of poly-substituted-thiazolo[3,2-a]indoles from 3-alkylated indoline-2-thiones and 2-halo-ketones has been developed. This metal-free approach consists in a complete chemo/regioselective formal [3+2] annulation that occurs in air, at 60 °C, and in water as the sole reaction medium. The opportunity to vary the substitution pattern up to six different positions, the odourless manipulation of sulfurylated compounds, the very easy product isolation, the mild reaction conditions are the main synthetic features of this method. The scaled-up experiment and the successive transformations of the products further demonstrate the utility of this chemistry.