Synthesis of spiroindene-1,3-dione isothiazolines via a cascade michael/1,3-dipolar cycloaddition reaction of 1,3,4-oxathiazol-2-one and 2-arylidene-1,3-indandiones

•Novel spiroindene-1,3-dione isothiazoline derivatives were synthesized.•Michael/1,3-dipolar [3+2]-cycloaddition reaction was investigated using 1,3,4-oxathiazol-2-one moiety.•Two regioisomers of spiroindene-1,3-dione isothiazoline was separated.•The regioisomer 18a was successfully separated into its two enantiomers.