3,4,5,6-Tetrahydrophthalic anhydride → 6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-5-(4,5,6,7-tetrahydro-2H-isoindole-1,3-dion-2-yl)-2(3H)-benzothiazolone

Participants

Reaction Steps

A mixture of 5-amino-6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-2(3H)-benzothiazolone (2.8 g) and acetic acid (20 ml) was admixed with 3,4,5,6-tetrahydrophthalic anhydride (1.6 g), stirred at a temperature of 20° to 30° C. for 30 minutes, and then heated under refluxing for 2 hours. The reaction mixture was distilled under a reduced pressure to remove the acetic acid therefrom, and the residue was worked up by chromatography, wherein a silica gel column was used together with an eluant. comprising a tetrahydrofuran/toluene mixture (a 1:3 mixture), so that the aimed compound, i.e. 6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-5-(4,5,6,7-tetrahydro-2H-isoindole-1,3-dion-2-yl)-2(3H)-benzothiazolone (2.9 g) was obtained. m.p. 198°-199° C.

Provenance & Evidence