2-Methylbenzenesulfonic acid → ortho-aminophenylbenzoxazole

Participants

Reaction Steps

Isatoic anhydride (0.2 m), o-anisidine (0.22 m), and xylene (200 ml) were placed in a 3-neck, 300 ml round bottom flask fitted with thermometer, condenser, and magnetic stirrer. The reaction mixture was heated to reflux and allowed to stir at reflux overnight. Gas evolution appeared to be vigorous. Added a Dean-Stark trap and attempted to collect water. No water was evident after eight hours. Reaction mixture was cooled and allowed to stand overnight. Toluenesulfonic acid (1.5 g) was added and reaction mixture heated to reflux. Water was azeotroped from the reaction mixture. The xylene was stripped from the reaction mixture under aspirator vacuum. The residue was leached with benzene (500 ml). The benzene extract was then washed with 2% caustic until no further color was extracted. The benzene solution was filtered and evaporated to dryness. The residue was dissolved in boiling ethanol and allowed to stand in the refrigerator. The reddish crystals were filtered out and dried. Obtained 10 grams (23% yield); m.pt.=104°-107° C. Structure was confirmed by infra red (IR) and nuclear magnetic resonance (NMR) analysis.

Provenance & Evidence