Glyoxylic Acid → HCID 18620256, compound

Participants

Reaction Steps

2.8 g of 2-tert-butyl-4-chlorophenol [J. Amer. Chem. Soc. 78, 4604 (1956)] are heated under reflux with 2.45 g of 50% by weight aqueous glyoxylic acid and 50 mg of p-toluenesulfonic acid in 20 ml of 1,2-dichloroethane for 3¼ hours. A further 2.45 g of 50% by weight aqueous glyoxylic acid are then added and boiling is continued for 18 hours. The reaction mixture is then washed with water, dried over MgSO4 and concentrated by evaporation using a rotary evaporator. Crystallisation of the residue from hexane yields 1.15 g of 7-tert-butyl-5-chloro-3-hydroxy-3H-benzofuran-2-one (melting point : 423-427 K). 1.1 g of that compound are placed in 5 ml of toluene with 1 ml of thionyl chloride and the reaction mixture is then slowly heated to 373 K at such a rate that the evolution of HCl and SO2 remains vigorous yet controllable. The reaction mixture is then stirred at 373 K for a further hour. Approximately 5 ml of liquid are then distilled off in order to remove the excess thionyl chloride. The residue is diluted with 13 ml of toluene and, at room temperature, 0.6 ml of triethylamine is added dropwise thereto. The thick, red reaction mixture is then heated to reflux temperature and boiled for 45 min. After cooling to room temperature, the isoxindigo which has precipitated is filtered off, freed of triethylamine hydrochloride by washing with water and methanol and dried, yielding 0.47 g (46% of the theoretical yield) of 7,7′-di-tert-butyl-5,5′-dichloro-[3,3′]bibenzofuranylidene-2,2′-dione of formula (LIXa).

Provenance & Evidence