Water → 5-tert-butyl-3-hydroxy-7-(1-methylpentadecyl)-3H-benzofuran-2one

Participants

Reaction Steps

18.7 g of 4-tert-butyl-2-(1-methyl-pentadecyl)-phenol (J.Amer.Chem.Soc., 74, 1952, 3599), 5.06 g of glyoxylic acid monohydrate and 0.05 g of p-toluenesulfonic acid are heated in 40 ml of 1 ,2-dichloroethane for 7 hours using a water separator. The reaction solution is then cooled, washed three times with 80 ml of water each time and freed of solvent using a rotary evaporator. 21.4 g of 5-tert-butyl-3-hydroxy-7-(1-methyl-pentadecyl)-3H-benzo-furan-2-one are obtained in the form of a yellowish oil. That yellowish oil is placed in 25 ml of toluene with 8 ml of thionyl chloride and 3 drops of DMF 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 that temperature for a further hour. Approximately 25 ml of liquid are then distilled off in order to remove the excess thionyl chloride. The residue is diluted with 80 ml of toluene and, at room temperature, 7 ml of triethylamine are added dropwise thereto. The thick, red reaction mixture is then heated under reflux for 30 min. After cooling to room temperature, the triethylamine hydrochloride which has precipitated is filtered off and the filtrate is concentrated to an oily consistency using a rotary evaporator. The isoxindigo is isolated from the residue, in the form of a waxy red mass, by chromatography on silica gel (hexane/ethyl acetate 99:1). 4.1 g (20% of the theoretical yield, based on 4-tert-butyl-2-(1-methyl-pentadecyl)-phenol) of 5,5′-di-tert-butyl-7,7′-bis(1-methyl-pentadecyl)-[3,3′]bibenzofuranylidene-2,2′-dione of formula (LIIIa) are obtained.

Provenance & Evidence