Glyoxylic acid, monohydrate → 5-tert-butyl-3-hydroxy-7-(1-methylpentadecyl)-3H-benzofuran-2one

Participants

Reaction Steps

18.7 g of 4-tert-butyl-2-(1 -methylpentadecyl)phenol, 5.06 g of glyoxylic acid monohydrate and 0.05 g of p-toluenesulfonic acid are heated for 7 h under a water separator in 40 ml of 1,2-dichloroethane. The reaction solution is then cooled down, washed 3 times with 80 ml of water each time and freed of solvent in a rotary evaporator to leave 21.4 g of 5-tert-butyl-3-hydroxy-7-(1-methylpentadecyl)-3H-benzofuran-2one as a yellowish oil. This yellowish oil is introduced in 25 ml of toluene as initial charge together with 8 ml of thionyl chloride and 3 drops of DMF and then gradually heated to 100° C. so that the evolution of HCl and SO2 remains lively, but still controllable. The reaction mixture is then stirred at 100° C. for a further 1 h. About 25 ml of liquid are subsequently distilled off to remove excess thionyl chloride. The residue is diluted with 80 ml of toluene and admixed at room temperature with 7 ml of triethylamine added dropwise. The thick red reaction mixture is then refluxed for 30 min. The precipitated triethylamine hydrochloride is filtered off after cooling down to room temperature, and the filtrate is concentrated to an oily consistency in a rotary evaporator. The residue is chromatographed over silica gel (hexane:ethyl acetate 99:1) to isolate the isoxindigo as a waxy red material, obtaining 4.1 g (20% of theory, based on 4-tert-butyl-2-(1-methylpentadecyl)phenol) of 5,5′-di-tert-butyl-7,7′-bis(1-methylpentadecyl)-[3,3′]bibenzofuranylidene-2,2′-dione of the formula:

Provenance & Evidence