反应详情

78.7 g of 5,7-di-tert-butyl-3-hydroxy-3H-benzofuran-2-one (prepared as in Ex. 2b) are placed in 150 ml of toluene, and 3 drops of dimethylformamide (DMF) and 45 ml of thionyl chloride are added thereto. The solution is then slowly heated to 373 K at such a rate that the evolution of HCl and SO2 remains vigorous yet controllable. It is then stirred at that temperature for a further hour. Approximately 150 ml of liquid are then distilled off in order to remove the excess thionyl chloride. The residue is diluted with 480 ml of toluene and, at room temperature, 42 ml of triethylamine are added dropwise. The thick, red reaction mixture is then heated under reflux for 15 min. After cooling to room temperature, the triethylamine hydrochloride which has precipitated is filtered off, and the filtrate is washed with water and concentrated NaCl solution and concentrated to an oily consistency using a rotary evaporator. The isoxindigo is crystallised out by adding 225 ml of acetonitrile, is filtered off, washed with acetonitrile and dried, yielding 57.7 g (78.7% of the theoretical yield) of 5,7,5′,7′-tetra-tert-butyl-[3,3′]bibenzofuranylidene-2,2′-dione of formula (LIa).

1. distillationApproximately 150 ml of liquid are then distilled off in order
2. customto remove the excess thionyl chloride
3. additionThe residue is diluted with 480 ml of toluene and, at room temperature
4. addition42 ml of triethylamine are added dropwise
5. temperatureThe thick, red reaction mixture is then heated
6. temperatureunder reflux for 15 min
7. customthe triethylamine hydrochloride which has precipitated
8. filtrationis filtered off
9. washthe filtrate is washed with water and concentrated NaCl solution
10. concentrationconcentrated to an oily consistency
11. customa rotary evaporator
12. customThe isoxindigo is crystallised out
13. additionby adding 225 ml of acetonitrile
14. filtrationis filtered off
15. washwashed with acetonitrile
16. customdried
17. customyielding 57.7 g (78.7% of the