Add 4.5g magnesium powder, 5ml anhydrous ethanol, and 0.5ml carbon tetrachloride to a 500ml three-necked flask with a drying section.
After a few minutes of reaction, add 20ml tetrahydrofuran, and add a mixture of 30ml diethyl malonate, 20ml anhydrous ethanol, and 40ml tetrahydrofuran with stirring.
Add the mixture dropwise for about 0.5h~1h, and reflux and keep warm until the black solid disappears completely. After cooling (room temperature),
start to add the above-mentioned standby 3,5-diacetoxybenzoyl chloride solution dropwise, add it dropwise in 45min~60min, slowly increase the temperature,
and reflux for 3min~5min. Cool to room temperature and add 250g of 15% sulfuric acid aqueous solution. Stir well and let it stand for stratification.
Separate the upper organic layer, recover tetrahydrofuran, and add 200g of 30% sulfuric acid aqueous solution to the residue.
Heat and reflux to hydrolyze until no CO2 is released. Desolventize under reduced pressure, and the residue is crystallized in an ice bath for several hours.
The crude product was filtered and recrystallized with 3 times the amount of water and decolorized with activated
carbon to obtain 12 g of white crystals with a content of 98.5% according to liquid chromatography analysis and a melting point of 144°C~146°C.
The total yield of the latter two steps was 47%. |
