| 49% |
With hydrogen bromide; bromine; In water; at 100℃; for 9h; |
To a flask equipped with a reflux device, 25.0 g (183.7 mmol) of the compound (a), and 150 mL of 48percent hydrobromic acid were added. After heating to 100° C., 8.5 mL (165.4 mmol) of bromine was dropped, the resultant was stirred at 100° C. for nine hours, and then it was let cool. After a reaction was finished, 200 mL of dichloromethane was added, precipitated solid was dissolved, and further 100 mL of an aqueous sodium sulfate solution was added. An organic layer was collected, washed with a saturated aqueous sodium hydrogen carbonate solution, dried with anhydrous sodium sulfate, and then a solvent was removed under reduced pressure to obtain an unrefined compound (b). The compound (b) was suspended in 200 mL of hexane/ethyl acetate (4:1, volume ratio), remaining solids were filtered to thereby remove 4,7-dibromo-2,1,3-benzothiadiazole being a by-product. The filtrate was condensed again, suspended in 200 mL of hexane, and remaining solids were filtered, to thereby obtain 11.2 g of the compound (b). Further, the filtrate was condensed, and refinement was performed by a column chromatography method using hexane/ethyl acetate (97:3, volume ratio) as a developing solution, to thereby obtain 8.0 g of the compound (b). A sum total was 19.2 g (89.3 mmol), and a yield was 49percent. |
|
With hydrogen bromide; bromine; at 150℃; for 2h; |
In a first step, 10 g (73.52 mmol) of 2,1,3-benzothiadiazole (1) was added to a 100 ml round-Suspended in 50 ml HBr solution (48percent),A solution of 2.8 ml (54.26 mmol) of bromine was added dropwise with vigorous stirring,After all the drops were added, the mixture was heated to 150 ° C and refluxed for 2 hours.After completion of the reaction, the mixture was cooled to room temperature,The reaction mixture was poured into 500 ml of water,The precipitated solid was filtered to give 10.4 g of crude product;The crude product contains a small amount of dibromo substituted product as well as the starting material.The crude product is directly put into the next step.Under nitrogen protection,To a 500 ml two-necked round bottom flask equipped with a condenser tube was added 8.556 g of crude product (assuming all 4-bromo-2,1,3-benzothiadiazole (2), 40 mmol)10.208 g (44 mmol) of 4-formylphenylboronic acid pinacol ester,2.32 g (2.0 mmol) of tetrakis (triphenylphosphine) palladium and 200 ml of THF,Followed by the addition of 200 ml of an aqueous solution of potassium carbonate (11.06 g, 80 mmol), heated to reflux and stirred for 12 h.After completion of the reaction, the mixture was cooled to room temperature and the mixture was extracted three times with dichloromethane. The separated organic layer was dried over anhydrous sodium sulfate. The crude product obtained by distilling off the solvent under reduced pressure was treated with dichloromethane / petroleum ether (2: 1) as the eluent,Silica gel column chromatography afforded 8.2 g of pale yellow 4-formylphenyl-2,1,3-benzothiadiazole (3). |
Chemistry
Pharmaceutical Intermediates
Inhibitors/Agonists
Material Science
For Research Only
120K+ Compounds
Competitive Price
1-2 Day Shipping
