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112669-50-8

2H-1-Benzothiopyran-6-carboxylic acid, 3,4-dihydro- synthesis

5synthesis methods
-

Yield:112669-50-8 81%

Reaction Conditions:

in tetrahydrofuran;hexane;

Steps:

8.6 6)

6) Thiochroman-6-carboxylic acid n-Butyllithium in hexane (1.59M solution, 20 ml, 31.80 mmol) was added dropwise at -78°C under nitrogen atmosphere to a solution of 6-bromothiochromane (7.00 g, 30.55 mmol) in tetrahydrofuran (30 ml). The mixture was stirred at the same temperature for 1 hour. The reaction mixture was poured into finely divided dry ice and stirred for 3 hours. The reaction mixture was concentrated under reduced pressure. To the residue, saturated aqueous sodium hydrogencarbonate solution was added and mixture was extracted with diethyl ether. The pH of the aqueous layer was adjusted to 2 using aqueous sulfuric acid solution (20%) and extracted with ethyl acetate. The organic layer was washed with water, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was washed with a large amount of water to afford the desired compound (4.80 g, yield 81%) as a pale brown powder. Nuclear magnetic resonance spectrum (270MHz, CDCl3) δppm: 7.79-7.76(2H,m), 7.18(1H,d,J=9Hz), 3.12-3.08(2H,m), 2.70(2H,dd,J=6Hz,5Hz), 2.21-2.12(2H,m).

References:

EP1031572,2000,A1

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