2,6-dichloro-4-fluorobenzene-1-sulfonyl chloride synthesis

Yield:88972-04-7 71%

Reaction Conditions:

Stage #1: 2,6-dichloro-4-fluorobenzenaminewith tert.-butylnitrite;boron trifluoride diethyl etherate in tetrahydrofuran;dichloromethane at -15 - 5; for 0.5 h;
Stage #2: with hydrogenchloride;sulfur dioxide;acetic acid;copper dichloride in water;acetonitrile at 20; for 0.5 h;

Steps:

CXXXVI

PREPARATION CXXXVI; 2,6-dichloro-4-fluorobenzenesulphonyl chloride; A solution of 4.75 g (25 mM) of 2,6-dichloro-4-fluoroaniline in 50 ml of dichloromethane are added, at -15° C., to 4.75 ml of boron trifluoride etherate. 5 ml of tetrahydrofuran are added to dissolve the precipitate formed, then, slowly, 3.6 ml of t-butyl nitrite in solution in 25 ml of dichloromethane are added. The reaction mixture is agitated 10 minutes at -15° C. and then 20 minutes at +5° C. 200 ml of pentane are added, and agitation is maintained at 0° C. for 30 min and the precipitate is filtered off. After drying, 7.2 g of the diazonium salt are obtained. This salt is dissolved in 30 ml of acetonitrile and is added, at 10° C., to a mixture of a solution of sulphur dioxide in 90 ml of acetic acid to which 1.4 g of anhydrous copper (II) chloride and 23 ml of concentrated hydrochloric acid have been added. The reaction mixture is agitated 30 min at ambient temperature and then concentrated under reduced pressure. The residue from evaporation is taken up into 60 ml of dichloromethane and the insoluble salts are removed by filtration. The filtrate is concentrated under reduced pressure to give 4.71 g of the product sought after as orange crystals (yield=71%). M.Pt.=57° C.

References:

US2006/178360,2006,A1 Location in patent:Page/Page column 24