Sulfamic Acid → 3-(Cyclopropylmethoxy)-4-(difluoromethoxy)benzoic Acid

Participants

Reaction Steps

In WO9501338 the reaction of 3-(cyclopropylmethoxy)-4-hydroxy-benzaldehyde with chlorodifluoromethane in the presence of sodium hydroxide and benzyl-trimethylammonium chloride (BTMA) in dioxane/water leads to 3-(cyclopropylmethoxy)-4-(difluoromethoxy)-benzaldehyde, which by oxidation with sodium chlorite and sulphamic acid yields 3-(cyclopropylmethoxy)-4-(difluoromethoxy)-benzoic acid. Chlorination of this acid with thionyl chloride in reflux toluene provides the corresponding acyl chloride, which is finally condensed with 3,5-dichloropyridine-4-amine in the presence of sodium hydride in tetrahydrofuran to thus reach roflumilast (I). These procedures are set out in Scheme 1.

Provenance & Evidence