Furosemide → (rac)-(R*,S*)-2-((2-(3,5-difluorophenyl)-2-hydroxy-1-methylethyl)amino)-(R)-2-methylethyl 5-(aminosulfonyl)-4-chloro-2-[(2-furanylmethyl)amino]benzoate

Participants

Reaction Steps

The free base of (rac)-(R*,S*)-2-((2-hydroxy-(R)-1-methylethyl)amino)-1-(3,5-difluorophenyl)propanol (21) (0.023 mole) and benzene (30 mL) (or toluene) is added to a round-bottomed flask. Furosemide (5-(aminosulfonyl)-4-chloro-2-[(2-furanylmethyl)amino]benzoic acid (10), (Aldrich) (0.025 mole), benzene (30 mL), and p-toluenesulfonic acid (0.026 mole) catalyst is added to the flask. A Dean-Stark trap is filled with benzene, and the contents of the flask is refluxed with stirring for several hours or until no additional water is collected in the trap. The reaction is cooled, extracted with sodium bicarbonate solution, washed with water, and then with a saturated sodium chloride solution. The organic layer is dried over sodium sulfate, filtered and concentrated in vacuo to give crude product, which may be purified by column chromatography on silica gel with hexanes/ethyl acetate as eluent. The fractions that contain pure product may be combined and spin evaporated in vacuo to give a solid that may be recrystallized to give (rac)-(R*,S*)-2-((2-(3,5-difluorophenyl)-2-hydroxy-1-methylethyl)amino)-(R)-2-methylethyl 5-(aminosulfonyl)-4-chloro-2-[(2-furanylmethyl)amino]benzoate (210). [See eg., Sandier et al., Organic Functional Group Preparations, p. 249 (1968)]

Provenance & Evidence