Boron tribromide → 2-(4-bromo-5-chloro-2-hydroxyphenyl)-2,4-dihydro-5-(5-bromothien-2-yl)-3H-1,2,4-triazol-3-one

Participants

Reaction Conditions

Reaction Steps

2-(4-Bromo-5-chloro-2-methoxyphenyl)-2,4-dihydro-5-(5-bromothien-2-yl)-3H-1,2,4-triazol-3-one (Intermediate 3) (1.395 g) was suspended in anhydrous dichloromethane (20-25 mL/mmol of Intermediate 3) under argon and cooled to −78° C. A 1 M solution of BBr3 (9 mL) in anhydrous dichloromethane was added via a dropping funnel over a 45 minute period. After the addition was complete, the reaction was warmed to room temperature and stirred for 5 hours. The reaction was quenched by the addition of 5-10 mL water. Volatile solvent was removed under vacuum and the crude product was filtered and washed with water. The solid was refluxed in a mixture of acetone and ethanol for 15 minutes. After cooling to room temperature, the purified product was filtered and washed with acetone and ethanol. The solid was dried under high vacuum to yield 1.1 g (81%) of the desired product, Compound II.

Provenance & Evidence