Efficient Synthesis of 3-Hydroxy-1,4-benzodiazepines Oxazepam and Lorazepam by New Acetoxylation Reaction of 3-Position of 1,4-Benzodiazepine Ring

Simple, efficient, and scalable syntheses of 3-hydroxy-1,4-benzodiazepines, oxazepam (1), and lorazepam (2) were developed. The syntheses are based on the new acetoxylation reaction of the 3-position of the 1,4-benzodiazepine ring. The reaction involves iodine (20−50 mol %)-catalyzed acetoxylation in the presence of potassium acetate (2 equiv) and potassium peroxydisulfate (1−2 equiv) as a stoichiometric oxidant affording the corresponding 3-acetoxy-1,4-benzodiazepines in good-to-high yields. The latter were converted by selective saponification to 3-hydroxy-1,4-benzodiazepines of very high purity (>99.8%) in an overall yield of 83% (oxazepam) and 64% (lorazepam).