This step was telescoped to react with acetylhydrazine
to form 36 and then treated with mesyl
chloride and triethylamine, the crystalline mesylate
37 was isolated in 75% overall yield over three steps.
The beauty of this design is that chromium has been
replaced by air, hydrazine by the less dangerous
acetylhydrazine, and there is no further need for the
persistent environmental pollutant perchloric acid to
form the oxonium salt. The subsequent cyclization
cleanly formed the benzodiazepine 32 in 93% isolated
yield