Ring contraction of 1,4-benzodiazepines to 3,4-dihydroquinazolines during macro scale reduction (example 5: Cyprazepam)

Article abstract of DOI:10.1002/ardp.19923250810

Cyprazepam (1) is reduced in 3 steps with consumption of 6 Θ at the DME as well as at the stirred Hg-cathode. During these processes ring contraction is observed with formation of 6-chloro-2-methyl-4-phenyl-3,4-dihydroquinazoline accompanied by elimination of cyclopropylmethylamine. This is the fifth example of a reductive ring contraction, which occurs only at a Hg-cathode but not during catalytic hydrogenation.