Naphtho[1′,2′:5,6]pyrano[2,3–6][1,5]benzodiazepine Derivatives

The reaction of 3-(dimethylamino)-1-oxo-1H-naphtho2,1-b]pyran-2-carbaldehyde (Ia) with o-phenylenediamines or N-monosubstituted o-phenylenediamines in refluxing glacial acetic acid afforded the corresponding naphtho1′,2′:5,6]pyrano2,3-b]1,5]benzodiazepin-15-(8H)ones V in very good yields. A similar result was achieved when the reaction was carried out in refluxing pyridine, using N-monosubstituted o-phenylenediamine hydrochlorides. The isolation of a significant intermediate as well as the synthesis through a different univocal pathway confirmed the structure of the compounds V. Moreover the reaction of Ia with N-monosubstituted o-phenylenediamines in refluxing pyridine generally afforded only low yields of compounds V, sometimes together with naphtho1′,2′:5,6]pyrano2,3-b]1,5]benzodiazepin-15-(13H)ones VII, isomers of V.