Synthesis of New Functionally Substituted Aryl- and Hetarylcarbamates Based on Ninhydrin

The condensation of methyl (ethyl) phenylcarbamates with ninhydrin in concentrated sulfuric acid gave dialkyl [1,3-dioxoindan-2,2-diyldi(4,1-phenylene)]biscarbamates. Treatment of the latter with hydrazine hydrate resulted in the transformation of the indandione fragment into phthalazinone. Ninhydrin reacted with methyl (hydroxyphenyl)carbamates in glacial acetic acid to produce dihydroxy derivative of oxotrihydroindeno[ 1,2-b][1]benzofuran possessing a carbamate group. Tandem reaction of ninhydrin with methyl (acetylphenyl) carbamates on heating in boiling glacial acetic acid, followed by addition of hydrazine hydrate in acetonitrile, afforded methyl (5-oxo-5H-indeno[1,2-c]pyridazin-3-yl)phenylcarbamates.