title: Novel rearrangements in the reactions directed toward preparation of spiro-N,N-ketals: reactions of naphthalene-1,8-diamine with ninhydrin and isatin.
abstract: Spiro-N,N-ketal 5, consisting of a phthaloperine heterocyclic ring and a naphtha[1,8-ef][1,4]diazepine ring, was obtained along with spiro-N,N-ketal 2 via  2,2-condensation in the reaction of ninhydrin with naphthalene-1,8-diamine. Their molecular structures were elucidated by X-ray crystal structural analysis. Aside from these spiro compounds, the diazapleiadiene compound 3 formed by 1,2-condensation and the  1,4-isoquinolinedione compound 4 arising from ring expansion were isolated. When isatin was reacted with naphthalene-1,8-diamine, spiro-N,N-ketal 6 and the two 1H-perimidine-based compounds 7 and 8 were isolated. Compound 8 was revealed to undergo a fast dynamic prototropic tautomerization in solution. Plausible mechanisms of the formation of the products are proposed.
authors.affiliation: Graduate School of Science, Josai University, Sakado, Saitama 350-0295, Japan.
authors.forename: Motoko
authors.initials: M
authors.lastname: Akita
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Seto
authors.forename: Reiko
authors.initials: R
authors.lastname: Aoyama
authors.forename: Junko
authors.initials: J
authors.lastname: Kimura
authors.forename: Keiji
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D018360:Crystallography, X-Ray; D003959:Diamines / Q000737:chemistry; D004987:Ethers / Q000737:chemistry; D007510:Isatin / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D009281:Naphthalenes / Q000138:chemical synthesis / Q000737:chemistry; D009555:Ninhydrin / Q000138:chemical synthesis / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D003959:Diamines; D004987:Ethers; D009281:Naphthalenes; D013141:Spiro Compounds; D007510:Isatin; D009555:Ninhydrin