Heterocyclic Spiro‐naphthalenones. Part I: Synthesis and reactions of some spiro [(1 H‐naphthalenone)‐1,3′‐piperidines

Abstract

AbstractThe title compounds 14–16 were obtained via an intramolecular Mannich condensation by treating 11–13 with CH2O at RT. The unsaturated ketones 14 and 15 were reduced to the allylic alcohols 18 and 19 respectively. Ring cleavage of compound 18 on treatment with 2N HCl gave the substituted aminopropanol 20. The allylic alcohols 18 and 19 were hydrogenated to 22 and 23 respectively. With CH2O, the amino‐alcohol 23 gave the methano‐naphthoxazocine 24, whereas 22 and 23, on heating in polyphosphoric acid (PPA), afforded the naphthazepines 25 and 26 respectively. With organolithium compounds, the unsaturated ketones 14 and 16 gave the teriary allylic alcohols 27–29, which were hydrogenated and dehydrated to the olefins 36–40; these were cyclized via an intramolecular alkylation to the methanodibenzo‐octahydrocyclooctapyridines 41–43. On heating in PPA, the allylic alcohol 29 was converted into the naphthazepine 44. With CH2O, the naphthol 49 gave the naphthoxazocine 50, in equilibrium with the spiro‐naphthalene‐pyrrolidinone 51 in solution. Finally, in the presence of CH2O, the naphthazepine 57 afforded the methano‐naphthazepinone 58, which, by a 4‐stage degradation, was transformed to the benzisoquinoline 62.