title: Efficient Synthesis of 1-Amino-2-naphthalenecarboxylic Acid Derivatives via a Sequential Michael Addition/Enolate-Nitrile Coupling Route and Its Application to Facile Preparation of 9-Amino Analogues of Arylnaphthofuranone Lignans.
abstract: The reaction of 2-(alpha-lithioalkyl)benzonitriles, generated in situ by treatment of 2-alkylbenzonitriles with LDA in diglyme, with alpha,beta-unsaturated carboxylates and nitriles produced 1-amino-3,4-dihydro-2-naphthalenecarboxylates and carbonitriles in 54-98% yields through Michael addition of the lithio nitriles to alpha,beta-unsaturated carboxylic acid derivatives, followed by zinc iodide-promoted intramolecular enolate-nitrile coupling of the resulting enolate intermediates. The dihydronaphthalenecarboxylic acid derivatives were converted to the corresponding 1-amino-2-naphthalenecarboxylic acid derivatives in 43-99% yields on dehydrogenation with palladium on activated carbon in refluxing p-cymene. Subsequently, we showed that, by using a similar reaction sequence, 9-amino analogues of arylnaphthofuranone lignan derivatives {9-amino-4-arylnaphtho[2,3-c]furan-1(3H)-ones} could also be prepared from 2-(arylmethyl)benzonitriles and furan-2(5H)-one in good overall yields (59-61%).
authors.affiliation: Department of Materials Science, Faculty of Engineering, Tottori University, Tottori 680, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Uneda
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Takada
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tanaka
authors.forename: Tomohide
authors.initials: T
authors.lastname: Kitamura
authors.forename: Osamu
authors.initials: O
authors.lastname: Morikawa
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Konishi