Carbopalladation of nitriles: synthesis of 3,4-disubstituted 2-aminonaphthalenes and 1,3-benzoxazine derivatives by the palladium-catalyzed annulation of alkynes by (2-Iodophenyl)acetonitrile.
Intramolecular carbopalladation of the cyano group has been employed for the synthesis of 3,4-disubstituted 2-aminonaphthalenes. (2-Iodophenyl)acetonitrile reacts with a variety of internal alkynes to afford 2-aminonaphthalenes in high yields with good regioselectivity. The scope and limitations of this process, which proceeds by the intramolecular addition of a vinylpalladium species to the triple bond of the cyano group, have been studied. The annulation of certain hindered propargylic alcohols affords 1,3-benzoxazine derivatives, rather than the expected 2-aminonaphthalenes. The involvement of trialkylamine bases in the formation of these heterocyclic compounds has been established. A proposed mechanism for the synthesis of 1,3-benzoxazine derivatives involves the formation of the expected 2-amino-3-(1-hydroxyalkyl)naphthalenes, followed by their condensation with an iminium ion species formed from the trialkylamine base used in the reaction.
Tian
Qingping
Q
Department of Chemistry, Iowa State University, Ames 50011, USA.
Pletnev
Alexandre A
AA
Larock
Richard C
RC