Carbocycle synthesis via novel organopalladium addition to nitriles

Rarely observed carbopalladation of the cyano group has been investigated. Synthetic methodology for 2,3-diarylindenones by the palladium-catalyzed annulation of alkynes with 2-iodoarenenitriles has been developed. This methodology has also been adapted to the annulation of bicyclic olefins. The reaction affords 2,3-diarylindenones and polycyclic aromatic ketones in very good to excellent yields and tolerates a number of functional groups, making it an efficient synthetic route to these compounds. The reaction is believed to proceed via (1) oxidative addition of the aryl iodide to Pd(0), (2) arylpalladium addition to the carbon-carbon multiple bond, (3) addition of the resulting vinylic or alkylpalladium species across the triple bond of the cyano group to produce an iminopalladium moiety, and (4) hydrolysis of the imine intermediate. A model accounting for the electronic effects of substituents on the aromatic ring of the nitrile has also been proposed.;The palladium-catalyzed annulation of alkynes with iodoarenes containing a cyano group has been extended to 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. In many cases, the regioselectivity of this reaction is excellent. The scope and limitations of this process, which proceeds via a mechanism similar to the reaction between 2-iodoarenenitriles and alkynes, have been studied. When introduced into the reaction, certain hindered propargylic alcohols have been found to afford 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 and a mechanism for this transformation has been proposed.;A general and efficient procedure for the synthesis of 2,2-disubstituted indanones by the palladium-catalyzed cyclization of 3-(2-iodoaryl)propanenitriles has been developed. This process is also based on intramolecular carbopalladation of the cyano group. A variety of indanones have been prepared in high yields from readily available starting materials containing various functional groups that are compatible with the reaction conditions. The reaction is not limited to the synthesis of indanones as other benzocyclic ketones, as well as a number of substituted cyclopentenones, have been synthesized by this methodology