Divergent Palladium Iodide Catalyzed Multicomponent Carbonylative Approaches to Functionalized Isoindolinone and Isobenzofuranimine Derivatives

2-Alkynylbenzamides underwent different
reaction pathways when
allowed to react under PdI2-catalyzed oxidative carbonylation
conditions, depending on the nature of the external nucleophile and
reaction conditions. Thus, oxidative carbonylation of 2-ethynylbenzamides,
bearing a terminal triple bond, carried out in the presence of a secondary
amine as external nucleophile, selectively led to the formation of
3-[(dialkylcarbamoyl)­methylene]­isoindolin-1-ones through the intermediate
formation of the corresponding 2-ynamide derivatives followed by intramolecular
nucleophilic attack by the nitrogen of the benzamide moiety on the
conjugated triple bond. On the other hand, 3-[(alkoxycarbonyl)­methylene]­isobenzofuran-1­(3H)­imines were selectively obtained when the oxidative carbonylation
of 2-alkynylbenzamides, bearing a terminal or an internal triple bond,
was carried out in the presence of an alcohol R′OH (such as
methanol or ethanol) as the external nucleophile and HC­(OR′)3 as a dehydrating agent, necessary to avoid substrate hydrolysis.
In this latter case, the reaction pathway leading to the isobenzofuranimine
corresponded to the 5-exo-dig intramolecular
nucleophilic attack of the oxygen of the benzamide moiety on the triple
bond coordinated to the metal center followed by alkoxycarbonylation.
The structures of representative products have been confirmed by X-ray
crystallographic analysis.