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.