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 oxidativecarbonylation conditions, depending on the nature of the external nucleophile and reaction conditions. Thus, oxidativecarbonylation of 2-ethynylbenzamides, bearing a terminal triple bond, carried out in the presence of a secondary amine asexternal nucleophile, selectively led to the formation of 3-[(dialkylcarbamoyl)methylene]isoindolin-1-ones through theintermediate formation of the corresponding 2-ynamide derivatives followed by intramolecular nucleophilic attack by thenitrogen 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 aterminal or an internal triple bond, was carried out in the presence of an alcohol R′OH (such as methanol or ethanol) as theexternal nucleophile and HC(OR′)3 as a dehydrating agent, necessary to avoid substrate hydrolysis. In this latter case, thereaction pathway leading to the isobenzofuranimine corresponded to the 5-exo-dig intramolecular nucleophilic attack of theoxygen of the benzamide moiety on the triple bond coordinated to the metal center followed by alkoxycarbonylation. Thestructures of representative products have been confirmed by X-ray crystallographic analysis.