Three-Component Coupling Strategy to Benzoannulated N- or O-Heterocycles

Significance

Reported is a three-component reaction of arynes, isocyanides and either aldehydes, ketones, or sulfonylimines promoted by KF/18-crown-6 ether to give iminodihydroisobenzofurans or iminoisoindolines in moderate to good yields. The reaction is proposed to commence by a nucleophilic addition of an isocyanide to an aryne, followed by a nucleophilic attack of the resulting zwitterion to an electrophile (aldehyde, ketone, or sulfonylimine). The resulting species then undergoes an intramolecular cyclization to provide the products. The scope of the reaction, as well as the solvent effect, was reasonably well studied. The regioselectivity of the nucleophilic attack on the substituted arynes was rationalized by steric and electronic effects.