Hydriodic Acid-Mediated Cyclization of alpha-Substituted Secondary 2-Ethenylbenzamides: Synthesis of 2-Substituted 2,3-Dihydro-3,3-dimethyl-1H-isoindol-1-ones and 3,3-Disubstituted (E)-1-(Arylimino)-1,3-dihydroisobenzofurans

A new and facile method for the preparation of 2-substituted 2,3-dihydro-3,3-dimethyl-1H-isoindol-1-ones 3 and 3,3-disubstituted (E)-1-(arylimino)-1,3-dihydroisobenzofurans 6 has been developed. Thus, treatment of N-alkyl(or aryl)-2-(1-methylethen-1-yl)benzamides 2 with concentrated hydriodic acid (HI) in MeCN at room temperature afforded 3. Similar treatment of N-aryl-2-(1-phenylethen-1-yl)benzamide 5 with concentrated HI at 0 degrees afforded 6.