Formation, Selective Encapsulation, and Tautomerization Control of Isoindolone Utilizing Guanidinium Sulfonate Frameworks

Herein we report the use of tetrakis (guanidinium) pyrenetetrasulfonate (G₄PYR) and bis (guanidinium) 1,5-napthalene disulfonate (G₂NDS) to catalyze the cyclization of 2-cyanobenzamide (1) to isoindolone (2). Moreover, we demonstrate the remarkable selectivity of these guanidinium organosulfonate hosts in encapsulating 2 over 1. By thoroughly investigating the intramolecular cyclization reaction, we determined that guanidinium and the organosulfonate moiety acts as the catalyst in this process. Additionally, 2 is selectively encapsulated, even in mixtures of other structurally similar heterocycles like indole. Furthermore, the tautomeric state of 2 (amino isoindolone (2-A) and imino isoindolinone forms (2-I)) can be controlled by utilizing different guanidinium organosulfonate frameworks.