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

Abstract Herein we report the use of tetrakis (guanidinium) pyrenetetrasulfonate ( G 4 PYR ) and bis (guanidinium) 1,5‐napthalene disulfonate ( G 2 NDS ) 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.