Experimental and Theoretical Investigation of an Azaoxyallyl Cation‐Templated Intramolecular Aryl Amination Leading to Oxindole Derivatives
Résumé
Abstract Herein, development and detailed investigation of a S N ′‐type intramolecular aromatic substitution reaction involving α‐arylazaoxyallyl cation intermediate, is disclosed. The study showcased that while α‐aryl‐α‐chlorohydroxamate could be activated by a combination of base and 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) into the corresponding azaoxyallyl cations, it could further emerge into a π‐extended species involving the adjacent α‐aryl moiety, and this transition is contingent on electronic effects of the aromatic ring as well as on α‐substituents. An effective activation of the α‐aromatic ring could pave the path for intramolecular Ar(C sp 2 )‐N bond formation towards oxindoles. Control experiments and DFT calculations suggested that a non‐pericyclic nucleophilic amination pathway is most likely operative and precluded the possibility of concerted or electrophilic amination mechanism. HFIP as the reaction solvent plays pivotal roles in the transformation.