N-Heterocyclic Carbene Catalysis Exploiting Oxidative Imine Umpolung for the Generation of Imidoyl Azoliums
Tamal Das, Krishnaprasad Madica, Jagadeesh Krishnan, Udaya Kiran Marelli, Akkattu T. Biju
Abstract
Although NHC-catalyzed umpolung of imines are known, the related reactions under oxidative conditions are limited. Described herein is the two-step process involving the initial formation of aldimines from the corresponding aldehydes and 2-amino benzyl alcohols followed by NHC-catalyzed cyclization proceeding via the imidoyl azoliums under oxidative conditions. The reaction allowed the synthesis of trifluoromethylated 3,1-benzoxazines in good yields and broad scope. The role of NHC in the intramolecular cyclization and preliminary mechanistic experiments are also provided.
Topics & Concepts
UmpolungChemistryAldimineImineCarbeneIntramolecular forceCatalysisOxidative additionOxidative phosphorylationCombinatorial chemistryOrganocatalysisOrganic chemistryMedicinal chemistryEnantioselective synthesisNucleophileBiochemistryN-Heterocyclic Carbenes in Organic and Inorganic ChemistryCatalytic Cross-Coupling ReactionsSynthetic Organic Chemistry Methods