01299nas a2200193 4500008004100000022001400041245011200055210006900167260000900236300001400245490000700259520059300266100002200859700002600881700002400907700002600931700002200957856012600979 2020 eng d a0022-326300aN-heterocyclic carbene catalysis exploiting oxidative imine umpolung for the generation of imidoyl azoliums0 aNheterocyclic carbene catalysis exploiting oxidative imine umpol cAPR a5114-51210 v853 a
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.
1 aDas, Tamal, Kanti1 aMadica, Krishnaprasad1 aKrishnan, Jagadeesh1 aMarelli, Udaya, Kiran1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/n-heterocyclic-carbene-catalysis-exploiting-oxidative-imine-umpolung-generation-imidoyl