Reaction of difluorocarbene with diarylmethanimines leads to the formation of gem-difluorinated NH-azomethine ylides, two types of competing transformations of which are found to be characteristic: a formal 1,2-H shift into N-(difluoromethyl)imines and 1,3-dipolar cycloaddition to electron-deficient multiple bonds. α,α,α-Trifluoroaceto- phenones are efficient dipolar traps for difluoro NH-ylides, the addition of which to the dipole proceeds regioselectively with the formation of 4-fluoro-2,5-dihydrooxazoles. According to the quantum-chemical calculations by the DFT B3LYP/6-31G*method, 1,3-dipolar cycloaddition of difluorinated NH-azomethine ylides to a C=O bond with the formation of 4-fluoro derivatives of oxazole has lower barrier of activation than the reaction, leading to another regioisomer; the formal 1,2-H shift in the ylide occurs intermolecularly with participation of an imine, a precursor of the ylide.

Original languageEnglish
Pages (from-to)1070-1079
Number of pages10
JournalRussian Chemical Bulletin
Volume57
Issue number5
DOIs
StatePublished - 1 May 2008

    Scopus subject areas

  • Chemistry(all)

    Research areas

  • Azomethine ylides, Cycloaddition, Difluorocarbene, Fluorine-substituted heterocycles

ID: 28188201