(3-iminio-1-propenyl)oxy-borates: New acyclic betaines from enaminocarbonyl compounds and boron trifluoride or triphenylboron - Synthesis, crystal structure analysis, and quantum chemical calculations

摘要

Adducts of various acyclic enaminoketones and enaminoaldehydes with the Lewis acids boron trifluoride and triphenylboron were prepared. The adducts were characterized by NMR (H-1, C-13, B-11) and IR spectroscopy, FAB-MS, and X-ray crystal structure analysis of the adducts of (E)-3-diethylamino-3-phenyl-2-propenal with BF3 (4a) and BPh3 (5a), respectively. The adduct formation occurs at the oxygen atom of the enaminocarbonyl compound and gives rise to a betainic structure with expressed equalization of the bond orders in the enaminocarbonyl moiety. The gas-phase structures of complexes 4a and 5a and of the corresponding free enaminoaldehyde were determined computationally, by RHF and DFT methods, and a Natural Bond Orbital (NBO) analysis was undertaken. [References: 34]