New, simple and efficient method for the synthesis of imidazo-azines by flash vacuum thermolysis of tert-butylimines of pyrimidine-2-, pyrazine-2-, quinoline-2-, quinoxaline-2- and isoquinoline-1-carbaldehydes
Résumé
Flash vacuum thermolysis reactions of N-(tert-butyl)-N-(pyrimidin-2-ylmethylidene)amine (1), N-(tert-butyl)-N-(pyrazin-2-ylmethylidene)amine (2), N-(tert-butyl)-N-(quinolin-2-ylmethylidene)amine (3), N-(tert-butyl)-N-(quinoxalin-2-ylmethylene)amine (4) and N-(tert-butyl)-N-(isoquinolin-2-ylmethylidene)amine (5) have been investigated. The formation of 3-methyl-imidazo[1,5-a]pyrimidine(6), 3-methyl-imidazo[1,5-a]pyrazine (7), 1-methyl-imidazo[1,5-a]quinoline (8), 3-methyl-imidazo[1,5-a] quinoxaline (9) and 3-methyl-imidazo[5,1-a]isoquinoline (10) as reaction products was observed. Excellent yields of imidazoazines from monocyclic imines 1 and 2 were found, whereas from bicyclic imines 3–5 slightly lower yields (50–75%) of the major products and formation of byproducts such as quinolone and isoquinoline were observed. These cyclizations were found to occur fully regioselectively onto the nitrogen atom of the adjacent ring. UV-photoelectron spectroscopy combined with FVT and quantum chemical calculations were applied for direct monitoring and characterization of the thermolysis products. The proposed mechanism of these reactions are substantiated by DFT calculations.
Mots clés
Aromatic compounds
Byproducts
Density functional theory
Nitrogen compounds
Photoelectron spectroscopy
Photoelectrons
Photons
Quantum chemistry
Aza-heterocycles
Carbaldehydes
DFT calculation
Direct monitoring
Flash vacuum thermolysis
Isoquinolines
Quantum chemical calculations
UV photoelectron spectroscopy
Thermolysis