New functionalisation chemistry of 2- and 4-pyridones and related heterocycles

2016-06-16T14:41:31Z (GMT) by Beatriz Fernandez
New methodology for the synthesis of several 4H-pyrido[1,2-a]pyrimidin-4-ones has been developed from commercially available 2-aminopyridines and β-oxo esters catalysed by Montmorillonite under solvent-free conditions in good yields. This methodology was expanded for the synthesis of 4H-pyrimido[1,2-a]pyrimidin-4-one derivatives from 2-aminopyrimidine and different β-keto esters. The new methodology for the synthesis of N-alkylated 6-methyl 2-pyridones and N-alkylated 2-methyl 4-pyridones, from commercially available starting materials was developed. For the synthesis of N-alkylated 6-methyl 2-pyridones, 2-methoxy-6-methyl pyridine and a number of different alkylating reagents have been employed as starting materials. For the synthesis of N-alkylated 2-methyl 4-pyridones, 4-chloro 2-methyl pyridine was used successfully to make the desired pyridone in 3 steps. Selective mono-metallation at the 6-methyl substituent of N-alkylated 6-methyl 2-pyridones and N-alkylated 2-methyl 4-pyridones with n-BuLi/KHMDS at -78 °C proceeded smoothly, and the reactivity of the lithiated intermediates towards a wide range of electrophile (diketones, aldehydes, alkylating reagents) was studied. A straightforward synthesis of desirable 4H-quinolizin-4-one scaffolds by condensation of N-benzyl 6-methyl 2-pyridones with dicarbonyl compounds, and the formation of the desired quinolizinone after the condensation step was achieved. An unexpected quinolizinone bearing a fused β-lactam ring was isolated and its structure confirmed by single crystal X-ray diffraction analysis.