Studies on isocyanides and related compounds: a facile synthesis of 1, 6-dihydro-6-oxopyrazine-2-carboxylic acid derivatives via Ugi four-component condensation
Abstract The Ugi four-component condensation (U-4CC) between arylglyoxals 7, amines 6, benzoylformic acid (4) and isocyanides 5 afforded the expected products 8 which were cyclized in a 5+ 1 fashion with ammonium acetate to give 1, N-disubstituted 4-aryl-1, 6- dihydro-6-oxo-5-phenylpyrazine-2-carboxamides 9 in good yields. Evidence for the assigned structures 9 was provided by 13 C NMR spectra and X-ray analysis of 9a.
