Studies on Isocyanides and related compounds: A facile synthesis of 1,6-dihydro-6-oxopyrazine-2-carboxylic acid derivatives via ugi four-component condensation

摘要

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 C-13 NMR spectra and X-ray analysis of 9a. [References: 37]