An efficient synthesis of 3-alkyl-2-diversity-substituted benzofuro[3,2-d]pyrimidin-4(3H)-one derivatives

Abstract

Benzofuro[3,2- d]pyrimidine derivatives are prepared using aza-Wittig reactions of iminophosphoranes with n-butyl isocyanate at 40–50 °C to give carbodiimide intermediates, which are reacted with nitrogen-oxygen-containing nucleophiles to give 3-alkyl-2-amino (aryloxy/alkoxy)-benzofuro[3,2- d]pyrimidin-4(3 H)-ones in satisfactory yields in the presence of a catalytic amount of sodium ethoxide or K2CO3. The iminophosphorane also reacts directly with excess carbon disulfide, followed by n-propylamine; further reaction with alkyl halides or halogenated aliphatic esters in the presence of anhydrous K2CO3 produces the corresponding 2-alkylthio-3-n-propyl-benzofuro[3,2- d]pyrimidin-4(3 H)-ones in good yields. Their structures of the products are confirmed by 1H NMR, 13C NMR, mass spectrometry, infrared and elemental analysis.