The clean and mild synthesis, crystal structure, and intra-molecular hydrogen bond study of substituted new 4,8-dihydropyrano[3,2-b]-pyrans containing chlorokojic acid moiety

Abstract

A safe, green and convenient process was developed for the synthesis of a novel group of 4,8-dihydropyrano[3,2-b]-pyrans by dialkyl acetylenedicarboxylates and alkyl isocyanides being trapped by chlorokojic acid in good to excellent yields at ambient temperature. Characterization of all structures was carried out by FT-IR and H-1 and C-13 NMR spectrometers, and two compounds were analyzed using X-ray diffraction technique. Crystal structures showed an intramolecular hydrogen bond and stacking of the dimeric (RS) molecules with the unit cell along the a-axis.