Synthesis and high resolution proton NMR studies on isomeric N-1-/N-2-,5,7-trisubstituted-4,6-dioxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidines

摘要

Unambiguous synthesis of all six possible 1/2, 5,7-trisubstituted (monobenzyl, dimethyl)-4,6-dioxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidines has been described. High resolution (400 MHz) proton NMR data of these compounds (10,13,19,25a,15b and 25c) have been discussed and some unusual features observed for phenyl protons have been rationalized due to hindered rotation when two substituents are simultaneously present at 1- and 7-positions.