Solid-State Nuclear Magnetic Resonance Study of Ureidopyrimidinone Model Compounds
Résumé
High-resolution 1Hand 15N{1H} solid-stateNMRexperiments were conducted on two ureidopyrimidinone model compounds: dimeric 2-butylureido-6-methyl-4-pyrimidinone (1) and its bifunctional analogue N,N- 1,6-hexanediyl(2-ureido-6-methyl-4-pyrimidinone) (4).High magic angle spinning rates and 1Hdecoupling schemes were used to increase the proton spectral resolution. Upon heating 1 to 440 K, an increase in mobility was observed for non-hydrogen-bonded protons; the dimer remained in keto tautomeric form, which is capable of much stronger intermolecular hydrogen bonding than the enol tautomer. From these findings, it was concluded that this ureidopyrimidinone moiety should allow the design of strongly bonded molecular assemblies whose thermal stability compares favourably with that of conventional engineering polymers.