RESUMO
3D structures in solution of highly symmetrical N,P-containing macrocycles were established by a variety of 2D NMR correlation techniques. It was shown that a number of magnetically equivalent fragments in such symmetrical systems can be estimated by NMR diffusion measurement. The title compounds adopt a helical conformation of the macrocycles in solution. The extent of twisting and the size of the intramolecular cavity are determined by steric hindrance of the aromatic substituents on the exocyclic phosphorus atoms with phenylene and dimethylmethylene groups forming the macrocycle. In solution these macrocycles host aromatic guests inside the cavity.
Assuntos
Compostos Aza/química , Compostos Macrocíclicos/química , Compostos Organofosforados/química , Compostos Aza/síntese química , Hidrocarbonetos Aromáticos/síntese química , Hidrocarbonetos Aromáticos/química , Compostos Macrocíclicos/síntese química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Compostos Organofosforados/síntese química , SoluçõesRESUMO
Protonation (alkylation) sites of several thiopyrimidine derivatives were directly determined by 1H-15N (1H-13C) heteronuclear single quantum coherence/heteronuclear multiple bond correlation methods, and it was found that in all compounds, protonation (methylation) occurred at the N1 nitrogen. GIAO DFT chemical shifts were in full agreement with the determined tautomeric structures. According to ab initio calculations, the stability of the different protonated forms and methylated derivatives was favored due to thermodynamic control and not kinetic control.