title: A switchable intramolecular hydrogen bond in polysubstituted 5-nitrosopyrimidines.
abstract: The formation of strong intramolecular hydrogen bonds was observed in a series of 2-amino-5-nitrosopyrimidines with alkylamino and arylamino substituents at positions 4 and 6. Mixtures of two rotamers differing in the orientation of the nitroso group were observed in the NMR spectra of the compounds where two distinct intramolecular hydrogen bonds could be formed. The ratio of the two rotamers depends strongly on the character of the substituents at positions 4 and 6 and can be finely tuned over a broad range of conformation ratios. The experimental results were supported by DFT calculations, which also made it possible to explain the apparent contradiction in the experimental dependence of the rotamer ratio on the Hammett constants for the arylamino substituents. The UV/vis spectra of the compounds also significantly depend on the nature of the substituents; however, the orientation of the nitroso group does not have any influence on the position of the absorption bands in the spectra.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nam. 2, 166 10 Prague, Czech Republic.
authors.forename: Eliška
authors.initials: E
authors.lastname: Procházková
authors.forename: Lucie
authors.initials: L
authors.lastname: Čechová
authors.forename: Zlatko
authors.initials: Z
authors.lastname: Janeba
authors.forename: Martin
authors.initials: M
authors.lastname: Dračínský
mesh_terms: D000042:Absorption; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009603:Nitroso Compounds / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D009603:Nitroso Compounds; D011743:Pyrimidines