Takeuchi, Yoshio published the artcileAdjacent lone pair (ALP) effects in heteroaromatic systems. 2. Isotope exchange of ring hydrogens in nitro- and fluoroimidazoles, Formula: C3H3FN2, the main research area is adjacent lone pair effect; hydrogen exchange nitroimidazole fluoroimidazole; imidazole nitro fluoro exchange.
The ring protons of nitro- and fluoroimidazoles (and their N-Me derivatives) undergo base-catalyzed exchange in D2O by a combination of carbanion (C) and ylide (Y) pathways, which involve proton abstraction from the neutral imidazole species and from the imidazolium ion, resp. In 4-substituted imidazoles, C exchange occurs more readily at C-5 than at C-2, log kC correlating with σo° for the NH- and with σp° for the N-Me series. For 1-methyl-4-nitroimidazole, t1/2 = 2 min at C-5 (50°, 0.2 N NaOD). In 1-methyl-5-X-imidazoles, exchange at C-4 occurs only via the Y pathway, carbanion formation in the neutral species being retarded by the adjacent lone pair (ALP) effect at N-3. The same effect is seen in the lack of C exchange at C-4 in 1-methylimidazoles. The ALP effect is considerably weaker or nonexistent at C-2. Most exchanges across the ring show correlations of log k with ςm°. 4-Alkylimidazoles (but not 1,4-dialkylimidazoles) show enhanced C exchange at C-5, which may result from the existence of a trace concentration of the ketimine tautomer. Enhanced exchange at C-5 in 2-fluorohistidine is ascribed to a combination of the ketimine effect, C exchange involving catalysis by OH and intramol. general-base catalysis by the side-chain primary-amine function. The use of buffer catalysis for the T labeling of poorly reactive imidazoles is described.
Journal of Organic Chemistry published new progress about Exchange reaction. 30086-17-0 belongs to class imidazoles-derivatives, name is 5-Fluoro-1H-imidazole, and the molecular formula is C3H3FN2, Formula: C3H3FN2.
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem