109705-15-9Relevant academic research and scientific papers
Synthesis and Properties of N-Fluoropyridinium Salts
Umemoto, Teruo,Harasawa, Kikuko,Tomizawa, Ginjiro,Kawada, Kosuke,Tomita, Kyoichi
, p. 1081 - 1092 (2007/10/02)
Various stable N-fluoropyridinium salts with a non- or weakly nucleophilic counter anion such as TfO-, FSO3-, BF4-, ClO4-, CH3SO3- etc., or with an electron-donating or -withdrawing substituent(s) on the pyridine ring were synthesized and their properties investigated.N-Fluoropyridinium-2-sulfonates, N-fluoroquinolinium triflate, and highly hindered N-fluoro-2,6-di-t-butylpyridinium salts were also synthesized.They were synthesized by counter anion displacement reactions of unstable pyridine-F2 conpounds, fluorination of salts of pyridines with protonic acids or silyl esters with F2, and/or fluorination of Lewis acid complexes of pyridines.The scope of each method was examined in detail.Each of the N-fluoropyridinium salts was assigned as the first stable 1:1 salt structure of the pyridine nucleus and halogen atom on the basis of the spectral and elemental analysis.The stability depended on the nucleophilicity or basicity of the counter anions and electronic nature or position of the ring substituents.These results and NMR analyses clearly showed the unstable pyridine-F2 compounds to have N-fluoropyridinium fluoride salt structure.Some N-fluoropyridinium triflates were hydrolyzed and the products were examined, suggesting a unique hydrolysis mechanism.
Preparation of 2-Fluoropyridines via Base-Induced Decomposition of N-Fluoropyridinium Salts
Umemoto, Teruo,Tomizawa, Ginjiro
, p. 1726 - 1731 (2007/10/02)
N-Fluoropyridinium salts with either BF4-, SbF6-, or PF6- as a counteranion were treated with excess base such as triethylamine at room temperature to give 2-fluoropyridine in good yield.This method was succesfully applied to the preparation of 2-fluoropyridine derivatives possessing electron-donating or -withdrawing substituents using substituted N-fluoropyridinium tetrafluoroborates.Pyridine-F2 compounds produced through reactions of pyridines with molecular fluorine were also treated with base to give 2-fluoropyridines but in low yields.These reactions are considered to occur through a carbene mechanism as follows: a novel N-F-containing cyclic carbene (3), generated from the N-fluoropyridinium salts by 2-proton abstraction, reacts with fluorine atoms from counteranions such as BF4-, SbF6-, or PF6-, followed by elimination of F- from the N-F moiety, to yield 2-fluoropyridines.Previously reported findings in reactions of pyridines with molecular fluorine are explained on the basis of this mechanism.
