- Efficient hydrolysis of dithioacetals by the N-fluoro-2,4,6-trimethylpyridinium triflate-water system
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Dithioacetals including 1,3-dithianes and 1,3-dithiolanes are efficiently cleaved by the title reagent system to the parent carbonyl compounds. The cleavage of diprotected symmetrical α-diketones and p-phenylenediketones gives monoketones in good yields. Amide, 1,3-dioxolane, disulfide, ester, ether, hydroxy, nitrile, nitro, and sulfide functions are relatively stable under the cleavage conditions but thiols are oxidized to disulfides.
- Kiselyov,Strekowski,Semenov
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p. 2151 - 2158
(2007/10/02)
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- Synthesis and Properties of N-Fluoropyridinium Salts
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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.
- Umemoto, Teruo,Harasawa, Kikuko,Tomizawa, Ginjiro,Kawada, Kosuke,Tomita, Kyoichi
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p. 1081 - 1092
(2007/10/02)
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- N-FLUOROPYRIDINIUM TRIFLATE AND ITS ANALOGS, THE FIRST STABLE 1:1 SALTS OF PYRIDINE NUCLEUS AND HALOGEN ATOM
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N-Fluoropyridinium salts having non-nucleophilic counter-anions and their derivatives were synthesized by treating pyridine-F2 adducts with strong Broensted acids, their salts or trimethylsilyl esters, of Lewis acids, or by allowing F2 to react with N-trimethylsilylpyridinium salts.
- Umemoto, Teruo,Tomita, Kyoichi
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p. 3271 - 3274
(2007/10/02)
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