Deprotometalation of substituted pyridines and regioselectivity-computed CH acidity relationships
作者:Madani Hedidi、Ghenia Bentabed-Ababsa、Aïcha Derdour、Yury S. Halauko、Oleg A. Ivashkevich、Vadim E. Matulis、Floris Chevallier、Thierry Roisnel、Vincent Dorcet、Florence Mongin
DOI:10.1016/j.tet.2016.03.022
日期:2016.4
Interestingly, clean dideprotonation was noted from 3-fluoropyridine (at C2 and C4) and 2,6-difluoropyridine (at C3 and C5). The obtained regioselectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase (DFT B3LYP and G3MP2B3 levels) and in THF solution. In the case of methoxypyridines, the pKa values have also been calculated for complexes with
室温下,通过使用从ZnCl 2 ·TMEDA(TMEDA = N,N,N ',N'-四甲基乙二胺)和LiTMP(TMP)获得的混合的锂锌混合物,在四氢呋喃中对一系列甲氧基和氟吡啶进行了脱金属化处理。= 2,2,6,6-四甲基哌啶子酮)的比例为1:3,金属化的物质被碘拦截。从4-甲氧基,2-甲氧基,2-甲氧基,2,6-二甲氧基,2-氟和2,6-二氟吡啶观察到在3位的有效官能化,并且从3-甲氧基和2,3-二甲氧基吡啶观察到在4位的高效官能化。有趣的是,注意到3-氟吡啶(在C2和C4处)和2,6-二氟吡啶(在C3和C5处)有干净的双质子化。 根据底物的CH酸(在气相(DFT B3LYP和G3MP2B3含量)和THF溶液中测定)的CH酸性,已经讨论了所获得的区域选择性。在甲氧基吡啶的情况下,还计算了与LiCl和LiTMP的配合物的p K a值。