Orientation and Alkylation Effects on Cation-π Interactions in Aqueous Solution
摘要:
We have investigated the orientation dependence of the cation-pi interaction between a phenyl ring and a pyridinium ring in the context of a flexible model system in water. Of the four possible positions of the pyridinium nitrogen, ipso, ortho, meta, and para, we found a variation in the interaction energy of about 0.75 kcal mol(-1), with the stacking of the ipso-pyridinium ring providing the strongest interaction. The observed stability is attributed to the maximization of the electrostatic interaction, minimization of rotamers, and possible differences in hydration phenomena arising from alkylation.
A facile synthesis of functionalized 4-benzylpyridines by using mixed copper, zinc benzylic organometallics
作者:Win-Long Chia、Min-Jen Shiao
DOI:10.1016/s0040-4039(00)78900-3
日期:1991.4
A general approach by use of highly functionalized mixed copperzinc, benzylicorganometallics to react with N-ethoxycarbonylpyridinium chloride to give regioselectively 4-benzylpyridines after oxygen oxidation in 30–75% yield is described.
Functionalized 4-benzylated pyridines can be efficiently prepared by a transition-metal-freecross-coupling between various benzylic zinc chlorides and substituted 4-cyanopyridines in THF/DMPU under microwave irradiation (40 °C, 0.5–1.5 h). Selective benzylations on polycyano-aromatics have also been achieved under these mild conditions. We also report a novel oxidative nucleophilic substitution of
Direct Methenylation of 4-Alkylpyridines Using Eschenmoser’s Salt
作者:F. Christopher Pigge、Grant N. Shivers、Soe L. Tun、Shay L. McLean
DOI:10.1055/a-1916-5335
日期:2022.12
4-Alkylpyridines are converted into conjugated 1,1-disubstituted alkenyl pyridines (vinyl pyridines) upon treatment with excess ethyl chloroformate, triethylamine, and Eschenmoser’s salt. The reaction proceeds under mild conditions via alkylidene dihydropyridine intermediates.
Transition-Metal Free Chemoselective Hydroxylation and Hydroxylation–Deuteration of Heterobenzylic Methylenes
作者:Yonghai Liu、Yang Yu、Chengyu Sun、Yiwei Fu、Zhiguo Mang、Lei Shi、Hao Li
DOI:10.1021/acs.orglett.0c03108
日期:2020.10.16
We developed an approach for direct selective hydroxylation of heterobenzylic methylenes to secondary alcohols avoiding overoxidation to ketones by using a KOBu-t/DMSO/air system. Most reactions could reach completion in several minutes to give hydroxylated products in 41-76% yields. Using DMSO-d6, this protocol resulted in difunctionalization of heterobenzylic methylenes to afford α-deuterated secondary alcohols (>93% incorporation). By employing this method, active pharmaceutical ingredients carbinoxamine and doxylamine were synthesized in two steps in moderate yields.