A simple, powerful, and efficient method for transesterification
作者:Otto Meth-Cohn
DOI:10.1039/c39860000695
日期:——
Aromatic and α,β-unsaturated methyl esters undergo efficienttransesterification at ambient temperature or below with primary, secondary, or (particularly) tertiary alcohols in the presence of butyl-lithium in tetrahydrofuran solution.
Direct Synthesis of <i>N</i>-Difluoromethyl-2-pyridones from Pyridines
作者:Sen Zhou、Xiaoya Hou、Kai Yang、Minjie Guo、Wentao Zhao、Xiangyang Tang、Guangwei Wang
DOI:10.1021/acs.joc.1c00228
日期:2021.5.7
A novel method for the synthesis of N-difluoromethyl-2-pyridones was described. This protocol enables the synthesis of N-difluoromethyl-2-pyridones from readily available pyridines using mild reaction conditions that are compatible with a wide range of functional groups. The preliminary mechanistic study revealed that N-difluoromethylpyridinium salts were the key intermediates to complete this conversion
Metal-Free Difunctionalization of Pyridines: Selective Construction of <i>N</i>-CF<sub>2</sub>H and <i>N</i>-CHO Dihydropyridines
作者:Sen Zhou、Ze-Ying Sun、Kongying Zhu、Wentao Zhao、Xiangyang Tang、Minjie Guo、Guangwei Wang
DOI:10.1021/acs.orglett.1c00352
日期:2021.3.19
N-difluoromethylpyridinium salts is seldom explored because of their instability and low availability. Here we present a novel nucleophilic addition of N-difluoromethylpyridinium salts with nitroalkanes to synthesize N-CF2H-dihydropyridines and N-CHO-dihydropyridines in a highly efficient and regioselective pathway. This protocol exhibits good functional group tolerance and good to excellent yields.
C3-Selective Trifluoromethylthiolation and Difluoromethylthiolation of Pyridines and Pyridine Drugs via Dihydropyridine Intermediates
作者:Xin-Yue Zhou、Ming Zhang、Zhong Liu、Jia-Hao He、Xiao-Chen Wang
DOI:10.1021/jacs.2c06776
日期:2022.8.17
difluoromethylthiolation of pyridines. The method relies on borane-catalyzed pyridine hydroboration for generation of nucleophilic dihydropyridines; these intermediates react with trifluoromethylthio and difluoromethylthio electrophiles to form functionalized dihydropyridines, which then undergo oxidative aromatization. The method can be used for late-stage functionalization of pyridine drugs for the generation
derivatives, affording unique 7-membered structures. Mechanistic evidence supports the transient presence of a diazanorcaradiene species. Finally, pertinent transformations of the products, including ring contraction reactions to form pyrazoles, were conducted and paved the way to a broad application of the developed protocol.