provides a series of chiral γ,γ-difluoroallylboronates. Asymmetric fluoroallylboration of aldehydes with a 2-phenylbornane-2,3-diol-derived reagent provides gem-difluorinated homoallylalcohols in good yields and 77–95% ee. Preparation of a chiral α-pyrone in >99% ee has also been described.
A simple, rapid procedure for nucleophilic radiosynthesis of aliphatic [18F]trifluoromethyl groups
作者:Patrick J. Riss、Franklin I. Aigbirhio
DOI:10.1039/c1cc15342k
日期:——
A procedure for the radiosynthesis of aliphatic [18F]trifluoromethyl groups by reacting 1,1-difluorovinyl precursors with [18F]fluoride ions, resulting in the equivalent of direct nucleophilic addition of H[18F]F, has been developed. A variety of 18F-labelled model compounds were then obtained and two potential [18F]radiotracers were synthesised by a two step process starting from 1,1-difluorovin-2-yl 4-toluenesulfonate. The method is widely applicable for the synthesis of novel radiotracers in high radiochemical yields and good specific activity.
Synthesis of Small 3-Fluoro- and 3,3-Difluoropyrrolidines Using Azomethine Ylide Chemistry
作者:Indrawan McAlpine、Michelle Tran-Dubé、Fen Wang、Stephanie Scales、Jean Matthews、Michael R. Collins、Sajiv K. Nair、Mary Nguyen、Jianwei Bian、Luis Martinez Alsina、Jianmin Sun、Jiaying Zhong、Joseph S. Warmus、Brian T. O’Neill
DOI:10.1021/acs.joc.5b00853
日期:2015.7.17
Here, we report accessing small 3-fluoropyrrolidines and 3,3-difluoropyrrolidines through a 1,3-dipolar cycloaddition with a simple azomethine ylide and a variety of vinyl fluorides and vinyl difluorides. We demonstrate that vinyl fluorides within alpha,beta-unsaturated, styrenyl and even enol ether systems can participate in the cycloaddition reaction. The vinyl fluorides are relatively easy to synthesize through a variety of methods, making the 3-fluoropyrrolidines very accessible.
<i>Gem</i>-Difluorinated Homoallyl Alcohols, β-Hydroxy Ketones, and <i>syn</i>- and <i>anti</i>-1,3-Diols via γ,γ-Difluoroallylboronates
gamma,gamma-Difluoroallylboronates have been prepared from trifluoroethanol and utilized for the allylboration of a variety of aldehydes to provide gem-difluorinated homoallylic alcohols. alpha-Chiral aldehydes were allylborated in 4:1-13:1 diastereoselectivity favoring the anti-isomer. A representative series of difluorinated hydroxyl enol ethers were converted to the corresponding alpha,alpha-difluoro-beta-hydroxy ketones. Diastereoselective reduction of one of these to either syn- and anti-1,3-diol was also studied.
Facile allylboration of ketones with β-benzyloxy-γ,γ-difluoroallylboronate: Preparation of gem-difluorinated homoallylic tert-alcohols
The reaction of beta-benzyloxy-gamma,gamma-difluoroallylboronate, at room temperature and in the absence of catalysts, with a variety of aromatic and aliphatic ketones of varying sterics and electronic requirements furnishes fluorinated homoallylic tert-alcohols in 62-82% yields. Representatives of these alcohols were converted to their corresponding alpha,alpha-difluoro-beta-hydroxy ketones in 73-85% yields. (C) 2008 Elsevier B.V. All rights reserved.