Streamlined Electrochemical Dihalogenation (F, Cl, and Br) of gem‐Difluoroalkenes Using Hydrogen Halides as Reagents
摘要:
We established a straightforward electrochemical dihalogenation (F, Cl, and Br) process for gem‐difluoroalkenes. This reaction exhibits a broad functional group tolerance and has been effectively utilized in the construction of complex molecules. The subsequent synthetic transformations of the products have highlighted the adaptable nature of the dihalogenated compounds, demonstrating their potential application in drug discovery and the investigation of innovative materials. The effective utilization of the dihalogenated product for 18F‐labeling represents a novel approach in generating highly potent 18F‐labeled tracers.
The development of efficient protocols for the synthesis of gem-difluoroolefins has received increasing attention. Given the ubiquity of hydroxyl group in biologically active molecules and synthetic intermediates, we developed a one-step protocol for the conversions of alcohols into gem-difluoroolefins. The reactions of alcohols with Ph3P+CF2CO2−/Burgess reagent in DMSO occurred smoothly to afford
合成宝石-二氟烯烃的有效方案的开发受到越来越多的关注。考虑到生物活性分子和合成中间体中普遍存在羟基,我们开发了一种将醇类转化为宝石-二氟烯烃的一步方法。的Ph醇的反应3 P + CF 2 CO 2 - / Burgess试剂在DMSO发生顺利,得到最终的产品在较高产率。DMSO不仅是氧化过程所必需的,而且对于通过捕集二氟卡宾来稳定叶立德也很重要。
Palladium-Catalyzed Direct Approach to α-Trifluoromethyl Alcohols by Selective Hydroxylfluorination of <i>gem</i>
-Difluoroalkenes
作者:Bin Zhang、Xiaofei Zhang、Jian Hao、Chunhao Yang
DOI:10.1002/ejoc.201800468
日期:2018.9.30
A mild and efficient synthesis of α‐trifluoromethyl alcohols derivatives was achieved via Pd‐catalyzed selective hydroxylfluorination of gem‐difluoroalkenes using NFSI as the fluoride source.
salts has rendered the products easily isolable, which greatly improved the synthetic practicality of the monodefluoroborylation reaction. Stoichiometric experiments indicate that the fate of the regioselectivity depends on the mode of β-fluorine elimination, which depends on the substrate. Further transformation of the boryl group has allowed facile preparation of fluoroalkene derivatives as exemplified
described. This novel catalytic transformation proceeds in the presence of Pd(acac)2/1,2‐bis((di‐tert‐butylphosphan‐yl)methyl)benzene (btbpx) (L4) and allows for an efficient and straightforward access to a range of difluoromethylated esters in high yields and regioselectivities. The synthetic utility of the protocol is showcased in the practical synthesis of a Cyclandelate analogue using this methodology
which otherwise are essentially reluctant towards F‐nucleoplilic addition, now readily participate in this fluoroallylation reaction. Furthermore, this strategy provides an elegant example for the generation, as well as functionalization, of α‐CF3‐substituted benzylic radical intermediates using cheap and readily available starting materials.