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1.
Rongyi Zhang Qigang Li Dr. Qiqiang Xie Prof. Dr. Chuanfa Ni Prof. Dr. Jinbo Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(71):17773-17779
The ring-opening difluoromethylation-halogenation of cyclic (thio)ethers is reported through a simple strategy relying on carbon-chalcogen bond activation with difluorocarbene. The reaction proceeds through in situ protonation of the previously little-known difluoromethylene oxonium or sulfonium ylide intermediate followed by ring-opening with halide ion to afford halogenated acyclic difluoromethyl (thio)ethers that can then be employed for further elaboration. TMSCF2X (X=Br, Cl) are unique reagents to achieve this synthetic purpose, which serve as both the difluorocarbene source and the halide ion source. 相似文献
2.
Xanath Ispizua-Rodriguez Dr. Socrates B. Munoz Dr. Vinayak Krishnamurti Dr. Thomas Mathew Prof. Dr. G. K. S. Prakash 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):15908-15913
A simple and straightforward approach to the synthesis of trifluoromethyl and difluoromethyl ketones from widely available carboxylic acids is disclosed. The transformation utilizes an acyloxyphosphonium ion as the active electrophile, conveniently generated in situ from the carboxylic acid substrate by using commodity chemicals. The utility of the reaction system is exemplified by its chemoselectivity, with tolerance to a variety of important functional groups. The late-stage functionalization of carboxylic acid active pharmaceutical ingredients and pharmaceutically relevant compounds is also discussed. 相似文献
3.
gem‐Difluoroolefination of Diaryl Ketones and Enolizable Aldehydes with Difluoromethyl 2‐Pyridyl Sulfone: New Insights into the Julia–Kocienski Reaction
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Bing Gao Dr. Yanchuan Zhao Dr. Mingyou Hu Dr. Chuanfa Ni Prof. Dr. Jinbo Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7803-7810
The direct conversion of diaryl ketones and enolizable aliphatic aldehydes into gem‐difluoroalkenes has been a long‐standing challenge in organofluorine chemistry. Herein, we report efficient strategies to tackle this problem by using difluoromethyl 2‐pyridyl sulfone as a general gem‐difluoroolefination reagent. The gem‐difluoroolefination of diaryl ketones proceeds by acid‐promoted Smiles rearrangement of the carbinol intermediate; the gem‐difluoroolefination is otherwise difficult to achieve through a conventional Julia–Kocienski olefination protocol under basic conditions due to the retro‐aldol type decomposition of the key intermediate. Efficient gem‐difluoroolefination of aliphatic aldehydes was achieved by the use of an amide base generated in situ (from CsF and tris(trimethylsilyl)amine), which diminishes the undesired enolization of aliphatic aldehydes and provides a powerful synthetic method for chemoselective gem‐difluoroolefination of multi‐carbonyl compounds. Our results provide new insights into the mechanistic understanding of the classical Julia–Kocienski reaction. 相似文献
4.
Keith Ramig Fernando Quiroz Gerald G. Vernice Leonid A. Rozov 《Journal of fluorine chemistry》1996,80(2):101-104
Treatment of 1,1-dichloro-2,2,2-trifluoroethyl difluoromethyl ether (3) with 2-propanol followed by either irradiation with UV light or heating with radical initiators gives the inhalational anesthetic isoflurane. Unlike most other common dechlorination methods, monoreduction is the exclusive process and the by-products acetone and HCl are relatively benign. Some comments about the mechanism of the reduction will be presented, along with solutions to problems encountered during scale-up. 相似文献
5.
Romana Pajkert 《Journal of fluorine chemistry》2007,128(10):1260-1263
A short synthesis of some 1,1-difluoro-2-hydroxymethylphosphonates in good yields is described. This procedure involves the regioselective 1,2-addition of [(diethoxyphosphoryl)difluoromethyl]lithium toward unsaturated aldehydes and ketones. 相似文献
6.
《中国化学》2018,36(1):55-58
Highly regiodivergent copper‐catalyzed allylic/propargylic difluoromethylation reactions by employing different ligands are described. When 5,6‐dimethyl‐1,10‐phenanthroline was used as the ligand, exclusively α‐difluoromethylated products were obtained, while γ‐selective difluoromethylated products were generated when N‐heterocyclic carbene‐SIPr was used as the ligand. Likewise, high α‐ vs. γ‐selectivities were achieved in the presence of similar copper catalysts for the reactions of propargyl bromides. Moreover, a copper‐catalyzed asymmetric allylic difluoromethylation reaction with moderate to good enantioselectivity by the use of chiral ligands was developed. 相似文献
7.
Laijun Zhang 《Journal of fluorine chemistry》2007,128(7):755-761
1-Aryl-2,2-difluoro enol benzoates 4 has been prepared from α-(phenylsulfonyl)-difluoromethylated benzoates 3, which can be readily obtained from the reactions between simple aldehydes and PhSO2CF2H (or TMSCF2SO2Ph). 2,2-Difluoro enol esters 4 are relatively more stable compounds than 2,2-difluoro enol sily ethers, and they promise to act as interesting fluorinated building blocks for further elaborations. 相似文献
8.
Due to its unique physical and electrophilic properties, the difluoromethyl group (−CF2H) has been playing an irreplaceable role in the field of pharmaceutical and agrochemical industry. Methods that could efficiently incorporate the difluoromethyl group into the target molecules are increasing in the recent years. Developing a stable and efficient difluoromethylating reagent is thus highly attractive. In this review, we describe the development of a nucleophilic difluoromethylation reagent [(SIPr)Ag(CF2H)], including its elemental reaction, difluoromethylation reaction with different types of electrophiles, and its application in the synthesis of a nucleophilic and an electrophilic difluoromethylthiolating reagent. 相似文献
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10.
Tanatorn Khotavivattana Stefan Verhoog Dr. Matthew Tredwell Lukas Pfeifer Samuel Calderwood Dr. Katherine Wheelhouse Dr. Thomas Lee Collier Prof. Véronique Gouverneur 《Angewandte Chemie (International ed. in English)》2015,54(34):9991-9995
We report that halogenophilic silver(I) triflate permits halogen exchange (halex) nucleophilic 18F‐fluorination of aryl‐OCHFCl, ‐OCF2Br and ‐SCF2Br precursors under mild conditions. This AgI‐mediated process allows for the first time access to a range of 18F‐labeled aryl‐OCHF2, ‐OCF3 and ‐SCF3 derivatives, inclusive of [18F]riluzole. The 18F‐labeling of these medicinally important motifs expands the radiochemical space available for PET applications. 相似文献