458-92-4Relevant academic research and scientific papers
Redox-Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C?H Di- and Trifluoromethoxylation
Lee, Johnny W.,Lim, Sanghyun,Maienshein, Daniel N.,Liu, Peng,Ngai, Ming-Yu
supporting information, p. 21475 - 21480 (2020/10/02)
Applications of TEMPO. catalysis for the development of redox-neutral transformations are rare. Reported here is the first TEMPO.-catalyzed, redox-neutral C?H di- and trifluoromethoxylation of (hetero)arenes. The reaction exhibits a broad substrate scope, has high functional-group tolerance, and can be employed for the late-stage functionalization of complex druglike molecules. Kinetic measurements, isolation and resubjection of catalytic intermediates, UV/Vis studies, and DFT calculations support the proposed oxidative TEMPO./TEMPO+ redox catalytic cycle. Mechanistic studies also suggest that Li2CO3 plays an important role in preventing catalyst deactivation. These findings will provide new insights into the design and development of novel reactions through redox-neutral TEMPO. catalysis.
Catalytic radical difluoromethoxylation of arenes and heteroarenes
Lee, Johnny W.,Zheng, Weijia,Morales-Rivera, Cristian A.,Liu, Peng,Ngai, Ming-Yu
, p. 3217 - 3222 (2019/03/21)
Intermolecular C-H difluoromethoxylation of (hetero)arenes remains a long-standing and unsolved problem in organic synthesis. Herein, we report the first catalytic protocol employing a redox-active difluoromethoxylating reagent 1a and photoredox catalysts for the direct C-H difluoromethoxylation of (hetero)arenes. Our approach is operationally simple, proceeds at room temperature, and uses bench-stable reagents. Its synthetic utility is highlighted by mild reaction conditions that tolerate a wide variety of functional groups and biorelevant molecules. Experimental and computational studies suggest single electron transfer (SET) from excited photoredox catalysts to 1a forming a neutral radical intermediate that liberates the OCF2H radical exclusively. Addition of this radical to (hetero)arenes gives difluoromethoxylated cyclohexadienyl radicals that are oxidized and deprotonated to afford the products of difluoromethoxylation.
DIFLUOROMETHOXYLATION AND TRIFLUOROMETHOXYLATION COMPOSITIONS AND METHODS FOR SYNTHESIZING SAME
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Page/Page column 82, (2019/09/18)
The present invention provides a compound having the structure (I), a processing of making the compound; and a process of using the compound as a reagent for the difluoromethoxylation and trifluoromethoxylation of arenes or heteroarenes.
Fluorodecarboxylation: Synthesis of aryl trifluoromethyl ethers (ArOCF3) and thioethers (ArSCF3)
Krishanmoorthy, Sankarganesh,Schnell, Simon D.,Dang, Huong,Fu, Fang,Prakash, G.K. Surya
, p. 130 - 135 (2017/09/06)
Fluorodecarboxylation of aryloxydifluoroacetic acid (ArOCF2CO2H) and arylmercaptodifluoroacetic acid (ArSCF2CO2H) towards ArXCF3 (X = O, S) using silver (I) salts in the presence of Selectfluor in a biphasic system with trifluoroacetic acid additive is discussed.
Iron-Catalyzed Isopropylation of Electron-Deficient Aryl and Heteroaryl Chlorides
Sanderson, James N.,Dominey, Andrew P.,Percy, Jonathan M.
, p. 1007 - 1017 (2017/03/27)
Traditional methods for the preparation of secondary alkyl-substituted aryl and heteroaryl chlorides challenge both selectivity and functional group tolerance. This contribution describes the use of statistical design of experiments to develop an effective procedure for the preparation of isopropyl-substituted (hetero)arenes with minimal isopropyl to n-propyl isomerization. The reaction tolerates electronically diverse aryl chloride coupling partners, with excellent conversion observed for strongly electron-deficient aromatic rings, such as esters and amides. Electron-rich systems, including methyl- and methoxy-substituted aryl chlorides, were found to be less reactive. Furthermore, the reaction was found to be most successful when heteroaryl chlorides were submitted to the cross-coupling protocol. By mapping substituent effects on reaction selectivity, we were able to show that electron-deficient aryl chlorides are essential for efficient coupling, and use electronic structure calculations to predict the likelihood of successful coupling through the estimation of the electron affinity of each aryl chloride. Moderate isolated yields were achieved with selected aryl chlorides, and moderate to good isolated yields were obtained for all the heteroaryl chlorides coupled. Excellent selectivity was observed when a 2,6-dichloroquinoline was used, allowing mono-substitution on a challenging substrate. (Figure presented.).
Difluoromethyl bioisostere: Examining the lipophilic hydrogen bond donor concept
Zafrani, Yossi,Yeffet, Dina,Sod-Moriah, Gali,Berliner, Anat,Amir, Dafna,Marciano, Daniele,Gershonov, Eytan,Saphier, Sigal
, p. 797 - 804 (2017/02/05)
There is a growing interest in organic compounds containing the difluoromethyl group, as it is considered a lipophilic hydrogen bond donor that may act as a bioisostere of hydroxyl, thiol, or amine groups. A series of difluoromethyl anisoles and thioanisoles was prepared and their druglike properties, hydrogen bonding, and lipophilicity were studied. The hydrogen bond acidity parameters A (0.085-0.126) were determined using Abraham's solute 1H NMR analysis. It was found that the difluoromethyl group acts as a hydrogen bond donor on a scale similar to that of thiophenol, aniline, and amine groups but not as that of hydroxyl. Although difluoromethyl is considered a lipophilicity enhancing group, the range of the experimental Δlog P(water-octanol) values (log P(XCF2H) - log P(XCH3)) spanned from -0.1 to +0.4. For both parameters, a linear correlation was found between the measured values and Hammett σ constants. These results may aid in the rational design of drugs containing the difluoromethyl moiety.
Efficient Difluoromethylation of Alcohols Using TMSCF2Br as a Unique and Practical Difluorocarbene Reagent under Mild Conditions
Xie, Qiqiang,Ni, Chuanfa,Zhang, Rongyi,Li, Lingchun,Rong, Jian,Hu, Jinbo
supporting information, p. 3206 - 3210 (2017/03/17)
A general method for the efficient difluoromethylation of alcohols using commercially available TMSCF2Br (TMS=trimethylsilyl) as a unique and practical difluorocarbene source is developed. This method allows primary, secondary, and even tertiary alkyl difluoromethyl ethers to be synthesized under weakly basic or acidic conditions. The reaction mainly proceeds through the direct interaction between a neutral alcohol and difluorocarbene, which is different from the difluoromethylation of phenols. Moreover, alcohols containing other moieties that are also reactive toward difluorocarbene can be transformed divergently by using TMSCF2Br. This research not only solves the synthetic problem of difluorocarbene-mediated difluoromethylation of alcohols, it also provides new insights into the different reaction mechanisms of alcohol difluoromethylation and phenol difluoromethylation with difluorocarbene species.
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-promoted decomposition of difluorocarbene and the subsequent trifluoromethylation
Zheng, Jian,Lin, Jin-Hong,Deng, Xiao-Yun,Xiao, Ji-Chang
, p. 532 - 535 (2015/03/04)
Difluorocarbene derived from various carbene precursors could be effectively decomposed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). This decomposition process was successfully applied in the subsequent trifluoromethylation of a variety of (hetero)aryl iodides without the addition of an external fluoride ion. Mechanistic investigation revealed the detailed difluorocarbene conversion process in which the decomposed difluorocarbene is finally transformed into a fluoride ion and carbon monoxide.
Three step procedure for the preparation of aromatic and aliphatic difluoromethyl ethers from phenols and alcohols using a chlorine/fluorine exchange methodology
Dolbier Jr., William R.,Wang, Fei,Tang, Xiaojun,Thomoson, Charles S.,Wang, Linhua
, p. 72 - 76 (2014/03/21)
Difluoromethyl ethers are prepared from phenols in three steps via their respective formate ester derivatives. The formates are first converted to dichloromethyl ethers by treatment with PCl5. These ethers are then induced to undergo chlorine/fluorine exchange to form the respective difluoromethyl ethers. The chlorine/fluorine exchange is carried out by either a room temperature, solvolytic process using THF-5HF or Et3N-3HF as exchange medium, where HF is the ultimate source of fluorine, or by a direct displacement process in sulfolane at 125 C, where KF is the source of fluorine. By one or another of these processes, virtually all phenols, electron-rich and electron-poor, can be converted to their respective difluoromethyl ethers in good yields. Aliphatic alcohols are also able to be converted to their difluoromethyl ether derivatives using the Et3N-3HF exchange medium.
DIFLUOROCARBENE FROM FLUOROFORM FOR PREPARATION OF DIFLUOROMETHYOXYARENES, DIFLUOROTHIOMETHOXYARENES AND HETEROARENES
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Page/Page column 4, (2014/08/06)
A method for the transformation of hydroxyarenes, hydroxyheteroarenes, thiohydroxyarenes or thiohydroxyheteroarenes involves reaction with fluoroform in the presence of base comprising solution to yield a difluoromethoxyarene, diflurothiomethoxyheteroarene, or diflurothiomethoxyheteroarene. The transformation can be carried out at ambient room pressure or at elevated pressures. The transformation can be carried out at temperatures of 0 to 70 °C.
