- Regio- and chemoselectivity in S- and O- difluoromethylation reactions using diethyl (bromodifluoromethyl)phosphonate
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The effective difluoromethylations of various S- and O- based- nucleophiles, presenting a wide range of pKa values, using diethyl(bromodifluoromethyl) phosphonate (1) under basic conditions is described. These reactions, which rely on the quantitative generation of difluorocarbene formed through the hydrolysis of 1, were found to be effective only once the starting materials had pKa values of less than ca. 11. Importantly, in cases in which the substrates held two or three nucleophilic centers this feature was successfully implemented to achieve a high chemo- or regioselective difluoromethylation of the center exhibiting the lowest pKa value and the highest polarizability.
- Amir, Dafna,Binyamin, Iris,Drug, Eyal,Fridkin, Gil,Gershonov, Eytan,Marciano, Daniele,Redy-Keisar, Orit,Yehezkel, Lea,Zafrani, Yossi
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- Redox-Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C?H Di- and Trifluoromethoxylation
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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.
- Lee, Johnny W.,Lim, Sanghyun,Maienshein, Daniel N.,Liu, Peng,Ngai, Ming-Yu
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supporting information
p. 21475 - 21480
(2020/10/02)
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- Difluoromethylation of Phenols and Thiophenols with the S-(Difluo-romethyl)sulfonium Salt: Reaction, Scope, and Mechanistic Study
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A facile and practical approach for the difluoromethylation of phenols and thiophenols was described. Making use of the recently developed bench-stable S-(difluoromethyl)sulfonium salt as the difluorocarbene precursor, a wide variety of diversely functionalized phenols and thiophenols were readily converted to their corresponding aryl difluoromethyl ethers in good to excellent yields in the presence of lithium hydroxide. Chemoselectivity of various O,S-nucleophiles toward difluorocarbene was systematically studied, suggesting the reactivity order ArS- > RS-, ArO- > ROH > RO-, ArSH, ArOH, RSH.
- Liu, Guo-Kai,Qin, Wen-Bing,Li, Xin,Lin, Li-Ting,Wong, Henry N. C.
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p. 15948 - 15957
(2019/11/16)
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- Catalytic radical difluoromethoxylation of arenes and heteroarenes
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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.
- Lee, Johnny W.,Zheng, Weijia,Morales-Rivera, Cristian A.,Liu, Peng,Ngai, Ming-Yu
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p. 3217 - 3222
(2019/03/21)
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- DIFLUOROMETHOXYLATION AND TRIFLUOROMETHOXYLATION COMPOSITIONS AND METHODS FOR SYNTHESIZING SAME
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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.
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Page/Page column 75; 79; 89; 92
(2019/09/18)
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- Visible-Light Photoredox Difluoromethylation of Phenols and Thiophenols with Commercially Available Difluorobromoacetic Acid
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A simple and efficient visible-light photoredox one-pot method for difluoromethylation of phenols and thiophenols has been developed. The protocol uses commercially available, inexpensive, and easy handling difluorobromoacetic acid as the difluoromethylating agent, and the diverse O- and S-difluoromethylated products were prepared in good yields with tolerance of many functional groups.
- Yang, Jinyan,Jiang, Min,Jin, Yunhe,Yang, Haijun,Fu, Hua
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supporting information
p. 2758 - 2761
(2017/05/24)
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- Xenon Difluoride Mediated Fluorodecarboxylations for the Syntheses of Di- and Trifluoromethoxyarenes
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XeF2 is demonstrated to be a more proficient fluorine-transfer reagent than either NFSI or Selectfluor in fluorodecarboxylations of both mono- and difluoroaryloxy acetic acid derivatives. This method efficiently converts a wide range of neutral and electron-poor substrates to afford the desired di- and trifluoromethyl aryl ethers in good to excellent yields. The purifications are facile, and the reaction times are less than 5 min, which makes these fluorodecarboxylations promising for future PET-imaging applications.
- Chatalova-Sazepin, Claire,Binayeva, Meruyert,Epifanov, Maxim,Zhang, Wei,Foth, Paul,Amador, Carolyn,Jagdeo, Manu,Boswell, Benjamin R.,Sammis, Glenn M.
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p. 4570 - 4573
(2016/09/28)
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- Decarboxylative Trifluoromethylating Reagent [Cu(O2CCF3)(phen)] and Difluorocarbene Precursor [Cu(phen)2][O2CCF2Cl]
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This article describes the new economic decarboxylative trifluoromethylating reagent [Cu(phen)(O2CCF3)] (1; phen=1,10-phenanthroline) and the efficient difluorocarbene precursor [Cu(phen)2][O2CCF2Cl] (2). Treatment of copper tert-butoxide with phen and subsequent addition of trifluoroacetic acid or chlorodifluoroacetic acid afforded air-stable complexes 1 and 2, respectively, which were characterized by X-ray crystallography. The copper(I) ion in 1 is coordinated by a bidentate phen ligand, a monodentate trifluoroacetate group, and a molecule of CH3CN in a distorted tetrahedral coordination geometry. The molecular structure of 2 adopts an ionic form that consists of a [Cu(phen)2]+ cation and a chlorodifluoroacetate anion. Complex 1 reacted with a variety of aryl and heteroaryl halides to form trifluoromethyl (hetero)arenes in good yields. The corresponding Hammett plot exhibited a linear relationship and a reaction parameter (ρ)=+0.56±0.02, which indicated that the trifluoromethylation reaction proceeded via a nucleophilic reactive species. Complex 2 reacts with phenols to produce aryl difluoromethyl ethers in modest-to-excellent yields. Mechanistic investigations revealed that the difluoromethylation reaction proceeds by initial copper-mediated formation of difluorocarbene and subsequent concerted addition of difluorocarbene to the phenol to form a three-center transition state.
- Lin, Xiaoxi,Hou, Chuanqi,Li, Haohong,Weng, Zhiqiang
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supporting information
p. 2075 - 2084
(2016/02/12)
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- 18F-Labeling of Aryl-SCF3, -OCF3 and -OCHF2 with [18F]Fluoride
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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. A halogen exchange (halex) 18F-fluorination process offers access for the first time to 18F-labeled arylOCF3, arylOCHF2 and arylSCF3, three motifs of established medicinal importance in PET radiotracers. The use of silver(I) triflate is critical to permit 18F-labeling under mild conditions.
- Khotavivattana, Tanatorn,Verhoog, Stefan,Tredwell, Matthew,Pfeifer, Lukas,Calderwood, Samuel,Wheelhouse, Katherine,Leecollier, Thomas,Gouverneur, Vronique
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supporting information
p. 9991 - 9995
(2015/08/19)
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- Fluorine in drug design: A case study with fluoroanisoles
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Anisole and fluoroanisoles display distinct conformational preferences, as evident from a survey of their crystal structures. In addition to altering the free ligand conformation, various degrees of fluorination have a strong impact on physicochemical and pharmacokinetic properties. Analysis of anisole and fluoroanisole matched molecular pairs in the Pfizer corporate database reveals interesting trends: 1) PhOCF3 increases log D by ～1 log unit over PhOCH3 compounds; 2) PhOCF3 shows lower passive permeability despite its higher lipophilicity; and 3) PhOCF3 does not appreciably improve metabolic stability over PhOCH3. Emerging from the investigation, difluoroanisole (PhOCF2H) strikes a better balance of properties with noticeable advantages of log D and transcellular permeability over PhOCF3. Synthetic assessment illustrates that the routes to access difluoroanisoles are often more straightforward than those for trifluoroanisoles. Whereas replacing PhOCH3 with PhOCF3 is a common tactic to optimize ADME properties, our analysis suggests PhOCF2H may be a more attractive alternative, and greater exploitation of this motif is recommended.
- Xing, Li,Blakemore, David C.,Narayanan, Arjun,Unwalla, Ray,Lovering, Frank,Denny, R. Aldrin,Zhou, Huanyu,Bunnage, Mark E.
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p. 715 - 726
(2015/04/14)
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- Three step procedure for the preparation of aromatic and aliphatic difluoromethyl ethers from phenols and alcohols using a chlorine/fluorine exchange methodology
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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.
- Dolbier Jr., William R.,Wang, Fei,Tang, Xiaojun,Thomoson, Charles S.,Wang, Linhua
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- Use of fluoroform as a source of difluorocarbene in the synthesis of N-CF2H heterocycles and difluoromethoxypyridines
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Fluoroform is used as a source of difluorocarbene to convert various N-, O-, and C-nucleophiles to their difluoromethylated derivatives. Imidazole, benzimidazole, benztriazole, hydroxypyridines, and their derivatives underwent reaction at moderate temperatures and atmospheric pressure, using potassium hydroxide as base in a two-phase (water/acetonitrile) process to provide moderate to good yields of the respective products. Nitrophenols required addition of a co-solvent (methanol) to obtain good yields of products.
- Thomoson, Charles S.,Wang, Linhua,Dolbier, William R.
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- SYNTHESIS OF DIFLUOROMETHYL ETHERS AND SULFIDES
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The synthesis of difluoromethyl ethers and sulfides with a simple, non-ozone- depleting reagent is described. The difluoromethylation of phenols with this reagent occurs at room temperature within minutes with exceptional functional group tolerance. The mild conditions makes possible tandem processes for the conversion of aryl boronic acids, aryl halides and arenes to difluoromethyl ethers. Mechanistic studies support a reaction pathway involving nucleophilic attack of the phenolate to difluorocarbene.
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Paragraph 00157-00162
(2014/07/22)
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- Use of fluoroform as a source of difluorocarbene in the synthesis of difluoromethoxy- and difluorothiomethoxyarenes
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Fluoroform, CHF3, a non-ozone-depleting, nontoxic, and inexpensive gas can be used as a difluorocarbene source in a process for the conversion of phenols and thiophenols to their difluoromethoxy and difluorothiomethoxy derivatives. The reactions are carried out at moderate temperatures and atmospheric pressure, using potassium hydroxide as base in a two-phase (water/dioxane or water/acetonitrile) process to provide moderate to good yields of the respective products.
- Thomoson, Charles S.,Dolbier, William R.
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p. 8904 - 8908
(2013/09/24)
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- Structure-activity relationship studies and sleep-promoting activity of novel 1-chloro-5,6,7,8-tetrahydroimidazo[1,5-a]pyrazine derivatives as dual orexin receptor antagonists. Part 2
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Replacement of the dimethoxyphenyl moiety in the core skeleton of almorexant by appropriately substituted imidazoles afforded novel 1-chloro-5,6,7,8-tetrahydroimidazo[1,5-a]pyrazine derivatives as potent dual orexin receptor antagonists. We describe in th
- Sifferlen, Thierry,Koberstein, Ralf,Cottreel, Emmanuelle,Boller, Amandine,Weller, Thomas,Gatfield, John,Brisbare-Roch, Catherine,Jenck, Francois,Boss, Christoph
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p. 3857 - 3863
(2013/07/27)
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- Photo-fluorodecarboxylation of 2-aryloxy and 2-aryl carboxylic acids
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Coming to light: The title reaction simply requires an aqueous alkaline solution of Selectfluor and light. The method is inexpensive and effective for a wide range of neutral and electron-poor 2-aryloxy and 2-aryl acetic acids to provide fluoromethyl ethers (see scheme) and benzyl fluorides, respectively. The mechanism most likely proceeds through an initial aryl excitation with a subsequent single-electron transfer. Copyright
- Leung, Joe C. T.,Chatalova-Sazepin, Claire,West, Julian G.,Rueda-Becerril, Montserrat,Paquin, Jean-Fran?ois,Sammis, Glenn M.
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p. 10804 - 10807
(2013/01/15)
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- Oxidation of primary aliphatic and aromatic aldehydes with difluoro(aryl)-λ3-bromane
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Oxidation of primary aliphatic aldehydes with p- trifluoromethylphenyl(difluoro)-λ3-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses.
- Ochiai, Masahito,Yoshimura, Akira,Hoque, Md. Mahbubul,Okubo, Takuji,Saito, Motomichi,Miyamoto, Kazunori
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supporting information; experimental part
p. 5568 - 5571
(2011/12/03)
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- Chlorodifluoromethyl phenyl sulfone: A novel non-ozone-depleting substance-based difluorocarbene reagent for O- and N-difluoromethylations
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Chlorodifluoromethyl phenyl sulfone, a previously unknown compound that can be readily prepared from non-ODS-based precursors, was found to act as a robust difluorocarbene reagent for O- and N-difluoromethylations. The Royal Society of Chemistry.
- Zheng, Ji,Li, Ya,Zhang, Laijun,Hu, Jinbo,Meuzelaar, Gerrit Joost,Federsel, Hans-Juergen
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p. 5149 - 5151
(2008/09/18)
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- 2-Chloro-2,2-difluoroacetophenone: A non-ODS-based difluorocarbene precursor and its use in the difluoromethylation of phenol derivatives
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A novel and non-ODS-based (ODS = ozone-depleting substance) preparation of 2-chloro-2,2-difluoroacetophenone (1) was achieved in high yield by using 2,2,2-trifluoroacetophenone as the starting material. Compound 1 was found to act as a good difluorocarbene reagent, which readily reacts with a variety of structurally diverse phenol derivatives 4 in the presence of potassium hydroxide or potassium carbonate to produce aryl difluoromethyl ethers 5 in good yields. This new and easy-to-handle synthetic methodology offers an environmentally friendly alternative to other Freon- or Halon-based difluoromethylating approaches.
- Zhang, Laijun,Zheng, Ji,Hu, Jinbo
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p. 9845 - 9848
(2007/10/03)
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- N-Isoxazolyl-biphenylsulfonamide derivatives, their preparation and their use as endothelin antagonists
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A compound of the formula I an enantiomer, diastereomer or pharmaceutically acceptable salt thereof, wherein: one of X and Y is N and the other is O; R2,R3,R4 and R5 are each independently (a) hydrogen;(b) alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl, cycloalkylalkyl, cycloalkenyl, cycloalkenylalkyl, aryl, aryloxy, aralkyl or aralkoxy, any of which may be substituted with Z1, Z2 and Z3;(c) halo;(d) hydroxyl;(e) cyano;(f) nitro;(g)-C(O)H or-C(O)R6;(h)-CO2H or-CO2R6;(i)-SH,-S(O)nR6 ,-S(O)m-OH,-S(O)m-OR6,-O-S(O)m-R6,-O-S(O)mOH or-O-S(O)m-OR6;(j)-Z4-NR7R8; or(k)-Z4-N(R11)-Z5-NR9 R10; R4 and R5 together are alkylene or alkenylene, either of which may be substituted with Z1,Z2 and Z3, completing a 4-to 8-membered saturated, unsaturated or aromatic ring together with the carbon atoms to which they are attached; G1 is (a) hydrogen; or(b) alkyl; G2 is (a) hydroxyalkyl;(b)-(CH2)mOR6; or(c)-(CH2)m-NR12 R13;(d) mono-to hexa-halo substituted alkyl; or(e)-(CH2)n OR14; and the remaining symbols are as defined in the description.The compounds of formula I are antagonists of ET-1, ET-2 and /or ET-3 and are useful in treatment of conditions associated with increased ET levels (e.g., dialysis, trauma and surgery) and of all endothelin-dependent disorders. They are thus inter alia useful as antihypertensive agents.
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- Fluorinated liquid crystal compounds and liquid crystal medium containing same
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The invention relates to liquid crystal compounds having a terminal structure in accordance with formula 1, 2, 3 or 4: wherein A2, A3, X1 and X2 and are defined herein. The invention further relates liquid c
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- SYNTHESIS AND REACTIONS OF DIFLUOROMETHOXY- AND DIFLUOROCHLOROMETHOXY DERIVATIVES OF BENZENE
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Difluoromethoxybenzaldehydes were synthesized by difluoromethylation of aromatic o- and p-hydroxyaldehydes by chladone-22 in alkaline medium.Chlorination of the difluoromethoxybenzene derivatives under illumination gave difluorochloromethoxy benzene with various function groups (F, Cl, CN, COCl, COOH).The values of the ?-constants of the OCF2Cl group have been determined.In its electronic characteristics it is similar to the OCF3 group.
- Shelyazhenko, S. V.,Fialkov, Yu. A.,Yagupol'skii, L. M.
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p. 1317 - 1324
(2007/10/02)
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