- Oxygenation of alkane C-H bonds with methyl(trifluoromethyl)dioxirane: Effect of the substituents and the solvent on the reaction rate
-
The mechanism of the oxygenation of alkane C-H bonds with methyl(trifluoromethyl)dioxirane (1a) is studied through the effect of the substituent and solvent on the rate of oxygenation of 2-substituted adamantanes (2). The results suggest a remarkable elec
- Gonzalez-Nunez, Maria E.,Royo, Jorge,Mello, Rossella,Baguena, Minerva,Ferrer, Jaime Martinez,De Arellano, Carmen Ramirez,Asensio, Gregorio,Prakash, G. K. Surya
-
-
Read Online
- Hyperconjugative control by remote substituents of diastereoselectivity in the oxygenation of hydrocarbons
-
(figure presented) The oxidation of 2-substituted adamantanes (2) with TFDO (1) is reported. The data show a stereodifferentiation of the chemical environments induced by remote electron-withdrawing substituents which produces remarkable Z/E diastereosele
- Gonzalez-Nunez, Maria E.,Royo, Jorge,Castellano, Gloria,Andreu, Cecilia,Boix, Carmen,Mello, Rossella,Asensio, Gregorio
-
-
Read Online
- SYNTHESES AND 13C NMR SPECTRA OF FLUORINATED ADAMANTANE DERIVATIVES
-
The syntheses of a variety of fluorine-containing adamantane derivatives are described.The 13C NMR spectra of those compounds with different configurations are interpreted in terms of through-bond and through-space substituent interactions.
- Duddeck, Helmut,Islam, Md. Rabiul
-
-
Read Online
- ELECTROPHILIC ATTACK OF ELEMENTAL FLUORINE ON ORGANIC HALOGENS. SYNTHESIS OF FLUOROADAMANTANES
-
Elemental fluorine acts on bromo- and iodoadamantanes in an electrophilic mode to produce the corresponding fluoroadamantanes.The course of the reaction was investigated in several solvents.It was found that the best yields of the fluoroadamantanes were obtained when Freon (CFCl3) or Freon-chloroform was used.Using methylene chloride as a solvent with iodoadamantanes-but not with the bromo derivatives-resulted in considerable amounts of the corresponding chloro compounds.
- Rozen, Shlomo,Brand, Michael
-
-
Read Online
- Applications of the bloch-siegert shift in solid-state proton-dipolar-decoupled 19F MAS NMR
-
In solid-state proton-dipolar-decoupled 19F MAS NMR spectroscopy, 19F chemical-shift data need to be corrected for the BlochSiegert shift. Assigning the single sharp 19F resonance of 2-fluoroadamantane to its proton-coupled 19F shift of -174.4 ppm results in chemical-shift referencing that is independent of the amplitude of the proton-decoupling field. The Bloch-Siegert shift is also a useful tool to characterize the amplitude and homogeneity of the proton-decoupling field, H1H, and to monitor probe performance. Considerable inhomogeneity in H1H along the long axis of the rightcylinder sample rotor was detected. In our commercial 7 mm H-F MAS probe, the proton field strength, A HH1H, decreases to 25% of the maximum value across the usable sample volume. Measurement of the Bloch-Siegert shift revealed that the proton-decoupling field strength decreases during the first few scans of an acquisition. Reductions in the proton field strengths can exceed 10%, and they are explained by the heating of the RF coil circuitry which is caused by high-power proton decoupling. The extent of reduction in field amplitude is a function of the decoupling duty cycle. Losses in A HH1H can be avoided by tuning the probe proton RF circuitry at the operating temperature of the probe, using the Bloch-Siegert shift as an optimization parameter.
- Vierkoetter, Stephanie A.
-
-
Read Online
- FLUORINATION WITH CAESIUM FLUOROXYSULPHATE. PART XI. MILD FUNCTIONALIZATION OF SATURATED HYDROCARBONS
-
Several hydrocarbons reacted with caesium fluoroxysulphate in acetonitrile at 35 deg C yielding mono and disubstituted products.Fluorocyclohexane, fluorocycloheptane, and 2-exo-fluoronorbornane formed in the reactions with the corresponding hydrocarbons were accompanied by up to 15percent of other unidentified fluoro products, but their amount was strongly diminished when fluoronation was performed in the presence of nitrobenzene.Fluorination of adamantane resulted in 1-fluoro, 2-fluoro, and 1,3-difluoro substituted products, with the substitution at the tertiary carbon atom strongly predominating.The presence of nitrobenzene did not influence the rate of reaction and the product distribution when the reaction was carried out in acetonitrile, while the introduction of methanol or methanol and nitrobenzene into the reaction mixture slowed down the reaction, with no evidence of the presence of methoxy derivatives.
- Stavber, Stojan,Zupan, Marko
-
-
Read Online
- Photoredox-catalyzed deoxyfluorination of activated alcohols with Selectfluor
-
Herein we disclose a deoxyfluorination of alcohols with an electrophilic fluorine source via visible-light photoredox catalysis. This radical-mediated C–F coupling is capable of fluorinating secondary and tertiary alcohols efficiently, complementing previously reported nucleophilic deoxyfluorination protocols.
- González-Esguevillas, María,Miró, Javier,Jeffrey, Jenna L.,MacMillan, David W.C.
-
supporting information
p. 4222 - 4227
(2019/06/13)
-
- 2-Substituted and 2,2-disubstituted adamantane derivatives as models for studying substituent chemical shifts and C-Hax?Yax cyclohexane contacts - results from experimental and theoretical NMR spectroscopic chemical shifts and DFT structures
-
Abstract The complete 1H and 13C NMR chemical shifts assignment for various 2-substituted and 2,2-disubstituted adamantane derivatives 1-38 in CDCl3 solution was realized on the basis of NMR experiments combined with chemical structure information and DFT-GIAO (B3LYP/6-31+G(d,p)-GIAO) calculations of chemical shifts in solution. Substituent-induced 13C NMR chemical shifts (SCS) are discussed. C-Hax?Yax contacts are a textbook prototype of steric hindrance in organic chemistry. The nature of these contacts will be further investigated in this work on basis of new adamantane derivatives, which are substituted at C-2 to provide models for 1,4-C-Hax?Yax and 1,5-C-Hax?Yax contacts. The B3LYP/6-31+G(d,p) calculations predicted the presence of NBO hyperconjugative attractive interactions between C-Hax and Yax groups along C-Hax?Yax contacts. The 1H NMR signal separation, Δδ(γ-CH2), reflects the strength of the H-bonded C-Haxa?Yax contact.
- Kolocouris, Antonios,Koch, Andreas,Kleinpeter, Erich,Stylianakis, Ioannis
-
p. 2463 - 2481
(2015/03/30)
-
- C-HALOGEN BOND FORMATION
-
Methods of halogenating a carbon containing compound having an sp3 C-H bond are provided. Methods of fluorinating a carbon containing compound comprising halogenation with Cl or Br followed by nucleophilic substitution with F are provided. Methods of direct oxidative C-H fluorination of a carbon containing compound having an sp3 C-H bond are provided. The halogenated products of the methods are provided.
- -
-
Paragraph 0139-0140; 0142-0144; 0151; 0163-0164
(2013/03/26)
-
- Oxidative aliphatic C-H fluorination with fluoride ion catalyzed by a manganese porphyrin
-
Despite the growing importance of fluorinated organic compounds in drug development, there are no direct protocols for the fluorination of aliphatic C-H bonds using conveniently handled fluoride salts. We have discovered that a manganese porphyrin complex catalyzes alkyl fluorination by fluoride ion under mild conditions in conjunction with stoichiometric oxidation by iodosylbenzene. Simple alkanes, terpenoids, and even steroids were selectively fluorinated at otherwise inaccessible sites in 50 to 60% yield. Decalin was fluorinated predominantly at the C2 and C3 methylene positions. Bornyl acetate was converted to exo-5-fluoro-bornyl acetate, and 5a-androstan-17-one was fluorinated selectively in the A ring. Mechanistic analysis suggests that the regioselectivity for C-H bond cleavage is directed by an oxomanganese(V) catalytic intermediate followed by F delivery via an unusual manganese(IV) fluoride that has been isolated and structurally characterized.
- Liu, Wei,Huang, Xiongyi,Groves, John T.,Cheng, Mu-Jeng,Nielsen, Robert J.,Goddard III, William A.
-
p. 1322 - 1325,4
(2020/08/31)
-
- METHOD OF FLUORINATION
-
A method of fluorination comprising reacting monosaccharides, oligosaccharides, polysaccharides, composite saccharides formed by bonding of these saccharides with proteins and lipids and saccharides having polyalcohols, aldehydes, ketones and acids of the polyalcohols, and derivatives and condensates of these compounds with a fluorinating agent represented by general formula (I) thermally or under irradiation with microwave or an electromagnetic wave having a wavelength around the microwave region. In accordance with the method, the fluorination at a selected position can be conducted safely at a temperature in the range of 150 to 200°C where the reaction is difficult in accordance with conventional methods. The above method comprising the irradiation with microwave or an electromagnetic wave having a wavelength around the microwave region can be applied to substrates other than saccharides. When a complex compound comprising HF and a base is reacted under irradiation with microwave, fluorination at a specific position which is difficult in accordance with conventional methods proceeds highly selectively, efficiently in a short time and safely.
- -
-
Page/Page column 16-17
(2008/06/13)
-
- Elementalfluorine. Part 14.1 Electrophilic fluorination and nitrogen functionalisation of hydrocarbons
-
Selective fluorination of a range of hydrocarbons was achieved by reaction with either elemental fluorine or Selectfluor, an electrophilic fluorinating reagent of the N-F class. An electrophilic mechanism is envisaged. On prolonged reaction, the strongly acidic reaction medium that is formed upon substitution of hydrogen by fluorine when Selectfluor is used as the fluorinating reagent, promotes loss of fluoride from the initial fluorinated product. Trapping of the subsequent carbocation by the acetonitrile solvent in a Ritter type process gives overall nitrogen functionalisation of hydrocarbons. Amidation of hydrocarbons could also be achieved in a one-stage process by reaction of the hydrocarbon with fluorine and a Lewis acid, such as boron trifluoride-diethyl ether, in acetonitrile.
- Chambers, Richard D.,Kenwright, Alan M.,Parsons, Mandy,Sandford, Graham,Moilliet, John S.
-
p. 2190 - 2197
(2007/10/03)
-
- 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine: A new selective fluorinating agent
-
The title compound has been prepared in 96-98% yield by the reaction of tetrafluoroethylene and dimethylamine. 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine (1) is found to be an effective reagent for the conversion of alcohols into alkyl fluorides. Reaction of 1 and primary alcohols proceeds with high yield formation of the corresponding alkyl fluorides at elevated temperature. However, the reaction of secondary and tertiary alcohols rapidly takes place at 0-10°C, producing corresponding alkyl fluorides as major product along with some olefins.
- Petrov,Swearingen,Hong,Chris Petersen
-
-
- A convenient synthesis of trifluoromethyl ethers by oxidative desulfurization-fluorination of dithiocarbonates
-
Trifluoromethyl ethers R-OCF3 are easily synthesized from the corresponding dithiocarbonates R-OCS2Me (R = aryl or primary alkyl) by a reagent system consisting of 70% HF/pyridine and an N-halo imide. When the reaction is applied to R-OCS2Me wherein R = secondary alkyl, tertiary alkyl, or benzylic group, fluorination leading to the corresponding alkyl fluorides R-F is achieved, whereas a combination of 50% HF/pyridine and N- bromosuccinimide affords the corresponding trifluoromethyl ethers R-OCF3 (R = secondary).
- Kanie, Kiyoshi,Tanaka, Yoichiro,Suzuki, Kazundo,Kuroboshi, Manabu,Hiyama, Tamejiro
-
p. 471 - 484
(2007/10/03)
-
- Fluorination of secondary and primary alcohols by thermal decomposition of electrochemically generated alkoxy triphenylphosphonium tetrafluoroborates
-
Replacement of hydroxyl groups in secondary and primary alcohols (1) with a fluorine atom arising from tetrafluoroborate anion has been performed by the electrochemical formation of alkoxy triphenylphosphonium tetrafluoroborates (2) from 1, followed by their thermal decomposition. The procedure is quite simple, involving: (1) constant-current electrolysis of a mixture of 1, Ph3P, and Ph3PH·BF4 in CH2Cl2 in an undivided cell; (2) refluxing a tetrahydrofuran or dioxane solution of the residue afforded by evaporation of the solvent in vacuo after the electrolysis. Cyclic secondary alcohols such as 3β-hydroxy steroids and 2-adamantanol are transformed into the corresponding fluorides in satisfactory yields when the geometry of the leaving group in 2 is suitable for the substitution or an elimination process for 2 to give an alkene is stereochemically forbidden. The fluorination of steroidal alcohols and 4-phenyl-1-cyclohexanol proceeded with complete inversion, demonstrating that a fluorine atom from the tetrafluoroborate anion attacks from the side opposite to the phosphonium moiety in 2 via an SN2 mechanism rather than an SN1 mechanism. The fluorination of acyclic secondary and primary alcohols was performed by the present method in reasonable yields, although the reaction for the latter required more forcing conditions, such as refluxing in dioxane.
- Maeda, Hatsuo,Koide, Takashi,Matsumoto, Sayaka,Ohmori, Hidenobu
-
p. 1480 - 1483
(2007/10/03)
-
- Observations on the Reaction of Xanthate Esters with 4-Methyl(difluoroiodo)benzene: a New Method for the Conversion of Alcohols to Alkyl Fluorides
-
Treatment of a range of S-methyldithiocarbonates (xanthates) with 4-methyl(difluoroiodo)benzene gives the corresponding alkyl fluorides.
- Koen, Mark J.,Guyader, Frederic Le,Motherwell, William B.
-
p. 1241 - 1242
(2007/10/02)
-
- Poly-4-vinylpyridinium poly(hydrogen fluoride): A solid hydrogen fluoride equivalent reagent
-
Poly-4-vinylpyridinium poly(hydrogen fluoride) (PVPHF), containing 35-60% hydrogen fluoride by weight, was prepared as a solid hydrogen fluoride equivalent reagent. PVPHF with 60% hydrogen fluoride by weight was found to be a versatile fluorinating agent for the hydrofluorination and bromofluorination of alkanes and alkynes, fluorination of alcohols as well as other fluorination reactions. Low hydrogen fluoride content PVPHF (3 equivalents of hydrogen fluoride to 1 equivalent of 4-vinylpyridine unit) was also found to be an efficient reagent for bromofluorination of alkenes in the presence of 1,3-dibromo-5,5-dimethylhydrantoin. Fluorosulfonic acid-modified PVPHF showed enhanced reactivities for the fluorination of secondary alcohols.
- Olah,Li,Wang,Surya Prakash
-
p. 693 - 699
(2007/10/02)
-
- Transmission of Polar Substituent Effects in the Adamantane Ring System As Monitored by 19F NMR: Hyperconjugation as a Stereoinductive Factor
-
A limited series of (E)- and (Z)-5-substituted adamant-2-yl fluorides 8 and 9, respectively, has been synthesized and characterized, and 19F chemical shifts have been measured in several solvents.A wide range of 19F substituent chemical shifts (SCS, ppm)
- Adcock, William,Trout, Neil A.
-
p. 3229 - 3238
(2007/10/02)
-
- Thermically-Initiated Fluorinations at Saturated Carbon Atoms with Xenon Difluoride
-
The heating of several hydrocarbons with xenon difluoride at 95-120 deg C in stainless steel reactor equipped with teflon jackets resulted in mono-, di-, and trisubstituted products.
- Zajc, Barbara,Zupan, Marko
-
p. 1659 - 1661
(2007/10/02)
-
- FLUORINE DERIVATIVES OF ADAMANTANE. VIII. FLUORINATION OF TRIMETHYLSILOXY DERIVATIVES OF ADAMANTANE BY SULFUR TETRAFLUORIDE
-
By the action of sulfur tetrafluoride, 1-(trimethylsiloxy)- and 2-(trimethylsiloxy)adamantanes are converted into 1-fluoro- and 2-fluoroadamantanes respectively. 2-(Trimethylsiloxy)-2-adamantanecarbonitrile reacts with sulfur tetrafluoride to form 2-fluoro-2-adamantanecarbonitrile.Fluorination of (trimethylsiloxyalkyl)adamantanes by sulfur tetrafluoride takes place either with retention of the adamantane structure or with isomerization to derivatives of homoadamantane, depending on the nature of the substituents in the side chain.
- Sorochinskii, A. E.,Aleksandrov, A. M.,Gamaleya, V. F.,Kukhar', V. P.
-
p. 1461 - 1466
(2007/10/02)
-