Reaction Prediction Continued Potassium Plus Fluorine

Potassium Fluoride

The neutral potassium fluoride and nitrite-containing solution is fed to the bipolar membrane electrodialysis unit in which the salts are converted to the corresponding acids and potassium hydroxide.

From: Comprehensive Membrane Science and Engineering , 2010

Attachment at Ring Positions

Gordon W. Gribble , ... Qi-Xian Lin , in Pyridines: from lab to production, 2013

2-(Trifluoromethyl)pyridine ³⁵⁶

Potassium fluoride (6.4  g, 0.11   mol) and cuprous iodide (21   g, 0.11   mol) were thoroughly mixed and flame heated under gentle shaking and at reduced pressure (1   Torr) during some 30   min until a greenish colour appeared. 2-Iodopyridine (21   g, 0.10   mol), (trifluoromethyl)trimethylsilane (15   mL, 14   g, 0.10   mol), anhydrous N,N-dimethylformamide (0.10   L), and anhydrous N-methylpyrrolidone (0.10   L) were added and the slurry, which eventually became a brown solution, was vigorously stirred for 6   h at 25   °C before being poured into 6.4   M aqueous ammonia (0.20   L). The product was then extracted with diethyl ether (3   ×   0.10   L). The combined organic layers were washed with 6.4   M aqueous ammonia (3   ×   50   mL), 1.0   M hydrochloric acid, a saturated aqueous solution (0.10   L) of sodium hydrogen carbonate and brine (0.10   L), dried, and the solvents evaporated. Upon distillation, a colourless oil was collected, bp: 138–140   °C; yield: 10.0   g (68%). ¹H NMR: δ 8.74 (d, J  =   4.7   Hz, 1H), 7.89 (tm, J  =   7.8   Hz, 1H), 7.70 (d, J  =   7.9   Hz, 1H), 7.50 (ddm, J  =   7.4, 4.8   Hz, 1H).

Goossen and co-workers have introduced potassium (trifluoromethyl)trimethoxyborate as a new trifluoromethyl nucleophile in copper-catalysed trifluoromethylation reactions. ³⁶³ Thus, both 5-bromo-2-iodopyridine 415 and 3-iodopyridine 51 are converted in good yield to 5-bromo-2-(trifluoromethyl)pyridine 416 and 3-(trifluoromethyl)pyridine 417, respectively.

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Transition Elements, Lanthanides and Actinides

S. Riedel , in Comprehensive Inorganic Chemistry II (Second Edition), 2013

2.08.3.4 Period IV – K–Kr

2.08.3.4.1 Potassium

Potassium fluoride can be prepared from its hydroxides or carbonates in HF. Similar to other alkali fluorides, it is a white crystalline solid which crystallizes in the NaCl structure. ^{69, 91, 179} In the gas phase, KF forms higher oligomers of dimers and trimers, which have been observed in mass spectroscopy experiments. ⁶⁴ Furthermore, their IR spectra have been recorded under cryogenic conditions in Ar by matrix-isolation spectroscopy. ^{65, 66}

2.08.3.4.2 Calcium

CaF₂ can be prepared from the respective carbonate by reaction with excess HF: CaCO₃  +   2HF   →   CaF₂  +   CO₂  +   H₂O. The most prominent and important compound is fluorspar, CaF₂. It is used, together with sulfuric acid, for the production of HF which can then be further processed by electrolysis to elemental fluorine. ⁷⁶ This process still represents the most important source for the production of F₂.

2.08.3.4.3 Gallium

GaF₃ is prepared by reacting elemental gallium or Ga₂O₃ with F₂ or HF at higher temperatures. ^{70, 191} It shows colorless rhombohedral crystals and sublimes at ca. 950   °C. Gallium fluorides in oxidation state III show a large variety of ionic complexes such as M₃[GaF₆], M[GaF₄], and M₂[GaF₅]. ^{69, 192–195}

2.08.3.4.4 Germanium

The gaseous GeF₄ is prepared by heating Ba[GeF₆] or by reaction of the elements. It is a slightly stronger Lewis acid like its lighter homolog SiF₄. ¹⁹⁶ In the presence of water, it hydrolyzes to GeO₂ and the corresponding acid H₂GeF₆ from which several salts have been investigated. ^197–199 Larger cations such as tetrapropyl- or tetrabutyl-ammonium are able to stabilize the pentafluoridogermanate [GeF₅]⁻. ²⁰⁰ Photolyzation of O₂/F₂ or NF₃/F₂ mixtures with GeF₄ builds the following ion-pair complexes O₂ ⁺[GeF₅]⁻ and NF₄ ⁺[GeF₅]⁻, which show cis-F-bridge connections. ^{99, 201}

2.08.3.4.5 Arsenic

Arsenic pentafluoride can be prepared by fluorination of elemental arsenic or As₂O₃. It is an even stronger Lewis acid than its lighter homolog PF₅ and a strong fluoride-ion acceptor. Both compounds are colorless gases with a trigonal bipyramidal structure. AsF₅ reacts with fluorides to the octahedral hexafluoridoarsenate anion: MF _x   +   AsF₅  →   [MF _{x−   1}]⁺[AsF₆]⁻. The cation/anion interaction depends on the fluoride-ion affinity of the base and lies in between the ionic and covalent bonding. At lower temperatures (−   78   °C) with excess of AsF₅ the hexafluorido arsenate anion [AsF₆]⁻ is able to form the perfluorodiarsenate anions [As₂F₁₁]⁻. ^{202, 203} The cation [AsF₄]⁺ can be prepared by the following reaction, Pt   +   AsF₅  +5/2F₂  →   [AsF₄]⁺[PtF₆]⁻, forming a yellow salt which can be characterized by IR and Raman spectroscopy. ²⁰⁴

2.08.3.4.6 Selenium

Similar to its lower homologs, selenium is also known in its hexafluoride form, SeF₆. This species is much more reactive than SF₆. It is able to react with NH₃ upon heating, forming Se, N₂, and HF. However, it cannot react as a Lewis acid, which is why no higher fluoride anions such as [SeF₇]⁻ are known.

2.08.3.4.7 Bromine

The chemistry of the highly oxidized bromine is very similar to that of chlorine. In its binary fluorine compounds the oxidation state VII is only reached by its cationic species [BrF₆]⁺. It can be prepared by further oxidation of bromine pentafluoride using krypton-fluoride salts, BrF₅  +   [KrF]⁺[AsF₆]⁻  →   [BrF₆]⁺[AsF₆]⁻  +   Kr. ¹⁸⁹ The neutral BrF₇ species is experimentally not known for the same reason as in the ClF₇ case (see above). Attempts to photochemically prepare BrF₇ from BrF₅ and F₂ were unsuccessful. ²⁰⁵

Unfortunately, no detailed quantum-chemical investigation exists about the stability of this species. There is only one older attempt found in the literature to locate a minima structure of BrF₇, but without any success. ²⁰⁶

2.08.3.4.8 Krypton

So far, the highest experimentally well-established stable oxidation state of krypton is II. It is represented by KrF₂ which is a volatile, colorless, crystalline solid and is surprisingly stable at −   78   °C. ^207–210 The first krypton compound was prepared by the photolysis of F₂ in a solid mixture of Ar and Kr at 20   K and was characterized by IR spectroscopy showing sharp absorptions at 580   cm^{−   1} and a second band at 236   cm^{−   1}. ²¹⁰ Many other compounds in this oxidation state have been prepared, for example, the krypton bis[pentafluoridooxidotellurate(VI)], Kr(OTeF₅)₂, which represents the first compound with a Kr–O bond. ²¹¹ However, krypton bonds with other elements, nitrogen in [RCNKrF]⁺[AsF₆]^{− 207} or carbon in HKrCCH, ²¹² are also known. The latter might not represent the oxidation state II. The cationic species such as [KrF]⁺ and [Kr₂F₃]⁺ have also been prepared as ion-pair complexes and they are known to be one of the most powerful oxidizing agents known. ²⁰⁷

First claims about the successful preparation of KrF₄ ²¹³ by an electric discharge have never been confirmed. ²¹⁴ Quantum-chemical calculations at a CCSD(T) level predict the concerted F₂ elimination of KrF₂, KrF₄, and KrF₆ to be exothermic and therefore thermochemically unstable. ^{215, 216} However, all of these show kinetic stabilities against the fluorine atom loss which is predicted to be a limiting factor. This energy barrier is computed to be 41.9 and 3.8   kJ   mol^{−   1} for KrF₄ and KrF₆, respectively. However, the simultaneous reactions of 2F or 4F atoms with KrF₂ are computed to be exothermic. The most plausible reaction path is the formation of F₂ and KrF avoiding the oxidative fluorination of the krypton atom. ²¹⁵ It looks as though, based on quantum-chemical calculations, that the preparation of a higher oxidation state of krypton, if there is one, is only possible under cryogenic conditions ( Table 3 ).

Table 3. Summary of the highest oxidation states along the fourth period of periodic table as represented by its fluorides

Element	Fluorides	QC-Calc. a
Period IV
K	KF 69, 91, 179	K2F2 137
Ca	CaF2 69, 91 [CaF3]− 180	[CaF3]− 144, 217 [CaF4]2   − 146
Ga	GaF3 191, 218–220 [GaF4]− 195, 221 [GaF5]2− 222, 223 [GaF6]3   − 192–194	GaF4 224 [GaF4]− 224 [GaF5]2− 224 [GaF6]2− 224 [GaF6]3− 224 [Ga2F10]4− 224
Ge	GeF4 69, 149, 183, 225–230 [GeF7]3   − 184 [GeF6]2   − 197–199 [GeF5]− 200
As	AsF5 69, 231, 232 [AsF6]− 69, 91 [AsF4]+ 204
Se	SeF6 187, 188, 233, 234	SeF6 235 [SeF7]− 236
Br	BrF5 237, 238 [BrF6]+ 189 [BrF6]− 69	(BrF7) 206
Kr	KrF2 208, 210, 239	KrF4 215

a

Quantum-chemically predicted to be stable: normal text style, thermochemically stable; italic, kinetically stabilized; in parenthesis, predicted to be unstable; and bold, further calculated properties.

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Furans and their Benzo Derivatives: (iii) Synthesis and Applications

D.M.X. Donnelly , M.J. Meegan , in Comprehensive Heterocyclic Chemistry, 1984

3.12.3.4 Miscellaneous

The enedione ( 283 ) is a useful starting material for a two-step synthesis of 2,3,4,5-tetrasubstituted furans which are not otherwise readily accessible 〈81JCS(P1)2398〉. Michael addition of an active methylene compound, e.g. ( 284 ), to the enedione ( 283 ) led to the two regioisomeric adducts ( 285) and (286 ) which could then be cyclized to furans ( 287) and (288 ) under mild conditions (Scheme 75). The formation of Michael adducts was successful with both β-ketoesters ( 284 ) and cyclic 1,3-diones. Normal routes to furans require much more drastic conditions; the Michael addition allowed the preparation of 1,4-diones particularly activated by the presence of an easily enolizable group. This is a useful synthetic pathway because alternative routes for the preparation of complex furans are not at present available.

Scheme 75.

Isocyanide–mercury(II) chloride complexes when reacted with acetylacetone in the presence of triethylamine yield furan derivatives ( 290 ) 〈75CPB2842〉. The aminofuranones ( 291 ) have been prepared by triethylamine catalyzed cyclization of ethyl γ-chloroacetoacetate with isocyanates 〈76CB212〉.

A general method for producing bicyclic heterocycles by dipolar cycloaddition to dipolarophiles possessing additional functionality is demonstrated by the synthesis of the furan ( 292 ) from the aroylaziridine ( 293 ) and the imine ( 294 ) (Scheme 76) 〈74CJC798〉.

Scheme 76.

The potassium fluoride catalyzed reaction of 1,3-dicarbonyl compounds with nitroalkenes results in the direct formation of 2-alkyl-4-acylfurans. Miyashita et al. have reported the preparation of 1-nitro-1-(phenylthio)propene as a new nitroalkene reagent for 3-methyl-furan annelation and its application to the synthesis of some furanoterpenoids 〈80JOC2945〉. 1-Nitro-1-(phenylthio)propene ( 295 ) was synthesized from (phenylthio)acetic acid in five steps (Scheme 77). This nitroalkene reacted with dimedone ( 296 ) catalyzed by potassium fluoride to yield the dihydrofurans ( 297 ), both of which were converted to 3-methylfuran ( 298 ) on sodium periodate oxidation followed by elimination of benzenesulfenic acid from the resulting sulfoxides in good overall yields (Scheme 78). As an application of this reagent the furanomonoterpenoid evodone ( 300 ) and furanosesquiterpenoids ligularone ( 303 ) and isoligularone ( 304 ) were synthesized from the diones ( 299) and (302 ) respectively. The stereoselective synthesis of the dione ( 302 ) from the known enone ( 301 ) was also described.

Scheme 77.

Scheme 78.

299.

301.

Furan derivatives have been prepared by the intramolecular cyclization of β,γ-unsaturated enolates. The reaction proceeds through a nucleophilic attack at the unsaturated bond by the enolate ion oxygen (Scheme 79) 〈77H(8)417〉. This reaction is facilitated by a decrease of the electron density at the unsaturated bond, e.g. by the presence of groups which are able to stabilize the negative charge. 2,3-Dihydrofurans ( 305 ) have been obtained from the reactions of ethyl acetoacetate or acetoacetamides with ethyl 4-bromo-2-butenoate 〈77H(8)417〉.

Scheme 79.

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Advanced Functional Materials

Paolo Barone , ... Silvia Picozzi , in Science and Technology of Atomic, Molecular, Condensed Matter & Biological Systems, 2012

3.3.1 ${\text{K}}_{0.6}{\text{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_{\mathrm{f}3}$ in the Tetragonal Tungsten-Bronze Structure: ${\text{Fe}}^{2+}$ / ${\text{Fe}}^{3+}$ CO as Source for FE

Iron-potassium fluoride, ${\text{K}}_{0.6}{\text{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_3$ , is an interesting fluoride where many coexisting exotic effects such as ferroelectricity, charge-ordering, multiferroicity, and ferroelasticity were put forward (see below). It shares a crystalline arrangement (conventionally referred to as tetragonal tungsten bronze (TTB) structure) with one of the most common ferroelectrics, i.e., barium sodium niobate, ${\text{Ba}}_2{\text{NaNb}}_5{\text{O}}_{15}$ [63]. The latter shows a large ferroelectric polarization along the c axis (about $40\mathrm{\mu }\text{C}/{\text{cm}}^2$ ), microscopically due to the conventional ${\text{d}}^0$ -ness mechanism [27] (off-centered Nb is here formally 5+) based on cross-gap Nb–O hybridization.

As for ${\text{K}}_{0.6}{\text{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_3$ , early experiments reported coupled ferroelectricity and ferroelasticity to occur below 490   K [64], along with CO [65]. More recently, Mezzadri et al. reported several transitions [66]: a first structural transition at 570   K from tetragonal to orthorhombic, a second transition at 490   K where ${\text{Fe}}^{2+}/{\text{Fe}}^{3+}$ CO arises (with an unknown pattern), and a third transition around 290   K to monoclinic structure, coupled with ferroelasticity.

The orthorhombic $\mathit{Pba}2$ symmetry was experimentally reported for ${\text{K}}_{0.6}{\mathit{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_3$ , with $a=12.751\AA \text{,}b=12.660\AA$ , and $c=7.975\AA$ [66], with the unit cell including two TTB layers along c (see Figure   9(a)). The $\mathit{Pba}2$ group has four symmetry operations: { $E\text{,}{C}_{2z}\text{,}{\sigma }_x+(\frac{1}{2}\frac{1}{2}0)\text{,}{\sigma }_y+(\frac{1}{2}\frac{1}{2}0)$ }; with these constraints, polarization can only occur along the z axis. However, in the experimental structure, we find $10{\text{Fe}}^{2+}$ , $6{\text{Fe}}^{3+}$ , and 4 mixed-valent ${\text{Fe}}^{2.5+}$ ions (see Figure 9(b) for the charge-density distribution), although a "full" CO would imply the presence of 12 Fe ions to be ${\text{Fe}}^{2+}$ ( ${\text{d}}^6$ ) and 8 Fe ions to be ${\text{Fe}}^{3+}$ ( ${\text{d}}^5$ ), consistent with the stoichiometry ( ${\text{K}}_{12}{\text{Fe}}_{12}^{\text{II}}{\text{Fe}}_8^{\text{III}}{\text{F}}_{60}$ /cell). By performing DFT calculations [67] for the experimental $\mathit{Pba}2$ structure [60], we find, as expected, a metallic state due to the presence of ${\text{Fe}}^{2.5+}$ ions. Clearly, this is incompatible with reported ferroelectricity and an insulating state must be present. One of the possible routes for an energy-gap to arise is by further reducing the symmetry, so as to obtain a "full" CO (i.e., no mixed-valent ${\text{Fe}}^{2.5+}$ ions).

Figure 9. (a) Projection in the ab plane of the TTB iron-fluoride unit cell; octahedral ${\text{F}}_6$ cages around Fe ions (light blue spheres) are highlighted. Purple and yellow spheres denote K and F ions, respectively. (b) Down-spin charge of Fe $t_{2g}$ states in the energy range 1   eV below the Fermi level for the $\mathit{Pba}2$ symmetry in the $z\sim$ 3/4 plane. Blue circles denote ${\text{Fe}}^{2.5}$ ions. Panels (c), (d), and (e) show how CO can be obtained by turning four ${\text{Fe}}^{2.5}$ ions into two ${\text{Fe}}^2$ , and two ${\text{Fe}}^3$ ions in different configurations: c) COI, keeping $C_{2z}$ symmetry; (d) COII, keeping ${\sigma }_x$ symmetry and (e) COIII, keeping ${\sigma }_y$ symmetry. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this book.)

For computational reasons, we did not consider in our calculations a large monoclinic supercell, previously suggested to explain the twinning satellite observed by electron-diffraction patterns below 290   K [66,68], and we assumed that the CO pattern, determined in the (small) $\mathit{Pba}2$ -like unit cell, is not affected by expanding the unit cell. Three CO patterns were considered: COI, CO-II, and CO-III, each obtained by keeping one of the three symmetry operations and breaking the other two among $C_{2z}\text{,}{\sigma }_x+(\frac{1}{2}\frac{1}{2}0)$ , and ${\sigma }_y+(\frac{1}{2}\frac{1}{2}0)$ , respectively (cf.Figure 9(c)–(e)). Whereas the induced polarization $P_z$ is allowed by the prototype $\mathit{Pba}2$ crystal symmetry, $P_y$ and $P_x$ are additionally allowed in COII and COIII, respectively. Indeed, when performing a full structural optimization of the internal atomic positions, we found an insulating state and polar structure with sizeable polarization along different directions, as reported in Tables 1 and 2.

Table 1. Total energy difference (meV/Fe), energy gap (eV) and induced FE polarization calculated by Berry phase ${\mathrm{P}}^{\text{Berry}}$ ( ) at partial CO pattern in ${\text{K}}_{0.6}{\text{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_3$ for the experimental crystal structure (first column), optimized structure keeping experimental symmetry (second column), full CO patterns: COI, COII, COIII (third, fourth and fifth column, respectively, with given symmetry).

	Exp.	Opt.	COI $C_{2\mathrm{z}}$	COII ${\sigma }_{\mathrm{x}}$	COIII ${\sigma }_{\mathrm{y}}$
	$\mathrm{Pba}2$	$\mathrm{Pba}2$	$\mathrm{P}2$	Pc	Pc
$\mathrm{\Delta }{\mathrm{E}}^{\text{tot}}$	0	−31.3	−44.3	−57.3	−51.6
${\mathrm{E}}^{\text{gap}}$	0	0	0.91	1.28	1.08
${\mathrm{P}}^{\text{Berry}}$	–	–	(0 0 0.09)	(0 − 0.50 − 0.19)	(−5.14 0 0.03)

Table 2. FE polarization $\mathrm{P}$ of ${\text{RNiO}}_3$ (R   =   Ho, Lu, Pr) in $\mathrm{\mu }$ C/c $m^2$ for the experimental structure for Ho, Lu and Ref. [71] for Pr), for either S or T-type magnetic ordering, with $\text{P}{2}_1$ and Pn symmetry, respectively. For ${\text{HoNiO}}_3$ , the FE polarization resulting from the N-type ordering is also reported.

Rare earth	T-type			S-type	N-type
	${\mathrm{P}}_{\mathrm{tot}}$	${\mathrm{P}}_{\mathrm{a}}$	${\mathrm{P}}_{\mathrm{c}}$	${\mathrm{P}}_{\mathrm{b}}$	${\mathrm{P}}_{\mathrm{tot}}$	${\mathrm{P}}_{\mathrm{a}}$	${\mathrm{P}}_{\mathrm{c}}$
Lu	10.31	9.91	2.84	5.21		–
Ho	8.66	8.05	3.19	3.60	0.10	0.02	−0.10
Pr	14.80	13.23	6.64	1.81		–

In these structures, ferroelectricity is purely induced by CO, with magnetism playing no relevant role; we further remark that the size of polarization is much smaller than in ${\text{Ba}}_2{\text{NaNb}}_5{\text{O}}_{15}$ , due to the different microscopic origin of polarization (CO in ${\text{K}}_{0.6}{\mathit{Fe}}_{0.6}^{\text{II}}{\text{Fe}}_{0.4}^{\text{III}}{\text{F}}_3$ vs. second-order Jahn–Teller effect in Nb-based oxide). We note from Table   1 that COII is the energy ground state, which should be stabilized when applying an electric field $E_y$ ; however, COI and COIII are predicted to be energetically competing states. We here speculate that the competing COIII pattern inducing a large $P_x$ might be realized upon applying an electric field $E_x$ . In the case of a (strong enough) applied electric field which rotates in the xy plane, the induced P along the field would therefore change its saturation value. We define the "ferroelectric anisotropy" (FEA) as the energy required to modify the direction (as well as size) of the polarization by switching the crystal symmetry between different CO phases (in this case COII and COIII); the FEA may find useful applications in future devices, such as multiple-state memories where the information can be stored by exploiting not only the sign of P, but also its direction. The FEA is peculiar for ferroelectricity induced by electronic degrees of freedom in "improper" multiferroics. For example, the control over the direction of P in spin-spiral manganites by means of a magnetic field was already proven and suggestions toward devices harnessing FEA already came in that framework, so we propose that similar arguments might be valid for CO-induced ferroelectrics [69].

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Synthesis: Carbon With Two Attached Heteroatoms With at Least One Carbon-to-Heteroatom Multiple Link

R.J. Anderson , ... M. Nyerges , in Comprehensive Organic Functional Group Transformations II, 2005

5.17.1.4 From Imidoyl Halides

A new reagent, calcium-fluoride-supported potassium fluoride, has been used for the preparation of imidoyl fluorides. The imidoyl chloride 8 with an excess of this reagent in refluxing acetonitrile (Equation (26)) gave the halogen-exchanged compound 9 as an unstable, readily hydrolyzed liquid <1999AJC807>.

(26)

Perfluorinated imidoyl iodides were prepared by the substitution of the chloride atom of an imidoyl chloride by sodium iodide (Equation (27)) <2000JOC3404>.

(27)

In the reaction of perfluoro-5-azanon-4-ene 10 with urea (Equation (28)), the imidoyl fluoride 11 was described as an intermediate which cyclized to a triazine <2000JFC105>.

(28)

Treatment of the readily accessible phosphonium salt PhCClNCH₂P⁺Ph₃Cl⁻ with Et₃N yields an ylide PhCCl:NCH:PPh₃, which contains an electrophilic imidoyl chloride group together with a nucleophilic center (the PC bond), and can thus undergo cyclocondensations with carboxylic acid chlorides, CS₂, or acyl isothiocyanates <1999JGU1583, 1999ZOB1652>.

The reaction of imidoyl chloride ( 12 , X   =   F) with dry potassium fluoride in a polar solvent (Equation (29)) leads to the formation of a mixture of isomeric azaalkenes <2001JFC123>, which are reported to exist in equilibrium <1975IC592>. The analogous imidoyl chloride ( 12 , X   =   Cl) also reacts with dry caesium fluoride to give a mixture of azaalkenes.

(29)

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Synthesis: Carbon with Three or Four Attached Heteroatoms

Geoffrey E. Gymer , Subramaniyan Narayanaswami , in Comprehensive Organic Functional Group Transformations, 1995

6.14.3.3.1.(vi) Carbamoyl fluorides from trifluoromethylamines, R¹R²NCF₃

N,N -Disubstituted formamides can be fluorinated by silicon tetrafluoride in the presence of potassium fluoride to give trifluoromethylamines, R ¹R²NCF₃. Where R¹ and R² are alkyl groups, addition of these compounds to crushed ice results in the carbamoyl fluorides R¹R²NCOF in over 70% yield <83JFC(23)207>. Perfluoroalkyl tertiary amines bearing at least one CF₃ group, R_f ¹R_f ²NCF₃, are converted to the carbamoyl fluorides R_f ¹R_f ²NCOF in 38–62% yield by 30% oleum, preferably with catalysis by MoCl₅. Where more than one NCF₃ group is present, only one is converted to give the monofluorocarbonyl derivative <89JFC(45)293>.

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Synthesis: Carbon With Three or Four Attached Heteroatoms

J. Suwiński , K. Walczak , in Comprehensive Organic Functional Group Transformations II, 2005

6.02.1.2.1.(v).(a) From dithioesters

Thiocarbonyl group in dithioesters can be exchanged by difluoremethylene moiety using mercury(II) fluoride–potassium fluoride mixture in tetrahydrofuran in the presence of pyridinium hydrogen fluoride ( Equation (26)) <1996TL3223>.

(26)

Similar results (the exchange of sulfur atom by two fluorine atoms) were achieved using tetrabutylammonium–hydrogen fluoride complex in the presence of N-iodosuccinimide (Scheme 51) <1999BCJ805> or by treating dithioester with bis(2-methoxyethyl)aminosulfur trifluoride in the presence of antimony(III) fluoride (Scheme 51) <2000JOC4830>.

Scheme 51.

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Heterocycles from the Reaction of Thione Groups with Acetylenic Bonds

Ashraf A. Aly , ... Alaa A. Hassan , in Advances in Heterocyclic Chemistry, 2014

3.2.3 Oxathiolane

Reaction of 2-acetylenic alcohols 65 with carbon disulfide (CS₂ ) in the presence of potassium fluoride on alumina gave 4-alkylidene-2-thione-1,3-oxathiolanes 66 in good yields (Scheme 20, 1992SC1351).

Scheme 20.

Reaction of 3-(1-hydroxycyclohexyl)-2-propynenitrile 67 with quinoline-2-thione 68 in the presence of LiOH, afforded at 20–25   °C 1,3-oxathiolane 69a, but at 60–65   °C 1,4-oxathiane 69b (Scheme 21, 00ZOR444). The chemistry here begins with a simple conjugate addition; complex series of dimerization, extrusion, and rearrangement ensue.

Scheme 21.

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Synthesis: Carbon With One Heteroatom Attached by a Single Bond

A. Kotali , P.A. Harris , in Comprehensive Organic Functional Group Transformations II, 2005

2.01.2.3 Alkyl Fluorides from Alkyl Halides

1-Chlorododecane has been converted to 1-fluorododecane in 35% yield under treatment with potassium fluoride in DMF at 170  °C <1997LA1333>, whereas 1-bromobutane led to the formation of 1-fluorobutane in 69% yield by treatment with KF in tetrahydrothiophene 1,1-dioxide for 5   h at 180–200   °C <2000MI3018>. A semimolten mixture of tetrabutylammonium fluoride (TBAF) and an alkali metal fluoride (KF or CsF) has been reported to be an efficient reagent system for the fluoride-ion displacement reaction on organohalides in very good yields (69–91%) <1995JFC185>. Hydrated TBAF, in particular the pentahydrate, has also been used to successfully displace chlorides, bromides, and iodides <1998JOC9587>. Reaction of alkyl bromides with polymer-bound tetraalkylammonium fluorides resulted in the formation of alkyl fluorides <2001SL547>. Tetrabutylammonium hydrogen difluoride in the presence of pyridine, in dioxane or THF, has been proved to be an effective reagent for nucleophilic fluorination <1998TL7305>. The oxidative fluorination of alkyl iodides with p-iodotoluene difluoride and Et₃N-4HF is an interesting process for the conversion of primary alkyl iodides to the corresponding alkyl fluorides <2001T3315>. Under the same conditions, trans-2-alkoxyiodocyclohexane gives trans-2-alkoxyfluorocyclohexane in moderate yield. As the trans-stereochemistry was completely retained, the reaction may take place through an oxonium intermediate (Scheme 7) <2001T3315>.

Scheme 7.

Alkyl bromides were smoothly transformed to the corresponding alkyl fluorides by reacting with the fluoro complex [RuF(dppp)₂]PF₆ (dppp   =   propane-1,3-diylbis-[diphenylphosphine]) (Equation (18))<1999HCA2448>.

(18)

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Walther Grot , in Fluorinated Ionomers (Second Edition), 2011

Example 4

In the apparatus of Example 3, 23.0 g of the solid mixture of the object compound, potassium fluoride and potassium carbonate, which was obtained by the reaction of 17.0 g of the starting material and 8.3 g of potassium carbonate, is charged, and the reaction is carried out at 150–155°C under a reduced pressure of 2–4 mmHg for 3 h with stirring. In the trap maintained at –78°C, 13.3 g of a liquid is collected. The liquid is distilled in accordance with the process of Example 3 and 9.2 g of ethyl perfluoro-5-oxa-6-heptenoate is obtained. The chemistry of this monomer, its copolymerization with TFE and the properties of the resulting polymer are the subject of an excellent review [13].

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