Silver compounds in synthetic chemistry : Part 5: Selective syntheses of trifluoromethylketones, RCOCF3, from trifluoromethylsilver, AgCF3, and corresponding acyl chlorides, RCOCl

Trifluoromethylketones of aromatics, heteroaromatics and olefins are formed selectively from reactions of trifluoromethylsilver and the corresponding carboxylic acid chlorides in moderate to excellent yields. The conditions chosen are dependent on the nature of the acyl chloride. Attempts to prepare alkyl(trifluoromethyl)ketones yielded product mixtures of the corresponding acyl fluorides, trifluoromethyl-, pentafluoroethyl- and n-heptafluoropropyl ketones.     

The first example of fluoro-Meinwald rearrangement

Novel fluorinated norbornadienes were synthesized in up to 95% yield by the base-induced elimination of HNO₂ from 5-fluoro-5-nitro-6-arylbicyclo[2.2.1]hept-2-enes prepared, in turn, by the Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclopentadiene. The subsequent epoxidation initiated the Meinwald type rearrangement affording 6-aryl-bicyclo[3.1.0]hex-2-ene-6-carboxylic acid fluorides as individual (1SR,5RS,6RS)-diastereomers. The transformation is the first example of fluoro-Meinwald rearrangement to form the corresponding acyl fluorides.     

Chemical state analysis of fluorine in various compounds using X-ray fluorescence spectra

F Kα X-ray fluorescence (XRF) spectra of various fluorides were measured and to investigate the chemical state of fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass. The main peak (Kα_1,2) position and the relative intensity of the satellite peak attributable to Kα_3,4 were discussed relating to the M-F bond covalency. Results showed that the fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass had a completely different chemical state from that of starting materials. Quantitative analyses of the glasses were also undertaken using XRF measurements for each component. These results suggest that 30% fluorine in the 50HoF₃-20BaF₂-10AlF₃-20GeO₂ system is substituted by oxygen through pyrohydrolysis of the fluorides.     

Preparation of sulfonamides from N-silylamines

Sulfonamides have been prepared in high yields by the reactions of N-silylamines with sulfonyl chlorides and fluorides. In a competition experiment, the sulfonyl chlorides were found to be far more reactive than sulfonyl fluorides. The chemistry may be used to prepare aliphatic, aromatic, tertiary, secondary, and primary sulfonamides. It may also be done in the absence of solvent and the byproduct trimethylsilyl chloride recovered in good yield. Primary sulfonamides were synthesized from the sulfonyl chloride with aminotriphenyl silane (Ph₃SiNH₂), a conversion demonstrated with the synthesis of the carbonic anhydrase inhibitor, acetazolamide.     

Highly efficient synthesis of capsaicin analogues by condensation of vanillylamine and acyl chlorides in a biphase H2O/CHCl3 system

Highly efficient synthesis of capsaicin analogues was developed using condensation of vanillylamine with acyl chlorides in a biphase H₂O/CHCl₃ system under mild conditions. For C4-C18 aliphatic or aromatic acyl chlorides, the yields were up to 93-96% with high purity after a simple work-up procedure, and only 1-1.16 equiv of acyl chloride was needed in the reaction.     

Facile nucleophilic fluorination by synergistic effect between polymer-supported ionic liquid catalyst and tert-alcohol reaction media system

A highly efficient method was developed for nucleophilic fluorination using an alkali metal fluoride through the synergistic effect of the polymer-supported ionic liquid (PSIL) as a catalyst and tert-alcohol as an alternative reaction media. This PSIL/tert-alcohol system not only enhances the reactivity of alkali metal fluorides and reduces the formation of by-products but also allows the use of a polymer-supported catalyst protocol. As an example, the nucleophilic fluorinations of the model compound, 2-(3-bromopropoxy)naphthalene, with CsF using only tert-amyl alcohol as solvent (for 2 h reaction time), 0.5 equiv of PS[hmim][BF₄] in CH₃CN (for 12 h reaction time), and 0.5 equiv of PS[hmim][BF₄] in tert-amyl alcohol (which is a PSIL/tert-alcohol system for the synergistic effect; for 2 h reaction time) provided 18, 40, and 84% yield, respectively. The characteristics of the nucleophilic fluorination reactions of some halo- and alkanesulfonyloxyalkane systems to the corresponding fluoroalkanes using various alkali metal fluorides are also reported.     

Colorimetric detection of fluoride in an aqueous solution using Zr(IV)-EDTA complex and a novel hemicyanine dye

A new highly sensitive and selective colorimetric method for fluoride determination in water is described. The novel reagent used is a hemicyanine dye (HC), which forms a stable complex with Zr-EDTA, the fluoride-binding site, through the hydroxyl groups. The hemicyanine-chelating Zr-EDTA complex (HC-Zr-EDTA) is ready to react with fluoride ion to release HC. This result in remarkable color change of the sensing solutions from red (λ_max = 513 nm) to yellow (λ_max = 427 nm) at pH 4.40. When applied to the colorimetric determination of fluoride ions, a linear range from 3.0 × 10⁻⁶ to 5.0 × 10⁻⁵ mol/L and a detection limit of 2.8 × 10⁻⁶ mol/L with a correlation coefficient of 0.9993 can be achieved under the optimized conditions. Because of the specific affinity of fluorides for the [Zr-EDTA], there is little interference by other ions. This method has been successfully applied to the determination of fluorides in toothpaste samples.     

The reaction of biphenyl radical anion and dianion with alkyl fluorides. From ET to SN2 reaction pathways and synthetic applications

The reaction of dilithium biphenyl (Li₂C₁₂H₁₀) with alkyl fluorides has been studied from the point of view of the distribution of products. Two main reaction pathways, the nucleophilic substitution (S_N2) and the electron transfer (ET), can compete to yield the same alkylation products in what is known as the S_N2-ET dichotomy. S_N2 seems to be the main mechanism operating with primary alkyl fluorides (n-RF). Alkylation proceeds in good yields, and the resulting alkylated dihydrobiphenyl anion (n-RC₁₂H₁₀Li) can be trapped with a second conventional electrophile (E⁺) affording synthetically interesting dearomatized biphenyl derivatives (n-RC₁₂H₁₀E). The reaction gives a higher amount of ET products as we move to secondary (s-RF) and to tertiary alkyl fluorides (t-RF), in which case the mechanism seems to be dominated by ET. In this case, alkylation by radical coupling is still feasible, giving access to the synthesis of t-RC₁₂H₁₀E, although in lower yields. A rational interpretation of this S_N2-ET dichotomy is given on the basis of the full distribution of products observed when 5-hexenyl fluoride and 1,1-dimethyl-5-hexenyl fluoride were are used as radical probes in their reaction with Li₂C₁₂H₁₀ and LiC₁₂H₁₀.     

A palladium catalyzed atom-efficient cross-coupling reactivity of triarylbismuths with α,β-unsaturated acyl chlorides

An atom-efficient cross-coupling reactivity of triarylbismuths (1 equiv) was demonstrated by cross-coupling reaction with 3 equiv of α,β-unsaturated acyl chlorides under palladium catalysis in the synthesis of a series of functionalized α, β-unsaturated ketones in high isolated yields.     

Fluorodiazadiphosphetidine, 12. Mitt.: Reaktionen von Oktafluoro-1,3,2λ6,4λ6-diazoniadiphosphatetidinen

Reaction of (CH₃NHPF₄)₂ with selected organometallic reagents yields (CH₃NPF₃)₂, while reaction with non-nucleophilic bases such as 1,4-diazabicyclo[2.2.2]octane (DABCO) or 1,8-Bis(dimethylamino)naphthalin and with alkali fluorides yields ionic compounds with the diazoniadiphosphatetidine ring as a dianion.     

Selective synthesis of fluorinated carbohydrates using N,N-diethyl-α,α-difluoro-(m-methylbenzyl)amine

Deoxyfluorination of a hydroxy group in carbohydrates was carried out using N,N-diethyl-α,α-difluoro-(m-methylbenzyl)amine. A primary hydroxy group in carbohydrates was effectively converted to the corresponding fluoride under microwave irradiation or at 100 °C. Deoxyfluorination of hydroxy groups at the anomeric position proceeded at below room temperature, and glycosyl fluorides could be obtained in good yields. The reaction chemoselectively proceeded, and various protecting groups of carbohydrates can survive under the reaction conditions.     

Synthesis of О-2-(acyl)vinylketoximes and their unusual rearrangements into 2- and 3-acyl-substituted pyrroles

О-2-(Acyl)vinylketoximes (freshly prepared from ketoximes and acylacetylenes in the presence of Ph₃P as catalyst in up to 83% yields) rearrange upon heating (125-150 °C) to give 2- or 3-acylpyrroles, wherein the positions of the acyl substituents do not correspond to known O-vinyloxime rearrangements; the chemo- and regioselectivity of the rearrangements depend on the reaction conditions. The described rearrangement enables syntheses of previously inaccessible substituted 2- or 3-acylpyrroles.     

Rhodium-catalyzed interconversion between acid fluorides and thioesters controlled using heteroatom acceptors

A rhodium complex catalyzed the equilibrium acyl transfer reaction between acid fluorides and thioesters. In the presence of fluoride or thiolate acceptors, the reaction could be shifted to either product. RhH(PPh₃)₄-dppe catalyzed the reaction of acid fluorides and diorgano disulfides in the presence of triphenylphosphine giving thioesters, which was accompanied by triphenylphosphine difluoride. The same complex catalyzed the reaction of aryl thioesters and hexafluorobenzene giving acid fluorides, which was accompanied by 1,4-di(arylthio)-2,3,5,6-tetrafluorobenzenes.     

Tertiary-Amine-Initiated Synthesis of Acyl Fluorides from Carboxylic Acids and CF3SO2OCF3

A convenient method for deoxyfluorination of aromatic and aliphatic carboxylic acids with CF₃SO₂OCF₃ in the presence of a suitable base at room temperature has been developed. The reaction allows a straightforward access to a variety of acyl fluorides and proves that CF₃SO₂OCF₃ is an effective deoxyfluorination reagent for carboxylic acids. The method features simplicity, expeditiousness, high efficiency, ease of handling, good functional group tolerance, a wide range of substrates, excellent yields of products, compatibility of many amine initiators, use of environmentally friendly reagents, and effortless removal of byproducts. This reaction represents the first utilization of trifluoromethyl trifluoromethanesulfonate as a fluorination reagent.     

Synthesis and self-assembly properties of para-acyl-calix[8]arenes

The synthesis of a series of novel para-acyl-calix[8]arenes is described, while for acyl chain lengths of greater than eight carbon atoms total substitution at the para position occurs, in contrast to the para-acyl-calix[4]arenes, some esterification at the phenolic face may also occur, particularly for shorter acyl chain lengths. Simple saponification with potassium hydroxide in ethanol allows the pure compounds to be obtained in good yields. All the derivatives show amphiphilic behaviour with formation of stable monolayers at the air-water interface and apparent molecular areas between 150 and 275 Å².     

Les fluoronitrures de terres rares

The reaction of rare-earth nitrides with fluorides or the pyrolysis of these fluorides in gaseous ammonia atmosphere leads, in the case of lanthanum, cerium, and gadolinium, to nitride fluorides of general formula LnN_xF_3?3x. They crystallize with a fluorite-type structure which can be described in a consistent manner in terms of a Willis model. The magnetic properties of Gd₃NF₆ have been studied.     

Microscale cleavage reaction of (phenyl)benzyl ethers by ferric chloride

Anhydrous FeCl₃ in CH₂Cl₂ cleaves benzyl and p-phenylbenzyl ethers of sugars in 15–30 minutes and 2–3 minutes, respectively, at room temperature in >70% yields; methyl ethers and acyl groups are not affected.     

Direct synthesis of fluorinated peroxides. V. The preparation of pentafluorosulfurperoxy esters by reactions of pentafluorosulfur hydroperoxide with acyl fluorides

The reaction of SF₅OOH with acyl fluorides in the presence of NaF has been investigated and found to yield new peroxy esters of the type RC(O)OOSF₅. An alternate method of synthesis using SF₅OOCl and acyl chlorides is discussed and the cesium fluoride catalyzed conversion of two of the esters to RCF(OF)OOSF₅ is described.     

MoO2Cl2 as a novel catalyst for Friedel-Crafts acylation and sulfonylation

The use of MoO₂Cl₂ as a novel catalyst for Friedel-Crafts acylation and sulfonylation is described. A series of aromatic ketones and sulfones were prepared in moderate to good yields using acyl chloride or sulfonyl chloride in the presence of MoO₂Cl₂ (20 mol %), under solvent-free conditions.     

Some properties of polyfluoroacyl- and polyfluoroacetonyl fluorosulfates

Conclusions Polyfluoroacyl fluorosulfates are decomposed by the action of KF, SbF₅ and its mixtures with HSO₃F with the formation of the corresponding acyl fluorides. Pentafluoroacetonyl fluorosulfate reacts with SbF₅ to form hexafluoroacetone; the fluoride ion causes decomposition of 3-chlorotetrafluoroacetonyl fluorosulfate to chlorodifluoroacetyl fluoride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1368–1372, June, 1987.