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Relevant academic research and scientific papers

Mild and selective α-fluorination of carbonyl compounds (ketones, 1,3-diketones, β-ketoesters, α-nitroketones, and β-ketonitriles) with Selectfluor (F-TEDA-BF4) in imidazolium ILs [BMIM/PF6 or BMIM/NTf2] with Br?nsted-acidic IL [PMIM(SO3H)/OTf] as promoter

Structurally diverse ketones, 1,3-diketones, and β-ketoesters, were selectively monofluorinated with Selectfluor (F-TEDA-BF4) (1 equiv) in [BMIM][PF6] as solvent and [PMIM(SO3H)][OTf] as promoter under mild conditions. In selected cases, the monofluorinated products were transformed to the gem-difluoro derivatives by employing an additional equivalent of Selectfluor, and gem-difluoro-derivatives were synthesized directly from the substrates by employing 2 equiv of Selectfluor. The method was extended to monofluorination of representative α-nitroketones and β-ketonitriles using [BMIM][NTf2] without the need for promoters. The described method offers the added advantage of recycling and reuse of the IL solvent. (Chemical Equation Presented).

Apparent electrophilic fluorination of 1,3-dicarbonyl compounds using nucleophilic fluoride mediated by PhI(OAc)2

The apparent electrophilic fluorination of 1,3-dicarbonyl compounds using Et3N·3HF as a nucleophilic fluoride source is reported. This reaction requires PhI(OAc)2 as oxidant and can be conducted safely in standard laboratory glassware. Alternative selectivity compared to Selectfluor was observed in some cases. This approach may reduce our reliance on difficult-to-handle fluorine gas and expensive electrophilic fluorinating agents derived from elemental fluorine. Mechanistic analysis related to the active fluorinating species and fluoride/acetate exchange is presented. The apparent electrophilic fluorination of 1,3-dicarbonyl compounds using Et3N·3HF mediated by the in-situ formation of PhIF2 from PhI(OAc)2 is reported. This can be performed safely in standard laboratory glassware, and this approach may reduce our reliance on difficult-to-handle fluorine gas and expensive electrophilic fluorinating agents derived from elemental fluorine.

Solvent-free fluorination of organic compounds using N-F reagents

Efficient fluorination of 1,3-dicarbonyl compounds, enol acetates of aromatic ketones, and activated aromatic compounds was achieved under solvent-free conditions using Selectfluor F-TEDA-BF4 or Accufluor NFSi.

Electrophilic fluorination with N,N′-difluoro-2,2′-bipyridinium salt and elemental fluorine

NNpm-Difluoro-22pm-bipyridiniu m bis(tetrafluoroborate) (MEC-31) was shown to be a highly reactive electrophilic fluorinating agent with the highest effective fluorine content in its class. We have developed the perfect recycled fluorination system with MEC-31 for the lower-cost industrial fluorination and for an environment. MEC-31 can be completely recycled including the counter-anion. We found the fluorination of 2-naphthol in liquid CO2 with MEC-31 in the presence of catalytic amount of NaOTf proceeded quantitatively without the generation of by-product. In the fluorination of 1,3-dicarbonyl compounds with elemental fluorine, we found the introduction method of fluorine gas would be very important in order to make a reaction efficient. As fluorination goes on, the quantity of 1,3-dicarbonyl compounds of the starting material is reduced gradually, and therefore the quantity of fluorine must be reduced by the method to control the flow rate or the concentration of fluorine gas diluted with nitrogen, together the fluorination to proceed efficiently.

Preparation of fluorinated dicarbonyls

PCT No. PCT/GB94/02547 Sec. 371 Date Feb. 21, 1997 Sec. 102(e) Date Feb. 21, 1997 PCT Filed Nov. 18, 1994 PCT Pub. No. WO95/14646 PCT Pub. Date Jun. 1, 1995A method for the fluorination of 1,3-diketones and 1,3-ketoesters is disclosed.

Synthesis, Properties, and Reactivity of N,N'-Difluorobipyridinium and Related Salts and Their Applications as Reactive and Easy-To-Handle Electrophilic Fluorinating Agents with High Effective Fluorine Content

N,N′-Difluoro-2,2′-, -2,4′-, -3,3′-, -4,4′-bipyridinium and substituted N,N′-difluoro-2,2′-bipyridinmm bis(triflates), bis(tetrafluoroborates), bis(hexafluorophosphates), and bis(hexafluoroantimonates) 1-9 were synthesized in high yields by the direct fluorination of a mixture of a bipyridyl and a Lewis acid, a Br?nsted acid, or the alkali metal salt of an acid. The higher homologues, trimer 10 and polymer 11, were also synthesized. Unsubstituted or electron-donating group-substituted N,N′- difluorobipyridinium salts are stable nonhygroscopic crystals, while the electron-withdrawing group- substituted N,N′-diflurobipyridinium salts 3, 5, and 6 are moisture-sensitive crystals. Hydrolysis of 1b in boiling water gave 3,3′-dihydroxy-2,2′-bipyridyl. The reactivity determination indicated that the fluorinating capability decreased in the order 2,2′- ? 2,4' > 3,3′- ≈ 4,4′-isomer ? N-fluoropyridinium salt and that the two N-F moieties in a molecule were effective for fluorination. This fluorination occurred in a step-by-step manner, and the reactivity difference between the first and second fluorinations was very small. N,N′-Difluoro-2,2′-bipyridinium bis(tetrafluoroborate) (1b) is thus shown to be a highly reactive and easy-to-handle electrophilic fluorinating agent with the high effective fluorine content (103.3 g/kg) for preparing many fluoro organic compounds.

Direct fluorination of 1,3-dicarbonyl compounds

In acid media, 1,3-diketones and 1,3-keloesters can be fluorinated in high yield and often with high conversion mainly to the corresponding 2-fluoro- compounds. Diesters such as diethyl malonate do not react with fluorine under the same reaction conditions. The mechanism of these reactions has been investigated and while the identity of the electrophilic fluorinating species is uncertain, we believe that the essential features of the reaction pathway are understood. Copyright

Direct Fluorination of 1,3-Dicarbonyl Compounds

1,3-Dicarbonyls, such as 1,3-diketones and 1,3-ketoesters, react directly with elemental fluorine at room temperature to give the corresponding 2-fluoro- and, in some cases, 2,2-difluoro-compounds in high yield.

Highly Selective Fluorinating Agents: A Counteranion-Bound N-Fluoropyridinium Salt System

A series of alkyl- or (trifluoromethyl)-substituted N-fluoropyridinium-2-sulfonates 2a-h, differing in fluotinating power, were synthesized, and assessment was made of the effectiveness of each selective fluorinating agent.N-Fluoropyridinium-3- and -4-sulfonates 3 and 4 were also synthesized.Power-variables 2a-h were found to be highly selective fluorinating agents for a wide range of nucleophilic substrates such as activated aromatics, enol trialkylsilyl and alkyl ethers, active methylene compounds, activated olefins, and sulfides.Thus, phenol, naphthol, phenylurethane, and the trimethylsilyl ether of phenol were exclusively or highly selectively fluorinated at the o-position with 2f-h.Conjugated enol trialkylsilyl ethers of a steroid were regioselectively fluorinated at the 6-position with moderately powerful 2b-e.This regioselectivity increased with the bulkiness of the silyl part, and with the most bulky triisopropylsilyl group exclusive 6-fluorination was achieved.Preferential β-stereoselective fluorination at the 6-position was observed.N-Fluoropyridinium-2-sulfonates were activated with an acid.This acid-catalyzed fluorination led to the preferential p-fluorination of anisole.The present results can be explained based on the capacity of the 2-sulfonate anion to interact with the hydroxy group of phenol or naphthol, NH group of phenylurethane, silicon atoms of silyl ethers, or protons of acids.

Acetyl Hypofluorite, a New Moderating Carrier of Elemental Fluorine and Its Use in Fluorination of 1,3-Dicarbonyl Derivatives

Elemental fluorine and most of the fluoroxy reagents do not react efficiently or cleanly with 1,3-dicarbonyl derivatives or with their corresponding metal enolates even at -75 degC.It has been found that a suspension of sodium acetate in CFCl3 or in CFCl3-AcOH, when treated with elemental fluorine, forms a new electrophilic fluorinating reagent, CH3COOF (1), which reacts with substrates without further isolation or purification.This reagent is milder than F2, CF3OF, or CF3COOF and reacts successfully where the other reagents fail.When 1 reacts with 1,3-dicarbonyl compounds, the main product is the 1,3-dioxo-2-fluoro derivative in reasonable yields.When, however, the corresponding sodium enolates were treated with 1, the yields of the monofluoro derivatives were considerably higher.In the case of 1,3-dicarbonyl derivatives with low enol content, only the sodium enolates react with 1 to produce good to very good yields of the corresponding 2-monofluoro derivatives.Thus 1 can be considered as a moderating carrier of the highly reactive F2.