I. Introduction

An amazingly diverse and constantly expanding range of commercial products emanating from the fluorochemicals industry is driven by the dramatic changes in the physical and biological properties and chemical reactivities of organic materials that arise from the introduction of fluorine.¹ In particular, these changes, including enhanced stability and lipophilicity, have been exploited in the fields of pharmaceutical, agrochemical, and polymer chemistry.^2-4 The efficacy of many pharmaceuticals and agrochemicals is often enhanced by or is dependent on the presence of a single fluorine atom in the molecular structure.⁵ Frequently, such compounds can be synthesized from smaller molecules in which fluorine is located at a specific site, or often it is desirable to introduce the element directly in order to obtain the desired chemical composition.^6,7 Electrophilic fluorination is one of the most direct methods for selective introduction of fluorine into organic compounds. Elemental fluorine itself is one of the most powerful reagents.⁸ However, fluoroxy compounds, such as CF₃OF, CF₃C(O)OF, CsSO₄F, and CH₃C(O)OF, some of which are generated in situ, are exciting reagents for the introduction of fluorine electrophilically into a wide variety of organic compounds.⁹ The rather hazardous perchloryl fluoride has lost favor to other electrophiles, including xenon difluoride, which has been employed as a particularly interesting and easily handled source of electrophilic fluorine.¹⁰ More recently, much attention has been given to the fluoronitrogen compounds, including N-substituted fluoropyridinium and N,N'-difluorobipyridinium salts, such as N,N'-difluorobipyridinium tetrafluoroborate (MEC-31, Daikin)¹¹ and 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor, Air Products).¹² While the latter two reagents are readily available commercially, unfortunately some of the most powerful electrophilic NF reagents, e.g., the perfluoroalkylsulfonimides (R_fSO₂N(F)SO₂R_f'), have not been commercialized.¹³ These N-F compounds are generally somewhat less reactive than the fluoroxy reagents described above, but nevertheless they have proved to be particularly useful with a wide range of organic nucleophiles.

While these fluorinating reagents and methodologies have been developed to fulfill the increasing demand for site-selective fluorination of organic and biological molecules, the applications of Selectfluor (1) are remarkedly broad. Because it is a stable, nonvolatile, user-friendly reagent,¹² it has been used widely in one-step reactions to introduce fluorine into organic compounds electophilically. Our interest in applying electrophilic synthetic methods for introducing fluorine or a fluorinated group into a large variety of organic/inorganic compounds encouraged us to describe the recent highlights in fluorination reactions specifically using 1 as the key electrophilic fluorinating reagent. The literature from January 1999-January 2003 is reviewed.

II. 1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane Bis(tetrafluoroborate) (Selectfluor)

A. Synthesis. Selectfluor (1) is produced commercially by Air Products¹⁴ via the process in Scheme 1. The details of the chemistry are fully described.¹⁵

	Scheme 1
	Scheme 2

B. Properties. Selectfluor is a white solid (mp 190 C), stable in air and to moisture. The X-ray crystal structure has been reported.¹⁶ It is a dicationic salt that is very soluble in cold water or dilute hydrochloric acid. However, it decomposes in dilute sodium hydroxide and reacts with cold DMSO (rapidly and exothermally) and with DMF (slowly on heating). It is moderately soluble in acetonitrile, but only slightly soluble in lower alcohols and acetone, which makes the former the solvent of choice. Occasionally, reactions in these solvents were accelerated by adding a small amount of water or trifluoroacetic acid. Bulk quantities of 1 should be stored in a cool, dry place and should not be heated above 80 C. Fainzil'berg et al. have measured the reduction potentials of Selectfluor and other N-F compounds. With a positive reduction potential, E_1/2 = 0.33 V, Selectfluor is predicted to be a more reactive fluorinating reagent than, e.g., N-fluorobenzenesulfonimide, with E_1/2 = -1.24 V.¹⁷

III. Fluorination Reactions Using Selectfluor

Selectfluor is a reactive source of an electrophilic [F⁺] species that interacts with organic, inorganic, and biological molecules. It can be reacted with aromatic, aliphatic, alkene, amine, glycol, and silicon compounds. Most of the reactions have been performed in acetonitrile, but DMF and DMA have also been used. Reaction conditions depend on the substrate used and the nature of the products formed. In the case of less reactive substrates, a higher temperature is required. In asymmetric synthesis, lower temperatures are preferred in order to achieve high enantiomeric excess. Possible mechanisms of the reactions of "electrophilic" fluorinating reagents with organic compounds are not well understood. The question is whether the reactions occur via direct fluorine transfer or through discrete electron transfer (SET). As a classical S_N2 process, fluorine transfer results when nucleophilic attack of an electron-rich reaction center on fluorine displaces the ligand portion of the reagent. The SET mechanism demands the initial formation of a charge-transfer complex between an electron-rich organic molecule and the electron-deficient fluorinating reagent that transforms to an organic molecule cation radical active intermediate as the precursor of non-fluorinated or fluorinated products. While there is confirmation of cation radicals that tend to support the SET reaction pathway, it is generally accepted that the course of these fluorination reactions is strongly related to the structure of the N-F reagent, the organic molecule, and the reaction conditions used. It is very difficult to define unequivocally the reaction pathway through which the products are formed.^12b

The chemistry of Selectfluor with various classes of compounds is described in the following sections.

A. Electrophilic Fluorination of Aromatic Compounds and Their Derivatives. Arenes react with 1 with difficulty, but aromatic compounds with an electron-donating group in the ring were found to be reactive under appropriate conditions. Reaction of 3-substituted indoles with 1, either in acetonitrile/water¹⁸ or in an ionic liquid,¹⁹ led to the formation of the 3-fluorooxindole in good to high yields (Scheme 2). Formation of the non-fluorinated oxindole as a side product has also been reported. High yield and better chemoselectivity were claimed when ionic liquids were employed as the reaction media.¹⁹

A proposed reaction mechanism for the formation of fluorinated oxindoles is shown in Scheme 3. Reaction of indole (X) with 1 gave 3-fluoroindolenine (A) as an unstable intermediate that underwent loss of HF due to addition of water. A subsequent 1,5-prototropic shift gave the enol B. Fluorination of B with additional 1 resulted in oxindole (Y) as the final product. Formation of non-fluorinated oxindole (Z) as a minor side product was explained by the tautomerism of enol (B), catalyzed by water (solvent). An alternative pathway for the formation of Y from X can be considered via the formation of 2-fluoroendole (C) and 2,3-difluoroindolenine (D) intermediates, especially in nonaqueous media.

	Scheme 3
	Scheme 4

The fluorination of arenes using an ionic liquid as the reaction medium (assisted by sonication) was examined with 1. With reactive aromatics, the optimal fluorinated yields obtained with 1 equiv of 1 in ionic liquids are ~50% (Table 1).²⁰ Usually the yields are found to be comparable with, and in some cases exceed, those obtained in acetonitrile and trifluoroacetic acid but are not as high as in those obtained in trifluoromethanesulfonic acid. A comparative study has shown that 1 is more reactive than 1-fluoro-4-hydroxy-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate (Accufluor) and N-fluoropyridinium salts.²⁰

	Scheme 5
	Scheme 6
	Scheme 7
	Scheme 8

Aminofluorothiophenes are possible precursors that can be used in the synthesis of fluoroquinolone antibiotics.²¹ Although 1 has shown reasonable reactivity for the fluorination of acetanilide, it was incompatible with acetamidothiophene, and the fluorinated derivatives were obtained in very low yields.²² Two possible routes to 2,2-difluoro-1-keto-5-tosylbenzazepine using 1 are available.²³ In the first procedure, the 1-keto-5-tosylbenzazepine was reacted with lithium hexamethyldisilazane (LHMDS) in THF to generate lithium enolate and then with trimethylsilyl chloride to furnish the corresponding silylenol ether. The latter reaction, with 1 in acetonitrile, gave monofluorobenzazepine. The sequence of enolization, silyl ether formation, and fluorination with 1 was applied to the monofluoro derivative in order to obtain 2,2-difluoro-1-keto-5-tosylbenzazepine in 90% yield (Scheme 4). The second route involved the generation of an enol acetate derivative from 1-keto-5-tosylbenzazepine, followed by the reaction with 1 in acetonitrile to give the monofluorobenzazepine derivative, which was subsequently fluorinated with 1 to form the difluoro product in 85% yield. In both the processes, ~2-4% of the monofluoro derivative remained.

Stavber has utilized 1 in the high-yield, direct synthesis of 4-fluorocyclohexa-2,5-dienone derivatives. Estrogen steroids were also readily converted to 10-fluoro-1,4-estradiene-3-one derivatives in good yields (Table 2).^22b

	Scheme 9
	Scheme 10
	Scheme 11
	Scheme 12
	Scheme 13
	Scheme 14

Hindered 2,4,6-trialkyl-substituted phenols were also selectively converted to p-quinols in high yield by reaction with 1. The effects of temperature and the presence of different external nucleophiles have been studied (Scheme 5).^22c Reactions of hindered phenols with 1 require well-defined conditions in order to ensure the selectivity of the course of reaction. At least for phenols with 1, it appears that the ET process is the main and most probable reaction pathway via the formation of a cation radical as the key step.

B. Electrophilic Fluorination of Aliphatics and Hydrocarbons. Several diphosphonates and phosphonophosphates were shown to be valuable inhibitors of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) enzyme. It was demonstrated that ,-difluoromethyl--ketophosphonates have higher affinities than their corresponding non-fluorinated analogues for GAPDH. Thus, various ,-difluoro--ketophosphonates have been synthesized and characterized by addition of the [F⁺] electrophile from 1 to the enolate form of the corresponding dibenzyl--ketophosphonates (Scheme 6) that exist in equilibria with their hydrated forms.²⁴ Various -fluorophosphonates were synthesized by treatment of the -carbanions generated from several -(pyrimidine- or pyridine-2-ylsulfonylalkylphosphonates) with 1, followed by deprotection with tributyltin hydride/AIBN (Scheme 7).²⁵ This method has also been used to make non-phosphofluoro esters.²⁶ Chambers et al. have shown the transformation of carbon-hydrogen bonds to carbon-fluorine bonds at saturated secondary and tertiary carbon sites with 1. One major and several minor products are formed selectively, with concomitant formation of other isomers (Scheme 8).²⁷ When the reaction time was increased, an acidic medium was produced due to formation of HF, and the final products obtained were the hydrocarbon amides. The mechanism of the amide formation from admantane and other hydrocarbons during electrophilic fluorination reaction with Selectfluor in acetonitrile is shown in Scheme 9. Upon standing, HF was eliminated from the fluorinated admantane A to give the corresponding tertiary carbanion B. The latter reacted with acetonitrile in a Ritter-type process to give C, which was subsequently hydrolyzed to the amide.²⁷

	Scheme 15
	Scheme 16
	Scheme 17
	Scheme 18

A dithio heterocycle was found to be reactive with 1 to give the corresponding monofluoro derivative (Scheme 10).²⁸

C. Electrophilic Fluorination of Aliphatic Amines. Reactions of primary and secondary amines with 1 yield a straightforward route to RNHF, RNF₂, and R'₂NF at ambient temperature. While the reactions proceed smoothly in acetonitrile, DMA or DMF was found to be a more suitable solvent due to a greater difference in solvent/product boiling points (Scheme 11).²⁹

	Scheme 19
	Scheme 20 a a CD, cinchonidine; CN, cinchonine; QD, quinidine; QN, quinine; DHQD, dihydroquinidine; DHQN, dihydroquinin. bMeasured in acetone-d6, standard CFCl3.

We have also developed a new nucleophilic difluoroaminating reagent, (t-Bu)₃SiNF₂, whose synthesis takes advantage of the fluorination of a sterically hindered silylamine. Direct reaction of (t-Bu)₃SiNH₂ with 1 in acetonitrile resulted in marked cleavage of the silicon-nitrogen bond to form (t-Bu)₃SiF and (t-Bu)₃SiNHF in about 15% yield. Alternatively, (t-Bu)₃SiNHF was isolated in about 50% yield when the monolithium salt was reacted with 1. However, the desired product, (t-Bu)₃SiNF₂, was isolated in about 60% yield when the reaction of (t-Bu)₃SiNHF was carried out with approximately 1 equiv of 1 in acetonitrile (Scheme 12).³⁰

D. Electrophilic Fluorination of Alkenes and Their Derivatives. Fluorodesilylation of alkenyltrimethylsilanes, an easy route to fluoroalkenes as well as difluoromethyl-substituted amides, alcohols, and ethers, is realized by using 1. Reactions of various alkyltrimethylsilanes with 1 equiv of 1 led to the formation of monofluoroalkenes. When the reactions were carried out with 2.5 equiv of 1 in acetonitrile, the resulting products were difluoromethylated amides. The presence of an external nucleophile, such as water or alcohol, with acetonitrile gave difluoromethylated alcohols or ethers (Table 3).³¹

The reaction of trans-stilbene with 1 in the presence of weak nucleophiles (NuH, Nu = OMe, OH, OAc) in acetonitrile gave erythro/threo mixtures of monofluorinated compounds.³² The use of fluorinated alcohols as nucleophiles in acetonitrile did not give the desired product. At the end of the reaction, a Ritter-type monofluorinated amide was isolated in good yield.³³ However, the above reaction with trifluoroethanol, in the absence of acetonitrile, gave the -keto ether in moderate yield (Scheme 13).³⁴ The formation of benzil was also detected. The yields of the -keto polyfluorinated ethers were found to be higher when N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31, Daikin) was used as the electrophilic fluorinating reagent.

Interaction of 1 with 3,7-bis-methylenebicyclo[3.3.1]nonane derivatives in monoglyme results in the transannular cyclization of the dienes to form 1-fluoro-3-fluoroalkyladmantanes. In the presence of nucleophiles, using nitromethane as a solvent, monofluoro derivatives were produced (Scheme 14).³⁵

Fluorination of norbornene with 1 in acetonitrile resulted in the formation of two rearranged Ritter-type products, 2-exo-acetamido-7-syn-fluoronorbornane and 2-exo-acetamido-7-anti-fluoronorbornane, in a 1:1 ratio. The presence of an external nucleophile, e.g., water or methanol, resulted in formation of two additional rearranged products, 2-exo-hydroxy or methoxy-7-syn-fluoronorbornane and 2-exo-hydroxy or methoxy-7-anti-fluoronorbornane (Scheme 15).³⁶

	Scheme 21 a a CD, cinchonidine; CN, cinchonine; QD, quinidine; DHQD, dihydroquinidine; DHQN, dihydroquinin.
	Scheme 22
	Scheme 23
	Scheme 24
	Scheme 25

A plausible reaction mechanism for the formation of these monofluoronorbornane derivatives is shown in Scheme 16. The first step could be the -complex formation and its transformation through a three-centered transition state (A) to the -fluorocarbonium ion B. Formation of C can be expected by Meerwein-Wagner rearrangement. The reaction of C with acetonitrile as a nucleophile led to the formation of 2-exo-acetamido-7-syn-fluoronorbornane D after water workup. The hydride-shift rearrangement of fluorocarbonium ion C can give fluorocarbonium ion E, which reacts with acetonitrile, giving 2-exo-acetamido-7-anti-fluoronorbornane F. In the presence of an external nucleophile, hydroxy and methoxy derivatives can be obtained.³⁶

	Scheme 26
	Scheme 27
	Scheme 28

Reaction of 1 with cis-5-norbornene-endo-2,3-dicarboxylic acid, its monomethyl ester, and 5-norbornene-endo-2-carboxylic acid in acetonitrile led to the formation of the corresponding fluorinated -lactones (Scheme 17).³⁷

E. Electrophilic Fluorination of Glycals. Various glycals were found to react with 1 in acetonitrile in the presence of alcohol-type nucleophiles to give the monofluorinated disaccharides. Acetonitrile also participated in these reactions. Thus, to avoid solvent participation, nitromethane was found to be suitable. Reactivity of 1 as its triflate derivative was also compared and found to give higher yields (Table 4).^38a The authors attribute the higher yields with the triflate derivative vis-à-vis the tetrafluoroborate salt to a side reaction between the latter anion and one of the reaction products which does not occur with triflate. Earlier studies show no convincing evidence for the operation of a counterion effect and suggest that there is not much to choose from, from the viewpoints of handling and product yield, between triflate, tetrafluoroborate, and hexafluorophosphate. The tetrafluoroborate is most cost-effective.^38b Other researchers have also fluorinated glycals with 1 at position 2 to achieve additional fluorinated glycal products, as shown in Scheme 18.^39,40

	Scheme 29
	Scheme 30
	Scheme 31
	Scheme 32
	Scheme 33

Wong and co-workers have reported one-pot syntheses of 2-deoxy-2-fluoro sugars and their glycosides from glycals using Selectfluor (1) in the presence of nucleophiles. This methodology has been further extended to the synthesis of glycosyl fluorides and glycosides from anomeric hydroxy or thioglycoside derivatives (Table 5).^40b Interestingly, 1, in conjunction with methyl sulfide, transforms 1-OH monosaccharides to 1-F derivatives, presumably as does diethylamino sulfur trifluoride (DAST), proceeding via a fluorosulfonium ion. Similarly, DAST maybe replaced by 1 as a fluorinating reagent in the conversion of thioglycosides to glycosyl fluorides (Table 5, entries 6 and 7).

Scheme 34

IV. Stereoselective Electrophilic Fluorination Reactions

A. Syntheses of Chiral N-F Reagents and Their Uses in Asymmetric Syntheses. Selectfluor (1) has been used to transfer fluorine onto various cinchona alkaloids to generate chiral electrophilic fluorination reagents.⁴¹ The first enantioselective fluorinating reagent, the N-fluoro quaternary ammonium salt of cinchonidine, was prepared in a one-step transfer-fluorination of the quinuclidine moiety with 1 (Scheme 19).⁴² The X-ray crystal structure showed the N-F distance is 1.409(7) Å, which approaches that found in other N-F electrophilic fluorinating reagents. Later, various other chiral N-F electrophilic fluorinating reagents were synthesized and characterized (Scheme 20).⁴³ Using these reagents, enantioselective electrophilic fluorination of N-phthaloylphenylglycine derivatives resulted (Scheme 21). Under usual fluorination conditions, the enantiomeric excess of N-phthaloylphenylglycinonitrile was consistently higher than that of N-phthaloyphenylglycine ethyl ester, as determined by HPLC.

The fluorination of the enolate of 2-methyl-1-tetralone with F-QD-BF₄, F-CN-BF₄, F-QN-BF₄, and F-CD-BF₄ (Scheme 22) demonstrated that F-CD-BF₄ has better enantioselectivity. Thus, using F-CD-BF₄, various other enolates have been reacted to give chiral monofluoro derivatives (Table 6).⁴⁴

B. In Situ Generation of Chiral N-F Reagents and Their Uses in Asymmetric Synthesis. Cinchona alkaloid/Selectfluor combinations efficiently fluorinate a variety of carbonyl compounds in a highly enantioselective manner to furnish chiral -fluorocarbonyl compounds. The DHQB/Selectfluor and DHQDA/Selectfluor combinations were effective for the enantioselective fluorination of indanones, tertalone, and acyclic and cyclic ester derivatives (Scheme 23).⁴⁵

C. Direct Application of Selectfluor in Stereochemical Syntheses. Stereochemical syntheses of monofluoro ketomethylene dipeptide isosteres were also developed. N-Tritylated ketomethylene dipeptide isosteres (prepared from N-tritylated amino acids) were converted to the Z-trimethylsilyl enol ethers, which were fluorinated with 1 to yield monofluoro derivatives (Scheme 24).⁴⁶

Shibata et al. have recently shown the syntheses of fluorogypsetin and fluorobrevianamide with 1 (Scheme 25).⁴⁷

Bile acids are aliphatic compounds synthesized in the liver from cholesterol. Fluorination of these bile acids at the 6-position prevents bacterial dehydroxylation, and this concept led to the identification of 6-fluoroursodeoxycholic acid as a potential agent for the prevention and treatment of colorectal cancer.⁴⁸ The treatment of the silyl enol ether derivative of cholesterol with 1 gave the corresponding monofluorinated product in 93% yield (Scheme 26)^49a

Scheme 35

Catalytic enantioselective fluorination of -ketoesters occurred with 1. However, the monosubstituted -ketoester does not react with Selectfluor in acetonitrile, which may be due to minimal enolization. However, addition of a range of Lewis acids efficiently catalyzed the reaction. Among various Lewis acids tested, it was evident that the titanium-based Lewis acids constitute the most potent catalysts and gave good % ee (Scheme 27).^49b

A reaction mechanism for the formation of chiral -keoesters using the chiral titanium catalyst was suggested.^49c It was assumed that, at first, the -ketoester coordinates to the catalyst as an enolate and substitutes one of the two chloride atoms and one of the acetonitrile molecules (Scheme 28). Thus, the octahedral monochloro Ti(enolate) complex is the reactive species and is fluorinated by Selectfluor in the C-F bond-forming step. Computational and experimental studies have been also explored.

Some chiral fluorinated ketones, TFK and BPHFK, have been synthesized using 1 (Scheme 29), and their potential as enantioselective catalysts for asymmetric epoxidation with Oxone (potassium peroxy monosulfate) has been evaluated.⁵⁰ The troponine-based fluoroketone (TFK) has shown excellent reactivity but only modest enantioselectivity. The biphenyl-based fluoroketone (BPHFK) exhibited only modest reactivity, but complete conversion occurred in a reasonable time. The enantioselectivity of this catalyst was much higher but also depended on the substrate (Scheme 30).

V. Selectfluor-Mediated Organic Reactions

Selectfluor (1) is an electrophilic fluorinating reagent, but under its mediation, additional organic syntheses were also performed. Electrophiles such as Cl⁺, Br⁺, SCN⁺, and NO₂⁺ can be generated from their respective sodium salts using 1 in acetonitrile solution at room temperature. These electrophiles subsequently react in situ with a variety of aromatic substrates containing one or more substituent groups, including H, F, Cl, CH₃, COOH, C(O)CH₃, and NO₂ (Scheme 31).⁵¹

Direct iodination reactions of various benzene derivatives under the mediation of 1 occur. The iodine atom was introduced at the most electron-rich and the least sterically hindered position on the benzene ring (Scheme 32).^52,53

The direct introduction of alkoxy, amido, azido, or halogeno functional groups at the benzylic position in hexamethylbenzene, mediated by 1 in the presence of alcohols, carboxylic acids, nitriles, or trimethylsilyl derivatives as sources of external nucleophiles, proceeds quite well. Functionalization of hexamethylbenzene with a perfluoroalkyl moiety containing a functional group also occurs smoothly in the presence of polyfluorinated alcohols or potassium salts of polyfluoroalkane carboxylic acids (Scheme 33).^54,55

Reactions of aryl alkyl ketones in methanol solution of iodine in the presence of 1 resulted in the formation of the corresponding -iodoketones in good yield (Scheme 34).⁵⁶

Reactions of aldehydes and imines with allyltributyltin, catalyzed by 1 in acetonitrile, gave homooallylic alcohols and amines (Scheme 35).⁵⁷

It was shown that 1 can cleave p-methoxybenzylidine (PMP), tetrahydropyranyl (THP), and 1,3-dithiane groups efficiently (Scheme 36).⁵⁸

Scheme 36

An attempt to fluorinate metal -diketonates with 1 resulted in the formation of a six-coordinate complex. In this case, 1 did not act as a fluorinating reagent, but fluorine was lost, and the remainder of the ligand formed a donor complex whose structure was confirmed by single-crystal X-ray (Scheme 37).⁵⁹

Scheme 37

Reaction of the cobalt bis(dicarbollide) anion [commo-3,3'-Co(3,1,2-CoC₂B₉H11)₂^-] with 1 in anhydrous acetone led to the formation of the corresponding 8,8'-difluoro derivative of the anion [commo-3,3'-Co-8F-3,1,2-CoC₂B₉H10)₂^-]. The structure of the NBu₄⁺ salt of the 8,8'-difluoro derivative has been determined by single-crystal X-ray crystallography.⁶⁰

VI. Conclusion

This Account has highlighted the chemistry of Selectfluor as an effective electrophilic fluorinating reagent with organic substrates. Fluorination of a wide variety of organic compounds, such as hydrocarbons, aromatics, alkenes, carbohydrates, etc., is described. Selectfluor has been utilized in the syntheses of various chiral cinchona alkaloid N-F reagents that show very good applications in asymmetric synthesis of chiral fluorine-containing compounds. In some reactions, novel organic syntheses of non-fluorinated compounds have been performed in the presence of Selectfluor.