I Tetrafluoroborate

Technetium-9 9m sestamibi is used in myocardial perfusion imaging for the evaluation of ischemic heart disease. It is prepared from a lyophilized kit containing tetrakis(2-methoxy isobutyl isonittile) copper(I) tetrafluoroborate stored under nitrogen. Upon reconstitution with up to 5.6 GBq (150 mCi) of 99mTc pertechnetate, the product is formed by boiling for 10 minutes. 

In the case of 2,3-dihydro-l-benzothiepin 1-oxide (5), alkylation with iodomethane and silver (I) tetrafluoroborate leads to the methoxysulfonium salt 6 in 65% yield.86... 

The selective insertion of diphenylacetylene in the cyciopaiiadated sulfide complex 1 leads to the stable organometallic complex 2, which can be depalladated with silver(I) tetrafluoroborate to give a mixture of the dibenzothiepinium salt 3 and the dibenzo[Z>,z ]thiepin 4.91 Demethyla-tion of 3 to yield 4 is complete after refluxing overnight in chlorobenzene. The synthetic scope of this method for thiepin derivatives is limited due to their thermal instability, but the method is very suitable for the synthesis of 1//-2-benzothiopyrans.91... 

Acyl-3.4-benzo-2-azabicyclo[3.2.0]hepta-3,6-dienes 1, on heating at 250-280 C for a short time without solvent, rearrange to the 1-acyl-1-benzazepines 2 (Method A).23-38 In some cases, rearrangement is accompanied by minor amounts of Ar-aeyl-l-naphthylamine and, at higher temperatures, the acylnaphthylatnine can become the major product (see Section 3.2.2.6.). In the presence of silver(I) tetrafluoroborate (Method B) rearrangement takes place at lower temperatures but the yields of benzazepine are inferior as the silver(I) ion also catalyzes the reverse reaction (see Section 3.2.2.1.). 

The thermally induced electrocyclic ring opening of 2-alkyl- and 2-acyl-3.4-benzo-2-azabicyclo-[3.2.0]hepta-3,6-dienes 2 to l//-l-benzazepines 1 (see Section 3.2.1.4.1.1.) are photorever-sible.23,37 38 Also, l-acyl-1//-benzazepines 1 (R = acyl), in refluxing xylene in the presence of silver(I) tetrafluoroborate, are in thermal equilibrium with their valence isomers the 2-acyl-3,4-benzo-2-azabicyclo[3.2.Oj nepia-3,6-uienes 2 (R = acyl).23-38... 

The benzothiazepinone 2 is converted into the Ar-methyl derivative 5 by treating its sodium salt with iodomethane and into 5-methoxy-l,4-benzothiazepine (6) with trimethyloxonium tet-rafluoroborate. Compound 6 gives the S-methyl salt 7 on methylation with iodomethanc/sil-ver(I) tetrafluoroborate.49... 

The gold complex, generated in situ from bis(4-isocyanocyclohexyl)gold(I) tetrafluoroborate and (A)-A-methyl-,V-[2-(dialkylamino)ethyl]-l-[(5)-r,2-bis(diphenylphosphino)ferrocenyl]eth-ylamine, is an effective catalyst for the aldol reaction of various aldehydes with methyl iso-cyanoacetate to give the trans- and cw-4,5-dihydro-l,3-oxazoles. Depending on the aldehyde, the transjeis product ratio ranges from 84 16 to 100 0, and the ee of the main diastereomer is between 72 and 97%26. 

Bis[Ar,Ar -di(2-pyridyl)- and -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(i) tetrafluoroborates have been prepared from the analogous silver complexes on reaction with (tht)AuCl and their structures determined. The configuration of the cations with sterically well-protected two-coordinate gold centers shows no anomalies. However, fascinating structures are found for the adducts with silver tetrafluoroborate obtained as acetonitrile... 

In a 25 mL Schlenk-type flask, equipped with a 10 mL pressure equalized dropping funnel and a magnetic stirring bar, were placed bis(l,5-cycloocta-diene)rhodium(I) tetrafluoroborate (111mg) and dichloromethane (5mL) under nitrogen. 

Barluenga et al. developed a novel exo-endo-cyclization of a,codiynes by use of bis(pyridyl) iodonium(I)-tetrafluoroborate (IPy2BF4) as catalyst.1171 The reaction follows a cationic-cationic pathway (scheme 6). First the electrophilic iodo ion reacts with the triple bond of 26 to give the relative stable vinyl cation 28. Ring closure leads to a seven-... 

Bis(5> m-collidine)iodine(I) tetrafluoroborate in DMSO has been found to be a convenient reagent for the conversion of alkanes to a-iodocarbonyl compounds. When dihydrofuran (305a) and dihydropyran (305b) are the substrates, this reaction affords the corresponding a-iodolactones 306 (Scheme 77). This method converts certain glycals such as 307 to their corresponding a-iodo-a,/3-unsaturated lactones 309, presumably because of elimination of a molecule of acetic acid from the initially formed lactone 308 (86S727) (Scheme 78). 

An jco-OT o-cyclisation of a,o -diynes promoted by bis(pyridyl)iodonium(i) tetrafluoroborate (IPy2BF4) has been described for the first time and is an excellent route for accessing a variety of sulfur-containing heterocycles when employing alkynyl sulfides (Scheme 49) <1998AGE3136>. 

Lastly, a formal synthesis of almotriptan (5) has been published by the Bosch group in Spain using an intramolecular Heck approach (Scheme 23). lodination of aniline 58 with bis(pyridine)iodonium(I) tetrafluoroborate followed by reaction with trifluoroacetic anhydride (TFAA) gave the o-iodotrifluoroacetanilide 66. Alkylation of 66 with methyl 4-bromocrotonate afforded 67, which underwent palladium catalyzed... 

Silver(I) tetrafluoroborate (2) is a yellowish powder which can be easily prepared from silver(I) oxide and boron trifluoride-diethyl ether complex (1). 

Like thallium(I) fluoride (see Section 18.2.), silver(I) tetrafluoroborate is used to convert chloro-formates into the corresponding fluoroformates, which are decomposed to the fluorides as described in Section 16.1.2. Phenyl fluoroformate (4) is obtained in moderate yield in this way from 3.68... 

Silver(I) tetrafluoroborate converts a-bromo-substituted ketones, e.g. 7, to the corresponding fluoro-substituted ketones, e. g. 8, under anhydrous conditions.69 Attempts to convert the a-chloro-substituted ketenes under the same conditions failed.69... 

The displacement of less activated halogen groups by silver(I) tetrafluoroborate to the corresponding fluorides is not so widespread. Although silver(I) tetrafluoroborate cannot be used to transform an aliphatic terminal dichloromethyl or trichloromethyl group to the corresponding fluoro compound, it has been known to work in many other cases (Table 13).70... 

Exchange-Fluorination by Reaction with Silver(I) Tetrafluoroborate General Procedure 70... 

The reaction of various bromocyclobutancs with silver(I) tetrafluoroborate gives partial or complete exchange of bromine for fluorine, depending on the reactant ratio. In some cases cyclopropanes and acyclic compounds have been formed.71... 

A method for the synthesis of glycosyl fluorides 11 starting from the glycosyl chlorides 10 with silver(I) tetrafluoroborate proceeds under very mild, homogeneous conditions.72,73 The ratio of isomers formed is dependent on the solvent used. The results are summarized in Table 14.72,73... 

Molar ratio of glycosyl chloride and silver(I) tetrafluoroborate was 1 1.2, unless otherwise stated. b Compounds obtained were proved to be identical with authentic samples. 

Chlorinated oxiranes can be treated with silver(I) tetrafluoroborate to yield the corresponding a-fluorocarbonyl compounds as major products and the isomeric a-chlorocarbonyl compounds as minor products.74... 

Trialkyl- or triaryl-1,l-difluoro-25-phosphorines can be prepared by treating the chloro or bromo derivatives with silver(I) tetrafluoroborate.75... 

Chlorosilanes78 and metal-bound chlorosilanes7980 and metal-bound chlorogermanes80 are converted with silver(I) tetrafluoroborate to the fluorides. 

Chloro- or bromocyclopentadienyl complexes of titanium and zirconium react with silver(I) tetrafluoroborate to form the corresponding fluoro complexes.81 Other complexes yielded the tetrafluoroborates. 

Glycosidation Allyl chloroformate, 9 Boron trifluoride etherate, 43 Silver(I) tetrafluoroborate, 273 Silver (I) trifluoromethanesulfonate, 274 Thallium zeolites, 296 Tin(II) trifluoromethanesulfonate, 301 Trichloroacetonitrile, 321 Grignard reactions and reactions of... 

Sodium triacetoxyborohydride, 283 Titanium(III) chloride, 302 Tributyltin hydride, 316 Zinc borohydride, 167 of alkenes to alkanes (R)-(-F)- and (S)-(-)-2,2 -Bis(di-phenylphosphine)-l,1 -binaphthyl, 36 [1,4-Bis(diphenylphosphine)-butanej(cycloheptatriene)-rhodium(I) tetrafluoroborate, 89 [ 1,4-Bis(diphenylphosphine)butane]-(norbornadiene)rhodium(I) tetrafluoroborate, 37... 

Ruthenium tetroxide, 268 Silver(I) tetrafluoroborate, 273 8-Lactams Iodine, 148... 

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