1.4- Bis tetrafluoroborate

Dimethylquinoxaline and trimethyloxonium tetrafluoroborate gave 1,4,6,7-tetramethylquinoxalinediium bis(tetrafluoroborate) (214) (excess synthon. 

Among the recently (as of 2003) described reactions of such quaternary salts, reduction to dihydroquinoxalines has been exemplified toward the end of Section 2.2.4 treatment of the diquaternary compound, 1,4,6,7-tetramethylquinox-alinediium bis(tetrafluoroborate) (215), with sodium iodide gave a well-characterized product that appears in X-ray studies to have the cation radical structure (216) ""° and a fundamental spectrophotometric study on the addition of hydroxyl and methoxyl ions to the 1-methylquinoxalinium cation has been reported. ... 

The reduction of 2,2/-dithiobis(l,3-dithiolanium) bis(tetrafluoroborate) to the thiocarbonate compound by triethylsilane takes place quantitatively (Eq. 343).565... 

Figure 8.7 shows such a flow plot for the radical cation of the viologen species, l,l -bis(p-cyanophenyl)-4,4 -bipyridilium ( CPQ ), as the bis(tetrafluoroborate) salt in propylene carbonate solution, with the radical having been formed at a polished platinum electrode. The plot is seen to be linear, implying that, once formed, the CPQ radical cation is chemically stable. 

Methyl acrylate 2-Propenoic acid, methyl ester (9) (96-33-3) Tetrakis(acetonitrile)palladium tetrafluoroborate Pal 1adium(2+), tetrakis(acetonitrile)-, bis[tetrafluoroborate (l-)] (8,9) (21797-13-7)... 

Methylene-l,3-benzoxazin-2-ones 194 were found to be susceptible to addition to the exocyclic double bond. On heating under reflux in ethanol, oxazinones 194 were transformed to the 4-ethoxy derivatives 195. Treatment of 194 with l-chloromethyl-4-fluoro-l,4-diazabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA-BF4), an electrophilic fluorinating reagent, in the presence of methanol, led to the 4-fluoromethyl-4-methoxy-substituted compounds 196 (Scheme 34) <2003T8163>. 

Piperazine-2,5-diones, in which both amino acid units are primary, lead to bislactim ethers on O-alkylation with Meerwein s reagents. No selectivity in this reaction has been demonstrated so far. Such bislactim ethers (171) have been prepared and extensively used by Schollkopf and his school [79AG(E)863, and later papers]. During the preparation of these bislactim ethers, neutralization of the initially formed bis-tetrafluoroborate salt is carried out with phosphate buffer to avoid racemization. 

The apparatus and techniques used are similar to those for the synthesis of tetrakis(acetonitrile)palladium(II) bis[tetrafluoroborate(l —)]. A 100-mL round-bottomed flask (B) is charged with 2.0 g (7.6 mmol) of hexacar-bonylmolybdenum (Alfa) and 1.77 g (15.2 mmol) of nitrosyl tetrafluorobo-rate (Aldrich, sublimed 220°C, 10-3torr). Dry acetonitrile (50mL) is added and the solution is allowed to stir at 25 °C until no hexacar-bonylmolybdenum remains (6 h). 

The resulting dark emerald green solution is filtered and the filtrate is concentrated to near dryness in vacuum. Diethyl ether (40 mL) is added and the solution is vigorously stirred to cause precipitation of the dark green molybdenum complex. The solution is filtered and the solid washed with two 5-mL portions of diethyl ether. The precipitate is dried in vacuum (10" 3 torr, 25 °C) to afford 3.36 g (90%) of dark emerald green cis-tetrakis(acetonitrile)-dinitrosylmolybdenum(II) bis[tetrafluoroborate(l —)]. 

In a procedure identical to that described in Section B, the reaction is performed using 2.5 g (7.1 mmol) of hexacarbonyltungsten (Alfa) and 1.66 g (14.2 mmol) of nitrosyl tetrafluoroborate (Aldrich, sublimed 220 °C, 10-3 torr) An emerald green complex is isolated to yield 3.95 g (96%) of cis-tetrakis-(acetonitrile)dinitrosyltungsten(II) bis[tetrafluoroborate(l —)]. 

FsB2MoN602Hi2, Molybdenum(II), tetrakis(acentonitrile)dinitrosyl-c -bis[tetrafluoroborate( 1 —)], 26 123 F8B2N4PdCnH,2, Palladium(II), tetrakis-(acetonitrile)-... 

A series of l,T-difluorobipyridinium salts [l.T-difluoro-4,4 -bipyridinium, -2,2 -bipyridinium, -2,4 -bipyridinium ditriflate or bis(tetrafluoroborate)] have been synthesized in high yield by direct fluorination of salts or complexes of bipyridines with Bronstcd or Lewis acids with fluorine diluted with nitrogen (10% F2/N2).67,68... 

The bridgehead-amine-derived electrophilic fluorinating reagents l-alkyl-4-fluoro-l,4-di-azoniabicyclo[2.2.2]octane ditriflate 5 a or bis(tetrafluoroborates) 5b and 6 can be prepared from l-alkyl-4-aza-l-azoniabicyclo[2.2.2]octane salts and elemental fluorine. For example, treatment of l-methyl-4-aza-l-azoniabicyclo[2.2.2]octane triflate (4a) and lithium triflate in acetonitrile at — 35CC with neat fluorine over three hours gives l-fluoro-4-methyl-l,4-dia-zoniabicyclo[2.2.2]octane ditriflate (5a).81 The reagents 5b, 6, 7, and 8 can be synthesized in a similar manner.76 83... 

The new family of l-alkyl-4-fluoro-l,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) salts (5a, 5b, 6, 7) (commercial F-Teda BF4, 6), which are selective and easy-to-handle fluorinating reagents76,80 87 90 are commercially available under the trade name Selectfluor. 

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