Pyridine boron trifluoride complex

Effect of reaction mixture composition on the acidity of supported boron trifluoride complex as measured by spectrosopic titration with pyridine. 

The synthesis of the representative compound of this series, 1,4-dihydro-l-ethyl-6-fluoro (or 6-H)-4-oxo-7-(piperazin-l-yl)thieno[2/,3/ 4,5]thieno[3,2-b]pyridine-3-carboxylic acid (81), follows the same procedure as that utilized for compound 76. Namely, the 3-thienylacrylic acid (77) reacts with thionyl chloride to form the thieno Sjthiophene -carboxyl chloride (78). Reaction of this compound with monomethyl malonate and n-butyllithium gives rise to the acetoacetate derivative (79). Transformation of compound 79 to the thieno[2 3f 4,5]thieno[3,2-b]pyhdone-3-carboxy ic acid derivative (80) proceeds in three steps in the same manner as that shown for compound 75 in Scheme 15. Complexation of compound 75 with boron trifluoride etherate, followed by reaction with piperazine and decomplexation, results in the formation of the target compound (81), as shown in Scheme 16. The 6-desfluoro derivative of 81 does not show antibacterial activity in vitro. 

There are some reactions in which boron trifluoride and boron trifluoride-diethyl ether complex are used as fluorinating agents, but they are not so frequently used and widespread. The best-known reaction is the decomposition of fluoroformates. In this type of reaction boron trifluoride or pyridine are essentially required as catalysts for the decomposition process. The formation of fluoroformates is established4 5 and the decomposition proceeds cither by heating in pyridine at higher temperature6 or by addition of boron trifluoride-diethyl ether complex at 0-50°C.7... 

While arsabenzene does not act as a nucleophile toward hard acids, it does form a-Mo(CO)5 complex 57 on treatment with pyridine-Mo(CO) and boron trifluoride etherate100). Qualitatively complex 57 seems rather weak since on heating it is destroyed, forming small quantities of tc-Mo(CO)3complex 58 101). This rt-complex is more conveniently prepared directly from arsabenzene and Mo(CO)6 or from acid-catalyzed displacement from tris-(pyridine)molybdenum tricarbonyl. 

If cyclopentadienyliron dicarbonyl halides are allowed to react with themselves in the presence of Lewis acids, cations are formed in which the new substituent is the cyclopentadienyliron dicarbonyl halide itself, for example, [CjH6Fe(CO)i-X-(CO)2-FeC8H8]+ (X = Cl, Br, I). All three cations can be prepared best by treatment of the corresponding halides with boron trifluoride diethyl etherate all are isolated as tetrafluoro-borates.18 The bromine complex can also be obtained by a more complicated procedure by the reaction between C8H8Fe-(CO)2Br and AlBr3 in liquid sulfur dioxide 16 the iodine cation can be isolated from a melt of cyclopentadienyliron dicarbonyl iodide and aluminum chloride.17 In the latter two cases the hexafluorophosphate salts can be obtained. These binuclear cations are of special interest, because they are cleaved by electron donors,16-17 e.g., aniline, pyridine, benzonitrile, acetonitrile, acrylonitrile, with the formation of the corresponding [C8H8Fe(CO)2L]+ cations and the parent halide. Equations for preparation of the tetrafluoroborate are ... 

Naturally, it is possible to synthesise a similar ligand system without central chirality and in fact without the unnecessary methylene linker unit. A suitable synthesis starts with planar chiral ferrocenyl aldehyde acetal (see Figure 5.30). Hydrolysis and oxidation of the acetal yields the corresponding carboxylic acid that is transformed into the azide and subsequently turned into the respective primary amine functionalised planar chiral ferrocene. A rather complex reaction sequence involving 5-triazine, bromoacetal-dehyde diethylacetal and boron trifluoride etherate eventually yields the desired doubly ferrocenyl substituted imidazolium salt that can be deprotonated with the usual potassium tert-butylate to the free carbene. The ligand was used to form a variety of palladium(II) carbene complexes with pyridine or a phosphane as coligand. 

Suitable catalysts are pyridine, - dimethylformamide, tertiary amines.or Lewis acids such as boron trifluoride-diethyl ether complex, e.g. fomiation of The decarboxylation reaction is carried out under anhydrous conditions and in an inert gas atmosphere. 

Boron trifluoride-diethyl ether complex is a very versatile and useful Lewis acid in several organic reactions. The polymeric ether-BFs complex poly(p-methoxystyrene)-BF3 (14) has been prepared and is more stable and has higher activity in several organic reactions such as isomerization and epoxide rearrangement [26]. The polymeric version of pyridine-BF3 complex 15 has also been prepared from poly(vinylpyridine) and BF3 [27]. By analogy with the polystyrene-AlCls complex, simple crosslinked polystyrene also forms a stable complex in chloroform with boron trifluoride 16 [27]. 

Borabicyclo[3.3.1] nonane, 47-49 9-Borabicyclo[3.3.1] nonane-pyridine, 4 Borane-Dimethyl sulfide, 49-50, 174 Borane-Pyridine complex, 50-51 Botch reduction, 452-453 Boron trifluoride etherate, 51-52, 354, 402,478,480,502... 

The rearrangement of glycal derivatives to l-substituted 2-enose derivatives has been applied to the preparation of i) 2,3-dideoxy-i-thiohex-2-enopyranosides (9, trimethylsilylated thiols and boron trifluoride details of the complexities of the reaction are reported) ii) 2,3-dideoxyhex-2-enopyranosyl fluorides [10, pyridine poly(hydrogen fluoride)iii) 2, 3 -unsaturated nucleosides (11, purine or pyrimidine derivatives with trityl perchlorate) (Scheme 7). 

The insoluble polymeric pyridine-borane system (20) has been reported to reduce aldehydes and ketones in high yields at room temperature in the presence of boron trifluoride-etherate, whereas acid derivatives and a,/3-enones are not reduced. The polymer is used in benzene, and reducing power is better if the polymer beads are swollen in benzene before use. The corresponding polymeric 4-pyridyl-borane (21) is sluggish in reductions but reactivity can be increased using a borane complex of the quaternary polymer (22), which is assumed to... 

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