Reactions with BF3 and

The reactions in the system OF2-B2H6 are of special interest because the mixture can be used as a space-storable bipropellant, see p. 9. Mixtures of OF2 and B2H6 can explode on warming from -195°C to ambient temperature. Between 120 and 170°Cand below 20 Torr, OF2 and B2H6 react slowly [2] according to 

The initial rates of consumption of OFg and BgHe and the initial rate of formation of BF3 were determined for the reaction between OFg and BgHe at 300 K. The initial partial pressures were 5 to 40 Torr for OFg and 1 to 30 Torrfor BgHe. In addition, the initial consumption rates of OFg and BgHe were determined between 300 and 330 K. These initial rates were correlated to initial reactant concentrations and to reactor temperature (p in Torr, t in min, T in K) [3]  

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Lewis acid (fluoride-ion acceptor) behaviour is exemplified by reactions with NOF and MF to give [N0]+[C1F2] and M+[C1F2] respectively (M = alkali metal or NH4). Lewis base (fluoride ion donor) activity includes reactions with BF3 and ASF5 ... 

The acidity of liquid HF is high enough that it can function as an acid catalyst in many instances. The cation characteristic of the solvent, H2F+, is generated when HF reacts with a strong Lewis acid that is capable of forming stable fluoride complexes. The reactions with BF3 and AsF5 are typical ... 

For the above reaction to occur, the aromatic nuclei in compound 1 should carry activating groups, such as hydroxyl, alkoxy, or fused ring aromatics". As a result of reaction with BF3 and phenol, the macromolecular structure of coal should undergo rupture at the aliphatic bridges, and these bridges are transferred to phenol molecules to produce bisphenols. Analysis of the bisphenols should provide information on the aliphatic bridges present in coal structure. 

My early work with acyl fluorides also involved formyl fluoride, ITCOF, the only stable acyl halide of formic acid, which was first made in 1933 by Nyesmeyanov, who did not, however, pursue its chemistry. 1 developed its use as a formylating agent and also explored formyla-tion reactions with CO and HF, catalyzed by BF3. 

In all its reactions the lone pair of thiazole is less reactive than that of pyridine. Table 1-61 shows three sets of physicochemical data that illustrate this difference. These are (1) the thermodynamic basicity, which is three orders of magnitude lower for thiazole than for pyridine (2) the enthalpy of reaction with BF3 in nitrobenzene solution, which is 10% lower for thiazole than for pyridine and (3) the specific rate of quaterni-zation by methyl iodide in acetone at 40°C, which is about 50% lower for... 

Oxazoborolidinone 8 is an example of catalyst supported on silica gel. It is prepared by immobilizing the N-tosyl-0-allyl-(S)-tyrosine with mercaptopropyl silica and treatment with BF3 and has been used to catalyze the Diels-Alder reaction of methacrolein with cyclopentadiene [17] (Equation 4.2). The cycloaddition occurs with good diastereoselectivity but with low enantioselec-tivity. 

When unsymmetrical ketones were used in this reaction (with BF3 as catalyst), the less highly substituted carbon preferentially migrated. The reaction can be made regioselective by applying this method to the a-halo ketone, in which case only the other carbon migrates. The ethyl diazoacetate procedure has also been applied to the acetals or ketals of a, P-unsaturated aldehydes and ketones. ... 

Reaction with nitrile and phosphine complexes 6.5.3.1 C4 Bf3 FeGaNa 2O4 Na2[(CO)4FeGaBr3]... 

Lewis acid catalysts can also effect dealkylation, i.e. the reaction is reversible. Thus ethylbenzene (22) with BF3 and HF, is found to disproportionate ... 

What would be the products of the reaction of BF3 with I2 Would you expect a similar reaction between BF3 and Cl2 to occur Explain your answer. 

Transalkylation involves the transfer of alkyl groups between aromatic nuclei, usually in the presence of strong Lewis acids. Heredy and Neuworth used this reaction to "depolymerize" coal. As a result of the reaction of coal with BF3 and phenol, the solubility of coal in phenol or pyridine increased substantially. Various modifications of this reaction have since been reported . Transall lation reactions in the presence of trifluoromethane sulfonic acid and aromatic hydrocarbons have recently been used by Benjamin et al. and Farcasiu et al. to identify structural features in coals and heavy petroleum ends, respectively. 

We are at a loss to explain the discrepancy in the BF3 enthalpies of interaction with the sulfur donors. Steric effects may be operative, but this is far from the whole story for the BCI3 interaction is much larger than BF3 with these donors. Furthermore, using the tentative ( 113)3 parameters to estimate those of ( 2115)3 , we calculate an enthalpy from E and of 11.1 k.cal mole- for the BF3-P( 2H6)3 adduct compared to a measured value of 9.5 k.cal mole i. The authors report much difficulty with the sulfur donor system, but their error estimates could not possibly account for the difference between our calculated and the observed result. The behavior of ( 2115)35 compared to ( 2115)3 is clearly inconsistent with the behavior of these two donors toward ( 2H5)sAl where both enthalpies are correctly predicted with our parameters. It may be that the BF3-( 2115)25 system has an even lower equilibrium constant than reported and is completely dissociated over the temperature range studied. (This would require a very different entropy if the — AH predicted by E and were correct.) A slight impurity (reported to be less than 0.1%) or decomposition product could interact appreciably with BF3 and changing pressure contributions from this adduct with temperature could be attributed incorrectly to the sulfur donor adduct. The actual BF3-sulfur donor adduct would then be a very common example of an adduct which cannot be studied by the vapor pressure technique because it is completely dissociated at the temperatures at which one of the components has appreciable vapor pressure. We have examined the reaction of BF3 ( 2Hs) 2O with large excess of ( H2) 4S in dichloroethane solution at 25 ° and have found the equilibrium constant to be too low to be measured calorimetrically. 

As mentioned above, besides the alkyl halide-Lewis acid combination, two other sources of carbocations are often used in Friedel-Crafts reactions. Alcohols can serve as carbocation precursors in strong acids such as sulfuric or phosphoric acid. Alkylation can also be effected by alcohols in combination with BF3 and A1C13 2 Alkenes can also serve as alkylating agents when protic acids, especially H2S04, H3P04, or HF, or Lewis acids, such as BF3 and A1C13, are used as catalysts.33... 

The 3-oxo-l,5-cyclocholestane (158) rearranges with BF3 and with HCOjH to give the enone (159) electrophilic attack at the carbonyl oxygen is followed by cleavage of the 1,5-bond to produce an intermediate C-5 carbocation. A minor product (160) in the BFs-catalysed reaction is derived from cleavage of the 1,10-bond. " Addition of methanol or ethanol across the 1,5-bond is catalysed by FeCU.bHzO. 

Methyl arylacetates.2 Aryl methyl ketones are converted into methyl arylacetates by reaction with BF3 etherate and lead tetraacetate in benzene at room temperature (equation I). Thallium(lll) nitrate (4, 496) has also been used for this modified Willgerodt-Kindler reaction. 

Ally lie y benzylic, or tertiary bromides (iodides). Allylic, benzylic, or tertiary alcohols are converted into bromides or iodides by reaction with BF3 etherate and (C2H5)4NBr or (C2H5)4NI in CH2C12 in 60-80% yield. NaBr or Nal can replace (C2H5)4NX in the case of allylic or benzylic alcohols.12 The combination of BF3 etherate and (C2H5)4NX is useful for cleavage of ethers.13... 

Crotyldlisopinocampheylborane. IpC2BCH2CH=CHCH3 (1). The (Z)-isomer is prepared by reaction of (Z)-crotylpotassium with methoxydiisopinocampheylbo-rane [obtained from (- )-a-pinene] to form an ate complex, which is converted into (Z)-l on reaction with BF3 etherate at -78°. The (E)-isomer is prepared similarly from (E)-crotylpotassium. Reaction of acetaldehyde with (Z)-l at - 78° results in (2S,3S)-3-methyl-4-pentene-2-ol (2) in 99% diastereoselectivity and 95% enantioselectivity (equation I). A similar reaction with (E)-l provides (2S,3R)-2. 

Ally lie iodides. Allylic and benzylic alcohols (primary and secondary) are converted into the corresponding iodides by reaction with Nal and BF3 etherate in 70-95% yield. The same system converts sulfoxides to sulfides in 90-98% yield. 

Periodyl fluoride can be prepared by passing fluorine through a solution of HI04 in HF (274) and by the reaction of KIOF4 with HS03F (260). It is a white crystalline solid, stable to 100°C. It possesses some fluoride ion-donating properties and a solution of the oxide fluoride in HF reacts with BF3 and AsFs (238) to yield compounds that contain the [I03T cation. 

As already discussed above several C-nucleophiles also add smoothly to y-lactols (Eq. 85, Table 9). BF3 is the promotor of choice allowing efficient and highly diastereo-selective reactions with allyl and cyanotrimethylsilane or with bis(trimethylsilyl)ace-tylene which introduce the corresponding substituents at C-5 of the methyl tetra-hydrofuran-3-carboxylates 204, In the case of propargyltrimethylsilane an allenyl group is transferred to the heterocyclic 93). 

Structures (316) with an oxetan ring, recently proposed250 for two iodo-compounds obtained during the hypoiodite reaction of cholesterol, have now been revised.251 Spectroscopic and X-ray data show the compounds to be iodo-acetals (317), converted by de-iodination and reaction with BF3-acetic anhydride into the dihydropyran (318). Photolysis of the oxime of a l,5-dien-3-one gave mainly rearranged ketonic products, isomers of type (319), which are also obtained by photo-rearrangement of the l,5-dien-3-one.252... 

With BF3 and PF5, SF5NH2 forms 1 1 adducts (183). Reaction occurs at room temperature between SF5NH2 and various acid chlorides and fluorides containing electron-deficient carbonyl groups to produce iV-pentafluorosulfanyl amides, F5SNHC(0)R (R = F, CF3, CH3) (149). The reaction of SF5NCO with certain carboxylic acids at room temperature provides an alternate route for the preparation of amides, SF5-... 

Boron trifluoride forms addition compounds that incorporate an sp hybridized boron into a tetravalent structure. Salts of BF4 are readily formed with BF3 and a suitable fluoride donor. Halogen fluorides such as chlorine trifluoride react with BF3 to generate interhalogen cations such as [C1F2]+[BF4]. Some further examples are shown in equations (43) and (44). In an organic application, the Schiemann reaction provides an entry into fluorinated aromatics by thermal decomposition of a diazonimn tetrafluoroborate (equation 45). 

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