Esters boron trifluoride complex

Perfluoroalkyllithium reagents react with electrophiles such as aldehydes, ketones, silicon and tin halides, alkyl halides, carbonates, esters, boron trifluoride-imine complexes, and sulfur dioxide. ... 

From Table III it is apparent that a number of different donors could be used to obtain very attractive fractionation factors. Indeed, at 30°C., the isotopic equilibrium constant was 1.03, or more, for phenetole, anisole, diethyl ether, ethyl formate, dimethyl selenide, dimethyl sulfide, and diethyl sulfide. However, all of these donors were not equally satisfactory for our purpose. The boron trifluoride complexes of the thioethers, the selenide, and the ester had a pronounced tendency toward irreversible decomposition and were too unstable to be seriously considered for an... 

Medium and large rings can be made via cationic intermediates which are usually generated by treatment of suitable precursors with acid. Reactions of this class are perchloric acid catalyzed rearrangements of bicyclo[n.l.0]alkan-2-ols (n > 5), solvolysis of the corresponding esters, boron trifluoride-diethyl ether complex catalyzed cleavage of epoxides, and tri-fluoroacetic acid catalyzed reactions of 7-(methylsulfanyl)bicyclo[n.l.0]alkanes. 

Once again the enantioselectivity is highly sensitive to even small changes. With 1.2 instead of 2 equivalents of the chiral triamine, the ee decreases to 34%. The enantioselectivity is also strongly diminished when the diisopropylamide substrate is substituted by the corresponding diethylamide (50% ee), dimethylamide (33% ee) or by the ethyl ester (<20% ee). Decreased ee occurs with a series of other Lewis acids, including the dimethylsulfide boron trifluoride complex (56% ee), and other solvents. 

The 8-ester group of 7-oxopyrido[3,2,l-t/]cinnoline-8-carboxylates (68, R- + H) was hydrolyzed under basic or acidic conditions. The carboxyl group of68(R = H) was esterified and the carboxyl group was converted to a boron complex (70) by treatment with the boron trifluoride-ether complex (92EUP470578). 

The reaction is irreversible and can be used to synthesize aliphatic and aromatic esters. In addition, there are no complications involving water removal or azeotrope formation. Boron tribromide can be used in place of boron trichloride, but the bromide has a stronger tendency to halogenate the alkyl group of the alcohol (26). Boron trifluoride does not give the ester, but gives either a complex or dehydrated product. 

Methyl perfluoromethacrylate reacts with allyl and propargyl alcohols to give the Michael addition products 19 and 20, respectively these eliminate hydrogen fluoride in the presence of the boron trifluoride-triethylamine complex and rearrange to acyl fluorides 21 and 22. Hydrolysis of the acyl fluorides with base results in decarboxylation to give the 2-(trifluoromethyl) esters 23 and 24.11... 

Oppolzer reports that similar additions of the ether soluble organocopper-boron trifluoride-tri-n-bu-tylphosphine complexes (87c) to chiral ot,3-unsaturated esters (Scheme 20) proceed with high dia-stereoselectivity. Subsequent hydrolysis or reduction of the chiral adducts, e.g. (115) and (116), affords... 

Reduction of esters, nitriles, and amides. These groups are rapidly reduced by horanc-dimcthyl sulfide in refluxing THF (b.p. 67°) if the dimethyl sulfide (b.p. 38°) is removed as liberated. Under these conditions, the reagent is comparable to uncomplexed diborane. Reduction of secondary and tertiary amides is best effected in the presence of boron trifluoride etherate otherwise, excess reagent is utilized for formation of complexes with the products. 

A selection of A//p gp values has already been given in Table 2-4 in Section 2.2.6. This new Lewis basicity scale is more comprehensive and seems to be more reliable than the donor number scale. Analogously, a Lewis basicity scale for 88 carbonyl compounds (esters, carbonates, aldehydes, ketones, amides, ureas, carbamates) has been derived from their standard molar enthalpies of complexation with gaseous boron trifluoride in dichloromethane solution [143]. The corresponding Aff Q gp values range from 33 kJ mol for di-t-butyl ketone to 135 kJ mol for 3-diethylamino-5,5-dimethyl-cyclohexen-2-one. 

However, these conditions have not been applied to other epoxides. Catalysis by the boron trifluoride -diethyl ether complex is very useful for the ring opening of cyano-substituted epoxides " and glycidic esters see the formation of and Table 14. This is demonstrated by the regioselective opening of the epoxide ring in 2,3-dimethyloxirane-2-carbonitrile to provide 3-fluoro-2-hydroxy-2.3-dimcthylbutanonitrile... 

Cobalt-complexed propargylic aldehydes can be alkylated using both cyclic and acyclic trimethylsilyl enol-ethers and -esters in the presence of a Lewis acid. Boron trifluoride etherate is the most frequently employed Lewis acid. 

Table 17 indicates some limitations of the amine hydrofluorides in the reaction with glycidic esters. In the least-substituted case (entry 1) the yield is low. On the other hand, the fully substituted glycidic esters (entries 8 and 9) do not react at all with the amine hydrofluoride, probably due to steric hindrance. This type of epoxide gives better results with other fluorination reagents, e.g. they can be opened to the fluorohydrins in good yield with hydrogen fluoride in the presence of the boron trifluoride-diethyl ether complex (sec Section 1.1.4.3.2.1.2.).37... 

While aromatic aldimines of amino acid esters are readily accessible from benzaldehyde or related derivatives and amino acid esters with concomitant removal of water,the corresponding ketimines require harsher reaction conditions, e.g. the benzophenone imine of glycine methyl ester is formed in boiling xylene in the presence of boron trifluoride-diethyl ether complex as a Lewis acid in 82% yield.P l These or similar reaction conditions lead also to piperazine-2,5-dione (DKP) formation therefore milder reaction conditions have been developed such as the transimination with benzophenone imine in dichloromethane, which occurs at room temperature overnight in 80-95% yield (Scheme The N -diphen-... 

Benzhydryl (diphenylmethyl, Dpm) esters are about as labile as ferf-butyl esters, thus they are quantitatively cleaved under mild acidic conditions, e.g. TFA (rt, 30 min), saturated HCl solution in AcOH at room temperature, AcOH at 70 °C, or fivefold excess of boron trifluoride-diethyl ether complex/AcOH in chloroform (rt, 1 To obtain good yields... 

Dimerization.- A reinvestigation of the dimerization of (124) in the solid phase has identified (125) as the product. The irradiation of microcrystalline methyl cinnamate (126) affords a complex mixture of products. However, the preparation of crystalline complexes of this ester with boron trifluoride or stannic chloride followed by irradiation affords high yields of the a-truxillate dimer (127). Ethyl cinnamate also forms complexes with the same reagents but irradiation of these crystalline complexes affords a mixture of dimers in low... 

Low temperature (-50 C) H and F NMR spectra of a- or -substituted ketones, esters and nitriles complexed to boron trifluoride showed that boron coordinates preferentially at the most basic and least-hindered base when more than one coordination site is present in the ligand. Ordinarily a relative measure of chemical shifts for each type of complex would be derived from the spectra of a number of model complexes. For example, F chemical shifts for BF3 complexes of ketones (acetone), esters (methyl acetate), nitriles (acetonitrile) and ethers (diethyl ether) were measured as 149 p.p.m., 150 p.p.m., 144 p.p.m. and 156 p.p.m., respectively. Inspection of the resonance frequency and relative intensities of each peak would then reveal Ae types and ratios of the complexes present in solution. 

Other Lewis acids, such as boron trifluoride-diethyl ether complex, titanium(IV) fluoride, and triethyloxonium tetrafluoroborate, were far less effective. a, -Unsaturated esters and nitriles cannot be cyclopropanated in this manner. 

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