Ether, dimethyl boron trifluoride complexes

Examination of possible systems for boron isotope separation resulted in the selection of the multistage exchange-distillation of boron trifluoride—dimethyl ether complex, BF3 -0(CH3 )2, as a method for B production (21,22). Isotope fractionation in this process is achieved by the distillation of the complex at reduced pressure, ie, 20 kPa (150 torr), in a tapered cascade of multiplate columns. Although the process involves reflux by evaporation and condensation, the isotope separation is a result of exchange between the Hquid and gaseous phases. 

Quinazoline-2,4(l//,3//)-dithione furnishes with iodomethane in aqueous sodium hydroxide 2,4-bis(methylsulfanyl)quinazoline," whereas with an excess of boron trifluoride-dimethyl ether complex in hot nitrobenzene, 2-(methylsulfanyl)quinazoline-4(3i/)-thione is obtained. ... 

C2H6BF30 boron trifluoride dimethyl ether complex 353-42-4 400.15 34.379 2 1180 C2H10N2O 1,2-ethanediamine monohydrate 6780-13-8 391.15 33.532 1,2... 

Indole and dimethyl acetylenedicarboxylate yield 2-(indol-3-yl)-2,3-dihydro-l//-l-ben-zazepine (mp 240-242 C) by addition of indole to the initially formed l//-l-benzazepinc,21 whereas 1,3-dimethylindole (10, R = H) fails to react with the diester under a variety of conditions.145 However, in the presence of boron trifluoride-diethyl ether complex at room tem-... 

Fluoromalonates can be obtained in moderate yields by fluorination of the corresponding carbanions with xenon difluoride, dimethyl sulfide and boron trifluoride-diethyl ether complex.29... 

After treatment of 2,6-dimethyl-5-heptenal with a boron trifluoride diethyl ether complex at 25 C. 2-isopropenyl-5-methylcyclopentanone is formed16 via a cyclization-[1.2] hydrogen shift sequence. Extensive studies have shown that the nature of the reaction can be influenced by the strength and concentration of the Lewis acid employed17. The appearance of several producLs with different constitutional and configurational characteristics can be explained by a common cationic intermediate (Prins or stepwise cne reaction). The results arc summarized in Table 2. 

By similar reduction procedures, amino alcohols can be derived from almost every amino acid. (S)-Valinol [(S)-4], (S)-leucinol [(S)-5], and (S -zm-leucinol [(S) ] are prominent examples of these compounds. A detailed procedure for the reduction of (S)-valine to (S)-valtnol by borane-dimethyl sulfide/boron trifluoride-diethyl ether complex has been reported6, as well as details on the preparation of (5)-leucinol2 and (S)-/m-leucinol ... 

C2HflBFjO Dimethyl ether-boron trifluoride(l l)-complex 353-42-4... 

Obtained by reaction of acetic anhydride with 4,6-dimethyl-resorcinol in the presence of 45% solution of boron trifluoride etherate at r.t. (15%) [2213] or boron trifluoride-acetic acid complex for 2 h at 100° [2997],... 

Preparation by reaction of phloroglucinol dimethyl ether with boron trifluoride-acetic acid complex at 100° (40%) [2242],... 

Any of these BH3 compounds adds readily to most alkenes at room temperature or lower temperatures. The reactions usually are carried out in ether solvents, although hydrocarbon solvents can be used with the borane-dimethyl sulfide complex. When diborane is the reagent, it can be generated either in situ or externally through the reaction of boron trifluoride with sodium borohydride ... 

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. 

For example, condensation of silyl enol ether (3.21) of 3-pentanone with 2-methylbutanal in the presence of TiC gives the Ti-complex 3.22, which on hydrolysis yields an aldol product, manicone (4,6-dimethyl-4-octen-3-one) (3.23), an alarm pheromone. Treatment of 3-pentanone with LDA results in the formation of an enolate, which is trapped with chlorotrimethylsilane to give 3.21. Other Lewis acids such as tin tetrachloride (SnCU) and boron trifluoride etherate (BF3-OEt2) can also be used. 

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... 

Borane, which is used as a complex with tetrahydrofuran [992] or dimethyl sulfide [611, 992] or generated in situ from lithium borohydride with boron trifluoride etherate [646] or sodium borohydride with aluminum chloride [184], reacts with 3 mol of an alkene to form a tertiary borane. The oxidation with alkaline hydrogen peroxide [183, 992, 1201] or with trimethylamine oxide [991, 992] yields an alcohol (equations 598 and 599). 

Table 12.5 compares four processes that have been used for concentrating The research that led to the first commercial production of was carried out by Crist and Kirshenbaum [C5] in the laboratory of H. C. Urey at Columbia University in 1943. As reported-by Kilpatrick and co-workers [Kl], it was concluded that the most satisfactory process consisted in the equilibrium distillation of the complex of boron trifluoride and dimethyl ether, BF3 (CH3)jO. When this substance vaporizes, it dissociates partially according to the reaction... 

The complexes of urea and thiourea with boron trifluoride have been studied and, as with other boron trifluoride complexes, the shifts are very similar namely 19 2+0-3 p.p.m. [with respect to (MeO)aB]. A similar shift was observed for the more complex adducts with cadmium chloride or nickel bromide. It was found that dimethyl ether-boron trifluoride (shift of 17-6) and di-t-butylthiourea-boron... 

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... 

A variation of the above reaction involves the boron trifluoride etherate-catalyzed condensation of gi OT-dihydroper-oxides 240 with dimethyl and diethyl acetals 243 (method C, Scheme 45) <2004S2356>. The gi OT-dihydroperoxides 240 were prepared from cycloalkanone dimethyl or diethyl acetals 242 by treatment with hydrogen peroxide catalyzed by boron trifluoride complexes <2003TL7359> or similarly from appropriate enol ethers <2004RCB681>. 

Organoboranes are obtained by addition of borane or alkyl boranes to alkenes (or alkynes). Borane itself can be prepared by reaction of boron trifluoride ether-ate with sodium borohydride. Borane exists as a dimer, but solutions containing an electron donor, such as an ether, amine or sulfide, allow adduct formation. The complexes BHa-THF and the borane-dimethyl sulfide complex BH3 SMc2 are commercially available and provide a convenient source of borane. The dimethyl sulfide complex is more stable than BHa-THF and has the additional advantage that it is soluble in a variety of organic solvents, such as diethyl ether and hexane. 

Preparative Methods made by the addition of equimolar amounts of the two components at —78°C. Dissociation of the complex reported as 96.2% at 12 °C and 97.4% at 340c 2a formed when crystalline bromodimethylsulfo-nium tetrafluoroborate is aspirated at rt to give a colorless product without change in crystal form. The reagent system is normally assembled by adding a large excess of dimethyl sulfide to an excess of boron trifluoride etherate. ... 

Boron trifluoride (Lewis acid) Dimethyl ether (Lewis base) Acid-base complex... 

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