Boron trifluoride—acetic acid, with

Boron trifluoride-acetic acid, with acetic anhydride and 2-heptanone to give 3-n-butyl-2,4-pentanedione, 51, 90... 

A solution of 3 g of the nitrile, water (5 moles per mole of nitrile), and 20 g of boron trifluoride-acetic acid complex is heated (mantle or oil bath) at 115-120° for 10 minutes. The solution is cooled in an ice bath with stirring and is carefully made alkaline by the slow addition of 6 A sodium hydroxide (about 100 ml). The mixture is then extracted three times with 100-ml portions of 1 1 ether-ethyl acetate, the extracts are dried over anhydrous sodium sulfate, and the solvent is evaporated on a rotary evaporator to yield the desired amide. The product may be recrystallized from water or aqueous methanol. Examples are given in Table 7.1. 

IA solution of the allylsilane (2 mmol) in chloroform (2 ml) was added all at lonce to boron trifluoride-acetic acid complex (2.2 mmol) with vigorous Ishaking until a single phase resulted. After 5 min, the solution was poured linto saturated sodium hydrogen carbonate solution (10ml) and extracted... 

Most of the synthetic approaches toward this ring system utilize N-amino pyridinium salts functionalized at the a-position with a carbonyl group. Thus, the amination of 2-(l,3-dioxolan-2-yl)pyridine with tosyl-hydroxylamine gave 78, whose reaction with urea in the presence of boron trifluoride-acetic acid gave 79, which gave the thermally unstable... 

Reaction of isothiocyanates with resorcinol derivatives in the presence of boron trifluoride-acetic acid complex for overnight at 0-5 °C affords the corresponding thioamides.25... 

A mixture of 28.6 g. (0.25 mole) of 2-heptanone (Note 1), 51.0 g. (0.50 mole) of acetic anhydride (Note 2), and 1.9 g. (0.01 mole) of p-toluenesulfonic acid monohydrate (Note 3) contained in a stoppered 500-ml. round-bottomed flask equipped with a magnetic stirrer is stirred at room temperature for 30 minutes. Then 55 g. (0.43 mole) of the solid 1 1 boron trifluoride-acetic acid complex (Note 4) is added some heat is evolved during this addition. The resulting amber-colored solution is stirred in the stoppered flask at room temperature for 16-20 hours (Note 5), and then a solution of 136 g. (1.00 mole) of sodium acetate trihydrate (Note 6) in 250 ml. of water is added. After the flask has been fitted with a reflux condenser, the reaction mixture is heated at reflux for 3 hours and then cooled,... 

The submitters employed 75 g. (0.5 mole) of the liquid 1 2 boron trifluoride-acetic acid complex obtained from Harshaw Chemical Company. Since the checkers were unable to obtain this complex from a commercial source, they prepared the solid 1 1 complex following published directions.3 4 A 2-1. threenecked flask is fitted with a mechanical stirrer, a gas outlet tube, and a gas inlet tube extending to the bottom of the flask. A solution of 230 ml. of acetic acid in 750 ml. of 1,2-dichloro-ethane is added to the flask and a stream of boron trifluoride gas is passed through the reaction flask while the solution is stirred and cooled with an ice bath. After approximately 1 hour, when the mixture is saturated, the addition of boron trifluoride is stopped and the insoluble 1 1 boron trifluoride-acetic acid complex is rapidly collected on a filter, washed with 200 ml. of... 

The ethyl ester 258 (Eq. 103) has been recovered unchanged after treatment with the boron trifluoride acetic acid complexin>, whereas cyclopropane 255 with an additional 2-methyl group opens under these conditions to provide y-butyrolactone 257112). Apparently the intermediate tertiary carbenium ion 256 is sufficiently stabilized by the trimethylsilylmethyl and the methyl group to be generated from 255. 

Dienes can be obtained from silylallenes by protodesilylation using boron trifluoride-acetic acid complex (equation 29). Since silylallenes can be obtained by the reaction of propargyl acetate with cuprous reagent derived from chloromethyltrimethylsilane, this reaction sequence constitutes conversion of propargylic acetate to butadiene through one carbon homologation. 

The reactions of trialkylallylsilanes with electrophiles proceed with allylic rearrangement. For example, the treatment with protic acids, such as hydrochloric acid or boron trifluoride /acetic acid, gives the corresponding olefins (eq (11)) [8]. 

Scheme 59 Acetylation with acetic anhydride and boron trifluoride-acetic acid complex...

A catalyst system159 consisting of a mixture of boron trifluoride, acetic acid and pyridine gives rapid and reproducible total hydroxyl analysis (silanol plus water) in a variety of silicone materials. This method avoids many of the interferences, empirical calibration and miscellaneous problems such as poor solubility, incomplete reaction and interfering siloxane cleavage associated with many earlier methods. Results obtained by this procedure compare well with results obtained by the lithium aluminium hydride procedure160. 

A complex is a compound formed when a metal ion shares an available electron and bonds with nonmetallic ions or an organic molecule. An example is the boron trifluoride acetic acid complex in which boron trifluoride and acetic acid are joined by the boron (a metal) and the oxygen in the acetic acid s hydroxyl group (-OH). 

Other condensing agents which have proved useful under certain conditions are boron trifluoride , formic acid with / -toluenesulphonic acid and hydrochloric acid in acetic acid - . One unusual example of a thioenol ether formed from a saturated ketone hasr been reported using hydrogen chloride as the catalyst . In this case, compound 96 was converted to either its benzylthioenol ether 97 or its ethylthioenol ether 98 (equation 79). Benzyl mercaptan normally seems to be the reagent of choice in most conversions because of its easily crystallized products. 

Preparation by reaction of boron trifluoride-acetic acid complex with the pyrogallol 2-methyl ether at 100° (79-85%) [2403,2818]. 

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],... 

Preparation by treatment of 2-fluoro-l,3-dinie-thoxybenzene with boron trifluoride-acetic acid complex at 80 for 4 h (98%) [4122]. 

The solid appears to be a mixture of the complexes CH,COOH.BF, and 2CH COOH.BF,. The latter appears to be a liquid and is alone soluble in ethylene dichloride the former is a solid. The solid moiioocetic acid complex is obtained by saturating an ethylene dichloride solution of acetic acid with boron trifluoride, filtering and washing the precipitate with the solvent it is hygroscopic and should be protected from moisture. It may be used as required 0-75 mol is employed with 0-26 mol of ketone and 0 6 mol of anhydride. 

Coumarone—Indene Kesins. These should be called polyindene resins (17) (see Hydrocarbon resins). They are derived from a close-cut fraction of a coke-oven naphtha free of tar acids and bases. This feedstock, distilling between 178 and 190°C and containing a minimum of 30% indene, is warmed to 35°C and polymeri2ed by a dding 0.7—0.8% of the phenol or acetic acid complex of boron trifluoride as catalyst. With the phenol complex, tar acids need not be completely removed and the yield is better. The reaction is exothermic and the temperature is kept below 120°C. When the reaction is complete, the catalyst is decomposed by using a hot concentrated solution of sodium carbonate. Unreacted naphtha is removed, first with Hve steam and then by vacuum distillation to leave an amber-colored resin. It is poured into trays, allowed to cool, and broken up for sale. 

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