Condensations boron trifluoride etherate

A 500-ml three-necked flask is fitted with a dropping funnel, a condenser, and a magnetic stirrer. The flask is charged with a mixture of 3.4 g (0.09 mole) of powdered sodium borohydride, 150 ml of THF, and 25.2 g (0.30 mole) of 4-methyI-I-pentene. A solution of 15.1 ml (17.0 g, 0.12 mole) of boron trifluoride etherate in 20 ml of THF is added over a period of 1 hour, the temperature being maintained at 25° (water bath). The flask is stirred an additional hour at 25° and the excess hydride is decomposed with water (10 ml). 

A 500-ml three-necked flask is fitted with a condenser, a pressure-equalizing dropping funnel, a magnetic stirrer, and a thermometer. The flask is charged with a mixture of 33.6 g (0.48 mole) of 2-methyl-2-butene and 180 ml of a 1 M solution of sodium boro-hydride in diglyme. The flask is cooled in an ice bath and stirring begun. Boron trifluoride etherate (0.24 mole) is added dropwise to the mixture and the solution is stirred at 0° for 2 hours. 

Phenacyl benzoate condenses with acetamide in boiling xylene under boron trifluoride etherate catalysis to give a high yield of 2,4-diphenyloxazole in a general synthesis of diaryloxazoles (Scheme 7) <96T10131>. 

A. Nortricyclyl acetate. A mixture of 156 g. (1.70 moles) (rf bicyclo[2.2.l]hepta-2,5-diene (Note 1), 105 g. (100 ml., 1.75 moles) of glacial acetic acid, and 3 ml. of boron trifluoride ether- ate (Note 2) is placed in a 500-ml. flask attached to a condenser equipped with a drying tube. The mixture is heated on a steam bath for 6 hours, cooled to room temperature, and diluted with 250 ml. of ether. The ethereal solution is washed successively with two 50-ml. portions of 3A ammonia and 50 ml. of water and dried over magnesium sulfate. The ether is removed by distillation through a short column of glass helices, and the dark... 

A. (S)-Phenylalanol. A dry, 3-L, three-necked flask is equipped with a mechanical stirrer and a reflux condenser connected to a mineral oil bubbler. The flask Is loaded with 165 g (1.00 mol) of (S)-phenylalanlne (Note 1), then equipped with a 250-mL pressure-equalized addition funnel capped with a rubber septum through which is Inserted a nitrogen-inlet needle. The flask Is swept with nitrogen and filled with 500 id. of anhydrous tetrahydrofuran, and the addition funnel is charged with 123 mL (1,00 mol) of freshly distilled boron trifluoride etherate via cannula (Note 2). The boron trifluoride etherate Is added dropwlse to the phenylalanine slurry over a 30-m1n period with stirring, and the mixture is heated at reflux for 2 hr, resulting in a... 

Boron trifluoride etherate is used as a catalyst in many organic reactions namely, alkylation, polymerization and condensation reactions. 

Sulfoxides can act as an S—O two-atom fragment in [4 + 2] condensations. Thus reaction of DMSO with benzoyl isocyanate in the presence of boron trifluoride etherate (75IZV1206) gives the 1,3,2,5-dioxathiazine (248). Boron trifluoride induced condensation of DMSO with Ar-benzoyl-S,5-bis(trifluoromethyI)sulfimide (249) gives the 1,3,2,4,5-dioxadithiazine (117) (78JA985), and the iV-acylimine (250) also gives a 1,3,2,5-dioxathiazine (251) on reaction with DMSO (80ZOR463). 

This borane reagent may be prepared as follows.6 In a dry 500-ml flask equipped with a condenser, a thermometer and a pressure-equalising dropping funnel are placed 80 ml of diglyme, 23.1 g of 2-methylbut-2-ene (0.33 mol) in 20ml of diglyme and 4.7 g of sodium borohydride (0.125 mol). The flask is immersed in an ice bath and 23.5 g of boron trifluoride-etherate (0.165 mol) is added dropwise over a period of 30 minutes. The semi-solid reaction mixture containing 0.165 mol of disiamylborane is permitted to remain an additional 15 hours at 0-5 °C, and then used for hydroboration. Examples of the use of disiamylborane are described in Sections 5.4.3 p. 542 and 5.7.1, p. 588. 

Similarly, condensation of the disaccharide derivative (404) [125] via the imidate (405) with the trisaccharide (392) in the presence of boron trifluoride — etherate gave a pentasaccharide in 40 % yield and this was converted into the imidate (403), using the same techniques as described for the preparation of (402). Condensation (33 % yield) of the imidate (403) with a 3-O-benzoylceramide (63) and deprotection of the product gave the ganglioside GMI (401). 

Condensation polymerization of functional ferrocenes generally yields medium- or low-molecular-weight polymers with broad molecular-weight distributions.12 For example, ferrocenylcarbinol, 6.9, has been condensation-polymerized to polymers 6.10 and 6.11 in the presence of boron trifluoride etherate or zinc chloride (reaction (5)).910 Species 6.11... 

The tiyptophol was condensed with methyl propionylacetate using boron trifluoride etherate as the catalyst to produce tetrahyropyranoindole. Basic hydrolysis of the ester gave [3-14C] etodolic acid (overall yield 26% from the labeled starting material). The compound was recrystallized in presence of an antioxidant to prevent formation of peroxides and stored at -10°C. The radiochemical purity was determined to be 99%. 

The reaction vessel is designed to fit an ultrasound probe , and is fitted with a reflux condenser and a septum side-arm, and furnished with an inert atmosphere. Magnesium turnings (0.97 g, 40 mmol), a crystal of iodine, boron trifluoride etherate (1.42 g, 10 mmol) and dry ether (34.5 ml) are introduced into the flask. The ultrasound is switched on, and 1-bromopropane (4.31 g, 35 mmol) is added dropwise via the septum during 5 min, during which time an exothermic reaction starts. After 10 min the ultrasound is switched off and the magnesium salts are allowed to settle. The clear ether layer is transferred to another flask. The magnesium salts... 

Acyclic 295 and cyclic 296 hemithioacetals have been shown as precursors of formyl-lithium intermediates13. For the preparation of the starting methoxy(phenylsulfanyl) methane 295466 two main procedures can be used (a) nucleophilic substitution of chloro-methyl methyl ether with thiophenol under basic conditions467,468 and (b) boron trifluoride etherate-catalyzed condensation of thiophenol and dimethoxymethane166. 1,3-Oxathiane and its derivatives can be prepared by acetalization of the corresponding carbonyl compound with 3-mercaptopropanol. 

In a 1-1. three-necked round-bottomed flask with ground-glass fittings is placed a mixture of 36 ml. of boron trifluoride etherate, 72 ml. of glacial acetic acid, and 120 ml. of chloroform (Note 1). The flask is equipped with a spiral reflux condenser, an efficient mechanical stirrer, and a dropping funnel (Note 2). The chloroform solution in the flask is heated and maintained at reflux with vigorous stirring, and a solution of 30 ml. of 1,3-propanedithiol (0.30 mole) and 29 ml. of methylal (0.33 mole) in 450 ml. of chloroform (Note I) is added at a constant rate... 

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. 

Anions formed from group 6 and manganese Fischer carbene complexes undergo aldol condensations with aldehydes and ketones. Allylic carbenes exclusively react in the y position with aldehydes affording dienyl-substituted carbenes. For alkoxy-substituted carbenes, the presence of an excess Lewis acid see Lewis Acids Bases), such as boron trifluoride etherate, titanium tetrachloride, or tin tetrachloride is required for the reaction to proceed in reasonable yield. The initial aldol product can be isolated without elimination (Scheme 12). ... 

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