Acids Boron trichloride

Treatment of commercially available and symmetrical 3,4,5-tri-methoxytoluene (37) with iodine, periodic acid, and acetic acid under the conditions of Suzuki19 results in the formation of symmetrical diiodide 38 in 93 % yield. Although only one of these newly introduced iodine atoms is present in intermediate 13, both play an important role in this synthesis. Selective monodemethylation of 38 with boron trichloride furnishes phenol 39 in 53% yield together with 13 % of a regioisomer. Evidently, one of the Lewis-basic iodine substituents coordinates with the Lewis-acidic boron trichloride and directs the cleavage of the adjacent methyl ether... 

Methylation of carbazole phenolic oxygen has been achieved using dimethyl sulfate without reaction at nitrogen. Demethylation of carbazole methyl ethers has been achieved with hydrobromic acid-acetic acid, boron trichloride,and pyridine hydrochloride. Selective demethylation of methoxyl ortho to an aldehydo function has been achieved using boron trifluoride. ° ° Partial demethylation of 1-methoxy-3-formylcarbazole occurred during Wolff-Kischner reduction." ... 

Aromatization and eyclodeamination.2 The final steps in a synthesis of the antibiotic resistomycin (2) from 1 involved desilylative aromatization, dcmethylation, and cyclization. These were originally carried out sequentially with p-toluenesulfonic acid, boron trichloride, and concentrated sulfuric acid in 65% overall yield. Surprisingly, reaction of 1 with pyridinium chloride results directly in 2 in 84% yield. 

Boron halides are powerful Lewis acids and hydrolyze to strong protonic acids. Boron trichloride (BCI3) reacts with water to give HCl, and its fumes are corrosive, toxic, and irritating to the eyes and mucous membranes. 

The following species can all be defined as acids boron trichloride, BCI3, bromine, Br2, nitricfv) acid, HNO3, hydrogen iodide, HI, and water, HjO. Consider the chemical behaviour of each of these species in the following five reactions ... 

Fumaric Acid Boric Acid Sodium Borate Boric Acid Boron Trichloride Boron Tribromide Boron Trichloride Liquefied Petroleum Gas... 

The acid boron trichloride is neutralized by the base triethyl-amine when both substances are in the pure liquid or gaseous state ... 

Boron trichloride, BCI3. Colourless mobile liquid, m.p. — 107°C, b.p. 12-5°C. Obtained directly from the elements or by heating B2O3 with pels in a sealed tube. The product may be purified by distillation in vacuo. It is extremely readily hydrolysed by water to boric acid. TetrachJoroborates containing the BCJ4 " ion are prepared by addition of BCI3 to metal chlorides. 

Both boron and aluminium chlorides can be prepared by the direct combination of the elements. Boron trichloride can also be prepared by passing chlorine gas over a strongly heated mixture of boron trioxide and carbon. Like boron trifluoride, this is a covalent compound and a gas at ordinary temperature and pressure (boiling point 285 K). It reacts vigorously with water, the mechanism probably involving initial co-ordination of a water molecule (p, 152). and hydrochloric acid is obtained ... 

Boron trichloride, usually in conjunction with an additional Lewis acid, effects o-chloroacetylation of anilines. The resulting products are converted to indoles by reduction with NaBH4.[l], The strength of the Lewis acid required depends upon the substitution pattern on the ring. With ER substituents no additional... 

Phosphine Air, boron trichloride, bromine, chlorine, nitric acid, nitrogen oxides, nitrous acid, oxygen, silver nitrate... 

Hafnium Boride. Hafnium diboride [12007-23-7] HfB2, is a gray crystalline soHd. It is usually prepared by the reaction of hafnium oxide with carbon and either boron oxide or boron carbide, but it can also be prepared from mixtures of hafnium tetrachloride, boron trichloride, and hydrogen above 2000°C, or by direct synthesis from the elements. Hafnium diboride is attacked by hydrofluoric acid but is resistant to nearly all other reagents at room temperature. Hafnium dodecaboride [32342-52-2] has been prepared by direct synthesis from the elements (56). 

In 1846 the first boric acid esters were prepared by reacting aUphatic alcohols and boron trichloride (1). The chemistry and properties of boric acid esters from that first paper through 1961 have been extensively reviewed (2). Short reviews were pubUshed in 1964, 1978, and two in 1980 (3,4). 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Answer (a) hydrocyanic acid (b) boron trichloride (c) iodine pentafluoride ... 

In the presence of boron trichloride or trifluoride (Lewis acids), ammonia is likely to detonate. In contact with boron, it causes incandescence. 

Boron trichloride Boron trifluoride Fluoroboric acid Potassium tebafluoroborate Boric acid Boron nitride Sodium perborate Diborane... 

Ammonia reacts with boron trichloride to form a molecule called an adduct or Lewis acid base complex in which the lone pair on the ammonia molecule is shared with the boron atom to form a covalent bond and completing an octet on boron (Figure 1.16) ... 

See also Borates Boric acid Sodium borates boron oxides, 4 246-249 boron oxides table,4 242t environmental concerns, 4 284—285 health and safety factors, 4 285-288 occurrence, 4 245—246 Boron perchlorates, 18 278 Boron phosphate, 4 242t, 283 Boron removal, from water, 14 418 Boron-stabilized carbanions, 13 660-661 Boron subhalides, 4 141 Boron suboxide, 4 242t Boron tribromide, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t, 325 reactions, 4 141 specifications, 4 147t uses of, 4 149 Boron trichloride, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t reactions, 4 141... 

Enal (54) undergoes intramolecular carbonyl-ene cyclization to give cis- and trans-alcohols (55). Lewis acids such as boron trichloride and tin tetrachloride (and also dimethylaluminium chloride ) give predominantly the cis product, while the preference is reversed with the bulky MeALAr2(Ar = OC6H2 -Br-2, 6-di-Bu ). Open and closed chair-like transition states are considered and compared with previous... 

Bidentate boranes with an o-phenylene backbone constitute some of the simplest examples of polydentate Lewis acids with rigid backbones. They can be prepared by the reaction of boron halides with a 1,2-dimetallated benzene derivative. Thus, the reaction of 1,2-bis(chloromercurio)benzene (5) with boron trichloride affords 1,2-bis(dichloroboryl)benzene (6, Scheme 3). ... 

Bis(dichloroboryl)benzene (6) is an important starting material which lends itself to facile derivatization. As shown by Piers, it cleanly reacts with bis(penta-fluorophenyl)zinc to afford the corresponding bidentate Lewis acid 13 (Scheme 7) The molecular structure of diborane 13 has been determined and is shown in Fig. 1. In this structure, the vicinal boron atoms are held at 3.26 A and from one another and seem to be ideally positioned to cooperatively interact with monoatomic anions. The fully fluorinated version of this bidentate Lewis acid has also been prepared. Original efforts focused on the use of 1,2-bis(dichloroboryl)tetrafluorobenzene 14 as a starting material (Scheme 8). This compound could be observed in the early stage of the reaction of trimeric perfluoro-o-phenylenemercury (4) with boron trichloride, but was found to be unstable toward condensation into 9,10-dichloro-9,10-dihydro-9,10-diboraoctafluoroanthracene 15. The successful synthesis of the fully fluorinated... 

The thiophene derivatives are relatively stable in the pure state. The fluorine atoms of the trifluoromethylmercapto group can be quantitatively substituted with chlorine by boron trichloride with HjOg, oxidation to the sulfone takes place. Further substitution is achieved in both cases in the presence of perfluorosulfonic acids ... 

After some painstaking experimentation. Song was finally successful in a re-giospecific p o-displacement of one of the silyl groups with boron trichloride, furnishing presumably a dichloroborane (Scheme 29). The dichloroborane was not isolated and was hydrolyzed directly with either a dilute acid or a dilute... 

Reaction with hydrochloric acid or chlorine in the presence of carbon at elevated temperatures produces boron trichloride ... 

Boron trichloride can be prepared by high temperature chlorination of boron trioxide, boric acid, metal borates or other boron compounds. Chlorine, hydrogen chloride, phosgene, silicon tetrachloride, metal chlorides, carbon... 

Boron trichloride reacts with water forming boric acid and hydrogen chloride ... 

Methylbenzofuran-3-carbaldehydes undergo ready condensation with Meldrum s acid (isopropylidene malonate) to afford arylmethylene derivatives 83. These on flash vacuum pyrolysis at 500-600 C give 3-dibenzofuranols 84 (Scheme 21). The arylmethylene derivative, e.g., 85, presumably undergoes conversion to a methylene ketene (86, Scheme 22) on pyrolysis, which undergoes a [1,5-H] shift and subsequent cyclization and tautomerization, yielding the dibenzofuranol 87. The derived methyl ether 88 has been converted by mild acetylation with acetyl chloride and aluminum chloride and subsequent boron trichloride-induced demethylation to the natural product ruscodibenzofuran (8). A limitation is imposed on this method because 3-acetyl-2-methyldibenzofurans fail to condense with Meldrum s acid so that l-methyl-3-dibenzofuranols are not available by this method. ... 

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