Dimethyl boron trichloride

Other compounds containing lone pairs of electrons readily form co-ordinate links and in each case a change in spatial configuration accompanies the bond formation. The oxygen atom in dimethyl ether, CHj—O—CHj, has two lone pairs of electrons and is able to donate one pair to, for example, boron trichloride ... 

This compound, which contains atoms arranged tetrahedrally around the boron atom, can readily be isolated from a mixture of dimethyl ether and boron trichloride. On occasions a chlorine atom, in spite of its high election affinity, will donate an electron pair, an example being found in the dimerisation of gaseous monomeric aluminium chloride to give the more stable Al2Clg in which each aluminium has a tetrahedral configuration ... 

Although dichloroborane reacts direcdy with alkenes in the gas phase (118), its complexes with diethyl ether and dimethyl sulfide are so strong that direct hydroboration does not proceed (119,120). The addition of a decomplexing agent, eg, boron trichloride, is necessary for hydroboration. 

Tris(dimethylamino)borane has been prepared by dimethyl-aminolysis of boron trichloride, with or without solvent,1-5 and by the reaction of boron trifluoride with dimethylamine in the presence of a suitable Grignard reagent.6 The procedure described here is a modification of the reaction of dimethylamine with boron trichloride in pentane as the solvent. 

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." ... 

Gaines has isolated 2-(CH30)B5H8 from the reaction of I-IB5H8 with dimethyl ether 189>. The colorless liquid decomposes at or just below room temperature but in the gas phase at low pressure it is adequately stable. A 1 1 adduct is formed with boron trichloride and on heating the adduct to 50 °C, 2-CIB5H8 may be isolated 189>. 

The reaction of ( + )-bulbocapnine methyl ether (42) with excess boron trichloride in methylene chloride containing 0.3% ethanol produces the catechol (43) together with the monophenol (44). However, with boron tribromide, it is the diphenol (45) which is produced. Both compounds (44) and (45) can be O-methylated with diazomethane to the dimethyl ether (46), and hydrolysis of (46) with dilute hydrochloric acid leads to (+)-corytuberine (47).43 Alternatively, methylation of (43), using diazomethane, affords (+)-corydine methyl ether (48). 

Ethers Aluminum chloride-Sodium iodide. Aluminum iodide. Bis(isopropylthio)boron hromide. Boron trichloride. Boron trifluoride etherate. Bromotrimethylsilane. 2-Chloro-1,3,2-dithioborolane. Chlorotri-methylsilane-Acetic anhydride. Chlorotri-methylsilane-Sodium iodide. Dimethyl-boron bromide. Pyridinium p-toluenesulfo-nate. Sodium methaneselenolate. 

Bayer and Siebert reported the reaction of 3,3-dimethyl-l-butyne with -BuLi in pentane, followed by the addition of boron trichloride to afford the intermediate dichloro(3,3-dimethylbut-l-ynyl)borane that was hydroborated with dichloroborane formed in situ to give l,l-bis(dichloroboryl)-3,3-dimethylbutene 51 (Scheme 6) <2002ZN1125>. When the latter was subjected to halogen exchange with boron triiodide, it was converted into the corresponding tetraiodide 52, which underwent a redox reaction with hex-3-yne to give the 2-(2,2-dimethylpropylidene)-l,3-diborole 22 in 73% yield. 

Dehydrohalogenation Benzyltrimethylammonium mcsitoate. r-Butylamine. Calcium carbonate. j Uidine. Diazabicyclo[3.4.0]nonene-5. N.N-Dimethylaniline (see also Ethoxy-acetylene, preparation). N,N-Dimelhylformamide. Dimethyl sulfoxide-Potassium r-but-oxide. Dimethyl sulfoxide-Sodium bicarbonate. 2,4-Dinitrophenylhydrazine. Ethoxy-carbonylhydrazine. Ethyldicyclohexylamine. Ethyidiisopropylamine. Ion-exchange resins. Lithium. Lithium carbonate. Lithium carbonate-Lithium bromide. Lithium chloride. Methanolic KOH (see DimethylTormamide). N-PhenylmorphoKne. Potassium amide. Potassium r-butoxide. Pyridine. Quinoline. Rhodium-Alumina. Silver oxide. Sodium acetate-Acetonitrile (see Tetrachlorocyclopentadienone, preparation). Sodium amide. Sodium 2-butylcyclohexoxide. Sodium ethoxide (see l-Ethoxybutene-l-yne-3, preparation). Sodium hydride. Sodium iodide in 1,2-dimethoxyethane (see Tetrachlorocyclopentadienone, alternative preparation) Tetraethylammonium chloride. Tri-n-butylamine. Triethylamine. Tri-methyiamine (see Boron trichloride). Trimethyl phosphite. 

Whereas the addition compounds of boron trichloride with dimethyl ether and with diethyl ether are stable at room temperature, BCls eflfects cleavage of tetrahydro-furane, and it reacts with ethyleneglycol dimethyl ether even at 0° with evolution of methyl chloride, presumably with formation of the mono- and dichloroboronates ... 

TETROXIDO de NITOGENO (Spanish) (10544-72-6) Noncombustible, but supports combustion of combustible materials. A powerful oxidizer. Water contact produces nitric acid and nitric oxide. Incompatible with nitric oxide reacts with air, producing additional nitrogen tetroxide. Violent reaction with strong reducing agents, anhydrous ammonia, alcohols, barium oxide, boron trichloride, carbon disulfide, chlorinated hydrocarbons, cyclohexane, difluoro-trifluoromethylphosphine, dimethyl sulfoxide, formaldehyde, ethers, fluorine, formaldehyde, halocarbons, hydrocarbons, metal acetylides, metal carbides, metal powders, metal carbonyls. 

EtNH)2C-S-Me, BF3]I has a shift of -I-18-5, slightly lower than the thiourea complex. The disproportionation of the syw-dimethyl-urea—boron trichloride complex was followed by means of the spectra, and the formation of the tetrachloroborate ion and of a cyclic compound was suggested from the shift data. 

It is of interest to note in passing that In more recent work (ref.72), use has been made in synthesis of the transformation of chalcones to isoflavones with thallium(lll) nitrate. Thus, 6-acetyl-2,2-dimethyl-7-hydroxy-5-methoxychromanone was converted to the chalcone with 2,4-dibenzyloxybenzaldehyde. The O-acetyl derivative by treatment with the thallium reagent followed by acidic cyclisation gave a bischromanone structure. Selective reduction of the least hindered carbonyl group in the bischromanone, acidic dehydration of the resultant alcohol and final debenzylation with boron trichloride gave the linear isofiavone. 

A related sequence (b) with 3,5-dimethoxyfluorobenzene gave an approach to orsellinic acids as their dimethyl ethers (ref. 112). Demethylation with boron trichloride afforded a monomethyl product, resulting from complexation of the methoxyl group adjacent to the carboxyl group, while the use of aluminium chloride in chlorobenzene gave the orsellinic acid. 

For instance, attempts at isolating donor-free alkynylboranes have been hampered by spontaneous polymerization. The first donor-free tris(alkynyl)borane, tris(3,3-dimethyl-l-butynyl)borane (30), has only recently been obtained by reaction of deprotonated 3,3-dimethyl-l-butyne with boron trichloride at —78°C in pentane (equation 32). The alkynylborane (30) was fully characterized by multinuclear NMR spectroscopy, mass spectrometry, and X-ray crystallography. The NMR signal of (30) shows a remarkable shift of 5 = 48, which is upfield from typical shifts of alkyl-and alkenylboranes. The crystal structure of (30) shows similar C-C bond lengths, but significantly shorter B-C bonds in comparison to those observed for the donor-stabilized complexes (30) D indicative of a small degree of p - p interactions between the sp -boron atom and the sp-hybridized carbon. Weak r-overlap was further confirmed by ab initio calculations. It is this r-interaction that has been exploited for the development of nonlinear optical (NLO) materials based on alkynylboranes as described in Section 7.1. ... 

Monochioroborane-Dimethyl sulfide, H2BCI-S(CH3)2 Dichloroborane-Dimethyl sulfide, HBCI2 S(CH3)2. These stable hydroborating agents are prepared from borane-dimethyl sulfide (4, 124, 191 5, 47) and boron trichloride dimethyl sulfide (equations I and II). They possess the advantage over chloroborane etherates of indefinite stability. They show regiospecificity comparable to the... 

Hydroboration of Alkenes and Alkynes. The hydroboration of alkenes with dichloroborane-dimethyl sulfide (DCBS) in refluxing dichloromethane produces considerable quantities of R2BCI and R3B as impurities, presumably as the result of disproportionation of the reagent. The addition of boron trichloride liberates dichloroborane and the hydroboration proceeds cleanly at25°C (eq 1). ... 

Methylating agents for phenolic groups are a) diazomethane (the reaction time varies from minutes to 24 hours), b) dimethyl sulphate (DMS) - potassium carbonate in acetone or dimethylformamide (DMF) and c) methyl iodide - potassium carbonate in acetone. For demethylation of a methyl ether group ortho to a methyl ester group boron tribromide is used, while demethylation of a methyl ether para to a methyl ester group is carried out with boron trichloride (see Scheme 8). 

By means of conductometric titrations with boron trichloride in liquid hydrogen chloride as solvent the formation of salts of triphen-ylamine, triphenylphosphine, and triphenylarsine have been observed although no equivalence points were seen for dimethyl ether or dimethyl sulfide (274a). This is roughly consistent with the fact that the latter two compounds are probably several powers of ten less basic than the former three. 

---