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Boron compounds alkylation

Cis-olefins or cis./rjns-dienes can be obtained from alkynes in similar reaction sequences. The alkyne is first hydroborated and then treated with alkaline iodine. If the other substituents on boron are alkyl groups, a cis-olefin is formed (G. Zweifel, 1967). If they are cir-alkenyls, a cis, trans-diene results. The reactions are thought to be iodine-assisted migrations of the cis-alkenyl group followed by (rans-deiodoboronation (G. Zweifel, 1968). Trans, trans-dienes are made from haloalkynes and alkynes. These compounds are added one after the other to thexylborane. The alkenyl(l-haloalkenyl)thexylboranes are converted with sodium methoxide into trans, trans-dienes (E. Negishi, 1973). The thexyl group does not migrate. [Pg.37]

The selectivity to alcohol in LPO may be significantly increased when boric acid, meta-hotic acid, or boric anhydride is present in stoichiometric amounts (2). The boron compounds appear to convert alkyUiydroperoxides to alkyl borates and may also intercept alkylperoxy radicals, converting them to alkylperoxyboron compounds these are later converted to alkyl borates. The alkyl borates are resistant to further oxidation they are hydrolyzed to recover alcohols. [Pg.343]

Alkoxides of nonmetals are described in articles about the corresponding compounds (see Boron COMPOUNDS, Boron oxides Silicon compounds). Metal alkyls, in which the alkyl group is bound direcdy to the metal, are also discussed elsewhere (see Aluminum compounds). [Pg.21]

Much is known empirically on B-NMR data (39). Restricting boron compounds to noncyclic molecules with no or one nitrogen atom and two, three, or four carbon atoms bonded to boron and omitting sterically overcrowded alkyl groups R and R, we find four classes with the following typical chemical shift ranges (Et20 BF3 as the external standard) ... [Pg.137]

Linear polyethylene can further also be considered as polymethylene. Althoguh first prepared by the thermal decomposition of diazomethane,243 244 Meerwein should be credited to have prepared it by catalytic polymerization of diazomethane effected by boron compounds (esters, halides, alkyls)245-247 taking place with concomitant dediazotation ... [Pg.750]

Fuel additives - [AMNES-CYCLOALIPHATIC AMINES] (Vol 2) - [SULFONIC ACIDS] (Vol 23) -arsenic compds as [ARSENIC COMPOUNDS] (Vol 3) -boron compds as [BORON COMPOUNDS - BORIC ACID ESTERS] (Vol 4) -coordination compounds as [COORDINATION COMPOUNDS] (Vol 7) -ethers m [ETHERS] (Vol 9) -magnesium alkyls as [MAGNESIUM COMPOUNDS] (Vol 15) -polyamines as [DIAMINES AND HIGHER AMINES ALIPHATIC] (Vol 8) -htanates as [TITANIUM COMPOUNDS - ORGANIC] (Vol 24) -use of copper compounds [COPPER COMPOUNDS] (Vol 7)... [Pg.425]

Since the metal-alkene association preceding the peroxymetalation reaction in mechanism (B) is a pure Lewis acid/Lewis base interaction, it would be expected that compounds having alkylperoxy groups bonded to a Lewis acid center should be active for the epoxidation of alkenes. This is indeed found for boron compounds, which are active as catalysts for the epoxidation of alkenes by alkyl hydroperoxides.246,247 Isolated boron tris(alkyl peroxides), B(OOR)3, have been shown to epoxidize alkenes stoichiometrically, presumably through alkylperoxyboration of the double bond (equation 76).248... [Pg.345]

The influence of the metal atom on mechanism is particularly well illustrated by the pronounced tendency of the alkyls of boron and aluminium to react via coordination complexes in which the metal atom is four-co-ordinate. It is no coincidence that the prime examples of substitution by mechanism SE2(co-ord) occur in reactions of alkyl-boron compounds. [Pg.235]

So far wc have used only protic acids to help oxygen atoms to leave, Lewis acids work well too, and the cleavage of aryl alkyl ethers with BBr3 is a good example. Trivalent boron compounds have an empty p orbital so they are very electrophilic and prefer to attack oxygen. The resulting oxonium ion can be attacked by Br in an S 2 reaction. [Pg.434]

Some boron compounds containing oxygen are good oxygen sources in reactions with aluminum alkyls to form aluminoxanes and dialuminoxanes... [Pg.43]

Trivalent metals alkyl-aluminum and -boron compounds 1.33.7 Hydride Transferfr[Pg.79]

Trivalent metals alkyl-aluminum and -boron compounds... [Pg.99]

The synthesis of alkyl-, aryl-, and 1-alkenylboronic acids or their esters from Grignard or lithium reagents and trialkylborates is a classical and efficient method for making relatively simple boron compounds in large quantities (Scheme 2-6) [25]. The stereocontrolled synthesis of alkenylboronic acids and esters involves the reaction of a (Z)- or ( )-2-buten-2-ylmagnesium bromide with trimethyl borate [26]. [Pg.38]

As much recent work has concerned dimesitylboryl species, it is worth remarking that the related compounds (22)-(24) also readily yield carbanions. Unlike mesityl compounds, (22) cannot be deproton-ated at the 4 -methyl group, while compounds (23) have some special properties due to the great increase in steric hindrance around boron. Compounds (24) promise to be of utility due to their very ready solvolysis with water or alcohols in the presence of caudytic quantities of mineral acid. n>ey are even selectively hydrolyzed in preference to vinyl as well as alkyl groups (equation 23). ... [Pg.493]


See other pages where Boron compounds alkylation is mentioned: [Pg.209]    [Pg.551]    [Pg.874]    [Pg.299]    [Pg.300]    [Pg.235]    [Pg.6]    [Pg.96]    [Pg.392]    [Pg.246]    [Pg.37]    [Pg.313]    [Pg.69]    [Pg.178]    [Pg.246]    [Pg.20]    [Pg.147]    [Pg.184]    [Pg.265]    [Pg.148]    [Pg.34]    [Pg.35]    [Pg.433]    [Pg.127]    [Pg.124]    [Pg.1317]    [Pg.224]    [Pg.305]    [Pg.311]   
See also in sourсe #XX -- [ Pg.430 , Pg.476 ]




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Alkyl boron

Alkyl boronates

Alkyl derivatives boron compounds

Alkylating compounds

Alkylation compounds

Boron compounds

Boron compounds alkylation reactions

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