Borane reacting with

Enamines can also be converted to amino alcohols via hydroboration. Allene-boranes react with aldehydes to give alkyne-alcohols. ... 

Neutral carboranes and boranes react with transition-metal complexes forming metallocarboranes or metalloboranes, respectively. However, most metallocarboranes and metalloboranes are prepared from transition-metal halides and anionic carborane and borane species ( 6.5.3.4) or by reacting metal atoms and neutral boranes and carboranes. These reactions are oxidative addition reactions ( 6.5.3.3). 

B2H6 -I- 2N(C2H5)3 —> 2(C2H5)3N BH3 B2H6 -I- (CH3)2S —> 2(CH3)2S BH3 Boranes react with carbon monoxide forming more than one adduct ... 

A relatively new method for thermal radical initiation has gained popularity in synthetic applications. A small amount of Et3B is added to the reaction mixture that has not been rigorously deoxygenated." " The borane reacts with oxygen, apparently generating ethyl radicals. A major advantage for this mode of radical initiation is the low reaction temperatures (as low as —78 °C) that can be achieved when stereoselective reactions are desired." ... 

It is to be noted that boranes react with water in such a manner that the latter acts as oxidant, e.g. ... 

If, instead of diborane, a boron hydride substituted with bulky alkyl groups is added to a double bond, the regiospecificity increases. Thus 6u(3-methyl-2-butyl)borane reacts with 1-hexene to give 99 percent terminal boron incorporation (Equation 7.18).59... 

E)-, 3-Dienes. In the presence of Cl2Pd[P(C6H5)3]2 this borane reacts with a vinylzinc chloride to form an intermediate that couples with an alkyl chloride in the presence of a base (LiOH) to give an (E)-l,3-diene. 

Reaction of acetylenic derivatives of the elements of group 14 with triorganoboranes gives products of 1,1-organoboration [eq. (I)].1 At the same time, allylic boranes react with triple bonds by 1,2-addition mechanism through a six-membered transition state [eq. (2)].2 Therefore two different reaction pathways may be expected for interaction of A113B with Si-, Ge- and Sn-containing acetylenes. 

Tri(organoseleno)boranes 35 are prepared from boron trihalides and organic selenolates as stable compounds (Scheme 35) [63]. These selenoboranes have been shown to be useful for the conversion of carbonyl compounds into seleno-acetals 36 [64] and the selective ring opening of epoxides [65]. Recently, it was reported that tri(phenylseleno)borane reacts with cyclic ethers to produce m-hydroxyalkyl phenyl selenides 37 in the presence of a catalytic amount of Lewis acid [43]. 

Tris(methylseleno)borane and tris(phenylseleno)borane react with terminal alkynes in the presence of oxygen or in the presence of AIBN as radical initiator [97,98]. The mechanism of this reaction is not completely elucidated, however, the generation of phenylselenyl radical intermediates is assumed by the authors. When applied to enynes, this reaction furnish cyclic compounds. An approach to the frameworks of kainoids is depicted in Eq. (39). Treatment of the enyne... 

Alternatively, borane in tetrahydrofuran (BH3/THI ) is a useful reagent for reducing carboxylic acids to primary iilcohols. Reaction of an acid with BH / l HF occurs rapidly at room temperature, and the proceaurc is often preferred to reduction with I iAlH4 because of its relative ease and safety. Borane reacts with carboxylic acids faster than with any other functional group, thereby allowing selective transformations such as tliat shown below on / -nitrophenylacetic acid. If the reduction of p-nitrophcnylacetic acid were done with LiAll-14, both nitro and carboxyl groups would be reduced. 

Reduction of ketones. In usual solvents trimethylamine borane reacts with ketones only very slowly even at steam bath temperature, but in the presence of boron trifluoride etherate it is an effective reducing agent 4-r-butylcyclohexanone is reduced rapidly to a mixture of 46% of the cis alcohol and 54% of the trans isomer. Reduction of Schiff bases. Schiff bases, for example benzylideneaniline from ben-zaldehyde and aniline, are reduced rapidly and efficiently by the reagent in solution or suspension in acetic acid. Unlike other borohydrides, trimethylamine borane... 

Borane reacts with electron pair donors to form Lewis acid-base complexes. The most common forms for use in synthesis are the THF and dimethyl sulfide complexes. Stronger bases, particularly amines, form less reactive adducts. 

A.i. General Properties of Boranes. When borane reacts with alkenes there are several predictable characteristics.9... 

Borane reacts with alkenes and alkynes rapidly and quantitatively (in most cases) hy addition of the hydrogen-horon moiety to the Jt- bond of an alkene or an alkyne, to give an alkylborane or an... 

Trialkylboranes react with organic disulfides to give thioethers (sulfides) but air or light is required because tbe reaction proceeds by a radical chain process.This reaction is very slow in the dark and ultraviolet (UV) light is required for reasonable reaction rates. Tri octyl borane reacts with dimethyl disulfide under these conditions to give methyl 1-octyl sulfide in 95% yield. 6 The mixed borane B-cyclohexyl-3,5-dimethylborinane (220), gave 94% of cyclohexyl methyl sulfide (221) under the same conditions. ... 

Halogenated boranes react with the usual regioselectivity, with addition of the boron atom to the less-substituted end of the carbon-carbon double bond, although they do not always show the same reactivity as other borane derivatives. For example, the far higher reactivity of dibromoborane towards more-substituted alkenes, in contrast to disiamyborane, makes possible the selective hydroboration of the double bonds in 2-methyl-1,5-hexadiene (5.11). 

Borane reacts with carboxylic acids first of all to form triacylborates, with evolution of hydrogen gas. Esters are usually less electrophilic than ketones because of conjugation between the carbonyl group and the lone pair of the sp hybridized oxygen atom—but, in these boron esters, the oxygen next to the boron has to share its lone pair between the carbonyl group and the boron s empty p orbital, so they are considerably more reactive than normal esters. 

The overall reaction of BH3 with a C—C double bond occurs in three steps. Borane reacts first with one molecule of the alkene to form an alkylborane, then with a second molecule of alkene to form a dialkylborane, and finally with a third molecule of alkene to form a trialkylborane. Although borane reacts with three equivalents of alkene to form the trial-kylborane, we will focus on just the reaction of the first equivalent of C = C to explain the selectivities of the reaction. 

Draw the products formed when 60, 61, and 62 react with cyclo-pentene, assuming one equivalent of borane reacts with one equivalent of alkene. 

Trialkylamine-boranes will also react with polyolefins to form boron heterocyclics in special cases, the products can be distilled. Triethylamine-borane reacts with cyclododeca-l,5,9-trienes to form perhydro-9b-bora-phenalenes 30, 31, 31a, 45, 47, 48). 

The terminal alkynes react with 2 equiv of 9-BBN and affords, quantitatively, the corresponding 1,1-diboraylalkanes. Soderquist has reported that this trialkyl-borane reacts with 1 equiv of benzaldehyde or 1-NaphCHO in 2 h at 25 °C, and quantitatively form B-ArCH20-9-BBN and B-alkenyl-9-BBN, exclusively with tram configuration [18]. The frans-B-alkenyl-9-BBN undergoes selective oxidation [18] with 1 equiv of anhydrous trimethylamine-N-oxide (TMANO) [19] and affords almost quantitatively the corresponding stable fraws-B-vinyl-9-oxa-10-borabicyclo[3.3.2]decane derivatives (traws-B-vinyl-OBBD). tram-B-Yinyl-OBBD derivatives are inert to atmospheric oxygen and are unreactive toward protonolysis (HOAc, 25 °C, 8 h) or insertion process (PhCHO, neat, 80 C, 6 h). The reaction sequence for the synthesis of fraws-B-vinyl-OBBD is outlined in Scheme 20.6 [18]. 

Step 1 involves the anti-Markovnikov addition of water to the less hindered C=C bond in G (i.e. the bulky borane reacts with the C=C bond in the side chain, not the C=C bond in the ring). The bulky borane adds regioselectively to the least hindered end of the C=C bond, in the side chain, and oxidation using H2O2/HO produces a primary alcohol. In Step 2, the primary alcohol is oxidised by CrOs/H to form the carboxylic acid group in compound H. 

The reaction of BH3 with 3,3 -diaminodipropylamine produced (27) whereas tris(dimethylamino)borane reacted with the same amine to produce (28). The synthesis of boryl cyclotrisilazanes from the reaction of chlorodiorganyl-boranes and lithiated cyclotrisilazanes has been published. ... 

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