1.4- Dibromobutane bromide

Thionyl chloride readily converts butanediol to 1,4-dichlorobutane [110-56-5] (130) and hydrogen bromide gives 1,4-dibromobutane [110-52-1]... 

Finally, we mention the use of the polyquat bromide "Dab-4-Br" - easily prepared from Dabco and 1,4-dibromobutane - in the synthesis (ref. 7) of gmelinite (a 1-D 12-ring zeolite). 

In particular, H-H PIBs with molecular weights in the range of 3-10 k Dalton were prepared by the Grignard coupling polymerization of 2,2,3,3-tetramethyl-l,4-dibromobutane with copper(I) tris-(triphenylphosphino)bromide as catalyst (20). This catalyst is also referred to as the Yamamoto catalyst (21). The reaction is sketched out in Figure 6.2. 

Methylene bromide. Ethylidene bromide Ethylene bromide. Propylene bromide, Bromoform wo-Butylene bromide 2 3[Pg.296]

R,3R)-2,3 -Dibromobutane results from the bromide approaching according to the green arrow. Note that the two bromines have added anti to the double bond. 

S,3S)-2,3 -Dibromobutane results from the bromide approaching according to the red arrow. It is the mirror image, the enantiomer, of the compound above it. The two dibromides are formed in equal amounts. The product is racemic, as it must be because the starting materials are not chiral. 

Cyclohexyl bromide did not produce cyclohexyl phenyl tellurium under these conditions. In 1,3-dibromobutane only the bromine atom bonded to the methylene group reacted. With a large excess of dichloromethane the unstable chloromethylphenyl tellurium was obtained4. 

Heating aluminum telluride and excess 1,4-dibromobutane at 125° produced 4-bromobutyl tetramethylene telluronium bromide and butane-1,4-diyl bis[tetramethylene telluronium] dibromide2. 

Tetramethylene Telluronium Bromides2 30 g (69 mmol) of aluminum telluride and 67 g (310 mmol) of 1,4-dibromobutane are placed in a 250 ml, round-bottom flask fitted with a reflux condenser and a stirrer. The stirred mixture is heated at 125° when the reaction becomes too vigorous the flask is cooled. When the reaction has subsided the mixture is heated for 2 h, then cooled to 20°. The semi-solid mass is extracted in sequence with carbon tetrachloride, acetone, ethanol, and water. The acetone and ethanol extracts are combined, evaporated, and the residue is recrystallized from ethanol to give white crystals of 4-bromobutyl tetramethylene telluronium bromide. 

Problem 8.33 Show reagents and reactions needed to prepare the following compounds from the indicated starting compounds, (a) Acetylene to ethylidene iodide (1,1-diiodoethane). (b) Propyne to isopropyl bromide, (c) 2-Butyne to racemic 2,3-dibromobutane. (d) 2-Bromobutane to trans-2-butene. (e) n-Propyl bromide to 2-hexyne. (/) 1 -Pentene to 2-pentyne. ... 

Ethoxyphenyl Tetramethylene Telluronium Bromide A solution of 3.08 g (6.2 mmol) of bis[4-ethoxyphenyl] ditellurium in a mixture of 2.5 ml of benzene and 7.5 ml of ethanol is heated under reflux. 0.04 g (10 mmol) of sodium borohydride dissolved in 8.5 ml of 1 molar aqueous sodium hydroxide solution followed by 0.22 g (1 mmol) of 1,4-dibromobutane dissolved in 5 ml of benzene are added dropwise to the refluxing solution. The warm mixture is stirred for 30 min, filtered, the solid is washed with diethyl ether, and dried under vacuum yield 0.30 g (80%) m.p. 280° (from acetonitrile). 

Allyl halides have been reduced with electrogenerated tris(bipyridine)cobalt(I) to afford 1,5-hexadiene [369,370]. Some of the earliest work with cobalt(I) salen involved its use for the catalytic reduction of bromoethane [371], bromobenzene [371], and /er/-butyl bromide and chloride [372]. More recently. Fry and coworkers examined the cobalt(I) salen-cata-lyzed reductions of benzal chloride [373-375] and of benzotrichloride [376], and the catalytic reductions of 1-bromobutane [377,378], 1-iodobutane [378], 1,2-dibromobutane [378], benzyl and 4-(trifluoromethyl)benzyl chlorides [379], iodoethane [380], diphenyl disulfide [381], 1,8-diiodooctane [382], and 3-chloro-2,4-pentanedione [383] have been investigated. 

Rusling and coworkers have carried out extensive studies of the use of electrogenerated cobalt(I) complexes (including cobalt(I) salen, vitamin Bi2s, and cobalt(I) phthalo-cyanine) as catalysts both in homogeneous phase and in bicontinuous microemulsions [384] for the reductions of 1,2-dibromoethane and 1,2-dibromobutane [385], the debromi-nation of alkyl vicinal dibromides [386], the dechlorination of DDT [387], the reductions of 1-bromobutane, 1-bromododecane, and ran5-l,2-dibromocyclohexane [388,389], and the reduction of benzyl bromide [390]. 

Some papers have appeared that deal with the use of electrodes whose surfaces are modified with materials suitable for the catalytic reduction of halogenated organic compounds. Kerr and coworkers [408] employed a platinum electrode coated with poly-/7-nitrostyrene for the catalytic reduction of l,2-dibromo-l,2-diphenylethane. Catalytic reduction of 1,2-dibromo-l,2-diphenylethane, 1,2-dibromophenylethane, and 1,2-dibromopropane has been achieved with an electrode coated with covalently immobilized cobalt(II) or copper(II) tetraphenylporphyrin [409]. Carbon electrodes modified with /nc50-tetra(/7-aminophenyl)porphyrinatoiron(III) can be used for the catalytic reduction of benzyl bromide, triphenylmethyl bromide, and hexachloroethane when the surface-bound porphyrin is in the Fe(T) state [410]. Metal phthalocyanine-containing films on pyrolytic graphite have been utilized for the catalytic reduction of P anj -1,2-dibromocyclohexane and trichloroacetic acid [411], and copper and nickel phthalocyanines adsorbed onto carbon promote the catalytic reduction of 1,2-dibromobutane, n-<7/ 5-l,2-dibromocyclohexane, and trichloroacetic acid in bicontinuous microemulsions [412]. When carbon electrodes coated with anodically polymerized films of nickel(Il) salen are cathodically polarized to generate nickel(I) sites, it is possible to carry out the catalytic reduction of iodoethane and 2-iodopropane [29] and the reductive intramolecular cyclizations of 1,3-dibromopropane and of 1,4-dibromo- and 1,4-diiodobutane [413]. A volume edited by Murray [414] contains a valuable set of review chapters by experts in the field of chemically modified electrodes. 

For example, addition of 1,3-dibromopropane to the THF solution of 8 at — 78"C formed the intermediate 9a, which cyclized, when warmed to room temperature, to yield 1-methyl-l-(l-methylethenyl)cyclopentane 13 [11]. On the other hand, an acidic workup of 9a at — 35 C gave a single monoalkylated product, 6-bromo-2,3,3-trimethyl-l-hexene 12, in 72% isolated yield. Similar chemistry was observed with 1,4-dibromobutane, except that no cyclization would occur without refluxing conditions. Interestingly, the cyclization of 9a to 13 represents a cross-coupling of an organomagnesium reagent with an alkyl bromide, which is normally observed only in the presence of certain transition metal salts or complexes [12]. 

TosMIC can be efriciently alkylated with primary alkyl halides, isopropyl iodide and benzyl bromide both to the corresponding mono- or di-alkyl derivatives using NaH in DMSO or 40% aq. NaOH in and in the presence of Bu"4NI (Scheme 125). The resulting compounds have then been transformed to aldehydes and ketones, including cycloalkanones, and the method has been successfully applied to the synthesis of optically active 2-methylcyclobutanone from the chiral sulfonylmethyl isocyanide and 1,3-dibromobutane. ... 

Alkenes react with bromine to give the products of 1,2-addition. The reaction is classified as an electrophilic addition of bromine, and the two bromine atoms in the product, 1,2-dibromoalkane, are mutually trans. Therefore from the addition of bromine to trans-but-2-ene (2) the product is m o-2,3-dibromobutane (37). This result is explained as follows the initial step is nucleophilic attack by the double bond of the alkene on one bromine, with displacement of the other as bromide ion. The organic intermediate is a bromonium ion 36, whose formation is rationalized in Scheme 4.7. The bromide that was expelled in formation of 36 now becomes a nucleophile and attacks 36 with equal probability at C(2) or C(3). In each case the reaction occurs with inversion of configuration to produce 37. 

Spiro(5,5)phosphonium bromide (1 m = n = 5) was synthesized from 1-methylphosphorinan by monoalkylation with 1,4-dibromobutane followed by ylide intramolecular alkylation as shown in Scheme 9 <80ZN(B)990>. Dilithium biphenyl reacted with the phenylphosphine oxide (125) to displace... 

If BFj adds from the bottom, rather than the top as shown in Figure 11.3, the bromonium ion is the enantiomer of the one shown in Figure 11.3. However, attack of bromide anion at either carbon of the bromonium ion still gives only the meso-diastereomer of the product. Overall, then, both enantiomers of the bromonium ion are formed in the reaction, but the only product from either is meso-2,3-dibromobutane. 

Elimination from meio-dideuterodibromoethane and the diastereoisomeric 2,3-dibromobutanes with zinc shows anti stereospecificity - . However, such stringent stereochemical behaviour is not shown in elimination from the higher homologues such as the dibromo-pentanes, -hexanes or -octanes. In the cyclodecyl series a marked preference foriy/i-elimination is observed . These findings have a parallel in base-catalysed Hofmann eliminations, and explanations in terms of steric interactions which cause preferential substrate conformations to be assumed adequately account for the experimental results. An alternative approach is to invoke carbanion intermediates in which rotation about the Cg-Ca bond is more rapid or of a similar rate to the ejection of bromide ion ". As products characteristic of a solvent interaction on a carban-... 

The addition of deuterium bromide to both cis- and tra s-2-butene proceeds in a stereospecific trans manner at low temperature. The dx-olefin yields three while the trans gives the eryihro bromide. Similarly, the addition of HBr to isomeric 2-bromo-2-butenes is stereospecific at low temperature and in excess of HBr. The stereospecificity decreases as the temperature of the reaction is increased. At room temperature, both olefins yield the same mixture of products. Goering and Larsen first suggested that two different conformations are involved as intermediates from ds- and trons-olefins. The lifetime of these two conformations is so short that they cannot interconvert prior to the chain transfer step, which takes place from the less hindered side. At room temperature, however, these can obtain equilibrium rapidly because of easy C-C bond rotation, which results in the same mixture of meso- and d,l-2,3-dibromobutanes. Another reason may be that the addition of bromine radical (Br ) to noncyclic olefins is often reversible and may lead to nonstereospecific products. The second mechanism assumes a tr-complex formation between olefin and HBr. A bromine atom then collides with the complex leading to its attachment and simultaneous breaking of the HBr bond, which explains the decrease in stereospecificity with rising temperature (Scheme 4.53). 

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