Bromides, also

Bromine can function as a solvent. One of the very few metal bromides that has significant solubiUty in bromine is cesium bromide, 19.3 g/100 g of solution, thus providing a method of separating cesium bromide from the other alkah bromides (12). Aluminum bromide also is reported to have significant solubiUty in bromine but the pubUshed solubiUty values are not in good agreement (13). Bromine serves as the solvent in some brominations of organic compounds, such as 1,2-diphenylethane (14). 

Tetrahydrofuran, anhydrous, 99.9t (water content <0.006t) was purchased from Aldrich Chemical Company, Inc., and used as received. The vinyl bromide solution was prepared In a 500-mL, round-bottomed flask fitted with a glass stopper. The stoppered flask containing the tetrahydrofuran was chilled to about 5 C and weighed. The vinyl bromide, also chilled to about 5°C, was rapidly poured Into the tetrahydrofuran until the desired amount had been added. The flask was stoppered, the contents mixed by shaking, allowed to warm to about 16°C, and then added to the pressure-equalizing addition funnel. 

N Alkylation of 16 with benzyl bromide also occurs, and further heating of the reaction mixture leads to the C-alkylated product (25), probably by an intermolecular mechanism (33). 

A similar influence of the lithium-magnesium exchange is documented for tetrahydroisoquino-lines, derived from chiral oxazolines (see Section 1.3.2.3.3.2 ). The tuning by magnesium bromide also serves well in the carbonyl addition of lithiated tetrahydro-2-isoquinolinecarboxy-late24, prepared by the Katritzky protection/activation method27,28. 

Sulfinylacetamide anions, e.g., ( + )-(/J)-AfAr-dimethyl-2-(4-methylphenylsulfinyl)acctamide, when generated with fe/V-butyl magnesium bromide, also react with aldehydes to give aldol products with a high degree of stereoselectivity42,43. 

Allyl tosylate is also an excellent reactant (entry 2, Table 5.8), while allyl acetate is not under Cu(I)-catalyzed conditions. Not only saturated acylzirconocene chlorides, but also a,(3-unsaturated acylzirconocene chlorides give coupling products in good yields (entry 8, Table 5.8). Prenyl bromide also reacts with acylzirconocene chlorides under identical conditions to give a mixture of regioisomers (Scheme 5.30). However, a longer reaction time (10 h) is required for the completion of the reaction as compared to the reaction of allyl bromide (1 h). 

The solids may be examined as alkali halide mixture and usually NaCl is used because it is transparent throughout the infra red region. Potassium bromide also serves the purpose well. The substance under examination should also be perfectly dry because water absorbs strongly at about 3710 cm 1 and also at 1630 cm-1. 

Alkynes react with haloethenes [38] to yield but-l-en-3-ynes (55-80%), when the reaction is catalysed by Cu(I) and Pd(0) in the presence of a quaternary ammonium salt. The formation of pent-l-en-4-ynes, obtained from the Cu(I)-catalysed reaction of equimolar amounts of alk-l-ynes and allyl halides, has greater applicability and versatility when conducted in the presence of a phase-transfer catalyst [39, 40] although, under strongly basic conditions, 5-arylpent-l-en-4-ynes isomerize. Symmetrical 1,3-diynes are produced by the catalysed dimerization of terminal alkynes in the presence of Pd(0) and a catalytic amount of allyl bromide [41]. No reaction occurs in the absence of the allyl bromide, and an increased amount of the bromide also significantly reduces the yield of the diyne with concomitant formation of an endiyene. The reaction probably involves the initial allylation of the ethnyl carbanion and subsequent displacement of the allyl group by a second ethynyl carbanion on the Pd(0) complex. 

A number of methyl substituted PyO have been tried as ligands for coordination with the lanthanides. Depending on the position of the substituent, these ligands impart different degrees of steric strain for the formation of complexes. Since substituents in the 4 or 3 position do not introduce substantial steric hindrance to coordination, Harrison and Watson (160) could synthesize octakis-4-MePyO complexes. Subsequently, Koppikar and Soundararajan (161) could also synthesize octakis-3-MePyO complexes with lanthanide perchlorates. Complexes of 4-MePyO (162, 163) and 3-MePyO (164, 165) with lanthanide iodides and bromides also have a L M of 8 1. 

Pretreatment with nickel bromide also causes normally unreactive aryl chlorides to undergo Pd-catalyzed substitution.99 Aryl and vinyl triflates have also been found to be excellent substrates for Pd-catalyzed vinylations.100 Scheme 8.8 illustrates some of these reaction conditions. 

Later, a similar coupling reaction between allyl bromide or cinnamyl bromide with Ar3Bi was reported to provide the coupling products in good yields when the bromides were used in excess (Scheme 50) [65]. Under the same reaction conditions, arylation of propargyl bromide also proceeded to provide arylated allenes in moderate yields (Scheme 51) [65]. 

Magnesium bromide also can be made from its elements. Heating magnesium metal with bromine vapor yields the salt ... 

Potassium bromide also can be prepared by treating iron turnings with a 35 wt% aqueous solution of bromine. The product ferrosoferric bromide is boded in potassium carbonate solution containing a slight excess of 15% potassium carbonate (Dancy, W.B. 1980. Potassium Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology, 3 i ed. p. 963. New York Wiley Interscience). The method does not involve bromate formation. The second step of the process may be represented in the foUowing reaction ... 

Potassium bromide also can be produced by electrolytic process. 

Zinc bromide also may be prepared by the action of zinc with hydrobromic acid followed by crystaUization. 

Tosylcarbazole is efficiently converted to carbazole with sodium iso-amyloxide in isoamyl alcohol. Phenylmagnesium bromide also brings about this change, phenyl p-tolyl sulfone being isolated as a cleavage prod-... 

Nitrosyl bromide also added to imines but the yields of a-acetates after the addition of silver acetate were not better than these obtained by the addition of nitrosyl chloride. Because of their high reactivity, it was not possible to isolate a-bromodialkylnitrosamines in either case. Presumably, steric effects may also operate. 

After selective generation of the syn- or anH -enolate of an amide, it is usually reacted with a haloalkane, often the iodide. Allylic and benzylic bromides also react satisfactorily, and dimethyl and diethyl sulfate have also been used in some cases. A solution of the alkylating agent in an ethereal solvent, usually tetrahydrofuran, is added to the enolate, usually at low temperature. A polar, aprotic cosolvent, such as hexamethylphosphoric triamide, is frequently used as an additive in the alkylation step. The use of this suspected carcinogen is prohibited in some countries, which limits the usefulness of many of the reactions described below. However, similarly effective in many cases are some ureas, such as the commercially available 1,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidinone (DMPU)12. 

Lithium bromide also combines with gaseous ammonia to form four solid deliquescent substances. The monammine, [Li(NH3)]Br, is formed above 95° C. the diammine, [Li(NIi3)2]Br, between 87° and 95° C. the triammine, [Li(NH3)3]Br, between 71° and 87° C. and the tetrammine about —18° C.2 Ephraim prepared other ammino-salts of lithium, as, for example, tetrammino-lithium nitrate, [Li(NH3)J(N03), which is a colourless syrup at ordinary temperature and is more stable than the chloride tetrammino-lithium chlorate, [Li(NII3)Ll]C103, which is a fairly mobile liquid and tetrammino-lithium perchlorate, [Li(NH3)4]C104, a white solid which liquefies and decomposes at ordinary temperature.3... 

Beryllium bromide also absorbs gaseous ammonia and the iodide unites with dry ammonia. If dry gas be passed slowly over beryllium iodide in the cold, increase in bulk takes place, and a white powder of composition 2BeI2.8NII3 is left. By slightly warming and passing more ammonia gas over the compound a further quantity is absorbed and a white crystalline mass is formed. 

Strontium bromide also absorbs ammonia in the dry state, yielding octammino-strontium bromide, [Sr(NH3)8]Br2, and if this be degraded isothermally, the existence of the diammine, [Sr(NH3)2]Br, and the monammine, [Sr(NH3)]Br2, may be shown. The temperatures at which these ammines exert a dissociation pressure of 100 mm. are 30°, 68°, and 146° C. respectively.4... 

Under these conditions, a broad range of polyfunctional alkyl iodides are converted to the corresponding organozinc halides in high yields . In the case of primary alkyl iodides, the insertion occurs at 40-50 °C whereas secondary alkyl iodides already react at 25-30°C. Secondary alkyl bromides also react under these conditions , but primary alkyl bromides are usually inert with this type of activation and much better results are obtained by using Rieke zinc L Thus, the reduction of zinc chloride with finely cut lithium and naphthalene produces within 1.5 h highly reactive zinc (Rieke zinc). 

Allylic zinc bromides also generally couple with ketones and acid anhydrides. In the case of trifluoroprenyl bromide, the attempts were only successful with ethyl pyruvate. However, it appears that this reaction provides the transposition product in 50% yield (equation 20). 

Alkylation of 125,6,8,47 and 6747 gives the mono-N-alkyl cations in good to excellent yields. Generally the iodide has been used, but chlorides and bromides also apparently form salts at high temperatures prior to rearrangement.7 With methyl p-toluenesulfonate, compounds 23 form the corresponding 2-methyl cations.33... 

Y. Kamiya illustrates the influence on catalytic activity of the form of the catalyst. Thus, in the cobalt-catalyzed oxidation of hydrocarbons in acetic acid solution, introduction of bromide ions increases the activity of the catalyst, especially when the metal ion concentration is fairly high. The presence of bromides also results in a marked increase in the proportion of carbonyl compounds among the products and it is believed that these are formed as a result of a propagation step in which bromine-containing cobaltous ions react with alkylperoxy radicals. 

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