Bromide, 851 table

These studies were subsequently extended to the analogous stannanes and the 3-methyl and 2-methylcyclohexyl bromides (Table 9)47. The MesSnLi reactions, as expected, afforded similar ratios of isomeric product from a given set of stereoisomeric bromides. However, Pt SnLi led to clean inversion with 4-methyl and trans-3-methylcyclohexyl bromides. Evidently, the Ph3Sn radical is not easily formed under these conditions. 

Alternatively, l-oxo-l,2,3,4-tetrahydroquinolizinium ion (111 Scheme 73) and its congeners may be converted to derivatives of 1-hydroxyquinolizinium ion (63JCS2203). The bicyclic ketone (111) can be brominated to yield the 2-bromo (112) or the 2,2-dibromo derivative (113). Action of boiling acetic anhydride converts the monobromo ketone (112) to 2-bromoquinolizinium bromide (Table 2). If the same bromo ketone (112) is heated with ion-exchange resin (Amberlite IRA-400) loaded with hydroxyl ions or, alternatively, heated with silver acetate in water, the 1,2-dihydroxyquinolizinium ion is formed and may be recovered as the picrate (Scheme 74). 

The endocyclic silyl dienol ether is also obtained as the major product when the conjugated cyclic enone is successively treated with the Fe complex prepared according to Scheme 2, then with one equivalent of methylmagnesium bromide (Table 2). This is interesting since these products are difficult to obtain otherwise. The mechanism of this unusual reaction remains obscure. 

The results published thereafter by Kochi s group are especially interesting from a mechanistic point of view . Indeed, for preparative chemistry the yields are not satisfactory and the reaction is limited to reactive alkenyl bromides such as propenyl and styryl bromides (Table 4). Neumann and Kochi were the first to replace iron(III) chloride by iron(III) acetylacetonate or related complexes such as Fe(dbm)3 (iron tris-dibenzoylmethanato) that are less hygroscopic and easier to handle. 

The reaction can be applied to varions secondary and primary alkyl bromides (Table 8). 

Samples of both the bromide and chloride crude reaction mixtures were extracted with anhydrous chloroform to obtain a chloroform-soluble residue. Chloroform extraction was chosen here, because the niobium (IV) adducts appeared to be substantially insoluble in this solvent. Samples of the soluble residue were dissolved in anhydrous chloroform for infrared analysis. The resulting absorption spectra were then compared to those obtained in the same way for known samples of pyridinium chloride and bromide (Table VI). 

Lund and Iversen first showed that azobenzene was an effective probase it is reduced to radical-anion at a low potential (—0.9 V vi. Ag/AgCl) and the reduced form is sufficiently basic to deprotonate benzylphosphonium salts. Its usefulness as an alternative to conventional bases was illustrated by the near quantitative production of stilbene by electrolysis of azobenzene in the presence of benzaldehyde and benzyl-triphenylphosphonium bromide (Table 2, entry 1). However, the concomitant formation of the carcinogenic benzidene, by acidic work-up of a product mixture which contains hydrazobenzene, is a severe drawback for this system. 

Transition metal compounds with covalent carbon-metal bonds include organo-zinc, organo-cadmium, and organo-mercury compounds. Carbon-13 shifts of the methyl derivatives (Table 4.71) indicate a heavy atom deshielding. Diphenylmercury displays carbon shifts similar to those of phenyllithium and phenylmagnesium bromide (Table 4.53). 

Given the dearth of iodide in the ecosystem relative to chloride and bromide (Table 3.4), it is perhaps surprising that several other alkyl iodides are found in the environment. 

Other substituents, e. g. amino, have been found to induce fragmentation of the adamantyl nucleus. Quantitative studies of the solvolysis of aminosubstitu-ted adamantyl bromides (Table 16) suggest that fragmentation occurs simultaneously with ionization. The common product from each of the aminobromoada-mantanes in Table 16 is 3-keto-7-methylenebicyclo[3.3.1]nonane (e.g. Eq. (78))... 

Although benzenethiolate has not yet been observed in natural waters, this nucleophile was included in the tables in order to extend the range of substrates examined. This inclusion was justified on the basis of the similarity in reactivity between benzenethiolate and n-butanethiolate in their nucleophilic attack on n-butyl bromide (Table VII), as well as that between benzenethiolate and ethanethiolate in their dehydrohalogenation of DDT at 2S°C (Table Vm). 

All of the neutral (organo-)copper compounds just listed can be arylated by aryl iodides and/or -bromides Ar-Cu and R-C=C-Cu can also be alkynylated by alkynyl iodides and/or -bromides. Table 16.2 summarizes the whole spectrum of corresponding products. After having grasped the mechanism of these reactions by way of Figure 16.3, we will discuss their synthetic potential by means of the examples given in Figures 16.4-16.9. 

Prenyl bromide affords better chemical yields and better enantioselectivities than allyl bromide (Table 6). The best result (99% yield, 90% (R) ee) is obtained when benzaldehyde is treated with prenyl bromide in the presence of (—)-cinchonidine. A similar enantioselective propargylation reaction of aldehydes with enantioselectivity up to 85% has been achieved in organic solvents by using stoichiometric amounts of (—)-cinchonidine as the chiral source (Table 7).190... 

Interestingly, no correlation could be observed from their monomer ion-pair acidities (pAT0 in THF) and the second-order rate constant for the monomer in their reaction with m-chlorobenzyl bromide (Table 2, right), a linear relationship occurs when the corresponding cesium salts are alkylated with methyl tosylate. On the other hand according to the authors, this accounts for the fact that the lithium cation is as important as the basicity of the enolate. 

The synthesis of benzyl fluorides from benzyl halides is problematic due to the tendency to undergo Friedel-Crafts reactions.147-148 The fluorination of benzyl bromide with thallium(I) fluoride gives impure benzyl fluoride149 and attempts to fluorinate benzyl halides with anti-mony(III) fluoride, silver fluoride, and potassium fluoride were all unsuccessful.149 Benzyl fluorides with substituents which deactivate the aromatic system towards Friedel-Crafts reactions are successfully obtained through halogen exchange with mercury(II) fluoride (Table 9)148 and with silver(l) fluoride, e.g. formation of 14.150 Other benzyl fluorides are synthesized by heterogeneous fluorination of benzyl halides with lead(II) fluoride in the presence of sodium bromide (Table 10).151... 

Davanloo and Wai studied the reaction of hot tritium from the He(n, p)T reaction with gaseous cyclopropyl bromide. Table 6 gives the ratio of the yields in the presence of I2 as a scavenger. Due to the low vapor pressure of c-CjHsBr at room temperature, the effect of stabilization was observed by the addition of CHjBr. It acts both as a stabilizer and as a moderator, thus reducing the yields of all hot products, and the important results are the ratios of the yields of the various organic products. 

Br to react with cyclopropane in the solid phase at 77 K. In contrast to the reaction of the same atoms in the gaseous phase where De Jong and co workers found the major product to be methyl bromide, in the solid phase the major product is isopropyl bromide. Table 11 gives the yield of the various products in both gas and solid phases. The... 

The substitution reaction of cyanide with benzyl bromide (Table 1) was evaluated with and without silacrown promoted catalysis and compared with 18-crown-6 and decamethylcyclopentasiloxane (Dj). Reaction conditions and times were not optimized. The catalytic activity of the sila-17-crown-6 appeared to be equivalent to 18-crown-6. Dodecamethylcyclopentasiloxane did not demonstrate catalytic activity. The specificity of the sila-14-crown-5 for sodium ions and not potassium ions provides evidence for complex formation analogous to the crown ethers. 

C. W. Garland C.F. Yamell (1966). J. Chem. Phys., 44, 1112-1120. Temperature and pressure dependence of the elastic constants of ammonium bromide, (table 5). R.S. Seymour A.W. Pryor (1970). Acta Ciyst, B 26, 1487-1491. Neutron diffraction study of NH,Br andNH, . 

The Arrhenius parameters for a series of unimolecular dehydrohalo-genations are shown in Table 2 (chlorides), Table 3 (bromides), Table 4 (iodides) and for a series of dehydrocarboxylations in Tables 5 and 6. 

This point can also be seen from the temperature ranges over which elimination can conveniently be studied in a static system, namely 350-430°C for a primary, 300-360°C for a secondary and 210-290°C for a tertiary bromide (Table 3). 

Discussion and Conclusions. In the present work a large variety of Pd/C catalysts with different properties was studied as catalysts in Heck reactions of aryl bromides with olefins. The activity of the catalysts strongly depends on the Pd dispersion, the Pd oxidation state in the fresh catalyst, the water content (wet or dry catalysts) and the catalyst preparation conditions (in regnation method, pretreatment conditions). The effects are significant, i.e. Pd on the same activated carbon support is eitiier found to be a nearly inactive catalyst or, in the other extreme, a catalyst with the highest activity ever reported up to now for heterogeneous systems for the conversion of aryl bromides (Table 6.)... 

Moreover, cyclohexene can be used as the alkylating agent instead of cyclohexyl bromide. Table II gives comparative results obtained over a dealuminated Y zeolite (Si/Al =19.5). 

Steric interactions have been invoked to explain orientation in some unimolecular eliminations . In a series of tertiary bromides (Table 19) a gradual increase in the size of one of the branches causes an increase in the amount of... 

Heck Reactions of Non-activated Aryl Bromides (Table 10.1)... 

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