Bis bromide

Ammonium salts contain a nitrogen atom with four bonds that has a positive charge. Four-bonded nitrogen atoms derived from amines are ammonium ions (if they re derived from aniline, they re anilinium ions). If the four bonds are all to carbon atoms, the nitrogen atom is quaternary. Salts contain a cation (named first) and an anion (named last). Typical anions include Cl (chloride), Bi" (bromide), HSO (hydrogen sulfate or bisulfate), and NOj-(nitrate). Figure 13-5 shows two examples of ammonium ions. 

On the other hand, Maruoka and coworkers were intrigued with the preparation of symmetrical N-spiro-type catalysts to avoid the independent synthesis of two different binaphthyl-modified subunits required for 1. Along this line, 4,4, 6,6 -tetra-arylbinaphthyl-substituted ammonium bromide (S, S)-13 was assembled through the reaction of aqueous ammonia with bis-bromide (S)-14 on the basis of previous studies on the substituent effect of this type of salt. The evaluation of (S,S)-13 as a chiral phase-transfer catalyst in the alkylation of 2 uncovered its high catalytic and chiral efficiency (Scheme 5.9) [9]. 

The Sml2-mediated Barbier cyclisation of alkyl halides bearing cyclic ketones has been used extensively to form bicyclic systems.103 When the alkyl halide tether is attached a to the cyclic ketone carbonyl, cyclisation typically proceeds to give syn products. For example, Cook used such a cyclisation in a two-directional strategy for the synthesis of tetracyclic polyquinines treatment of bis-bromide 111 with Sml2 in THF-HMPA gave diol 112 in 68% yield (Scheme 5.80).133... 

The chalcogenide 97, 107/,127/-dibenzo[c/][l,5]selenathiocin, has been synthesized by the reaction between bis(2-bromomethylphenyl)sulfide 134 and sodium selenide in a mixture of THF and ethanol at 0°C for 17 h in rather poor yield (25%) <1998T11813>. A new phosphorus-selenium eight-membered heterocycle 136 has been synthesized from the bis-bromide 135 by treatment with sodium selenide in ethanol at room temperature in 81% yield (Scheme 13) <1995H(41)2647>. 

Condensation of bis-bromide 134 with bis-thiol 135 (cf. 98-105), or coupling of bis-bromide 134 with sodium sulfide, leads in acceptable yields to macrocycles 136 [Eq. (13)]. Examples of Ej and E2 include H, D, Br, I, CN, CO2H, CO2R. Larger phanes with intracavity functionality can be obtained, for example, by coupling two equivalents of bis-bromide 134 with o-, m or p-xylylene dithiols. The methodology is very versatile, since 3,3"-analogues of 134 and 135 are also readily prepared and coupled. 

Benzylic bromination of atropisomers has proven important in the preparation of a variety of dinapththazepine catalysts, like Maruoka s chiral, quaternary ammonium salt used for PTC. Amine 69 is considered a key building block for the preparation of this type of chiral catalyst. Bis-bromination of 67 provided 68 in 54% yield using NBS and catalytic AIBN in cyclohexane. Notably, the pure, bis-bromide 68 precipitates out of solution. Again, the benzyl bromide system was utilized as a leaving group. 

J.M.J. Frechet (C. J. Hawker, 1990) replaced the divergent synthesis by a convergent growth of a dendritic polymer. The repeatedly employed monomer, 5-hydroxymethyl-l, 3-benzenediol, was 1,3-O-dibenzylatcd with 3,5-bis(benzyloxy)benzyl bromide. The resulting benzyl alcohol containing 7 benzene rings was converted to the benzyl bromide which was... 

Oxidative cleavage of the complex 549 with CuCri affords 2,3-bis(chloro-methyl)-1,3-butadiene (550) and regenerates PdCri. Thus the preparation of this interesting dimerization product 550 can be carried out with a catalytic amount of PdCl2 and two equivalents of CuCb in MeCN[495], Similarly, treatment of allene with PdBr2 affords the dimeric complex 551. Treatment of this complex with 2 equiv, of bromine yields the dibromide 552. The tetra-bromide 553 is obtained by the reaction of an excess of bromine[496]. Similarly,... 

Usually, iodides and bromides are used for the carbonylation, and chlorides are inert. I lowever, oxidative addition of aryl chlorides can be facilitated by use of bidcntatc phosphine, which forms a six-membered chelate structure and increa.scs (he electron density of Pd. For example, benzoate is prepared by the carbonylation of chlorobenzene using bis(diisopropylphosphino)propane (dippp) (456) as a ligand at 150 [308]. The use of tricyclohexylphosphine for the carbonylation of neat aryl chlorides in aqueous KOH under biphasic conditions is also recommended[309,310]. 

The reaction of l,4-bis(trimethylsilyl)-l,3-butadiyne (174) with disilanes, followed by treatment with methylmagnesium bromide, produces i,l,4,4-tetra(-trimethylsilyl)-l,2,3-butatriene (175) as a major product[96]. The reaction of octaethyltetrasilylane (176) with DMAD proceeds by ring insertion to give the six-membered ring compounds 177 and 178[97], The l-sila-4-stannacyclohexa-2,5-diene 181 was obtained by a two-step reaction of two alkynes with the disilanylstannane 179 via the l-sila-2-stannacyclobutane 180[98],... 

Bis (meta or para haloacetyl) benzenes (C1CH2C0)2C6H4 condensed with thiourea yield the corresponding meta or para bis(4-thiazolyl-2-amino)phenylene (573, 574), analogous to 36 with R=NH2-By refluxing in alcohol solution m- or p-2-thiazolylphenacyl bromide (37) with thiourea, compound 111, in which R = H, Ph, P-CIC6H4, and p-OjNC H, was obtained (569). 

Isotopic molecular ion. A molecular ion containing one or more of the less abundant naturally occurring isotopes of the atoms that make up the molecular structure. Thus, for ethyl bromide there exist molecular isotope ions such as CCHjBi, C2H4DBi , C2H5 Bi, C2H5 Bi, etc. 

Butynediol. Butynediol, 2-butyne-l,4-diol, [110-65-6] was first synthesized in 1906 by reaction of acetylene bis(magnesium bromide) with paraformaldehyde (43). It is available commercially as a crystalline soHd or a 35% aqueous solution manufactured by ethynylation of formaldehyde. Physical properties are Hsted in Table 2. 

Pentafluorophenylmagnesium bromide or lithium can be converted to other pentafluorophenyl organometabics by reaction with the corresponding metal chloride (237). Bis(pentafluorophenyl)phenylphosphine [5074-71-5] (Ultramark 443), (CgF )2CgH P, is offered commercially as a marker for mass spectral standardi2ation (238). 

Medroxyprogesterone acetate (74) is stmcturaHy related to and has been prepared from hydroxyprogesterone (39) (Fig. 10). Formation of the bis-ketal accomplishes the protection of the ketones and the required migration of the double bond. Epoxidation with peracetic acid produces a mixture of epoxides (75), with a predominating. Treatment of the a-epoxide with methyl magnesium bromide results in diaxial opening of the epoxide. Deprotection of the ketones provides (76), which is dehydrated to (77) by treatment with dilute sodium hydroxide in pyridine. Upon treatment with gaseous hydrochloric... 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Other Complexes. Several other classes of organonickel complexes are known. AHyl bromide and nickel carbonyl react to give a member of the TT-aHyl system [12012-90-7], [7T-C3H3NiBr]2 (100). Tris(r -ethene)nickel [50696-82-7] reacts with acetylene and l,2-bis(diisopropylphosphino)ethane to... 

By-products include propylene dibromide, bis-(bromopropyl) ether, propylene glycol, and propionic acid. Bromide losses are to the brominated organics and bromate formation. Current efficiency is a function of ceU design and losses to bromate. Energy consumption decreases with an increase in electrolyte concentration and a decrease in current density. Space—time yield increases with current density. See Table 5 for performance data (see... 

Bismuth Tribromide. Bismuth(III) bromide is a hygroscopic, golden-yeUow, crystalline soHd made up of pyramidal molecules. X-ray analysis has shown that the three bromines are 0.263 0.002 nm from the bismuth and the Br—Bi—Br angles are 100 4°. More recent nqr experiments indicate that the bromines are not equivalent (20). The soHd has a density of 5.72 g/mL and that of the Hquid is 4.572 g/mL at 271.5°C. 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

---