Lithium bromide catalyst

Allenyl alcohols 10 react with lithium bromide in the presence of a palladium(II) catalyst to afford tetrahydrofurans and tetrahydropyrans 11 in good yield (Scheme 17.6) [7]. The mechanism of the reaction is similar to that discussed in Sect 17.2.1. i.e. it proceeds via a 2-bromo(jt-allyl)palladium(II) complex. In this case, however, the second nucleophile is not bromide ion but the alcohol moiety. As stoichiometric oxidant p-benzoquinonc (BQ) or copper(II) together with oxygen can be used. 

Lithium bromide is used in absorption, refrigeration and air-conditioning systems. A highly concentrated solution of the salt is an efficient absorbent of water vapor. The vapor pressure of such solution is very low. Other applications include the use of the salt as a swelling agent for wool, hair and other organic fibers as a catalyst in dehydrohalogenation reactions and as a sedative and hypnotic in medicine. 

Lithium bromide was a satisfactory ionic catalyst for the ring-opening polymerization reaction (Figure 2). The standard concentration of 0.258% gave good reaction. A lower concentration gave a slower reac-... 

Lithium-base greases, especially the stearate, are efficient over an extremely wide temperature range up to 160°C. Lithium hydroxide (LiOH) is a component of the electrolyte in alkaline storage batteries and is employed in the removal of carbon dioxide in submarines and space capsules. Lithium bromide (LiBr) brine is used for air conditioning and dehumidification. Lithium hypochlorite (LiOCl) is a dry bleach used in commercial and home laundries. Lithium chloride (LiCl) is in demand for low-temperature batteries and for aluminum brazing. Other uses of lithium compounds include catalysts, glass manufacture, and, of course, nuclear energy. 

The classical Bischler reaction has received relatively little attention in comparison with other methods for indole synthesis because of the harsh reaction conditions that it requires. The milder modifications involve the use of lithium bromide as a catalyst <2005T77> and a procedure under microwave irradiation conditions <2006SL91>. 

Easy access to peptide methyl esters is offered by the transesterification of peptides linked to benzyl alcohol type resins such as the HMBA resin.t l Tertiary amines generally serve as catalysts,although even better results are obtained with potassium cyanideor lithium bromide/DBUt as base catalysts. Note that Asp or Glu side-chain esters are likewise transformed under these conditions. 

Dimerizations of aryldiazomethanes to 1,2-diarylethylenes were reported to be catalyzed by cerium(IV) ammonium nitrate (4J), lithium bromide (42), copper(II) salts (43), and rhodium(II) acetate (44) and to be induced by photolysis (45). Catalysis of copper ion-exchanged zeolite (CuNaY) was compared with reactions of copper salts supported on AI2O3 and a homogeneous catalyst, Cu(C104)2, for the dimerization [Eq. (11)] of aryldiazomethane (Table XIII) (-/6). 

The catalysts used are bromine, iodine, haloamides I and/or polymerization inhibitors, in general in amounts of from 0.0001 to 0.1 preferably from 0.001 to 0.05, mole of catalyst per mole of methyi ketone. Instead of the above catalysts, it is also possible to usr compounds which form such catalysts under the reaction conditions, e.g to use bromides and iodides in place of bromine or iodine. Water-soluble halides are preferred and are advantageously used in the form of thei alkaline earth metal salts or, especially, their alkali metal salts, e.g calcium bromide, calcium iodide, magnesium bromide, magnesiais iodide, lithium bromide, lithium iodide and especially sodium bromide or iodide or potassium bromide or iodide... 

Ring-opening reactions to yield aldehydes or ketones were reviewed [7-10]. Isomerization may be thermally induced [7] or may occur in the presence of basic or acidic agents [11]. Lithium bromide associated with tributylphosphine oxide or hexamethylphosphoric triamide (HMPA) has been used [12,13], but transition metal complexes may be more attractive [14-21]. In this work the performances of catalytic systems, e.g. "LiBr/HMPA/toluene", "Co2(CO) /MeOH", "NiBr2(PPh3)2/ Zn/PPh3/THF", etc. are compared for the isomerization of 3a and of analogues. Supported catalysts have also been studied. 

Recently, the use of a chiral catalysts in the asymmetric biaryl synthesis has received some attention. Unsymmetrical chiral binaphthyls can be obtained in high enantiomeric excess by SnAt reactions of naphthylimines such as 39 with lithium bromide free 1-naphthyllithium catalysed by a chiral ether ligand 40 (ref. 29). Another example is the Ni(0) catalysed cross coupling of naphthyl Grignard reagents and naphthyl bromides in the presence of a chiral ferrocene ligand (ref. 30). 

Oxidative bromination of arenes can be achieved by the reaction with a source of bromide anion and an appropriate oxidant, possibly via intermediate formation of electrophilic bromoiodanes. In particular, an efficient and regioselective monobromination of electron-rich aromatic compounds has been developed, in which iodobenzene is used as the catalyst in combination with wCPBA as the terminal oxidant. The bromination of arenes 35 with lithium bromide is fast in THF at room temperature, providing regioselective monobrominated products 36 in good yields (Scheme 4.18) [46]. 

Chakraborti AK, Rudrawar S et al (2004) An efficient synthesis of 2-amino alcohols by silica gel catalysed opening of epoxide rings by amines. Org Biomol Chem 2 1277-1280. (b) Chakraborti AK, Rudrawar S et al (2004) Lithium bromide as an inexpensive and efficient catalyst for opening of epoxide rings by amines at room temperature under solvent-free condition. Eur J Org Chem 2004(17) 3597-3600... 

Lithium bromide, polyesterification catalyst, 483 Lithium chloride, polyesterification catalyst, 482 Lithium reagents, dialkyl maleate reactions, 234 Lumisterol, MA Diels-Alder adduct, 115 Lysergic acid, MA in synthesis, 231 Lytron resins, MA copolymers, 333, 366, 426, 440, 441, 452... 

Hasaninejad A, Zare A, Mohammadizadeh MR, Shekouhy M (2010) Lithium bromide as an efficient, green, and inexpensive catalyst for the synthesis of quinoxaline derivatives at room temperature. Green Chem Lett Rev 3(2) 143-148. doi 10.1080/17518251003619192... 

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