Halides methyl iodide

Route A 1- is very convenient for the substitution of OH groups by bromide or iodide. The reaction conditions are relatively mild (acetonitrile, room temperature, and reflux for 1—3 h, neutral medium). The activating halide (methyl iodide, ally or benzyl bromide) is added in excess (5 equivalents) or in large excess (10 equivalents) when the resultant halide is nearly as reactive as the activating halide. The imidazolium-iV-carboxylates are the important intermediates, which undergo a displacement reaction to give the halides,... 

The following qualitative observations on the action of liquid ammonia on organic compounds are mainly by E. C. Franklin and C. A. Kraus, those in brackets are by G. Gore. Aliphatic compounds.—Halides methyl iodide, m. chloroform, reacts, and m. bromoform, m. iodoform, v.s., ethyl bromide and iodide, s. ethylene bromide, s. ethylidene chloride, m. isobutyl bromide, s. amyl bromide, s.s. tribromomethane, v.s. nitrotriohloromethane, m. perehloroethane (n.s.) perchloroethylene (m.) dichloroacetylene (s.). Alcohols methyl, m. ethyl, m. propyl, m. normal butyl,... 

There are numerous variations on the general mechanism outlined in Figure 7.10. Glutathione forms conjugates with a wide variety of xenobiotic species, including alkenes, alkyl epoxides (1,2-epoxyethylbenzene), arylepoxides (1,2-epoxynaphthalene), aromatic hydrocarbons, aromatic halides, alkyl halides (methyl iodide), and aromatic nitro compounds. The glutathione transferase enzymes required for the initial conjugation are widespread in the body. 

You have already met phosphonium salts in Chapter 5 where you saw the reaction of a phosphine (triphenylphosphine) with an alkyl halide (methyl iodide). 

This protocol is representative of the Michaelis-Arbuzov reaction in its simplest form, on a large scale. Protocol 1 may be used with minor modification to synthesize other simple dialkyl alkylphosphonates.20 The combination of triisopropyl phosphite 9 and a primary alkyl halide (methyl iodide) means that the formation of the potential by-product diisopropyl isopropylphosphonate is negligible because the product alkyl halide (isopropyl iodide) is a secondary alkyl halide and thus reacts much more slowly with triisopropyl phosphite 9 than does the desired reactant methyl iodide. 

If an organic chemist wanted to put a methyl group on a nucleophile, methyl iodide would most likely be the methylating agent used. Of the methyl halides, methyl iodide has the most easily displaced leaving group because 1 is the weakest base of the halide ions. In addition, methyl iodide is a liquid, so it is easier to handle than methyl bromide or methyl chloride. The reaction would be a simple Sn2 reaction. 

Preparation. Tetraalkylammonium borohydrides can be prepared by addition of a slight excess of sodium borohydride to a solution or suspension of a tetraalkylammonium hydrogen sulfate in an aqueous solution of NaOH. The resulting tetraalkylammonium borohydride is extracted with methylene chloride. The solid salt can be obtained by evaporation of the methylene chloride and crystallization from ethyl acetate. These salts are mild reducing agents. They are converted into diborane and a tetraalkylammonium halide by treatment in methylene chloride with an alkyl halide (methyl iodide, ethyl bromide). The advantage of generation of diborane in this way is that anhydrous methylene chloride is easily obtained. 

The tertiary nature of the nitrogen in this strong base is demonstrated by its quantitative reaction with one mole of alkyl halide (methyl iodide (21), ethyl iodide (14) ) with the formation of quaternary salts. Secondly, the isolation of methylamine as one of the products of fusion of tropine with alkali (sodium hydroxide (22), barium hydroxide (14) ) suggests the... 

In l-hthio vinyl sulfides (sec. 8.6) the sulfur atom stabilized the carbanion, allowing either alkylation or condensation reactions. The sulfonyl moiety can also stabilize a vinyllithium derivative. Vinyl sulfone (321), for example, was converted to the 1-lithio derivative with methyllithium.332 xhis organometallic reacted in the usual manner with alkyl halides (methyl iodide) to give the coupling product, 322. 

Initiation of cationic ROP with Lewis acids such as BF3 and SbCls involves water or other compounds that can donate protons. ROP of TMC was conducted in bulk at 80—100°C using a BF3/OEt catalyst system (Albertson and Sjoeling, 1992). High molar mass up to 100,000 g/mol was obtained. In contrast, only low molar masses were obtained in the presence of other cationic catalysts such as AICI3/CH3 COO K and with alkyl halides (methyl iodide, benzyl bromide, and allyl iodide) (Ariga et al., 1997). 

Phosphites. The deprotonation of (7,0-dialky 1 phosphites (25) with KH or NaH generates metal phosphites (26), which can be reacted with CS2 followed by the reaction with alkyl halides to afford (7, (3-dialkyl phosphonodithioformates (27) (eq 18). The deprotonation with JCH is carried out at 0 °C for 3 h, whereas the reaction withNaH is performedinTHFatrefluxforS min. As alkyl halides, methyl iodide, trityl, fluorenyl, and benzyl bromides are used, and the products (27) are obtained in 65-85% yields. 

Deprotonation of Al,<9-bis(trimethylsilyl)hydroxylamine with n-butyllithium or potassium hydride at low temperature yields the nitrogen centered anion Al,<9-bis(trimethylsilyl)hydroxyl-amide. At higher temperatures the oxyanion Al,A -bis(tri-methylsilyl)hydroxylamide is formed by rearrangement. Each reacts with acyl chlorides chemospecifically by M-acylation and 0-acylation, respectively. The oxyanion also reacts with silyl halides, methyl iodide, and sulfonyl chlorides chemospecifically on oxygen. In a Peterson-type one-pot reaction, oximes and oxime derivatives can be prepared effectively from the N-anion of iV,0-bis(trimethylsilyl)hydroxylamine and an aldehyde or ketone (eq 5). Oximes of sterically hindered ketones can be formed in high yields by this procedure. 

Brandstrom and coworkers have shown that tetrabutylammonium borohydride in dichloromethane solution will react with alkyl halides (methyl iodide, ethyl bromide or 1,2-dichloroethane) to yield solutions of diborane (see Eq. 12.3). Although diborane cannot be distilled from these solutions and its presence is therefore not... 

The second method is more efficient because the aUcyl halide (methyl iodide) is not sterically hindered. The first method is not efficient because it employs a tertiary alkyl halide, and Sn2 reactions do not occur at tertiary substrates. 

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