Methyl halides compounds

In many cases, substituents linked to a pyrrole, furan or thiophene ring show similar reactivity to those linked to a benzenoid nucleus. This generalization is not true for amino or hydroxyl groups. Hydroxy compounds exist largely, or entirely, in an alternative nonaromatic tautomeric form. Derivatives of this type show little resemblance in their reactions to anilines or phenols. Thienyl- and especially pyrryl- and furyl-methyl halides show enhanced reactivity compared with benzyl halides because the halogen is made more labile by electron release of the type shown below. Hydroxymethyl and aminomethyl groups on heteroaromatic nuclei are activated to nucleophilic attack by a similar effect. 

Metallic tin reacts with methyl halides and 2-halogenopropanoates at 135°, catalyzed by magnesium and butyl iodide in tetrahydrofuran, to give compounds MeSnXjCHgCHgCOjR, from which various other derivatives were prepared (42). 

Indium-mediated allylation of an unreactive halide with an aldehyde132 was used to synthesize an advanced intermediate in the synthesis of antillatoxin,133 a marine cyanobacteria (Lyngbya majus-cula) that is one of the most ichthyotoxic compounds isolated from a marine plant to date. In the presence of a lanthanide triflate, the indium-mediated allylation of Z-2-bromocrotyl chloride and aldehyde in saturated NH4C1 under sonication yielded the desired advanced intermediate as a 1 1 mixture of diastereomers in 70% yield. Loh et al.134 then changed the halide compound to methyl (Z)-2-(bromomethyl)-2-butenoate and coupled it with aldehyde under the same conditions to yield the desired homoallylic alcohol in 80% yield with a high 93 7 syn anti selectivity (Eq. 8.55). 

More recently, a novel type of halogenating enzyme, named hydroperoxide halolyase, which generates halogenated aldehydes, has been described in the marine diatom Stephanopyxis turris (Wichard and Pohnert 2006). In other microalgae, halogenation of organic compounds was shown to mainly involve methyl halide transferases (Moore et al. 1996 Manley 2002), and no vHPO has yet been identified on genomic data obtained from diatoms (Scala et al. 2002 Armbrust et al. 2004). Clearly, these emissions are not directly associated with an oxidative burst. 

The reaction of Si-halide compounds with methyl dihalides is suitable for the preparation of C-Si bonds with the insertion of special halogen-CH2groups however the preparative value is rather limited because of low yields. Eq. (28b) accounts for the formation of all the observed compounds21- 3 ... 

The reaction of phenols with alkyl halides or dimethyl sulfate in the presence of alkali to combine with the acid liberated is, of course, well known. The following preparation2 is selected as an example of the variety of alkyl compounds that enter into tins reaction, it being, of course, possible to consider chloroacetic acid, CICHjCOjH, as a methyl halide in which one of the hydrogens has been replaced by a carboxyl group. 

Trimethylantimony dichloride, dibromide, and diiodide have been shown to consist of trigonal bipyramidal molecules with the halogens at the apices and the methyl groups in the planar positions. Although melting points have been reported for these compounds from time to time, they are not reproducible because the compounds loose methyl halide upon heating. This reaction is useful for the prepa-... 

Further alkylation of tertiary amines yields quaternary ammonium salts. These compounds are numerous and are readily prepared by heating the alkyl halide and tertiary amine in the absence of a solvent or in the presence of alcohol. Methylation of tertiary amines to quaternary ammonium salts can be accomplished with methyl halides or dimethyl sulfate. ... 

Linnett o gives a discussion of the use of valence force fieid with the addition ol selected cross terms. One method of reducing the number of constants to Tdc determined from the frequencies is to carry over from molecule to molecule certain force constants for squared terms and even for cross terms. Linnett mentions in this connection the work of Crawford and Brinkley who studied acetylene, ethane, methylacetylene, dimethylacetylene, hydrogen cyanide, methyl cyanide and the methyl halides in this way, and were able, for all the molecules, to account for 84 frequencies with 31 constants. Linnetttreated some of these compounds using a different force field. He was able to account satisfactorily for 25 frequencies using 11 force constants. From our point of view the trouble with these results is that Linnett obtained a value for the C - C force constant in these acetylene derivatives which was different from that obtained by Crawford and Brinkley. For C - C in methyl cyanide for example, Linnett obtained... 

A commonly used synthetic method for these substituted phosphines involves the deprotonation of phosphine (or methylphosphine ) by a sodium-ammonia solution, followed by treatment with a methyl halide. More recently, methylphosphine has been produced by the reduction of methyldichloro-phosphine (unfortunately, not a readily available compound) by lithium hydroaluminate. The present method is essentially the deprotonation-methylation procedure, but instead of sodium-ammonia solutions, relatively easily handled KOH-dimethyl sulfoxide suspensions are used. 

Chloropyrazine with trimethylamine in benzene at 100° did not give the trimethylammonio compound but gave 2-dimethylaminopyrazine with loss of methyl halide (936). 2-Chloro-5-phenylpyrazine heated with hexamethylphosphoric triamide at 200° for 1 hour gave 2-dimethylamino-5-phenylpyrazine, and similar reactions were observed with 3-chloro-2,5-diethyl-, 3-chloro-2,5-diisobutyl-,... 

Methyl Halides.— The mono-halogen substitution products of methane, of which we have been speaking, are known by this new system of names as methyl compounds so that we have the two sets of names for the same substances, both of which are correct and either of which expresses the relationship to methane. 

Nitrogen Linked to Carbon.—Now when the isomeric compound, formed with silver cyanide and the methyl halide, is decomposed with water the nitrogen of the cyanogen remains linked to the methyl carbon in the form of methyl amine and the other product contains the cyano-... 

Tellurium-containing heterocyclic compounds also react with methyl halides, ethyl halides, allyl halides, benzyl bromide, and benzoylmethyl bromides, with or without a solvent, to produce telluronium halides. Tetrahydrotellurophene, l-methyltetrahydrotellurophene, 2,7-dihydrobenzo[c] tellurophene, 1-benzotellurophene 2-oxo-2,3-dihydro-l-benzo-tellurophene, dibenzotellurophene , 1,4-oxatellurane l,4-thiatellurane °, 3,4-dihydro-l/f-2-benzotellurin, and 4-oxo-2,3-dihydro-47/-l-benzotellurin" reacted to produce telluronium halides. 

The ethereal solutions of these iodides do not fume in air, and removal of the solvent gives a liquid, which on further heating evolves dense white fumes, probably of beryllium oxide. Heating changes the alkyl beryllium halides to beryllium dialkyls. All the alkyl halide compounds are decomposed by water, with formation of the corresponding hydrocarbon. When carbon dioxide is passed through ethereal beryllium methyl iodide for three hours, the solution still gives a positive test and no acetic acid is found after hydrolysis. Acetanilide is formed from beryllium methyl iodide and phenyl isocyanate. 

In order to get some information about the fate of silylenes S-la-d in the presence of a second molecule of methyl halide 6a-d, we checked whether silylenes S-la-d can experience stabilization by donor/acceptor interaction with 6a-d. Indeed, the two partners form weak donor/acceptor complexes 7a-d. That means that if S-la-d is created in a matrix at very low temperature in the presence of an excess of a methyl halide 6a-d, complexes like 7a-d should be present. Such a solvation might be the prerequisite for the direct synthesis of silanes 8a-d. These compounds represent the global minima on the CiHaSiX potential energy surfaces and are expected to be generated fl-om the two educt molecules S-la-d and methyl halide 6a-d in rather exothermic (AH, = 65-95 kcal moP ) processes. In the chlorine series (Scheme 1) the value is 73.9 kcal moP. ... 

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