Benzyl methyl ether, cleavage

Benzyl derivatives of aliphatic alcohols 73> are not reduced below the discharge potential of (C2H5)4N + in DMF [—2.9 V(SCE)]. But, they show a wave around —3.1 V(SCE) in solutions of (C4H9)4N+. Efficient reductive cleavage of benzyl methyl ether was achieved n) in THF-8% H20 with 0.25 M (C4H9)4NBF4. Under these conditions, toluene, which is the cleavage product may also be reduced and the... 

Selective reduaion of aromatic acids and their derivatives to aldehydes can be achieved electrochemi-cally. Reduction of the carbinolamines is observed, as in the formation of anilinomethylpyridine (Scheme 13) and 4-methylpyridine. Reductive cleavage of benzyl methyl ethers can be achieved leading to hydrocarbons when the ring substituents are electron attracting. 

A similar cleavage of benzyl methyl ethers takes place when a solution of equimolar amounts of bromine in carbon tetrachloride is added dropwise to a refluxing solution of the ether in carbon tetrachloride under irradiation. Benzyl methyl ether gives a 11% yield of benzaldehyde, and benzhydryl methyl ether gives a 36% yield of benzophenone [731]. 

Benzyllithium, one of the more useful metalating agents, can be obtained in high yield by cleavage of benzyl methyl ether in tetrahydrofurane at —5° to —15°. Since benzyllithium is formed readily in tetrahydrofurane but is more stable in diethyl ether solution, dark brown solutions of concentrations as high as 1.2 At can be obtained in yields up to 83% by gradual addition of a solution of benzyl methyl ether in diethyl ether to a suspension of lithium in tetrahydrofurane. ... 

Optimum Conditions for Preparing Benzyllithium from Toluene. Both the TMEDA and TED complexes of benzyllithium were investigated. Toluene metalation proceeds much faster than does benzene metalation under similar conditions. The benzyllithium complexes were more soluble in hydrocarbon solvents than were the corresponding phenyllithium complexes. This method of preparation of benzyllithium is the most convenient of the few literature procedures available. Other procedures described are the cleavage of benzyl methyl ether with lithium... 

Reductive C-0 bond cleavage. Benzylic methyl ethers give benzyl anions which can be alkylated. The controlled stepwise cleavage of dimethyl acetals makes the method synthetically useful. 

Cleavage of a, -unsaturated p-tosyUiydrazones. Reaction of an a,)9-un-saliirated p-tosylhydrazone with sodium borohydride and methanol affords an allylic or benzylic methyl ether rather than a hydrocarbon as shown in the examples. Actually NaBH4 can be replaced by sodium methoxide or potassium carhoualc. The reaction is probably related to the Bamford-Stevens reaction. ... 

Preparative Methods benzyl alcohol plus aqueous formaldehyde and hydrogen chloride gas - reaction of benzyl methyl ether with boron trichloride cleavage of benzyloxymethyl methyl sulfide with sulfuryl chloride. ... 

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

The use of iodotrimethylsilane for this purpose provides an effective alternative to known methods. Thus the reaction of primary and secondary methyl ethers with iodotrimethylsilane in chloroform or acetonitrile at 25—60° for 2—64 hours affords the corresponding trimethylsilyl ethers in high yield. The alcohols may be liberated from the trimethylsilyl ethers by methanolysis. The mechanism of the ether cleavage is presumed to involve initial formation of a trimethylsilyl oxonium ion which is converted to the silyl ether by nucleophilic attack of iodide at the methyl group. tert-Butyl, trityl, and benzyl ethers of primary and secondary alcohols are rapidly converted to trimethylsilyl ethers by the action of iodotrimethylsilane, probably via heterolysis of silyl oxonium ion intermediates. The cleavage of aryl methyl ethers to aryl trimethylsilyl ethers may also be effected more slowly by reaction with iodotrimethylsilane at 25—50° in chloroform or sulfolane for 12-125 hours, with iodotrimethylsilane at 100—110° in the absence of solvent, " and with iodotrimethylsilane generated in situ from iodine and trimcthylphenylsilane at 100°. ... 

Cleavage of benzyl ethers3 Anhydrous FeCl3 in CH2C12 cleaves carbohydrate benzyl and p-phenylbenzyl ethers at 25° without effect on methyl ethers or acetate and benzoate groups. Yields are usually >70%. 

Selective cleavage of aryI methyl ethers.1 The sodium salt (NaH) of N-melhylaniline in the presence of HMPT cleaves methyl (and benzyl) aryl ethers in... 

Cleavage of dialkyl ethers.1 Methyl, allyl, and benzyl alkyl ethers are cleaved by this combination to the alcohols and methyl, allyl, and benzyl iodide (75-90% yield). The reagent also cleaves epoxides to frans-2-iodoalkanols (—70% yield). 

In turn, photosensitized electron transfer fragmentation of a benzylic bond has been among the first reaction reported when this branch of photochemistry began to take shape in the seventies, with the decarboxylation of phenylacetic acids reported by Libman [23] and the C-C cleavage in phenylethyl methyl ethers reported by Arnold [24]. 

Photoheterolytic cleavage of benzyl alcohol in neutral media occurs only when it gives rise to highly stabilized cations, such as triphenylmethyl cations (compare Sec. 15.1 the reaction may be at least in part adiabatic in this case and yield the excited cation) [79-81], xanthyl [82] or fluorenyl cations [83]. However, acid catalysis is effective and methyl ethers are by far the main products from benzyl alcohols in acidified aqueous methanol [84-88]. Electron donating substituents in the ortho and, to a lesser extent, in the meta position enhance the quantum yield (acid catalysis may be... 

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