Ethers, benzyl methyl

Ph.CH2.OMe, Ph.(CH2)2.0Me, Ph.(CH2)3.0Me (2-3, 3-4, 1-3), does not decrease steadily, but goes through a maximum. These two circumstances point to a specific -interaction in nitrations of the ethers with acetyl nitrate which is important with benzyl methyl ether, more important with methyl phenethyl ether, and not important with methyl phenpropyl ether. This interaction is the reaction with dinitrogen pentoxide already mentioned, and the variation in its importance is thought to be due to the different sizes of the rings formed in the transition states from the different ethers. 

The argtiments of Norman and his co-workers seem to give affirmative answers to the first and second of these questions, but it is doubtful if the available data further require such an answer for the third question. It can be argued that the crucial comparison made between the behaviour of benzyltrimethylammonium ion and protonated benzyl methyl ether is invalid, and that it is possible to interpret the results in terms of nitration by the nitronium ion, modified by protonation of the oxygen atom of the ether a case for the possible involvement of the nitro-nium ion in specific interaction leading to o-substitution has been made. ... 

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

Carbocations can also be generated during the electrolysis, and they give rise to alcohols and alkenes. The carbocations are presumably formed by an oxidation of the radical at the electrode before it reacts or diffuses into solution. For example, an investigation of the electrolysis of phenylacetic acid in methanol has led to the identification of benzyl methyl ether (30%), toluene (1%), benzaldehyde dimethylacetal (1%), methyl phenylacetate (6%), and benzyl alcohol (5%), in addition to the coupling product bibenzyl (26%). ... 

Imanishi and coworkers reported that thermolysis of the benzyl methyl ethers 98 (or benzyl-phosphonium salts) leads to high yields of indoles 99 in the absence of strong base. In the case of the methyl ethers, heating in the presence of an acid and catalyst and PPhs presumably involves in situ formation of a phosphonium salt intermediate <96JCS(P1)1261,96H(42)513>. 

Benzyl methyl ether produces methyl benzoate, benzaldehyde and benzoic acid but essentially no dibenzyl or benzyl alcohol. The initial radical is, therefore C6H5CHOCH3 and methyl benzoate is produced via the paths... 

OS 85] ]R 33] ]P 65] By means of HPLC analysis, it could be shown that all three types of products were formed during reaction in the micro reactor [69]. For a typical experiment, the main fraction was composed of 4-mefhoxybenzaldehyde dimethylacetal, the second largest fraction consisted of the aldehyde and 4-methoxy-benzyl methyl ether was generated in a smaller amoimt. 

Benzaldehyde, benzyl methyl ether, benzoic acid, methyl benzoate, and pheny-lacetic acid all undergo thallation initially in the ortho position. Explain this observation. 

As mentioned above, methyl loss from ionized methoxymethyl derivatives of methyl benzoate is not restricted to the ortho-isomet 93. 2H labelling has shown that the mita and para compounds 96 also eliminate CH3 specifically from the methoxymethyl group. Interestingly, neither from the unsubstituted benzyl methyl ether 97 (X = H) nor from the X-substituted analogues 97 (X = CH2OH, NQ2) loss of CH3 is observed (21). Thus, the earbomethoxy function seems to play a decisive role in the dissociation process. 

Unsymmetrical ethers may be produced from the acid-promoted reactions of aldehydes and organosilicon hydrides when alcohols are introduced into the reaction medium (Eq. 173).327,328 An orthoester can be used in place of the alcohol in this transformation.327 335 A cyclic version of this conversion is reported.336 Treatment of a mixture of benzaldehyde and a 10 mol% excess of triethylsilane with methanol and sulfuric, trifluoroacetic, or trichloroacetic acid produces benzyl methyl ether in 85-87% yields.328 Changing the alcohol to ethanol, 1-propanol, 2-propanol, or 1-heptanol gives the corresponding unsymmetrical benzyl alkyl ethers in 45-87% yield with little or no side products.328 A notable exception is the tertiary alcohol 2-methyl-2-propanol, which requires 24 hours.328 1-Heptanal gives an 87% yield of //-lie ply I methyl ether with added methanol and a 49% yield of benzyl n-heptyl ether with added benzyl alcohol under similar conditions.328... 

Thus, treatment of 28 with H2 (69 bar) for 20 hours at 100°C in decalin gave diphenylmethane (41%) together with small amounts of tetraphen-ylethene and tetraphenylethane. With 29, under somewhat milder conditions (H2, 1.8 bar, 140°C for 5 hours), a 92% yield of benzyl methyl ether was obtained. 

Alkenes are scavengers that are able to differentiate between carbenes (cycloaddition) and carbocations (electrophilic addition). The reactions of phenyl-carbene (117) with equimolar mixtures of methanol and alkenes afforded phenylcyclopropanes (120) and benzyl methyl ether (121) as the major products (Scheme 24).51 Electrophilic addition of the benzyl cation (118) to alkenes, leading to 122 and 123 by way of 119, was a minor route (ca. 6%). Isobutene and enol ethers gave similar results. The overall contribution of 118 must be more than 6% as (part of) the ether 121 also originates from 118. Alcohols and enol ethers react with diarylcarbenium ions at about the same rates (ca. 109 M-1 s-1), somewhat faster than alkenes (ca. 108 M-1 s-1).52 By extrapolation, diffusion-controlled rates and indiscriminate reactions are expected for the free (solvated) benzyl cation (118). In support of this notion, the product distributions in Scheme 24 only respond slightly to the nature of the n bond (alkene vs. enol ether). The formation of free benzyl cations from phenylcarbene and methanol is thus estimated to be in the range of 10-15%. However, the major route to the benzyl ether 121, whether by ion-pair collapse or by way of an ylide, cannot be identified. 

Hydrogenolysis Benzyl methyl ether Toluene + methanol [157]... 

Benzyl chloromethyl ether has been prepared from benzyl alcohol, aqueous formaldehyde solution, and hydrogen chloride. Gaseous formaldehyde and trioxane have also been used. This chloromethyl ether has also been prepared by the chlorination of benzyl methyl ether. The present procedure is based on the first method, but avoids the use of a large excess of formaldehyde and provides a considerably simplified isolation method. 

Acetals of aldehydes are usually stable to lithium aluminum hydride but are reduced to ethers with alane prepared in situ from lithium aluminum hydride and aluminum chloride in ether. Butyraldehyde diethyl acetal gave 47% yield of butyl ethyl ether, and benzaldehyde dimethyl acetal and diethyl acetal afforded benzyl methyl ether and benzyl ethyl ether in 88% and 73% yields, respectively [792]. 

Enantiomerically pure a-lithiated ethers have been prepared from stannanes and turned out to react with electrophiles under retention. The configurational stability of the hthium carbenoid 19 has been deduced from equation 10 . Lithiated benzyl methyl ether, chelated by a chiral bis(oxazoline) ligand, proved itself to be configurationally stable as welP . ... 

The arylamine 780c required for the total synthesis of carbazomycin E (264) was prepared in seven steps starting from vanillyl alcohol (803). Vanillyl alcohol (803) was transformed to the tetrasubstituted aryl derivative 804 via generation of the benzyl methyl ether followed by ortho-directed lithiation and subsequent... 

Trifluoromethylindole 181 is produced on heating 2-(A -trifluoroacetylamino)benzyl methyl ether in a sealed tube in the presence of triphenylphosphine and a catalytic quantity of /> rra-toluenesulfonic acid (Equation 117) <1996J(P1)1261>. 

Tricarbonylchromium-complexed benzyl methyl ether was deprotonated using (eri-butvllithi-um and alkylated at the benzylic position without any Wittig rearrangement1. 

The reaction patterns of arylcarbenes with solidified alcohol at 77 K are also completely different from those observed in alcohol solution. For example, generation of phenylcarbene (le) in methanol matrices at 77 K results in the formation of alcohol (63) at the expense of benzyl methyl ether (62), which is the exclusive product in the reaction in alcoholic solution at ambient temperatures (Scheme 9.14). A similar dramatic increase in the CH insertion products is observed in the reaction involving other carbenes with alcohols. ... 

---