Methoxy lithium aluminium hydride

The reduction of methyl 6-methoxy-2-naphthyl acetate with lithium aluminium hydride in refluxing ether gives 2-(6-methoxy-2-naphthyl)ethanol, which by treatment with PBr3 in refluxing benzene is converted into 2-(6-methoxy-2-naphthyl)ethyl bromide. Further reaction with KCN in refluxing ethanol-water affords 3-(6-methoxy-2-naphthyl) propionitrile, which is finally treated with methylmagnesium iodide in refluxing ethanol. 

Generally, however, lithium aluminium hydride reduction is used to convert isatins to indoles. Thus, 4,5,6-trimethoxyisatin,251 5-bromo-isatin,252 5-chloro-6-methoxy-l-methylisatin,253 1-ethyl- and 1-methyl-isatin,254 and 4,6-dimethoxyisatin94 all gave the corresponding indoles. 

Amino-4-methoxy-l-methoxymethylnaphthalene 120, obtained from the chloromethyl derivative 111, is transformed into azide 121. The latter undergoes photolytic heterocyclization to the labile 5-methoxyben-zo[cd]indole 117 which, on reduction by lithium aluminium hydride followed by acetylation, is converted into the stable l-acetyI-5-methoxy-l, 2-dihydrobenzo[o/]indole 119 (R = OMe) [71JCS(C)721]. The reduction of methyl or phenyl 8-nitro-1 -naphthyl ketones by hydrogen and platinum dioxide or by iron in acetic acid leads to a mixture of products (59M634). 

Methyl 4-0-(4-methoxybenzyl)2,3-di-0-methyl-oc-D-glucopyranoside has been prepared [371] by Liptak s procedure (see Sect. 2.6). This lithium aluminium hydride — aluminium trichloride method was also used in the synthesis of 4-hydroxy-3-methoxy-benzyl [372], 4-hydroxy-3,5-dimethoxybenzyl [372], and 1-phenylethyl [373] ethers from the 4,6-acetals derived from vanillin, syringealdehyde, and acetophenone. Various vinylbenzyl ethers were prepared by the reaction of carbohydrates with vinylbenzyl chloride, and copolymerized with styrene [374]. 

A solution of 2-(3-methoxy-phenoxy)-propionitrile in dry ether was added dropwise to a stirred suspension of lithium aluminium hydride in dry ether. 

The reaction of 3,3-dichloro-2-methoxyazetidine 35 with lithium aluminium hydride in ether afforded 3-chloro-azetidine 36 (Equation 8). The substitution of the methoxy group by hydride via an azetinium intermediate and subsequent conversion of the geminal dichloro derivative to the monochloroazetidine via a single electron transfer reaction yielded this compound <1998JOC6>. Treatment of 1-benzyl-3-hydroxyazetidine 37 with triphenylphos-phine in carbon tetrachloride yielded l-benzyl-3-chloroazetidine 38 (Equation 9) <2004JOC2703>. 

The starting materials, frans-3,4-methylenedioxycinnamyl alcohol (61a) and frans-2-methoxy-3,4-methylenedioxycinnamyl alcohol (61b) were prepared from the corresponding benzaldehyde via substituted ethyl cinnamate by means of the Horner-Emmons reaction and lithium aluminium hydride reduction. Condensation of compound (61 a) or (61 b) with compound (47) gave compound (62a) or (62b), respectively, followed by ring closure to afford compound (63a) or (63b). Intramolecular Diels-Alder reaction of compound (6 2) led to the formation of the aromatized compounds as by-product in both cases. Moreover, in the reaction of... 

The synthesis of buprenorphine has a certain similarity to that of etorphine. After the Diels-Alder reaction of thebaine with methyl vinyl ketone, the double bond is hydrogenated. Then follows a Grignard reaction with t-butyhnagnesium chloride. For modification of the tertiary amine, this is demethylated with cyanogen bromide (von Braun reaction) and treated with cyclopropanecarbonyl chloride. Following reduction with lithium aluminium hydride, the aromatic methoxy-group is finally replaced by nucleophihc substitution under forcing conditions. 

Epoxy fatty acids (as the methyl esters) give El mass spectra which are not easily interpreted in terms of the position of the oxygen atom (especially when double bonds are also present), although it is possible with some effort if suitable model compounds are available [116,473,481]. It is generally recommended that the epoxide be isomerised to a mixture of keto compounds [473], or that the ring should be opened with boron trifluoride-methanol reagent to a mixture of methoxy-hydroxy derivatives [481,833] or with lithium aluminium hydride to hydroxy derivatives followed by trimethylsilylation [940], for identification by GC-MS. MS was used to study the incorporation of into the oxirane ring of 9,10-epoxyoctadecanoic acid in wheat tissues [488]. If derivatization is undesirable, more useful spectra are obtained with chemical ionisation [474,717]. 

Certain sugar allylic acetals, such as the pyranoside (213), undergo an abnormal mode of reduction with lithium aluminium hydride to give vinyl ethers (Scheme 141) an intramolecular delivery of hydride ion is proposed, by co-ordination of the reagent with the methoxy-oxygen atom. 

Presence of carbon dioxide in solutions of the hydride in dimethyl or bis(2-methoxy-ethyl) ether can cause a violent decomposition on warming the residue from evaporation. Presence of aluminium chloride tends to increase the vigour of decomposition to explosion. Lithium tetrahydroaluminate may behave similarly, but is generally more stable. 

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