Ethers, methyl cleavage

Oxidation of the alkaloid Glaucin (136) resulted in the formation of a yellow alkaloid 137, which seemingly is contained in Glaucium flavum var. vestitum (Scheme 48). Addition of methyl iodide converted this compound via a methylation/ether cleavage sequence into Corunnine (127) and small amounts of Pontevedrine (138) which is not a mesomeric betaine (71TL3093). 

Methyl ether cleavage, 59, 39 Methyl cw-M(l-ethoxy-2,3-dimethyl-cyclopropyl)carbamate, 59,138 Methyl rrans-A -(l-ethoxy-2,3-dimethyl-cyclopropyl)carbamate, 59, 138 Methyl ethyl ketone, 55, 25 5 -Methyl ferrocenethiocarbonate, 56, 30 Methyl formate, 59, 183 Methyl fumarate, 56, 63... 

Aroylformic acids. l-Aryl-2-mtn HOAc-MeOH at 90° to afford the ketoacK only give the eoiresponding methyl ethers Cleavage of picolinic acid esters. protocol using picolinic acid as the nuc alcohols are readily reeovered, that is. alte... 

In the reaction of 10b with piperidine in DMF, a novel methyl ether cleavage reaction of the 1-methoxy group occurs in addition to the nucleophilic substitution reaction, resulting in the formation of l-hydroxy-6-nitroindole-3-carbaldehyde (5a, 10%) and 2-piperidinyl product (109, 59%, Scheme 15) [11]. 

C2-symmetric teraryls. The synthesis was accomplished by palladium-catalysed intramolecular coupling, with subsequent ester saponification, methyl ether cleavage and two-fold ring closure to give the expected bislactone (Scheme 5.52). ... 

Acid catalyzed cleavage of aromatic methyl or ethyl ethers Quantitative methoxy group determination Also ether cleavage with tnmethylsilyl Iodide ... 

Selective cleavage of an aiyl methylenedioxy group, or an aryl methyl ether, by boron trichloride has been investigated. 

Fluorination of aliphatic ethers at gentle conditions with cobalt trifluoride or potassium tetrafluorocobaltate do not give perfluorinated products and cause only negligible cleavage of the ether bond. Complex mixtures are formed from ethyl methyl ether and from diethyl ether [9] (equations 16 and 17)... 

This method is probably the most commonly used one for the cleavage of methyl ethers, because it generally gives excellent yields with a variety of structural types. The solid complex BBr3-Me2S that is more easily handled can also be used. BBr3 will cleave ketals. 

A study of the reductive cleavage of a series of alkoxymethyl ethers using the glucose backbone shows that, depending on the reagent, excellent selectivity can be obtained for deprotection vs. methyl ether formation for most of the common protective groups. ... 

Sodium ethanethiolate has been examined for the selective cleavage of aryl methyl ethers. Methyl ethers para to an electron-withdrawing group are cleaved preferentially. ... 

Repeat this analysis for the reaction of phenyl methyl ether with HI leading to phenol and methyl iodide or methanol and phenyl iodide and involving protonated phenyl methyl ether as an intermediate. (Note In this case, the appropriate empty molecular orbital is LUMO+2 the LUMO is concentrated primarily on the CO bond.) Which reaction, with ethyl propyl ether or phenyl methyl ether, appears to be more likely to give selective ether cleavage ... 

Bischler-Napieralski reaction of 139 to a 3,4-dihydroisoquinoline, oxidation, dehydrogenation and reduction of the nitro to the amino function gave 140 which was subjected to a Pschorr reaction (Scheme 49). Quaternization was accomplished by methyl iodide to furnish the isoquinolininium salt 141 which underwent an ether cleavage on heating a solid sample or benzene or DMF solution to Corunnine (127) (73TL3617). 

Treatment of commercially available and symmetrical 3,4,5-tri-methoxytoluene (37) with iodine, periodic acid, and acetic acid under the conditions of Suzuki19 results in the formation of symmetrical diiodide 38 in 93 % yield. Although only one of these newly introduced iodine atoms is present in intermediate 13, both play an important role in this synthesis. Selective monodemethylation of 38 with boron trichloride furnishes phenol 39 in 53% yield together with 13 % of a regioisomer. Evidently, one of the Lewis-basic iodine substituents coordinates with the Lewis-acidic boron trichloride and directs the cleavage of the adjacent methyl ether... 

The present procedure illustrates the facile demethylation of methyl aryl ethers by lithium diphenylphosphide.3 This reaction is specific for methyl ethers and may be carried out in the presence of ethyl ethers in high yield.4 Use of excess reagent allows cleavage in the presence of enolizable ketones.5 In the present case, the cleavage may be performed without protection of the aldehyde, but two equivalents of reagent are required, and the yield is reduced to ca. 60%. 

Preparation from hcxamethyldisiloxane and 12/AI powder in detail, followed by cleavage of cyclohexyl methyl ether, to give cyclohexanol (via the intermediate silyl ether). 

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. 

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