Methoxymethyl ethers stable

This derivative is stable to TsOH/benzene at reflux and to Cr03/H. It is stable to NBS// . In the formation of this derivative formaldehyde from formalin can react with a C,-hydroxyl group to form a methoxymethyl ether. Paraformaldehyde can be used to avoid formation of the ethers. ... 

R SiBr, trace MeOH. Methoxymethyl ethers are stable to these cleavage conditions. Methoxymethyl esters are unstable to silica gel chromatography, but are stable to mild acid (0.01 N HCl, EtOAc, MeOH, 25°, 16 h)." ... 

Hydroxyl groups protected as acetonides or as silyl, tetrahydropyranyl, benzyl, or methoxymethyl ethers are stable to these conditions. Yields with KMn04 are higher than those obtained with KMn04 and dicyclohexyl- 18-crown-6, Bu4NMn04, or NaMn04H20. ... 

Tetrahydropyranyl (THP) ethers, another species known to be unstable to acid, have similarly been reported to be cleaved by solutions of iodine in methanol.209 At room temperature, cleavage of the THP ethers was complete in 1.5 to 8 h. As with the previous example using iodine in methanol at lower than reflux temperature, TBDMS ethers were stable to these conditions. The ability to tune the reactivity of the iodine in methanol system by simply controlling the temperature is of value in selective deprotection. This is even more useful when fluorine, known to remove only silyl ethers,105 is exploited. Given that methoxymethyl ethers, essentially acetals, are known to be cleaved under acidic conditions, it seems likely they too should be subject to removal by solutions of iodine in methanol. Sundry examples of deprotections using iodine in methanol are presented in Table IV. 

Many functional groups are stable under conditions for the alkylation of pseudoephedrine glycinamide enolates, including aryl benzenesulfonate esters (eq 18), rert-butyl carbamate and rerf-butyl carbonate groups (eq 19), tert-butyldimethylsilyl ethers, benzyl ethers, ferf-butyl ethers, methoxymethyl ethers, and alkyl chlorides. The stereochemistry of the alkylation reactions of pseudoephedrine glycinamide and pseudoephedrine sarcosinamide is the same as that observed in alkylations of simple A(-acyl derivatives of pseudoephedrine. 

Weakly acidic phenols that do not react with diazomethane can be methylated with sodium hydride and methyl iodide in THF at room temperature. The methoxymethyl ether moiety can be used to protect phenols. It is stable to alkali, Grignard reagents, lithium aluminum hydride, and catalytic hydrogenation, and is readily removed by mineral acid. Dimethoxymethane can be used in lieu of the carcinogenic chloromethyl methyl ether for this purpose. Alternatively, phenols may be protected as methyl thiomethyl ethers.The (9-acetylation of phenols in the presence of primary and secondary amines can be carried out with acetyl bromide and TFA. ... 

The or//io-palladation of 3,4-dioxygenated benzylic tertiary amines by lithium tetrachloropalladate can be directed exclusively to either C-2 or C-6. Substitution at C-6 prevails when AcO, methylenedioxy, PhCH20, methoxymethyl ether, or HO substituents are attached to C-3, whereas palladation occurs exclusively at C-2 when C-3 bears methylthiomethyl ether or phenylthiomethyl ether substituents. The resulting organopalladium compounds are crystalline solids, stable to air and moisture, and can readily be carbonylated, alkylated, arylated, Kinetic studies of the acetoxylation of arenes by potassium peroxydisulphate and acetic acid in the presence of (2,2 -bipyridyl)palladium(ii) acetate catalyst have led to a revision of the mechanism. The reaction is now thought to proceed via... 

The construction of the five contiguous stereocenters required for a synthesis of compound 3 is now complete you will note that all of the substituents in compound 5 are positioned correctly with respect to the carbon backbone. From intermediate 5, the completion of the synthesis of the left-wing sector 3 requires only a few functional group manipulations. Selective protection of the primary hydroxyl group in 5 as the corresponding methoxymethyl (MOM) ether, followed by benzylation of the remaining secondary hydroxyl, provides intermediate 30 in 68 % overall yield. It was anticipated all along that the furan nucleus could serve as a stable substi-... 

Gilman and his co-workers prepared a large number of organolithium compounds by this method.35 An analogous reaction occurs with chloro ethers, yielding, e.g., from chloromethyl ether and lithium in methylal at —25° to —30° (methoxymethyl)lithium, which is stable for days at —70° but decomposes in a few hours at 0°.36... 

Ether cleavage. The polymer-bound reagent catalyzes hydrolysis of TBS ether and acetals in aqueous acetonitrile. Methoxymethyl and tetrahydropyranyl ethers are stable under such conditions. 

Both ADM [31] and Avantium [29,30] have reported on the oxidation of MMF, the more stable methyl ether of HMF. Avantium is currently scaling up its process based on an optimized process in its pilot plant, yielding greater than 96 mol% FDCA -I- FDCAMe from MMF. Though this compound could not be oxidized over heterogeneous catalyst systems (discussed earlier), facile oxidation using the Co/Mn/Br catalyst system has been reported (see Table 19.3). Since ethers are hydrolytically very stable, it clearly indicates that the activation of MMF must proceed via a direct oxidation of the methylene carbon of the methoxymethyl moiety. 

A soln. of 5.0 g. ethyl 8/, 8a/ -dimethyl-l-oxo-l,2,3,4,6,7,8,8a-octahydro-2-naph-thoate in hexamethylphosphoramide added at 5° under Ng to a stirred mixture of a 60%-dispersion ofNaHin mineral oil and hexamethylphosphoramide, stirring continued 1 hr. at room temp., cooled to 5°, 1.93 g. chloromethyl methyl ether added, and stirred 2 hrs. at room temp. 5.7 g. crude methoxymethyl enol ether dissolved in ether, added rapidly with Dry Ice-cooling under argon to a stirred dark blue soln. of Li in anhydrous NH3, and stirring continued 12 min. at -33°, the b. p. of liq. NHg 2.85 g. ethyl 8/, 8ai -dimethyl-l,2,3,4,6,7,8,8a-octahydro-2j -naphthoate. Overall Y 60%. - 0-Alkylation of the startg. -keto esters occurs under the above conditions to the complete exclusion of the C-alkylated isomer. The subsequent reduction gives the less stable axial isomer. R. M. Coates and J. E. Shaw, J. Org. Chem. 35, 2597 (1970) f. e. s. ibid. 35, 2601 carboxylic acids, also from a,/ -ethylenecarboxylic acids, cf. ibid. 36, 1151 (1971). 

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