Methoxymethyl formation

The Acid-Catalyzed Hydrolysis of Methoxymethyl-Formate. The acid-catalyzed hydrolysis of several alkoxymethyl esters was investigated by... 

Salomaa (146) in the temperature range between 0 and 60°C. In the case of methoxymethyl formate, deviations from the Arrhenius plot were observed, especially at low temperatures. This was explained by the author on the assumption of two simultaneous mechanisms, one unimolecular and the other bimolecular , the former having the higher energy of activation. Approximate values for Ei and k were calculated from the results at the two highest temperatures from these, ki at the lowest temperature, and hence ki = kob — ki, were calculated log kz was now plotted against IjT to give Ez and Az from which an improved k (=kobs — kz) was obtained. From this, an improved value of i and hence of ki at the lowest temperature were obtained, and the procedure repeated. By this trial and error method the authors arrived at... 

The acid-catalyzed hydrolysis of simple partial acylals has been studied in condensed phase, " " and a study of the behavior of methoxymethyl formate and methoxymethyl acetate in chemical ionization mass spectrometry was undertaken " to provide a comparison of the gaseous and solution phase chemistry of these simple partial acylals. Methoxymethyl formate and methoxymethyl acetate undergo hydrolysis in aqueous acid by an A lI mechanism,... 

The spectra of methoxymethyl formate are very similar to those of methoxymethyl acetate, but again with one significant difference. A fairly intense (M — 3) ion is observed in the acetate ester at mje = 101, but in the formate ester none of this ion is observed. However, the most intense ion in the spectrum (relative intensity = 51%) is mje = 101, which is the same mje value as is found for the (M — 3) ion in the acetate ester. From a study... 

Since methoxymethyl cation is not formed in the t-butyl chemical ionization of methoxymethyl formate and acetate, it is necessary to use a stronger gaseous acid to investigate the relative ease of formation of methoxymethyl cation from these two compounds. Consequently, methane chemical ionization spectra of the compounds have been obtained at several temperatures. We need not give the spectra, for it suffices to say that copious amounts of methoxymethyl methyl cation are formed from both esters by means of the reaction... 

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. ... 

The hindered 11 )5-hydroxyl group fails to react with dihydropyran. However, mixed acetals [e.g., methoxymethyl ether (97)] and hemiacetals e.g., hydroxymethyl ether (98)] are obtained as by-products in the formation of the BMD group. ... 

Treatment of 8-azidomethylperhydropyrido[l,2-c]pyrimidin-l-one 157 with methyl triflate and catalytic hydrogenation of the azide group led to the formation of tricyclic guanidine derivative 158 (01JA8851). Hydroxy group of 149 was protected with methoxymethyl chloride, and the p-methoxybenzyl protecting group (PMB) was eliminated by treatment with DDQ. 

Enhanced anti selectivity is observed in reactions of lithiated 4.5-dihydrooxazoles bearing an additional substituent which facilitates the formation of rigid azaenolates by internal chelation of lithium13. Thus, reaction of 2-ethyl-4,5-dihydro-4,4-dimethyloxazole (10) with 2-methylpropanal gives a 56 44 mixture of adducts while (R)-2-ethyl-4,5-dihydro-4-(methoxymethyl)-oxazolc (12) reacts with the same aldehyde to yield a 90 10 mixture of adducts 1313. 

An excellent synthetic method for asymmetric C—C-bond formation which gives consistently high enantioselectivity has been developed using azaenolates based on chiral hydrazones. (S)-or (/ )-2-(methoxymethyl)-1 -pyrrolidinamine (SAMP or RAMP) are chiral hydrazines, easily prepared from proline, which on reaction with various aldehydes and ketones yield optically active hydrazones. After the asymmetric 1,4-addition to a Michael acceptor, the chiral auxiliary is removed by ozonolysis to restore the ketone or aldehyde functionality. The enolates are normally prepared by deprotonation with lithium diisopropylamide. 

Recently, Aumann et al. reported that rhodium catalysts enhance the reactivity of 3-dialkylamino-substituted Fischer carbene complexes 72 to undergo insertion with enynes 73 and subsequent formation of 4-alkenyl-substituted 5-dialkylamino-2-ethoxycyclopentadienes 75 via the transmetallated carbene intermediate 74 (Scheme 15, Table 2) [73]. It is not obvious whether this transformation is also applicable to complexes of type 72 with substituents other than phenyl in the 3-position. One alkyne 73, with a methoxymethyl group instead of the alkenyl or phenyl, i.e., propargyl methyl ether, was also successfully applied [73]. 

Fraaije MW, WJH van Berkel (1997) Catalytic mechanism of the oxidative demethylation of 4-(methoxymethyl)phenol by vanillyl-alcohol oxidase. Evidence for formation of a /7-quinone intermediate. /Sio/ Chem 272 18111-18116. 

A similar ATI-bridged ONO-trident 151 was formed from the reaction of 7-oxabenzo norbomadiene 36 with the O-bridged A -methoxymethyl aziridine 146. However, in light of the bridged products discussed below, the mechanism for formation of the NH-compound may implicate neighbouring group participation of the O-bridge and a cyclic intermediate such as 150. 

These isomers resulted from the non-stereoselectivity of the initial coupling process typical of the aza-ACE reactions of the 7-isopropylidene-bridged dipolarophile 38, while molecular weight measurements and the presence of an isopropenyl group in the H NMR of each product supported C,A-methano-bridge formation. Such products were considered to arise via the bond reorganisation depicted by the arrows in adduct 156 in which one of the isopropylidene rc-bonds acted as the nucleophile to attack the methylene carbon of the adjacent A-methoxymethyl group. 

The stereoisomers 16c and 16d have also been prepared by a [3 + 3]-type annelation between a,a -dimethoxylated amides and allyltrimethylsilane (363). Compound 366 was synthesized by ring formation with 363 and 365, prepared by methoxymethylation of 364, in the presence of TiCl4. Hydrogenation of 366 foWov/ed by bulylalion with n-BuLi and reduction with sodium borohy dride gave a mixture of stereoisomers 16c and 16d (Scheme 41) (437). 

Treatment of isopropyl 6-hydroxy-4-methoxymethyl-/3-carboline-3-carboxylate 189 with a primary amine in the presence of an excess of manganese dioxide produces the oxazolo[4,5-g]-/3-carboline 190 in moderate yield (Equation 125) <1998H(48)31>. The efficiency of the reaction is limited by the formation of by-products. 

In contrast to earlier known imines, those imines derived from a-(methoxymethyl)benzene-ethanamine, which allow formation of a rigid chelate by additional coordination of the lithium with the methoxy group, enabled the preparation of a-alkylated cyclic ketones in very high enantiomeric excesses (90-99% ee)7,8. However, alkylations of imines derived from medium ring ketones were accomplished in 30-82% ee9. The alkylation of acyclic ketones was performed with enantiomeric excesses of more than 75 % and, in the case of the imine derived from 4-heptanone, proceeded with complete asymmetric induction10. 

The transition state of singlet carbene cycloaddition to alkenes involves an electrophilic approach of the vacant p orbital to the n bond of alkenes. By contrast, the first step of the triplet addition process may involve the in-plane a orbital of the carbene. As in the case of C—H insertion (see Section 5.1), the difference in the transition structure between the singlet and triplet cycloaddition becomes important in the intramolecular process, especially when approach to a double bond is restricted by ring strain. Direct photolysis of ( )-2-(2-butenyl)phenyldiazomethane (99) in the presence of methanol gives l-ethenyl-l,la,6,6fl-tetrahydrocycloprop [fljindene [100, 29%, (E/Z)= 10 1] and l-(2-butenyl)-2-(methoxymethyl)benzene (101, 67%). Triplet-sensitized photolysis results in a marked increase in the indene (52%, EjZ) = 1.3.T) at the expense of the ether formation (4%) (Scheme 9.30). On the other hand, direct photolysis of phenyldiazomethane in an equimolar mixture of... 

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