Methanolysis acid-catalyzed

The ethoxyethyl ether is prepared by acid catalysis from a phenol and ethyl vinyl ether and is cleaved by acid-catalyzed methanolysis. ... 

Acid catalyzed methanolysis of 5-R-thiophene-2-carboxylic acids MeOH 45 -0.34 0.10 0.07 0.884 5 e... 

Preparation of 2-fluorofuranoses is also important in relation to the synthesis of biologically active 2 -fluoro derivatives of nucleosides (see Section 111,4). Su and coworkers prepared the 2-triflates 236 and 239 through acid-catalyzed methanolysis of 3,5-di-O-benzyl-1,2-(9-isopropylidene-a-D-ribofuranose [to give 235 (major) and 238] and subsequent triflylation. On treatment with fluoride ion, the anomer 236 afforded exclusively the furan derivative 237, whereas the a anomer 239 gave the 2-fluoro compound 240... 

The phosphonyl adduct 300 reacted with a dilute solution of anhydrous hydrogen chloride in ethanol or with sodium ethoxide to afford an essentially quantitative yield of the P-N cleaved product 304 with inversion of configuration. Addition of sodium ethoxide to a solution of 304 in methanol resulted in the formation of enantiomerically pure (+)-(.V)-ethyl methyl phenylphosphonate (305). It also reacted quantitatively with methylmagnesium iodide at room temperature to give the product of P-S bond cleavage 306, which upon acid catalyzed methanolysis afforded enantiomerically pure (+)-(R)- methyl methylphenylphosphinate (307) (Scheme 72) [108],... 

The medicinal chemistry of this period relied on simple modifications of the complex alkaloids. Deacetylation of 1 produced 4-deacetylvinblastine (98), a perfect substrate for these first experiments. Treatment if 1 with hydrogen chloride in anhydrous methanol gives 98 directly (91). Cleavage of the 4-acetyl function can also be effected by methanolysis, but during this period the acid-catalyzed methanolysis method was regarded as the preferred method. 

The perchloric acid-catalyzed methanolysis of 2-methyloxetane gives a mixture of 4-methoxy-2-butanol and 3-methoxy-l-butanol, with the former somewhat predominating (equation 21). The effect of solvent on the product distribution and the reaction rates indicated that protonated 2-methyloxetane was reacting by a borderline n1-Sn2 mechanism (67MI51302). Similar studies with the acid-catalyzed methanolysis of oxetane itself indicated that methanol reacted with protonated oxetanium ion by the N2 process. The same type of studies with a series of 2-aryloxetanes indicated that methanolysis of these compounds involved the borderline mechanism for the protonated oxetanium ions (69MI5101, 72MI5102, 73MI5100). 

Substituent effects on aziridine formation from N-(2-halogenoethy 1) arylsulphonamides by cyclization in basic media have been studied,425 and Hammett equation studies have also been of utility in determination of mechanisms of thermal decomposition of 3-chloro-3-aryldiazirines,426 427 the acid-catalyzed methanolysis of arylepoxides,428 and the ring expansion reactions of 2-aryl-l,l-dimethylaziridinium salts with benzaldehyde to form 5-aryl-3,3-dimethyl-2-phenyloxazolidinium salts.429... 

Reaction data for phenyldimethylethoxysilane. Acid catalyzed methanolysis reaction at 25 C... 

Table 4. Reaction data for p-trifluoromethylphenyldimethylethoxysilane. reaction at 25°C Acid catalyzed methanolysis...

Table 6. Rate constants for the acid catalyzed methanolysis reactions at 25 C. Data are used to prepare a Hammett plot ...

Figure 8. Hammelt plot. The determination of p for ihe acid-catalyzed methanolysis of phenyi-di mei hylei hoxysilanes.

Normal human fibroblasts grown in media with 12% fetal calf serum were treated with or without galactose oxidase and then subjected to reduction with potassium borotritiide. GSLg were isolated and subjected to acid-catalyzed methanolysis (62) (see Materials and Methods). Methyl glycosides, methyl sphingosine, and fatty acid methyl esters were isolated by extraction of the total hydrolysate with solvents as described previously (62). Radioactivity was measured in triplicate in aliquots of these extracts. 

As with acid catalyzed methanolysis, added cations have a dramatic effect on base catalyzed methanolysis as well, Table II. 

Support for mechanism a has been provided by Rhind-Tutt and by Bunton and coworkers, who have studied the closely analogous, acid-catalyzed methanolysis of phenyl tetra-O-methyl-a-D-glucopyranoside. They have shown that the ratio of a to 3 anomer in the product is similar to the ratio obtained in the methanolysis of tetra-O-methyl-a-D-gluco-... 

Highly-functionalized piperidines are available from readily-available pyrazinones by way of Diels-Alder cyclization and acid-catalyzed methanolysis. Products are reported as single stereoisomers <03T5047>. 

A convenient three-component coupling reaction of Meldrum s acid, acrolein, and thioacetic acid was described <1997TL5785> for the synthesis of 2-(l,2-dithiolan-3-yl)acetic acid 315 (Scheme 58). As shown, diacetylthiolated propyl Meldrum s acid 311 was refluxed in methanol affording ester acid dithioacetate 312, which without purification was transformed upon acid-catalyzed methanolysis into diester 313. The subsequent oxidation step led to ester 314 which afforded the final acid 315 by a hydrolysis-decarboxylation sequence. 

The anodic oxidation of polyalkyl substituted cyclopropanes and spiro[2.n]alkanes gave mono- and dimethoxy products which resulted from the cleavage of the most highly substituted C-C bond, in contrast to the results obtained by acid-catalyzed methanolysis of alkyl-substituted cyclopropane by the same authors. Those results suggest that a direct (7-electron transfer from the most strained a bond of cyclopropane to the anode may be the initiation step. 

The partial data presented above seem to indicate that substituents which are capable of stabilizing a carbocationic center at a bridgehead position will favor the formation of cyclobutyl derivatives, whereas such a substitution on the methylene carbons results in cyclopropylcarbinyl derivative formation. This is consistent with the observation that the acid-catalyzed methanolysis of 3-/ -bicyclobutanecarbonitrile (35) yields 58 % and 42 % of... 

Byramova, N E, Ovchinnikov, M V, Backinowsky, L V, Kochetkov, N K, Selective removal of 0-acetyl groups in the presence of 0-benzoyl groups by acid-catalyzed methanolysis, Carbohydr. 

Acid-catalyzed hydrolysis of isobutylene oxide (8) is >750 times faster than that of ethylene oxide (6), and > 99% of the glycol product is from addition of solvent at the tertiary carbon.23 These results are consistent with a mechanism in which there is significant positive charge on the tertiary carbon at the transition state, as discussed in the previous section. Butadiene monoepoxide (10) is slightly less reactive than isobutylene oxide,36 and its acid-catalyzed hydrolysis can potentially proceed via a resonance-stabilized allyl cation (Scheme 6). However, the acid-catalyzed hydrolysis of 10 yields 96% of 3-buten-l,2-diol (15) and only 4% of 2-butene-1,4-diol (16),36 and the acid-catalyzed methanolysis of 10 is reported to yield only 2-methoxy-3-buten-l-ol.37 An A-2 mechanism proceeding via transition state 17 may account for the observation that 1,2-diol 15 is the predominant product from acid-catalyzed hydrolysis of 10. The minor yield of the 1,4-diol 16 may be formed from reaction of... 

In a study by Berti et al., acid-catalyzed hydrolysis of styrene oxide was reported to occur with 67% inversion and 33% retention at the benzyl carbon.45 In a later study, it was reported that the styrene glycol product formed in the acid-catalyzed hydrolysis of chiral styrene oxide is completely racemic, which would indicate an A-l mechanism.46 As these two results indicate quite different mechanisms for this reaction, the glycol product from acid-catalyzed hydrolysis of chiral styrene oxide was converted to its bis-( + )-a-(methoxy-a-trifluoromethyl)phenylacetate diester derivative, and the composition of the diastereomeric diester mixture was determined by H NMR.47 This study agreed with those of Berti et al. and showed that acid-catalyzed hydrolysis of styrene oxide occurs with 67% inversion and 33% retention at the benzyl carbon. Acid-catalyzed methanolysis of styrene oxide is reported to occur with 89% inversion at the benzyl carbon.48 The fact that the diol product from acid-catalyzed hydrolysis of chiral styrene oxide is not completely racemic demonstrates that the lifetime of the carbocation is not sufficiently long for it to become symmetrically solvated. 

The validity of these assumptions was tested by applying the derived steric substituent constants to reactions in which the transition states resembles that of the acid hydrolysis of esters. It was found that very few reactions obey equation 54. These are exemplified by the acid catalyzed methanolysis of 2-naphthyl esters in methanol (86) and the reaction of 2-alkylpyridines with methyl iodide (87) and with trimethylboron (88) in nitrobenzene. 

Acid-catalyzed methanolysis of tricyclo[4.1.0.0 ]heptanes (e.g. 8) essentially leads to nor-caranyl methyl ethers. Similarly, acetolysis gives the corresponding acetates. 

Dihalocycloproparenes, in particular the chloro derivatives, are extremely susceptible to hydrolysis and react via ring opening to give carboxylic acid derivatives. Typically, 1,1-dichloro-2,5-diphenylbenzocyclopropene was converted to trimethyl 2,5-diphenylorthobenzoate (12a, 94%) upon reaction with sodium methoxide in benzene and workup in the presence of base. Methanolysis in the absence of base afforded methyl 2,5-diphenylbenzoate. " The same behavior applies to 1,1-dichloro- or l,l-dibromo-2,7-diphenylcyclopropa[()]naphthalene. 1,1-Difluorobenzocyclopropene was hydrolyzed with water to benzoic acid, and the intermediate benzoyl fluoride was isolated and characterized. The hydrolysis of l,l-dihalocyclopropa[6]-naphthalenes afforded naphthalene-2-carboxylic acid, while acid-catalyzed methanolysis of... 

In the branched-chain series, the 4-thioapiofuranoside 78 was the first reported " example prepared from the apiose derivative 76 via acid-catalyzed methanolysis of thiol 77, with migration of the acetal group. 

An additional advantage of the use of AB monomers over AA-BB monomers is the lack of sensitivity on stoichiometric issues polymerization of the monomers (Scheme 11.14) employing Novozym 435 and Shvo s catalyst 2 was slow (reaction time = 170 h) but did result in chiral polymers of good molecular weigth and ee. For example, DKRP of Me-7HO resulted in a polymer with an Mp of 16.3 kg mol 1 and an ee of 92% (determined after acid-catalyzed methanolysis). 

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