Acetoxymethyl acetal

Secondary fragments are formed from the primary ones by single or consecutive eliminations of formaldehyde (30), methanol (32), ketene (42), acetic acid (60), methyl acetate (74), methoxymethyl acetate (104), or acetoxymethyl acetate (132). Mechanisms for elimination of formaldehyde from the primary fragment m/e 89 have already been described (see Section IV,3 p. 57), as well as those for the elimination of acetic acid (60) and the subsequent elimination of ketene (42) (see Section IV,1 p. 53). 

Some secondary fragments are best explained by elimination of methoxymethyl acetate (see Scheme 16) and acetoxymethyl acetate (see Scheme 17), respectively. 

Only one reaction of thiazole N-oxides has been studied in detail. The rearrangement in acetic anhydride of 2,4-dimethylthiazoIe-3-oxide gave 2-acetoxy-4-methylthiazole and 4-acetoxymethyl-2-methylthiazole in a ratio of about 4.5 to 1(264). 

The Prins reaction with formaldehyde, acetic acid, acetic anhydride, and camphene gives the useful alcohol, 8-acetoxymethyl camphene, which has a patchouli-like odor (83). Oxidation of the alcohol to the corresponding aldehyde also gives a useful iatermediate compound, which is used to synthesize the sandalwood compound dihydo- P-santalol. 

Cyanuric acid readily dissolves in aqueous formaldehyde forming tris(hydroxymethyl)isocyanurate [10471-40-6] (THMIC) which can be isolated by evaporation (11). THMIC in turn reacts with acetic anhydride to yield tris(acetoxymethyl)isocyanurate [54635-07-3], either thionyl chloride or phosphoms pentachloride to give tris(chloromethyl)isocyanurate [63579-00-0], and phenyl isocyanate in pyridine to yield tris(A/-phenylcarbamoxymethyl) isocyanurate [21253-39-4] in 87% yield (65). Reaction of CA with paraformaldehyde and 2,6-dicyclohexylphenol yields... 

For the reactions of methylpyridazine 1-oxides with benzaldehyde in the presence of sodium methoxide, the order of reactivity of methyl groups at various positions is 5 > 4,6 > 3. 3-Methylpyridazine 1-oxide is converted by acetic anhydride into the 3-acetoxymethyl compound, which is easily hydrolyzed to 3-hydroxymethylpyridazine. 

Hydroxy-4-oxa-5a-acetoxymethyl-androstan-3-one acetate, 305 17 -Hydroxy-4, 5/8 Oxidoandrostan-3-one, 20 3 -Hydroxy-16a, 17 a-oxidopregn-5-en-20-one, 196... 

The reaction of N-(3-hydroxymethylphenyl)aminomethylenemalonates (1510) and acetic anhydride by heating in acetic acid at 55-60°C for 20 hr gave the 3-acetoxymethyl derivatives (1511) in 71-97% yields (82CPB3517, 82CPB3530). 

However, these synthetic procedures were useful only in the preparation of primary a-acetoxymethyl alkylnitrosamines and a-chloromethyl alkylnitrosamines. The cleavage of secondary ethers, such as XIII with acetic anhydride or acetyl chloride was so vigorous that no characterizable substances could be isolated. In view of this problem, we looked for another synthetic route which would allow the isolation of secondary derivatives. The first experiment tried, namely that of nitrosyl chloride with N-methylene t-butylamine at -30° was successful. The addition of NOCl at this temperature... 

One very important method for the indirect oxidation of a 2-methyl substituent group in particular, in the azines, is the reaction of the corresponding A-oxide with acetic anhydride. This process, outlined in equation (75), gives initially the corresponding 2-acetoxymethyl derivative yields are generally good to excellent with only minor amounts... 

The methyl substituent of 2-methyl-4,8-dihydrobenzo[l,2- 5,4-. ]dithiophene-4,8-dione 118 undergoes a number of synthetic transformations (Scheme 8), and is therefore a key intermediate for the preparation of a range of anthraquinone derivatives <1999BMC1025>. Thus, oxidation of 118 with chromium trioxide in acetic anhydride at low temperatures affords the diacetate intermediate 119 which is hydrolyzed with dilute sulfuric acid to yield the aldehyde 120. Direct oxidation of 118 to the carboxylic acid 121 proceeded in very low yield however, it can be produced efficiently by oxidation of aldehyde 120 using silver nitrate in dioxane. Reduction of aldehyde 120 with sodium borohydride in methanol gives a 90% yield of 2-hydroxymethyl derivative 122 which reacts with acetyl chloride or thionyl chloride to produce the 2-acetoxymethyl- and 2-chloromethyl-4,8-dihydrobenzo[l,2-A5,4-3 ]-dithiophene-4,8-diones 123 and 124, respectively. 

The reaction of the monobromo derivatives 74a and 75 with silver acetate gave 3-(acetoxymethyl)fervenulin 80 and 3-acetylfervenulin 78, respectively, in excellent yields (Scheme 11) <1996JHC949>. 3-Acetylfervenulin 78 and 3-(acetoxymethyl)fervenulin 80 gave the corresponding alcohols 79 and 81 after hydrolysis in methanolic ammonia. 

Addition of acetic acid to 6-(acetoxymethyl)-5,6-dihydro-2-methoxy-2ff-pyran (223) gave117118 three stereoisomeric 2,4-diacetoxy-6-(ace-... 

Treatment of 2,3-dimethylquinoxaline dioxides and monoxides with acetic anhydride yield 2,3-bis(acetoxymethyl)quinoxalines and 2-acetoxymethylquinoxalines, respectively.112,208 Under alkaline conditions these derivatives are hydrolyzed to the corresponding hydroxy-methylquinoxalines. Thus, 2-methyl-3-phenylquinoxaline-1,4-dioxide... 

Chloromethylation occurred in high yield at C-3 and C-4 when thienothiophene (73) was treated with paraformaldehyde and HC1 at 50 °C, to give chloromethyl derivative (96 Scheme 28). Treatment of the chloromethyl compound (96) with sodium acetate or sodium ethoxide gave the corresponding acetoxymethyl or ethoxymethyl derivatives (97). Analogous reaction with primary amines led only to the formation of bis-aminoalkyl compounds (98) and no peri-annelated products (99) could be detected (Scheme 29) <76AHC(19)123>. 

An electrophilic substitution of potential synthetic value but one which is rarely utilized is the introduction of a mono- or di-acetoxymethyl group by the action of manganese(III) acetate on a coumarin. This ring system is more amenable than many to this reagent and a variety of products may be obtained by altering the ratio of reactants (Scheme 12) (79BCJ2386). 

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