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Acetone dimethyl acetal, reaction with

Acetone dimethyl acetal, reaction with n-butanol, 42,1... [Pg.105]

The most important and widely used ketal is the acetonide. It is prepared by the reaction of the diol with acetone " or acetone dimethyl acetal and an acid catalyst. Also 2-alkoxy and 2-silyloxy propenes can be applied for this purpose (Scheme 49). ° In the reactions with carbohydrates fiiranose rings are formed if possible, but under kinetically controlled conditions also 1,3-dioxanes may be constructed. In the cases of hexoses which do not contain cw-l,2-diols the reaction usually involves toe 6-OH group. [Pg.660]

Adipic acid (585 g, 4 mol) was added to 200 mL methanol containing 5 g p-toluenesulfonic acid. This mixture was stirred in a 2-L flask and maintained at 40-60°C. As the reaction progressed, acetone dimethyl acetal was added in increments. By the end of 30 min, 200 mL had been added, by the end of 1 h, 600 mL total had been added (at this point, all adipic acid was in solution), and by the end of 1.5 h, a total of 1 L of the acetone dimethyl acetal (8 mol) had been added. At the end of 2 h, only 10% of the acid remained unreacted. After 4 h, the reaction was 99% complete. One half of the crude solution was then distilled at a rate such that by the end of 3 h, all of the acetone and methanol had been removed. This left a 98.8% yield of crude, straw-colored dimethyl adipate. On further distillation, a 94% yield of pure dimethyl adipate with a boiling point of 109°C was recovered. [Pg.1096]

The Pd-catalyzed reaction of allylic carbonates with the lithio derivatives of diox-olanone prepared by the treatment of mandelic acid with acetone dimethyl acetal gives the desired a-allylation products in good yields. Upon treatment with HCl in ethanol the corresponding a-hydroxy ethyl esters can be obtained " (Scheme 11). [Pg.145]

Methyl, ethyl, benzyl, benzhydryl, p-nitrobenzyl, p-methoxy-benzyl, 4-picolyl, j3j -trichloroethyl, j3-methylthioethyl, /J-p-toluenesulphonylethyl, and -p-nitrophenylthioethyl esters may be prepared directly from the acid and alcohol. TTie most usual method [4, 5] consists of heating the acid and an excess of the alcohol with an acid catalyst (e.g., Fischer-Speier, hydrochloric or sulphuric acid). The extent of reaction is improved if the water formed is removed by azeotropic distillation with an inert solvent (benzene, carbon tetrachloride, or chloroform). Considerable variation is possible in the natvire of the acid catalyst thus phosphoric acid [6], aryl sulphonic acids [7, 8, 9], alkyl sulphates [10], and acidic ion-exchange resins [11] may be employed. Removal of the water by azeotropic distillation during the formation of methyl esters is difficult and Brown and Lovette [12] introduced the novel reagent acetone dimethyl acetal (7) for the direct formation of methyl esters. In the presence of a trace of methanol and an acid catalyst the reagent acts as a scavenger of water formed by esterification and liberates further methanol for reaction. [Pg.185]

Another appHcation of 4-chlorophenol is in the synthesis of a dmg, ethyl a, a-dimethyl-4-chlorophenoxy acetate [637-07-0] (60), used as a cholesterol-reducing agent. This synthesis involves reaction with acetone and chloroform, followed by ethanol esterification. [Pg.82]

The red and orange forms of RhCl[P(C6H5)3]3 have apparently identical chemical properties the difference is presumably due to different crystalline forms, and possibly bonding in the solid. The complex is soluble in chloroform and methylene chloride (dichloromethane) to about 20 g./l. at 25°. The solubility in benzene or toluene is about 2 g./l. at 25° but is very much lower in acetic acid, acetone, and other ketones, methanol, and lower aliphatic alcohols. In paraffins and cyclohexane, the complex is virtually insoluble. Donor solvents such as pyridine, dimethyl sulfoxide, or acetonitrile dissolve the complex with reaction, initially to give complexes of the type RhCl[P(C6H6)3]2L, but further reaction with displacement of phosphine may occur. [Pg.70]

The 1-fluoroquinuclidinium fluoride (NFQNF, 2) precipitates during the reaction and, after treatment with hot, dry acetone to remove quinuclidinium fluoride, is obtained as an extremely hygroscopic white solid which can be assayed iodometrically (reaction with aqueous acetonic KI occurs instantaneously at rt). l-Fluoroquinuclidinium fluoride (2) is readily soluble in water, methanol, ethanol, trifluoroacetic acid, and ethyl acetate, and reasonably so in acetonitrile, but appears to be insoluble in alkanes, arenes, chloromethanes, acetone, diethyl ether, tetrahy-drofuran, dimethylformamide and dimethyl sulfoxide. The fluoride 2 has a melting point of 126-128°C (dec.) and is less flammable than quinuclidine in air, igniting only on direct contact with a flame or after prolonged heating on a metal plate. It does not explode when struck with a hammer.73... [Pg.455]

Iwataki83 reported that l,l-dimethyl-2,4-dithiobiuret formed 3-(N, iVr-dimethylthiocarbamoyl)-2-iminothiazolidin-4-one upon reaction with chloroacetyl chloride in acetone in the presence of pyridine however, the same reaction with sodium acetate used as a base produced 2-(3,3-dimethylthiureido )-2-thiazolin-4-one.83... [Pg.119]

Comparisons of structurally related hydroxy- and methoxy-substituted cations show that hydroxy is more stabilizing by between 4 and 5 log units. This difference was recognized 20 years ago by Toullec who compared pifas for protonation of the enol of acetophenone and its methyl ether145 (-4.6 and 1.3, respectively) based on a cycle similar to that of Scheme 15, but with the enol replacing the hydrate, and a further cycle relating the enol ether to a corresponding dimethyl acetal and methoxycarbocation.146 Toullec concluded, understandably but incorrectly, that there was an error in the pA a of the ketone (over which there had been controversy at the time).147,148 In a related study, Amyes and Jencks noted a difference of 105-fold in reactivity in the nucleophilic reaction with water of protonated and O-methylated acetone and concluded that the protonated acetone lacked a full covalent bond to... [Pg.53]

The effect of reaction time on the major components of the reaction of cystine and DMHF in water is shown in Table IV. It is noteworthy that amounts of 2,4-hexanedione, 3,5-dimethyl-l,2,4-trithiolanes and thiophenones were found at a maximum after one hour. It was also found that the amount of 2-acetylthiazole increased with time and that acetol acetate decreased with time as expected. In the glycerol medium, the effect of reaction time on the major components is shown in Table V. Apparently, the 1,3-dioxo-lane, which is a ketal formed from glycerol and acetone, decreased over time. Also, long reaction time favors the formation of cyclic compounds, including 2,5-dimethyl-2-hydroxy-3(2H)-thiophene, cyclo-pentenones and 4,5-dimethyl-l,2-dithiolenone. [Pg.231]

Figure 9.19 shows a biacetalization of a pentaol. There, the existence of thermodynamic control leads to the preferential production of one, namely A, of three possible bis(six-mem-bered ring acetals)—A, B, and C. In the presence of catalytic amounts of />-toluenesulfonic acid, the pentaol from Figure 9.19 is converted into the bisacetal in acetone as the solvent but by a reaction with the dimethylacetal of acetone. From the point of view of the dimethyl-acetal, this reaction is therefore a transacetalization. Each of the two transacetalizations involved—remember that a bisacetal is produced—takes place as a succession of two SN1 reactions at the acetal carbon of the dimethylacetal. Each time the nucleophile is an OH group of the pentaol. [Pg.380]

During a synthesis of the Chlorothricolide, Roush and Sciotti encountered unexpected problems with the hydrolysis of the dimethyl acetal 54.1 [Scheme 2.54].112 Use of some of the standard hydrolysis conditions (oxalic acid, PPTS, PTSA, HO Ac, or trifluoroacetic acid — all in acetone) resulted in recovery of 54.1 or decomposition. Success was achieved by exploiting the mild Lewis acidic properties of the lithium cation under conditions first reported by Lipshutz and Harvey.113 Thus treatment of the dimethyl acetal 54,1 with lithium tetrafluoroborate in acetonitrile containing 2% water returned the desired aldehyde 54J in 97% yield after 2 h at room temperature. The reaction was also applied to the deprotection of a cyclic ketal in a synthesis of Pumi-liotoxin.114 115... [Pg.81]

A powerful oxidizer. Explosive reaction with acetaldehyde, acetic acid + heat, acetic anhydride + heat, benzaldehyde, benzene, benzylthylaniUne, butyraldehyde, 1,3-dimethylhexahydropyrimidone, diethyl ether, ethylacetate, isopropylacetate, methyl dioxane, pelargonic acid, pentyl acetate, phosphoms + heat, propionaldehyde, and other organic materials or solvents. Forms a friction- and heat-sensitive explosive mixture with potassium hexacyanoferrate. Ignites on contact with alcohols, acetic anhydride + tetrahydronaphthalene, acetone, butanol, chromium(II) sulfide, cyclohexanol, dimethyl formamide, ethanol, ethylene glycol, methanol, 2-propanol, pyridine. Violent reaction with acetic anhydride + 3-methylphenol (above 75°C), acetylene, bromine pentafluoride, glycerol, hexamethylphosphoramide, peroxyformic acid, selenium, sodium amide. Incandescent reaction with alkali metals (e.g., sodium, potassium), ammonia, arsenic, butyric acid (above 100°C), chlorine trifluoride, hydrogen sulfide + heat, sodium + heat, and sulfur. Incompatible with N,N-dimethylformamide. [Pg.365]

The choice of liquid phase can affect the course of ozonation. This has been shown with phenylindenes by Miura et al. (1985) and with lignin models by Kratzl et al. (1976), who found that 4-methylveratrole gave a higher yield of dimethyl -methyl-cis,cis-muconate in 45% aqueous acetic acid than in dichloromethane and that the yield of dimethyl oxalate from acetoveratrone was markedly dependent on the solvent. Eriksson and Gierer (1985) found that in methanol the benzene ring of vanillin is cleaved (albeit only very slowly, after acetalization has occurred), but that in nonprotic solvents, such as acetone, the initial reaction is oxidation of the aldehyde function to a carboxyl group. [Pg.210]

A similar strategy starting from 4-nitrobenzaldehyde dimethyl acetal (116) involves the subsequent aldol reaction of the obtained 4-nitrobenzaldehyde (109) with acetone for the production of p-hydroxyketone 117 (Scheme 3.33). ... [Pg.139]

Commercially available Amberlite IR-120 (H -form) was used as an acid catalyst this resin is a divinylbenzene-crosslinked partially sulfonated gel-type polystyrene. As a base catalyst, PEG-PS resin-supported proline was employed. The reaction was performed in water-acetone-tetrahydrofuran (1 1 1 v/v/v) at room temperature in the presence of 20 mol. % of resin-supported proline and Amberlite. After 20 h, the reaction mixture contained the starting 4-nitro-benzaldehyde dimethyl acetal, 4-nitrobenzaldehyde and the corresponding aldol product with acetone in a ratio of 4 9 87. This means that both the... [Pg.139]

The reactions of 1,1-dimethyl-2,2-bis(trimethylsilyl)silene (54) with carbonyl compounds such as acetone and ethyl acetate, and particularly with benzophenone imine, are very much faster than its ene reactions with hydrocarbons such as isobutene244,246,266, pointing to the involvement of the nucleophilic lone pairs in the former case. [Pg.1095]


See other pages where Acetone dimethyl acetal, reaction with is mentioned: [Pg.16]    [Pg.1095]    [Pg.94]    [Pg.242]    [Pg.217]    [Pg.14]    [Pg.75]    [Pg.447]    [Pg.132]    [Pg.165]    [Pg.75]    [Pg.3]    [Pg.390]    [Pg.33]    [Pg.132]    [Pg.488]    [Pg.447]    [Pg.660]    [Pg.54]    [Pg.65]    [Pg.94]    [Pg.149]    [Pg.301]    [Pg.561]   


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Acetals reactions with

Acetates reactions with

Acetic acetone

Acetone acetals

Acetone reactions

Acetone, reactions with

Dimethyl acetate

Dimethyl reactions

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