Trimethylacetic anhydride

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

Trimethylacetamide, d678 Trimethylacetic acid, d679 Trimethylacetic anhydride, d680 Trimethylacetyl chloride, d681... 

Steele, W.V., Chirico, R.D., Cowell, A.B., Knipmeyer, S.E., and Nguyen, A. Thermodynamic properties and ideal-gas enthalpies of formation for trans-methyl cinnamate, a-methyl cinnamaldehyde, methyl methacrylate, l-non3me, trimethylacetic acid, trimethylacetic anhydride, and ethyl trimethyl acetate, J. Chem. Eng. Data, 47(4) 700-714, 2002. 

A re-investigation of the mechanism of the hydrolysis of acetic anhydrides in water was made by Bunton and Fendler4. They found that the hydrolysis of trimethylacetic anhydride follows an A-2 mechanism both in water and in aqueous dioxan and is slower than that of acetic anhydride. If acetic anhydride follows an A-l mechanism in water, both anhydrides should have the same mechanism and both should have similar reactivities in aqueous acids. If the A-2 mechanism is followed, steric effects should make trimethylacetic anhydride the less reactive compound. The entropy of activation of the hydrolysis catalysed by perchloric acid was re-estimated, taking into account the electrolyte effect of the perchlorate ions upon the rate of spontaneous hydrolysis, and a new value for A5 of—35 eu (for the spontaneous hydrolysis) and — 10 eu at 2 M HC104 for the acid-catalysed hydrolysis was obtained, compared with the value of + 2.2eu obtained previously. The new value is in the order of magnitude of A 5 for A-2 reactions but smaller than that observed for trimethylacetic anhydride under similar acidic conditions (— 26 eu). Plots... 

Trimethylacetic anhydride, d599 Trimethylacetyl chloride, d600... 

Por the formylation of amines with the mixed anhydride of formic and trimethylacetic acid, see Vlietstra, E.J. Zwikker, J.W. Nolte, R.J.M. Drenth, W. Reel. Trav. Chim. Pays-Bas, 1982, 101, 460. 

The C2-symmetrical chiral amine tran.v-(2/ ,6y )-2,6-bis(benzyloxymethyl)piperidine (1), prepared15 from commercially available (S)-2-(benzyloxymethyl)oxirane, has been used in diastereoselective amide alkylations. Thus, the chiral amine of 76% ee is acylated [anhydride or mixed trimethylacetic acid anhydride, 1.2 equivalents of triethylamine and 0.05 equivalents of 4-(dimethylamino)pyridine] and the resulting amide 2 treated with 2.1 equivalents of lithium diisopropylamide at —78 CC to give the enolate. This is then alkylated to give high diastereo-meric ratios (>94 6) of alkylation products 3 in 60-93% yield16. 

FORMYLATION Oxalyl chloride. Trimethylacetic formic anhydride. 

Trimethylacetic formic anhydride, (CHr)iCC02CH0 (1). The anhydridesis prepared in high yield by reaction of trimethylacetyl chloride and sodium formate (1.05 equiv.) in the presence of 18-crown-6 (10 mol %) at 0° the yield of slightly impure material is 95-98%. The material can be stored in a freezer for several months. 

Cleavage of ketones by oxidation is infrequently used for preparation of monocarboxylic acids. Trimethylacetic acid is made in 75% yield from pinacolone, (CHj)jCCOCHj, by oxidation with chromic anhydride in aqueous acetic acid. Cleavage on only one side of the carbonyl group is possible in this case. 

Poly(3-acyl-2-oxazolone) is a highly selective acylating agent for amines. An improved method of preparation and the use of trimethylacetic formic anhydride as a selective iV-formylating reagent have been reported. Thioamides (250) are prepared by the reaction of the nitrile (249) with H2S (Scheme 127). ... 

TrimethyLacetic formic anhydride, which is a valuable reagent... 

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