Acetylations acetic anhydride

A stirred mixture of methyl 2,3-di-0-acetyl-4,6-dichloro-4,6-dideoxy-a-D-galactopyrano-side (41, 1 mmol) [prepared by acetylation (acetic anhydride-pyridine) of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 37], sodium azide (4 mmol), and dry N,N-... 

The pyrrolopyridimidazole (36) from (199 R1 = H R = Me) (Section 3.09.4.3.3) bromi-nates (bromine in chloroform) and acetylates (acetic anhydride) at position 3, but when C-3 is blocked by a methyl group reaction occurs, under the same conditions, at C-8 (77JCS(P1)465). The 5-cyanopyrrolo[2,3-d]pyrimidine (37 R = /3-D-ribofuranosyl) is bromi-nated at C-6 by bromine water <75jcs(Pi)i253). 

ACETYLATION Acetic anhydride-Boron trifluoride etherate Alumina. 

Acetylation Acetic anhydride. N-Acetoxyphthalimide. 2- and 3-Acetoxypyridine. Acetyl chloride. N-Acetylimidazole. Boron trifluoride. Catalysts (see Acetic anhydride). Ketene. Magnesium. Methyl oxocarbonium hexafluoroantimonate. Perchloric acid. Phenyl acetate. Pyridine. Sodium acetate. Tetraelhylammonium acetate. p-Toluenesulfonic acid. Tri-n-hexylethyl ammonium hydroxide. 2,4,6-Triisopropylbenzenesulfonyl chloride. Trityl-sodium. Zinc chloride. 

Meerwein-Ponndore reduction Aluminum r-butoxide. Aluminum isopropoxide. Reductive acetylation Acetic anhydride. 

Acetylation of 1-methoxycarbonylisoindole with acetic anhydride has been attempted without success.23 However, 1-phenylisoindole can be acetylated (acetic anhydride-pyridine) to give the 3-acetyl derivative (Eq. 16).83 An analogous reaction occurs with 2-alkyl-l-dialkylaminoisoindoles.105... 

The hydrochloride of the Wieland-Gumlich aldehyde is converted by boiling ethanol into the single ethyl acetal XIV (R = OEt). Diaboline hydrochloride is similarly converted into an acetal XV (R = OEt) which is also formed by acetylation (acetic anhydride in pyridine) of XIV (R = OEt). Consideration of the chemical shifts of the 0-17 protons in these acetals and of rotation shifts indicates the stereochemistry shown i.e., the acetal possesses the same configuration as the corresponding hemiacetal. 

Acetylation is mainly applied to stabilize the cell wall against moisture absorption for improving its stability and environmental degradability [48-52]. In acetylation, acetic anhydride substitutes the hydroxyl group of the cellulose with acetyl groups that modify the properties of fibers so that they become hydrophobic [50]. Moisture absorption of fiber reduces after acetylation, which is beneficial for composites application. It was reported that after acetylation reduction in moisture uptake was found to be around 50-65% [53]. 

Preparative Methods (i) from 3-trimethylsilyl-2-propyn-l-ol by reduction (sodium bis(2-methoxyethoxy) aluminum hydride (Red-Al), 70%) and acetylation (acetyl chloride, pyridine, 78%) (ii) from 3-trimethylsilyl-2-propyn-l-ol by reduction (P-2 raney nickel, H2, 86%) and acetylation (iii) from ally-loxytrimethylsilane by a metalation-rearrangement sequence (f-butyllithium, 90%) and acetylation (acetic anhydride, triethylamine, 76%). ... 

For their acetylation, acetic anhydride is used in a mixture of acetic and sulfuric acids. The reactivity of this acetylating reagent is closely dependent on the water content of cellulose the higher the water content, the faster the esterification of cellulose. Through the formation of hydrogen bonds with hydroxyl groups, water... 

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