Thiols acetylations, acetic anhydride

Keywords alcohol, amine, thiol, acetic anhydride, microwave irradiation, acetylation... 

Alcohols, phenols, thiols, and amines can be acetylated with acetic anhydride in the presence of montmorillonite K10 under mild conditions.239 Octyl acetate was obtained in 1 hr from 1-octanol, in 96% yield, using K10 at room temperature. Peracetylation of sugars, such as glucose, has been done in similar fashion in 92-99% yields.240... 

The Schiff base derivatives 73 of the 3-hetaryl-substituted 4-amino-3-thiol-l,2,4-triazoles, on treatment with acetic anhydride, undergo cyclization to give the corresponding 3-substituted-5-acetyl-5,6-dihydro-6-phenyl[l,2,4]triazolo[3,4-7][l,3,4]thiadiazoles 76 (Equation 16) <1990IJB135>. Similar treatment of 4-(A-bcnzoylamino)-4,5-dihydro-l-methyl-3-mcthylthio-1 //-[ 1,2,4 triazolc-5-thione 77 leads to the [l,2,4]triazolo[3,4-4][l,3,4]thiadiazolium trifluoromethanesulfonate 78 (Equation 17) <1986LA1540>. 

Acetyl euenfytne A (usually abbreviated m etyl CoA> is the inod common thiol ester in nature. Acetyl CoA is a much more complex molecule than acetyl chloride or acetic anhydride, yet it serves exactly the same pur< pose as thene simpler reagents. Nature uses acetyl CoA as a reactive acyV atiog agent in nucleophilic acyl stilntitution reactions. 

The acetolysis of S-acetyl-l,2-0-isopropylidene-3,5-di-0-methyl-6-thio-a-D-glucofiiranose with acetic acid—acetic anhydride—sulfuric acid gave a small yield of the crystalline septanose triacetate (271). The septanose structure of 271 was established by the absence of the thiol band in its infrared spectrum, and by the signals for three O-acetyl and two O-methyl groups found in its nuclear magnetic resonance spectrum. 

Neighbouring-group participation by a 5a-acetoxy-group in the substitution of a 3fi-OR group is paralleled by Sa-acetylthio-groups. The crystalline 3a,5a-cyclic onium perchlorate (31) was generated by reaction of the 3j9-hydroxy-compound (29) with acetic anhydride-sulphuric acid [via the 3/1-acetyl sulphate (30)], followed by the addition of perchloric acid. Hydrolysis of the onium salt gave the 3a-acetoxy-5a-thiol (32). 

Mukaiyama aldol reaction. With C cnol ethers with aldehydes can be carried oi Acetylation. Alcohols, thiols, and ar reaction with acetic anhydride at room tern are similarly transformed into gem-diaceiau N-Arylimidazoles. Together with I. as additives, Cu(OT02 and cesium carbonat... 

Acetylation. The acetylation of alcohols (including phenols), thiols, and amines by acetic anhydride is catalyzed by LiCl. 

From the thiol with acetyl chloride, or from the thiol with acetic anhydride and aqueous sodium hydroxide, or from the thiol with ketene... 

Acetic anhydride-pyridine on basic alumina has been used to conduct acetylations of hydroxy, thiol and amino groups under microwave irradiation conditions [35]. This rapid, safe, and eco-friendly technique can be applied for a broad variety of N, O, and S acetylations. 

Acetylation. The most notable use of acetic anhydride is for the acetylation reaction of alcohols, amines, and thiols. Acids, Lewis acids, and bases have been reported to catalyze the reactions. 

Thiols. 5-Acetyl derivatives can be prepared by the reaction of acetic anhydride and a thiol in the presence of potassium bicarbonate. Several disadvantages to the 5-acetyl group in peptide synthesis include /3-elimination upon base-catalyzed hydrolysis. Also, sulfur to nitrogen acyl migration may be problematic. 

Low loadings of Al(OTf)3 were sufficient to catalyze the rapid acetylation of alcohols, phenols, thiols, and sugars with acetic anhydride in high yields under solvent-free conditions (eq 12). ... 

Thiazolo[3,2-a]pyrimidines [C3NS-C4N2].—Condensation of 6-amino-4-hydroxy-pyrimidine-2-thiol with ethyl a-chloroacetoacetate yields a sulphide, which cyclizes on crystallization from ethanol to give a bicyclic product which is cither compound (82) or its isomer formed by ring-closure at the other nitrogen. Dehydration and acetylation of the amino-group occur with acetic anhydride. 

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