Acetic anhydride phenol acylation

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

The elaboration of 113 to (—)-kinamycins C, F, and J, is shown in Scheme 3.19. To access ( )-kinamycin C (3), the silyl ether function of 113 was cleaved with aqueous hydrochloric acid (95 %). Alternatively, treatment of 113 with lithium hydroxide served to liberate the phenol function and saponify the three acetate esters, to provide ( )-kinamycin F (6) in 92 % yield. Finally, acylation of the tertiary hydroxyl of 113 (acetic anhydride, triethylamine) afforded a tetraacetate. Cleavage of the silyl ether then provided ( )-kinamycin J (10) in 80 % over two steps. 

Esters of the phenolic hydroxyl are obtained easily by the Schotten-Baumann reaction. The reaction in many cases involves an acid chloride as the acylating agent. However, acylation is achieved more commonly by reaction with an acid anhydride. The single most important commercial reaction of this type is the acetylation of salicylic acid with acetic anhydride to produce acetylsalicylic acid [50-78-2] (aspirin). 

Fig. 21. Logarithmic plot of the second-order rate coefficients k2) for catalysis by imidazole of the hydrolysis of various esters, against the rate coefficients for alkaline hydrolysis. The most reactive compound is acetic anhydride the other open circles represent results for acetate esters of phenols, except for the two least reactive compounds, trifluorethyl acetate, and the acetate of acetone-oxime. The closed triangles represent data for ethyl esters with activated acyl groups, with the exception of the least reactive compound, which is ethyl acetate.

The preparation of yet another variant on the theme starts with quina-zolone (155). Treatmment with methanesulfonic acid selectively cleaves the ether at the more electron-rich position to give the phenol (156). This functional group is then acylated by means of acetic anhydride... 

Jin, T.-S., Xiao, J.-C., Wang, Z.-H., Li, T.-S. Silica gel-supported phosphotungstic acid (PTA) catalyzed acylation of alcohols and phenols with acetic anhydride under mild reaction conditions. J. Chem. Res., Synop. 2003, 412-414. 

Nencki reacUon. The general reaction, zinc chloride-catalyzed acylation of a phenol, is illustrated by the conversion of resorcinol into resacetophenone and of pyrogallol into gallacetophenone. The procedures are similar except that acetic acid is used in the first and acetic anhydride in the second. 

Pressurized LLE using acetic anhydride for simultaneous acylation was applied to the analysis of phenolic pollutants, sterols and carboxylic acids in environmental and microbial samples . ... 

Enol acetylation. Enol acetylation of steroidal ketones with acetic anhydride catalyzed by perchloric acid has been shown to be thermodynamically controlled (2,309). However, this acetylating reagent in the case of conjugated ketones gives complex mixtures of O-acylated and C-acylated products.1 Dienone-phenol rearrangements have been noted with A4-3-ketosteroids alkylated at C2 or C6.2... 

The acetylation of alcohols and phenols with acetic anhydride and HSZ-360 zeolite at 60oC used no solvent. The acetate of 1-dodecanol was obtained in 98% yield, and the acetate from 1 naphthol in 100% yield.183 The acylation of anisole with acetic anhydride at 100oC without solvent using zeolite H-/8 gave 4-methoxyacetophenone (6.30) in 98%yield.184 The catalyst could be recovered, regenerated, and reused with no decrease in yield. These reactions show that not all zeolites are used at high temperatures in the vapor phase. 

Most studies in which acid solids were used concern the synthesis of hydroxyacetophenones either by Fries rearrangement of phenyl acetate [3,5-15] or by acylation of phenol with acetic acid or acetic anhydride [11,16-21]. These reactions were conducted in the gas or liquid phase, zeolites being generally chosen as catalysts (Section 5.3.1). These shape-selective catalysts can also be used... 

Phenol acylation with acetic anhydride over MFI catalysts is also very o-HAP selective, although with this acylating agent o-HAP would result from direct C-acylation of phenol rather than secondary transformation of phenyl acetate [21]. 

During acylation of phenol with acetic anhydride on modified ZSM-5 catalysts (Subba Rao et al. 1995), it has been observed that Co, Cu, La and, especially, Ce show an important promoting effect in the formation of o-hydroxyacetophenone by C-acylation. Meanwhile the presence of others elements, such as Zr, V, Pd, Cr, Rh, favours the formation of phenylacetate by promoting the O-acylation of phenol. In addition, it has been observed that the reaction conditions, especially the phenol/acetic anhydride molar ratio and the reaction temperature, determine the distribution of O- and C-acylation. 

In diols containing both phenolic and alcoholic hydroxyl groups neutral conditions favour the acylation of the latter while the former are selectively acylated in the presence of triethylamine (ref. 57) doubtless due to the more nucleophilic phenoxide ion so formed, which is the basis of the Chattaway procedure originated many years ago. This is exemplified in the preferential formation in 95% yield of the phenolic acetate of estradiol in isopropanol containing 2.9 moles of sodium hydroxide in concentrated solution followed by the addition of 2.9 moles of acetic anhydride and then by stirring of the mixture for SOmins. at ambient temperature with maintenance of the pH at 7.8 (ref.58). 

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