Acetic-phosphoric anhydride, acylation

Alcohols can also be acylated by mixed organic-inorganic anhydrides, such as acetic-phosphoric anhydride, MeCOOPO(OH)2 (see 10-35). ... 

Phosphation can occur simultaneously with acylation. Such reaction of starch in a mixture of 87% phosphoric acid and acetic acid with acyl anhydrides produced a gummy substance, which transformed into an amorphous solid upon purification.1593... 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

For the regeneration of ATP, we chose the system based in the use of acetyl phosphate as final phosphoryl donor because this affords several advantages (i) acetyl phosphate is easily obtained by acylation of phosphoric acid with acetic anhydride in ethyl acetate [24], and (ii) the resulting sodium acetate is a non-toxic and an environmentally compatible compound. However, this regeneration system is quite sensitive to pH changes. Thus, a continuous adjustment of the pH to 7.5 is needed to maintain the proper operation of the system. Perhaps the main aspect of this approach is that the DHAP must be formed at the same rate as it is consumed by the aldolase. To avoid the accumulation of DHAP and minimize its non-enzymatic degradation, fine tuning of the aldolase/DHAK activities is needed. This adjustment must be experimentally optimized for some acceptors. 

In this paper we report the use of supported heteropoly acid (silicotungstic acid) and supported phosphoric acid catalysts for the acylation of industrially relevant aromatic feedstocks with acid anhydrides in the synthesis of aromatic ketones. In particular, we describe the acylation of thioanisole 1 with iso-butyric anhydride 2 to form 4-methyl thiobutyrophenone 3. The acylation of thioanisole with acetic anhydride has been reported in which a series of zeolites were used as catalysts. Zeolite H-beta was reported to have the highest activity of the zeolites studied (41 mol % conversion, 150°C) (2). 

Acylation of arenes. These mixed anhydrides have been used Tor acylation of arenes. However these reagents are sensitive to moisture and tend to disproportionate. One solution is to generate the reagents in situ. Thus acyl trifluoro-acetates can be generated in the presence of the arene from a carboxylic acid, TFAA, and 85% phosphoric acid (as catalyst) in CHjCN. Ketones of the type O II... 

The reaction of acetic anhydride with phosphoric acid will generate the same electrophile and offers the advantage that only the monoacyl produci results. Acylation of the first ring deactivates the second and the concentration of CH3C+=0 from the phosphoric ucid reaction is too small to produce the diacyl product. 

In Process a, vinyl methyl ketone reacts with hydrocyanic acid to give cyanohydrin, which is either dehydrated by spraying with phosphoric acid at 540°C (yield 74%) or, after acylation with acetic anhydride, pyrolized at 400°-550°C. In Process b, acrylonitrile is dimerized by UV irradiation to give 1,2-dicyanocyclobutane 8.5% of the acrylonitrile is converted after 84 hours. The cyclobutane derivative reacts by catalytic splitting at 455°C to give 2-cyanobutadiene (conversion 20%). Process c involves ammonoxidation of isoprene. One per cent by vol-... 

AcP can be prepared easily by acylation of phosphoric acid with acetic anhydride or with ketene, and isolated as a fairly... 

Friedel-Crafts Acylation of Cedrene. Let us now look in a little more detail at the Friedel-Crafts acylation of cedrene. This reaction can be carried out using acetic acid or acetic anhydride with an acid catalyst such as formic acid, phosphoric acid or sulfuric acid. The species which attacks the double bond of cedrene is the protonated acid or anhydride molecule. When sulfuric acid is used as a catalyst with acetic anhydride as the reagent, it is thought that the sulfuric acid first sulfonates the acetic anhydride to give sulfoacetic anhydride (6.122) as the acylating species. This results in a faster reaction as the sulfoacetate anion (6.126) is a... 

The Friedel-Crafts acylation of ferrocene, which was mentioned above, has been studied in considerable detail. Substitution can be effected under very mild conditions, for instance with acetic anhydride containing phosphoric add as catalyst, to give mono-acetylferrocene. With aluminium chloride as catalyst, good yields of either mono- or l,l -diacetylferrocene can be obtained according to the proportions of reagents taken. 

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