Acetic Anhydride related reagents

Scheme 6 depicts a typical penicillin sulfoxide rearrangement (69JA1401). The mechanism probably involves an initial thermal formation of a sulfenic acid which is trapped by the acetic anhydride as the mixed sulfenic-acetic anhydride. Nucleophilic attack by the double bond on the sulfur leads to an episulfonium ion which, depending on the site of acetate attack, can afford either the penam (19) or the cepham (20). Product ratios are dependent on reaction conditions. For example, in another related study acetic anhydride gave predominantly the penam product, while chloroacetic anhydride gave the cepham product (7lJCS(O3540). The rearrangement can also be effected by acid in this case the principal products are the cepham (21) and the cephem (22 Scheme 7). Since these early studies a wide variety of reagents have been found to catalyze the conversion of a penicillin sulfoxide to the cepham/cephem ring system (e.g. 77JOC2887).

The closely related o-iodylbenzoic acid (IBX) and Dess-Martin oxidations have proved to be effective methods for the synthesis of peptide aldehydes (Table 7, Scheme 6) 9 38 39] 2-Iodobenzoic acid is oxidized by potassium bromate to form 2-iodylbenzoic acid (IBX), which can be used directly for IBX oxidation. IBX can be further treated with acetic anhydride and TosOH at 100 °C for 40 minutes to form the more stable Dess-Martin periodinane reagent 45 46]... 

Huisgen and coworkers have also described the cycloaddition behavior of the munchnones , unstable mesoionic A2-oxazolium 5-oxides with azomethine ylide character.166 Their reactions closely parallel those of the related sydnones. These mesoionic dipoles are readily prepared by cyclodehydration of N-acyl amino acids (216) with reagents such as acetic anhydride. The reaction of munchnones with alkynic dipolarophiles constitutes a pyrrole synthesis of broad scope.158-160 1,3-Dipolar cycloaddition of alkynes to the A2-oxazolium 5-oxide (217), followed by cycloreversion of carbon dioxide from the initially formed adduct (218), gives pyrrole derivative (219 Scheme 51) in good yield. Cycloaddition studies of munchnones with other dipolarophiles have resulted in practical, unique syntheses of numerous functionalized monocyclic and ring-annulated heterocycles.167-169... 

Acylaminomalonic esters and related reagents are widely used for the synthesis of a-amino acids. The method differs from those syntheses already discussed in that the amino group is incorporated into the system from the outset. A popular reagent is diethyl acetamidomalonate (35). The acetamido group can readily be introduced into the reactive methylene position in diethyl malonate by first converting the latter into the hydroxy-imino derivative (33) by reaction with nitrous acid or an alkyl nitrite (cf. Section 4.2.7, p. 413). This derivative is then reduced catalytically to diethyl aminomalonate (34) which is acetylated using acetic anhydride. 

Trifluoroacetic anhydride is usually used without base " and derivatization of alcohols and polyols can be carried out without additional solvent. Pyridine bases should only be considered when phenols are trifluoroacetylated. Activation is possible w ith benzotri-azole/ l-methylpyrrolidin-2-one. pyridin-2-one, and pyridin-4-one, although the latter pyridinones are less effective than imidazole.Trifluoroacetyl acetate is less reactive than trifluoroacetic anhydride. Alternative reagents are trifluoroacetyl triflate " and the related trifluoroacetyl phosphate." ... 

Alcohol Compounds.—That the carbohydrates are, in fact, alcohol compounds is shown, both by their relation to poly-hydroxy alcohols and by their reactions. Carbohydrates possess alcohol characters in that they undergo distinctly alcoholic reactions. Like all alcohols they react with acetyl chloride or acetic anhydride. In.practice the latter reagent is used. They form acetyl derivatives, or esters, just as ethyl alcohol does. 

Even though formic anhydride is not a stable compound (see p. 723), amines can be formylated with the mixed anhydride of acetic and formic acids (HCOO-COMe) or with a mixture of formic acid and acetic anhydride. Acetamides are not formed with these reagents. Secondary amines can be acylated in the presence of a primary amine by conversion to their salts and addition of 18-crown-6. The crown ether complexes the primary ammonium salt, preventing its acylation, while the secondary ammonium salts, which do not fit easily into the cavity, are free to be acylated. Dimethyl carbonate can be used to prepare methyl carbamates in a related procedure. A-Acetylsulfonamides were prepared from acetic anhydride and a primary sulfonamide, catalyzed by Montmorillonite KlO-FeO or sulfuric acid. "... 

To start our investigations, we examined the conversion of 2,3-dimethyl-2-butene (1) into 3,3,4-trimethyl-4-penten-2-one (2) as a model reaction (eq. 1). The choice of acetic anhydride as the acetylating agent was made in the light of related studies on the acylation of aryl ethers. Our work in this field had shown that acetic anhydride was the most effective reagent for the Friedel-Crafts acylation of anisole in the presence of Hp zeolite. A lower degree of conversion was achieved with acetyl chloride, while hardly any reaction occurred with ethyl acetate or acetic acid [6]. 

Related Reagents. Boron Trifluoride-Acetic Acid Boron Trifluoride-Acetic Anhydride Boron Trifluoride Etherate Boron Trifluoride Dimethyl Sulfide Tetrafluoroboric Acid. 

Related Reagents. Dimethyl Sulfoxide-Acetic Anhydride Dimethyl Sulfoxide-Dicyclohexylcarbodiimide Dimethyl Sulfoxide-Methanesulfonic Anhydride Dimethyl Sulfoxide-Oxalyl Chloride Dimethyl Sulfoxide-Phosgene Dimethyl Sulfoxide-Phosphorus Pentoxide Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine Dimethyl Sulfoxide-Tiifluoroacetic Anhydride Dimethyl Sulfoxide-Triphosgene. 

Related Reagents. A/-Chlorosuccinimide-Dimethyl Sulfide Chromic Acid Dimethyl Sulfide-Chlorine Dimethyl Sulfoxide-Acetic Anhydride Dimethyl Sulfoxide-Dicyclo-hexylcarbodiimide Dimethyl Sulfoxide-Oxalyl Chloride Dimethyl Sulfoxide-Phosphorus Pentoxide Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine Dimethyl Sulfoxide-Trifluoroacetic Anhydride Dimethyl Sulfoxide-Triphosgene Manganese Dioxide Pyridinium Chlorochromate Pyridinium Dichromate Ruthenium(rV) Oxide Silver(I) Carbonate on Celite 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3( 1 H)-ons. 

Related Reagents. Acetic Anhydride Benzoyl Chloride Dimethyl Sulfoxide-Methanesulfonic Anhydride Methane-sulfonyl Chloride p-Toluenesulfonyl Chloride Trifluoroacetic Anhydride. 

Trimethylsilylacetone and related compounds have been prepared by the low-temperature reaction of trialkylsilylmethyl Grignard reagents with acetic anhydride at - 70° C, although the instability of the compounds has led to some difficulties in isolation at times (43, 63, 91-93). 

Related Reagents. Acetic Anhydride acetyl bromide acetyl fluoride. 

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