Acylation with acyl peroxides

By the interaction of an acyl chloride with hydrogen peroxide in the presence of alkali (H Oj + 2NaOH = Na Oj), for example ... 

Synthesis. Symmetrical diacyl peroxides (20, R = R = alkyl or aryl) are prepared by the reaction of an acyl chloride or anhydride with sodium peroxide or hydrogen peroxide and a base ... 

In titanium acylates, the carboxylate ligands are unidentate, not bidentate, as shown by ir studies (333,334). The ligands are generally prepared from the hahde and silver acylate (335). The ben2oate is available also from a curious oxidative addition with ben2oyl peroxide (335—338) ... 

At low temperature a 1 1 adduct of thioacetic acid and an enamine could be prepared (709). The previously described reaction of aminomethylene ketones with hydrogen peroxide was extended to bisaminomethylene compounds. However, acylated cyclohexenamines led to cyclopentane-carboxamides (770), Trichloromethyl adducts of enamines and the rearranged amine derivatives were described in a further study (777). 

A heterocyclic ring may be used in place of one of the benzene rings without loss of biologic activity. The first step in the synthesis of such an agent starts by Friedel-Crafts-like acylation rather than displacement. Thus, reaction of sulfenyl chloride, 222, with 2-aminothiazole (223) in the presence of acetic anhydride affords the sulfide, 224. The amine is then protected as the amide (225). Oxidation with hydrogen peroxide leads to the corresponding sulfone (226) hydrolysis followed by reduction of the nitro group then affords thiazosulfone (227). ... 

Reaction of acyl peroxides with copper azide... 

Attack of molecular oxygen on this carbanion should yield acyl radicals which could react with loss of carbon monoxide, yielding the respective radicals, or with the formation of acyl peroxide radicals ... 

The experimental data on the reactions of ketyl radicals with hydrogen and benzoyl peroxides were analyzed within the framework of IPM [68]. The elementary step was treated as a reaction with the dissociation of the O—H bond of the ketyl radical and formation of the same bond in acid (from acyl peroxide), alcohol (from alkyl peroxide), and water (from hydrogen peroxide). The hydroperoxyl radical also possesses the reducing activity and reacts with hydrogen peroxide by the reaction... 

Acyl nitroso compounds (3, Scheme 7.2) contain a nitroso group (-N=0) directly attached to a carbonyl carbon. Oxidation of an N-acyl hydroxylamine derivative provides the most direct method for the preparation of acyl C-nitroso compounds [10]. Treatment of hydroxamic acids, N-hydroxy carbamates or N-hydroxyureas with sodium periodate or tetra-alkyl ammonium periodate salts results in the formation of the corresponding acyl nitroso species (Scheme 7.2) [11-14]. Other oxidants including the Dess-Martin periodinane and both ruthenium (II) and iridium (I) based species efficiently convert N-acyl hydroxylamines to the corresponding acyl nitroso compounds [15-18]. The Swern oxidation also provides a useful alternative procedure for the oxidative preparation of acyl nitroso species [19]. Horseradish peroxidase (HRP) catalyzed oxidation of N-hydroxyurea with hydrogen peroxide forms an acyl nitroso species, which can be trapped with 1, 3-cyclohexanone, giving evidence of the formation of these species with enzymatic oxidants [20]. 

Recently, acylsilanes have been utilized as useful intermediates in organic synthesis [57], For example, treatment of acylsilanes with the fluoride ion generates the corresponding acyl anions which react with electrophiles. On the other hand, by using the electrochemical method, acylsilanes serve as acyl cation equivalents because nucleophiles are introduced at the carbonyl carbon. Chemical oxidation of acylsilanes with hydrogen peroxide which affords the corresponding carboxylic acids has been reported [58], However, the anodic oxidation provides a versatile method for the introduction of various nucleophiles... 

Reactions of O2 with esters R C(0)0R also pass nucleophilic substitution as an initial step (Sawyer and Gibian 1979). Final products are acyl peroxides or carboxylic acids. The following set of equations explains the product formation ... 

With radical sources other than acyl peroxides, the rearomatization of the a-complex can take place by various, not always well characterized, reactions, such as oxidation by metal salts, hydrogen abstraction by intermediate radicals, disproportionation, and induced decomposition. 

In this section we discuss the thermochemistry of some species with the general formulas, RC(=0)00H, RC(=0)00R and RC(=0)00C(=0)R. These species have the generic names peracids (peroxycarboxyUc acids), peresters (percarboxylate esters) and acyl peroxides. The enthalpy of formation values are in Table 3. Three formal reactions that are discussed here are conceptually the same as in the earlier sections. Because now there is a carbonyl group present, we rewrite equations 5, 6 and 9 as equations 14, 15 and 16. 

The oxidation of nonfluorinated aromatic amines with free peracids (not acyl peroxides) proceeded best with the basic amines. The reaction did not pass through the azo stage of oxidation since azo compounds could not be converted under the reaction conditions and hydrazo compounds were oxidized to azo compounds. Under the reaction conditions, p-toluidine was converted only into p-nitrotoluene [31]. 

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