Baeyer-Villiger oxidation of aromatic

SCHEME 159. Selenium-catalyzed Baeyer-Villiger oxidation of aromatic aldehydes and phenol formation via hydrolysis of the intermediary esters... 

Syper, L. The Baeyer-Villiger oxidation of aromatic aldehydes and ketones with hydrogen peroxide catalyzed by selenium compounds. A convenient method for the preparation of phenols. Synthesis 1989, 167-172. 

The Baeyer-Villiger oxidation of aromatic ketones by peroxyacids is a widely applicable method for the synthesis of phenols . This oxidation can be carried out by organic peroxyacids such as peroxyacetic , trifluoroperoxyacetic , 4-nitro-and 3,5-dinitroperoxybenzoic acids . However, m-chloroperoxybenzoic acid is most frequently used. Hydrogen peroxide is sometimes used, but it works only in the presence of strong acids . 

M. Renz, T. Blasco, A. Corma, V. Fornes, R. Jensen, L. Nemeth, Selective and shape-selective Baeyer-Villiger oxidations of aromatic aldehydes and cyclic ketones with Sn-beta zeolites and H2O2, Chem. Eur. J. 8 (2002) 4708. 

The mechanism for the Baeyer-Villiger oxidation of aromatic aldehydes catalyzed by Sn-beta zeolite is similar to that established for cyclic ketones. For this reaction, Corma et al. [40] suggested that the activation of the carbonyl bond is the result of the coordination to the Lewis acidic center followed by a nucleo-phihc attack of the hydrogen peroxide onto the more electrophilic carbonyl carbon atom. In the similar reaction, Bronsted sites are active for oxidation of aromatic aldehydes with H2O2 provided that the molecule does not contain ole-finic groups. 

Co(ni) alkyl peroxides have been prepared and used by Mimoun and coworkers in the hydroxylation of hydrocarbons with this metal a Haber-Weiss type of reactivity is suggested. Square-planar Pt(II) complexes, of the type [(dppe)Pt(CF3)(solv)], used by Strukul in the epoxidation of alkenes and in Baeyer-Villiger oxidations of ketones (Schemes 8 and 9), are effective catalysts also in the direct hydroxylation of aromatics with hydrogen peroxide. The reactivity increases in the presence of electron releasing substituents in the aromatic ring. Ortho and para derivatives are practically the only products observed and interesting selectivity toward the ortho products has been detected (equation 85). 

Figure 2.24 Reactions catalysed by mono-oxygenases, hydroxylation of carbon centres, aromatic hydroxylation, epoxidation of alkenes, heteroatom oxidation and Baeyer-Villiger oxidation of a ketone.

Baeyer- Villiger oxidations7 This peroxide in combination with trimethylsilyl Inflate (1 equiv.) is highly effective for selective Baeyer-Villiger oxidation of acyclic anil cyclic ketones, but not of aromatic ketones, without epoxidation of carbon-carbon double bonds, lixamples ... 

Compounds 19 and 20 have been obtained39 (equation 16) in less than 2 h synthesis time by Baeyer-Villiger oxidation of the corresponding 4-[18F]fluoro-2-alkoxybenzaldehydes 21 and 22 prepared through nucleophilic aromatic displacement reactions (equations 17a... 

Whereas empirical force-field calculations predict a ring A boat conformation for lanost-8-en-3-one, combined empirical force-field-extended Hiickel molecular orbital calculations favour a ring A chair conformation. Europium-shift n.m.r. results indicate that the molecule adopts the latter conformation. Studies on the peracetic acid-boron trifluoride etherate Baeyer-Villiger oxidation of 4,4-dimethyl-3-keto-triterpenoids to 5-lactones (18) and their subsequent ring contraction to y-lactones have been reported. Dehydrogenation of lanost-8-en-3j8-ol with 2,3-dichloro-5,6-dicyanobenzoquinone afforded, in addition to the corresponding 7,9(1 l)-diene, the aromatic seco-lanostane derivatives (19)... 

Oxidations catalyzed by monooxygenases Oxygenations of C-H and C=C bonds forming alcohols, epoxides enantioselective Baeyer-Villiger oxidations of ketones to chiral lactones and of sulfides to chiral sulfoxides nuclear and side-chain hydroxylation of aromatic compounds. 

Uses, (a) Oxidation of arylamines to nitroso compounds. - (b) Baeyer-Villiger oxidation of ketones to lactones (I) - or esters (3). When an aromatic ring is present (2), cleavage occurs adjacent to this ring. ... 

The oxidation of aromatic aldehydes to phenols via the aryl formates is known as the Dakin reaction and is evidently related to the Baeyer-Villiger oxidation of ketones. The use of MCPBA is well known [45]. The successful use of MMPP and UHP-acetic anhydride in these reactions (Eqs. 34 to 36) can be achieved with aromatic aldehydes that have an electron releasing substituent in an ortho- or para-position. In the absence of a suitable electron releasing substituent, aromatic aldehydes are oxidised to the corresponding carboxylic acid. 

Baeyer-Villiger oxidation of alkyl- and aryl-substituted C -C, cycloalkanones, steroid ketones and branched chain aliphatic ketones is catalysed by arsonated polystyrene resins [53], Larger size cycloalkanones and linear ketones react much slower. Water miscible and immiscible solvents can be used. With the latter, the resin behaves as an effective catalyst and a phase-transfer agent (triphase catalysis). The same compounds are also epoxidation catalysts. More recently, a method for the preparation of phenols by the oxidation of aromatic aldehydes and ketones has been reported. The most convenient catalysts are nitro-substituted arylseleninic acids and corresponding diselenides [54]. 

A two-phase capillary reactor was used for the oxidation of aromatic alcohols and Baeyer-Villiger oxidation of ketones using elemental fluorine [80]. The substrate in an appropriate solvent (acetonitrile or formic acid) was injected at a controlled rate by a syringe pump into the reaction channel. Compared to batchwise operation the yield and conversion was comparable or better using microstructured devices. 

Mehta et al. (1976) reported on the use of this reagent for the Baeyer-Villiger oxidation of polycyclic ketones like 1,3-bishomocubanone and 1,4-bishomocubanone into lactones. Ammonium tetrasulfatocerate(IV) dissolved in a mixture of dilute sulfuric acid and acetonitrile was applied as a reagent to transform polycyclic aromatic compounds into quinones (Peri-asamy and Bhatt, 1977a, 1977b). Skarzewski (1984) oxidized polycyclic aromatics with this reagent in a two-phase system with sodium dodecyl sulfate as a surfactant. CAS could be used in catalytic amounts if an excess of ammonium persulfate was present to steadily reconvert cerium(III) in cerium(IV). 

Obsolete uses of urea peroxohydrate, as a convenient source of aqueous hydrogen peroxide, include the chemical deburring of metals, as a topical disinfectant and mouth wash, and as a hairdresser s bleach. In the 1990s the compound has been studied as a laboratory oxidant in organic chemistry (99,100). It effects epoxidation, the Baeyer-Villiger reaction, oxidation of aromatic amines to nitro compounds, and the conversion of sodium and nitrogen compounds to S—O and N—O compounds. 

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