Isomeric peracetates

The conventional mass spectra obtained from saccharides transformed into their OTMS and -OCH3 derivatives were interpreted by using labeled derivatives. Systematic studies had never been performed on -OAc derivatives. However, in 1975, Das and Thayumanavan [230] studied various peracetylated disaccharides by their IKE spectra to resolve the ambiguity appearing in the El mass spectra of the isomeric peracetates of trehalose, sophorose, kojibiose, laminaribiose, maltose, melibiose and gentiobiose, all characterized by the same molecular weights (678). 

Two pieces of chemical evidence support the three-membered ring formulation. The bifunctional oxazirane prepared from glyoxal, tert-butylamine, and peracetic acid (6) can be obtained in two crystalline isomeric forms. According to the three-membered ring formula there should be two asymmetric carbon atoms which should allow the existence of meso and racemic forms. A partial optical resolution was carried out with 2-7i-propyl-3-methyl-3-isobutyloxazirane. Brucine was oxidized to the N-oxide with excess of the oxazirane. It was found that the unused oxazirane was optically active. 

In the presence of acids, linalool isomerizes readily to geraniol, nerol, and a-terpineol. It is oxidized to citral by chromic acid. Oxidation with peracetic acid yields linalool oxides, which occur in small amounts in essential oils and are also used in perfumery. Hydrogenation of linalool gives tetrahydrolinalool, a stable fragrance material. Its odor is not as strong as, but fresher than, that of linalool. Linalool can be converted into linalyl acetate by reaction with ketene or an excess of boiling acetic anhydride [34]. 

The possibility exists that strong acidic reaction systems such as hydrogen peroxide in glacial acetic acid may cause isomerization to hydrazones, particularly in the oxidation of aliphatic or aliphatic-aromatic azo compounds. Therefore the much milder perbenzoic acid in an inert solvent has been suggested as an oxidizing agent [7]. Peracetic acid (40% solution) has also been used in conjunction with an indifferent solvent [3, 6]. 

Di-f-butylallene oxide (64) is an isolable compound prepared by the oxidation of 1,3-di- -butylallene with m-chloroperbenzoic acid. Upon heating at 100 °C for 5 h, 50% of 64 is isomerized to trans-2,3-di-f-butylcyclopropanone (52).51> Likewise, oxidation of 1,1-di-f-butyl-allene (65) with buffered peracetic acid (equimolar quantities) affords 2,2-di-f-butylcyclopropanone (6(5).55a> Although the intermediate is presumably 3,3-di-f-butylallene oxide, it has not been detected. 

Despite many attempts it has not been possible to oxidize 2-substituted 1,2,3-triazoles 382 to the corresponding 1-oxides 326. Peracetic acid, 3-chloroperbenzoic acid, dichloropermaleic acid, trifluoroperacetic acid, peroxydisulfuric acid, and f-pentyl hydrogen peroxide in the presence of molybdenum pentachloride all failed to oxidize 382 (1981JCS(P1)503). Alkylation of 1-hydroxytriazoles 443 invariantly produced the isomeric 3-substituted 1,2,3-triazole 1-oxides 448 (see Scheme 132). However, the 2-substituted 1,2,3-triazole 1-oxides 326 can be prepared by oxidative cyclization of 2-hydroxyiminohydrazones (1,2-hydrazonooximes, a-hydrazonooximes) 345 or by cyclization of azoxyoximes 169. Additional methods of more limited scope are reaction of nitroisoxazoles 353 with aryl-diazonium ion and base, and reaction of nitroimidazoles 355 with hydroxy-amine- or amine-induced rearrangement of nitro-substituted furoxanes 357. 

Parent and cross diperoxides are produced when tetra-sub-stituted olefins containing suitable substituents are ozonized. Cross diperoxides are also produced when pairs of tetra-substituted olefins are ozonized together. Comparison samples of diperoxides are conveniently synthesized by treating the appropriate ketone with peracetic acid at low temperature. Peracetic acid oxidation of ketone pairs can also be used to prepare cross diperoxides. Low temperature NMR is used to study diperoxide stereochemistry as well as barriers to conformational isomerization. 

An interesting route to the cyclopropanone system involves the rearrangement of allene oxides, usually generated by the epoxidation of allenes. Thus, 1,3-di-t-butylallene oxide (11) may be prepared by the reaction of 1,3-di-t-butylallene with m-chloroperbenzoic acid. Heating 11 to 100 °C leads to isomerization, forming truns-2,3-di-t-butylcyclopropanone (10) (Scheme 4) Similarly, 1,1-di-t-butylallene (15) yields 2,2-di-t-butylcyclopropanone with peracetic acid (equation 7) ... 

Derivation (1) By-product of soap manufacture (2) from propylene and chlorine to form allyl chloride, which is converted to the dichlorohydrin with hypo-chlorous acid this is then saponified to glycerol with caustic solution (3) isomerization of propylene oxide to allyl alcohol, which is reacted with peracetic acid, (the resulting glycidol is hydrolyzed to glycerol) (4) hydrogenation of carbohydrates with nickel catalyst (5) from acrolein and hydrogen peroxide. 

Unsaturated Lignin Model Compounds Double bonds in lignin model compounds are attacked by peracetate ions. Dehydro-di-woeugenol (XXI, Figure 12.9) reacted with epoxidation of the aliphatic double bond and formation of the diol. The double bonds in stilbenes [59] and coniferaldehyde [90] are also cleaved. FemUc acid (IVa) and its ethyl ester reacted slowly at 50°C the methyl ether, 3,4-dimethoxy cinnamic acid, was much less reactive and was almost quantitatively recovered [55]. The reactions of ferulic acid and its ethyl ester (both in the trans form) were accompanied by trans-cis isomerization, perhaps an indication of reversible phenoxy radical formation. HomovanilUc acid (XXXa) was also formed the proposed mechanism involved epoxidation of the a-P double bonds followed by decarboxylation. 

H 4.26%, O 45.03%. HOOCCH = CHCH=CH-COOH. Prepd by oxidation of phenol and peracetic acid Boeseken. Engelberts, C.A. 26t 2970 (1932) by treatment of ethyl 1,4-dtbromoadipate with alcoholic potassium hydroxide Guha, Sankaran, Org, Syn. 26, 57 (1946) by isomerization of 3-hydroxy-4-carbomethoxybut-1-ene-1-carboxylic acid lactone Elvidge et at, J, Chem, Soc, 1950, 2235 by carbonylation of acetylene Tsuji er al. J. Am. Chem, Soc. 86, 2095 (1964). Configuration and separation of isomers Boeseken, Kerkhoven, Rcc Trav. Chim. Si, 964 (1932) Elvidge et at, J. Chem Soc. 1953, 708. 

Timell and coworkers found that isomeric methyl di-O-methyl-u-glucosides are well resolved as their peracetates. 

Alternatively, 5-substituted silylfurans (347), readily obtainable using new carbanion methodology, can be easily oxidized to butenolides (348) using peracetic acid and then isomerized to the conjugated isomers if desired.The related but-3-en-4-olides (349) can be prepared in two steps from... 

In the absence of radical initiators, cyclopentadiene and MA form a 1 1 Diels-Alder adduct, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride (see Chapter 4). The Jo-adduct formed below 170°C, undergoes isomerization above 170°C to the exo-adduct/ " Both the endo- and oxo-adducts undergo homopolymerization to yield polymer containing equimolar amounts of the two monomers/ " Copolymerization occurs in the presence of radical initiators at a temperature where the initiator has a short half-life. For example, heating molten adduct with 6.6 mol % crr-butylhydroperoxide for 1 h at 240°C gives 83% copolymer. Heating the exo-adduct with 10 mol % /-butyl peracetate in chlorobenzene for 1 h gives a 72% yield of copolymer. 

Propylene oxide (section 9.4.1(b)) is isomerized to allyl alcohol by heating at 200-250°C in the presence of a trilithium phosphate catalyst. The allyl alcohol is then epoxidized to glycidol with peracetic acid in ethyl acetate. The glycidol is then hydrolysed to glycerol. 

Colupulone is hydroxylated to 4-hydroxycolupulone (267, Fig. 110) upon treatment with potassium hydrogen peroxysulfate ("Caroat") in aqueous alkaline buffers. Peracids, such as m.-chloroperbenzoic acid or peracetic acid, can also be applied. Compound 267 is stable at room temperature over a period of months, but it is readily isomerized in NaOH 0.01 N to 5-(3-methyl-2-butenyl)isocohumulone (268, Fig. 110). Characterization is evident from the spectrometric data. Upon boiling of 268 for a short time in alkaline solution, 5-(3-methyl-2-butenyl)cohumulinic acid or dihydrocohulupone (202, Fig. 85) is obtained. This compound is also accessible by reduction of cohulupone with sodium borohydride (see 13.1.1.2.1.) (22). None of the three oxidized products leads to cohulupone in auto-oxidation reaction conditions. This confirms the proposed mechanism of formation of cohulupone via 4-hydroperoxycolupulone (see 13.1.1.1.2.). 

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