Oxidants mCPBA

Oxidation of A-diethylphosphito to A-diethylphosphono derivatives 151 has been performed using 2-picoline A-oxide, MCPBA, diphenyl selenoxide, or 7-butyl hydroperoxide (TBHP). The latter was selected as the most efficient reagent. Similarly, the N-phosphitylated /3-sultams undergo reactions of oxidative addition of elemental sulfur and selenium giving 2-thio- and 2-selenophosphono /3-sultams 152 and 153, respectively, in satisfactory yields (Scheme 46) <1999HAC61>. 

Instead of preparing the sulfoxide chirophore via a separation of diastereoisomers, the dia-stereoselective oxidation of a sulfide offers an interesting alternative. Thus Michael addition of 10-mer-captoisobomeol (414) to methyl propiolate furnished (Z)-vinyl sulfide (415) which underwent a hydroxy-directed oxidation (MCPBA) to give the (sulfur-R)-vinyl sulfoxide (416) in a highly selective manner (Scheme 100). ... 

Three new approaches to the construction of the dihydroxyacetone side chain were reported.195 197 Pregenolone was oxidized with PhlO-KOH-MeOH to the hydroxy-acetal (224) which, after acetylation and heating in xylene with toluene-p-sulphonic acid, gave the acetoxy-enol ether (225). Oxidation (MCPBA) and hydrolysis gave the required compound (266).195 The other two routes which started with 17-oxo-steroids are outlined, in part, in Schemes 9196 and 10.197 Tetrazolium salts were... 

Cyclohexanones can be dehydrogenated to enones by treatment of the corresponding enol silanes with DDQ in the presence of a catalytic amount of the bis-silyl derivative of acetamide. However, the yields fall off drastically when the reaction is applied to cyclopentanones and cyclo-heptanones. Another new method for dehydrogenation of carbonyl compounds consists of conversion to their pyridine-2-sulfIde derivatives, followed by oxidation (MCPBA), and by mild heat. ... 

Oxidation. MCPBA is useful for oxidation of a-dithiolactones to give 1,2-dithietan-... 

HPPO hydrogen peroxide-based propylene oxide mCPBA meta-chloroperbenzoic acid MTA metric tons per annum... 

Thioglycosyl pyridine iV-oxides, e.g. compound 42, have been prepared as latent glycosyl donors from peracetylated 1-thiosugars and 2-bromopyridine-N-oxide. MCPBA oxidation of ethyl 1-thio-p-glycopyranosides gave the corresponding Sj-sulfoxides, for example 43, as the major products. The preferred conformations of the minor Rj-epimers under the influence of the exo-anomeric effect are discussed in Chapter 21. ... 

Further studies have been reported on the mycinamycin complex (see Vol.14,p.157) N-oxidation (MCPBA) followed by acetylation removed the desosamine unit, and X-ray analysis was carried out on... 

The application of thioglycoside gained a new impetus by the finding of Kahne et al. [56] who observed that phenylsulfenyl glycosyl donors, readily accessible by oxidation (/mCPBA) of phenyl thioglycosides, can be effectively glycosylated using... 

In 2008 Kita developed a procedure for the asymmetric dearomatization of naph-thols via the formation of ortho-spirolactones using a C2-symmetrical chiral precatalyst 36 (Figure 19.11) and co-oxidant mCPBA with acetic acid [115] (Scheme 19.16). This reaction proceeds via the mCPBA/acetic acid-mediated oxidation of precatalyst 36 to the hypervalent iodine(III) active catalytic species 37. Ishihara has taken this work further with the development of the conformationally more flexible chiral organo-iodine precatalyst 38 [116], offering increased enantioselectivity at... 

Oxygenation takes place with peracids. The cyclopalladated benzylamine complex 466 is converted into the salicylaldamine complex 504 by the treatment with MCPBA[456] or /-BuO H[457]. Similarly, azobenzene is oxidized with MCPBA at the ortho position[458]. 

Both 2- and 7-methylthiopyrido[2,3- f]pyrimidines have been oxidized to sulfoxides and sulfones with hydrogen peroxide or MCPBA, as have 2-arylthio derivatives in the... 

Three preparations of 1-azetine iV-oxides have been reported. Oxidation of the 2-aryl-l-azetine (222) with MCPBA gives the nitrone (223) (79CB3914>. However, similar treatment of 2-alkoxy-l-azetines fails to give the corresponding iV-oxides but yields products derived from oxaziridines (cf. Section 5.09.4.2.3). 

In this type of cleavage reaction, it appears that the axial benzoate is the preferred product. If water is excluded from the reaction, a bromo benzoate is obtained.The highly oxidizing medium of 2,2 -bipyridinium chlorochromate and MCPBA in CH2CI2 at rt for 36 h effects a similar conversion of benzylidene acetals to hydroxy benzoates in 25-72% yield. ... 

This group is stable to TEA and morpholine in pyridine at 20°. It is cleaved by oxidation with MCPBA followed by elimination with TEA in Pyr, 10 min, 20°." The rate of cleavage is proportional to the strength of the electron-withdrawing group on the phenyl ring. ... 

Tlie reaction of 5,6-dithiabicyclo[2.1.1]hexaiie 11a with OXONE led to the corresponding dithiirane 12a, which was, however, stable only in solution (Amax at 442 nm in CH2CI2). Treatment of the reaction mixture containing 12a with MCPBA gave the dithiirane 1-oxide 13a (8%) (95TL1867). Tire introduction of electron-withdrawing substituents on the benzene rings provided the dithiirane oxide 13b in a better yield (21%). 

Tlie isolable dithiiranes (4 and 7) are fairly stable under acidic conditions but quickly lose a sulfur atom to give the corresponding thioketones under basic conditions (97BCJ509). Tliey are quite sensitive toward amines and phosphines. Oxidation with MCPBA gave the corresponding dithiirane 1-oxides in high yields. 

Oxidation of the dithiete 175 with MCPBA (1 equiv.) yielded the dithiete 1-oxide 202 which, when heated in refluxing toluene, formed a mixture of the ring-opened product sulflne 203 (blue, A ax 576 nm) and 202 in the ratio 7 1 (95TL8583). Further oxidation of 202 or oxidation of 175 with... 

The Baeyer-Villiger oxidation is a synthetically very useful reaction it is for example often used in the synthesis of natural products. The Corey lactone 11 is a key intermediate in the total synthesis of the physiologically active prostaglandins. It can be prepared from the lactone 10, which in turn is obtained from the bicyclic ketone 9 by reaction with m-chloroperbenzoic acid (MCPBA) " ... 

The action of aqueous potassium hydroxide on chloronitrile 14 in DMSO at 25-30°C accomplishes the hydrolysis of the chloronitrile moiety and furnishes ketone 13 in a yield of 80%. Treatment of a solution of ketone 13 in CH2CI2 with mCPBA and sodium bicarbonate results in a selective Baeyer-Villiger oxidation to give bicyclic lactone 12 in >95% yield. It is noteworthy that the Baeyer-Villiger oxidation is completely regioselective and that the... 

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