Oxidative with dimethyl dioxirane

The cyclohexyloxy(dimethyl)silyl unit in 8 serves as a hydroxy surrogate and is converted into an alcohol via the Tamao oxidation after the allylboration reaction. The allylsilane products of asymmetric allylboration reactions of the dimethylphenylsilyl reagent 7 are readily converted into optically active 2-butene-l, 4-diols via epoxidation with dimethyl dioxirane followed by acid-catalyzed Peterson elimination of the intermediate epoxysilane. Although several chiral (Z)-y-alkoxyallylboron reagents were described in Section 1.3.3.3.3.1.4., relatively few applications in double asymmetric reactions with chiral aldehydes have been reported. One notable example involves the matched double asymmetric reaction of the diisopinocampheyl [(Z)-methoxy-2-propenyl]boron reagent with a chiral x/ -dialkoxyaldehyde87. 

All classes of primary amine (including primary, secondary, and tertiary alkyl as well as aryl) are oxidized to nitro compounds in high yields with dimethyl dioxirane." Other reagents that oxidize various types of primary amines to nitro compounds are dry ozone, various peroxyacids," MeRe03/H202,"" Oxone ," ° tcrt-butyl hydroperoxide in the presence of certain molybdenum and vanadium compounds, and sodium perborate." ... 

The Diels-Alder reaction outlined above is a typical example of the utilization of axially chiral allenes, accessible through 1,6-addition or other methods, to generate selectively new stereogenic centers. This transfer of chirality is also possible via in-termolecular Diels-Alder reactions of vinylallenes [57], aldol reactions of allenyl eno-lates [19f] and Ireland-Claisen rearrangements of silyl allenylketene acetals [58]. Furthermore, it has been utilized recently in the diastereoselective oxidation of titanium allenyl enolates (formed by deprotonation of /3-allenecarboxylates of type 65 and transmetalation with titanocene dichloride) with dimethyl dioxirane (DMDO) [25, 59] and in subsequent acid- or gold-catalyzed cycloisomerization reactions of a-hydroxyallenes into 2,5-dihydrofurans (cf. Chapter 15) [25, 59, 60],... 

Aliphatic primary amines are known to be oxidized by dimethyl dioxiranes to various products such as oximes, nitroso dimers, nitroalkanes, nitrones and oxazrridines under various conditions depending upon the oxidation reaction . In contrast, when secondary amines lacking a-hydrogens are allowed to react with Oxone and PTC in buffered acetone solution at 0 °C, nitroxides are obtained in good yields in a few minutes (equation 61) . 

The same 1,4-dialdehyde can be made by oxidizing furan with the mild oxidizing agent dimethyl-dioxirane, which you met on p. 506. In this sequence, it is trapped in a Wittig reaction to give an E,Z-diene, which is easily isomerized to E,E. 

Major interest has been expressed in the synthesis of chiral sulfoxides since the early 1980s, when it was discovered that chiral sulfoxides are efficient chiral auxiliaries that are able to bring about important asymmetric transformations [22]. Sulfoxides are also constituents of important drugs (e.g., omeprazole (Losec , Priso-lec )) [23]. There is a plethora of routes of access to enantioenriched sulfoxides, and many involve metal-catalyzed asymmetric oxidations [24]. Examples of ruthenium metal-based syntheses of sulfoxides are scarce, presumably due to the tendency of sulfur atoms to bind irreversibly to a ruthenium center. Schenk et al. reported a dia-stereoselective oxidation of Lewis acidic Ru-coordinated thioethers with dimethyl-dioxirane (DMD) (Scheme 10.16) [25[. Coordination of the prochiral thioether to the metal is followed by diastereoselective oxygen transfer from DMD in high yield. The... 

The method is also successful for carboxyhc esters , and A,A-disubstituted amides, and can be made enantioselective by the use of a chiral oxaziridine. Dimethyldioxirane also oxidizes ketones (through their enolate forms) to a-hydroxy ketones. Titanium enolates can be oxidized with tert-butyl hydroperoxide or with dimethyl dioxirane and hydrolyzed with aqueous ammonium fluoride to give the a-hydroxy ketone. Ketones are converted to the a-oxamino derivative (0=C CH2- 0=C CHONHPh) with excellent enantioselectivity using... 

Simple alkanes can be converted to esters with dialkyloxrranes. Cyclic alkanes are oxidized to alcohols with dimethyl dioxirane. " Cyclohexane was converted to cyclohexyl trifluoroacetate with di(trifluoromethyl) dioxrrane and trifluoroacetic anhydride and also with RuCl3/MeC03H/CF3C02H. Dimethyl dioxrrane converts alkanes to alcohols in some cases. Adamantane is converted to adamantyl alcohol with DDQ (p. 1710) and triilic acid. The mechanism of oxygen insertion into alkanes has been examined. ... 

The highly potent antithrombotic (+)-rishirilide B was synthesized in the laboratory of S.J. Danishefsky. One of the tertiary alcohol functionalities was introduced via the Rubottom oxidation of a six-membered silyl dienol ether with dimethyl dioxirane (DMDO). The oxidation was completely stereoselective, and it was guided by the proximal secondary methyl group. Subsequently, the enone was converted to the enedione, which was used as a dienophile in the key intermoiecuiar Dieis-Aider cycioaddition step. 

On the other hand, oxidation of 161 with dimethyl dioxirane gave a 1 9 mixture of diols 165 and 166 (Scheme 31). Surprisingly and inexplicably the major product 166 results from attack on the double bond face syn to the arylsulfonyl moiety. Diol 166 could be converted to monoacetate 167 which underwent stereoselective alkylation with allyl trimethylsilane to yield 168. Similarly, acetate 167 could be converted to a single nitrile 169. Both of these transformations involve axial attack anti to the arylsulfonyl group on an intermediate N-sulfon-ium iminium ion. 

Note added in proof The tris(epoxide) 80 has been prepared by oxidation of 77 with dimethyl-dioxirane as a mixture of diastereomers. It proved to be extremely labile [80],... 

Oxidation of cyclic enol ether 35 with dimethyl dioxirane (DMDO) followed by in situ reduction of the intermediate epoxide with DIBALH gave secondary alcohol as a 10 1 mixture of diastereom-ers. Oxidation of these alcohols with TPAP/NMO afforded a 10 1 mixture of ketone 37 and its C16 epimer. The isomers were separated and the minor isomer was recycled to a 4 1 mixture of isomers by treatment with imidazole. Subsequent construction of the D-ring was performed by radical reduction of mixed thioacetal in the same way as that adopted by the Sasaki group, leading to octacycle 38. Stereoselective installation of the triene side chain was then carried out via (Z)-vinyl iodide 39... 

The epoxidation of PBD with dimethyl dioxirane (DMD) as the oxidizing species shows that the epoxidation proceeds as expected with high stereoselectivity cis double bonds give c -epoxides. The latter was confirmed by NMR spectroscopic analysis. DMD can be prepared by conversion of acetone with Oxone, a potassium monopersulfate compound (Scheme 9). Prepared in situ or purified by distillation, DMD is an efficient oxidizing species for polydienes (Scheme 10) [127, 130]. 

Methyl-2-iodoxybenzoate can be further converted to the diacetate 243 or a similar bis(trifluoroacetate) by treatment with acetic anhydride or trifluoroacetic anhydride, respectively (2005JOC6484). A single-crystal X-ray diffraction analysis of methyl-2-[(diacetoxy)(oxo)iodo]benzoate 243 revealed a pseudo-benziodoxole structure with three relatively weak intramolecular I 0 interactions. Esters of 2-iodoxyisophthalic acid (e.g., 244) were prepared by the oxidation of the respective iodoarenes with dimethyl-dioxirane. An X-ray structural analysis of diisopropyl 2-iodoxyisophthalate 244 has demonstrated strong intramolecular interaction with the... 

Dimethyl dioxirane in wet acetone oxidizes isocyanates to nitro compounds (RNCO —> RN02). Oximes can be oxidized to nitro compounds with peroxytri-fluoroacetic acid, or Oxone ," sodiumperborate," among other ways. " Primary and secondary alkyl azides have been converted to nitro compounds by treatment with PhjP followed by ozone. Aromatic nitroso compounds are easily oxidized to nitro compounds by many oxidizing agents. ... 

The oxidative cyclization of allenyl alcohol 135 with a small excess of dimethyl-dioxirane leads to an intermediate diepoxide that rearranges to hydroxyfuranone 136 in 55% yield (Eq. 13.44) [52]. If the oxidative cyclization is conducted in the presence of 0.5 equiv. of toluenesulfonic acid, the major product is the furanone lacking the a-hydroxy group of 136. Hydroxyfuranones or pyranones are available from the same kinds of reactions of 5-methylhexa-3,4-dien-l-ol. 

Steric effects were responsible for the complete diastereocontrol observed in the oxidation of various 6-halopenicillins by dimethyl dioxirane (DMD). Only one of the two possible diastereomeric sulfoxides has been obtained in each case23 (Table 1). Scheme 3 shows that perborate oxidation of optically active sulfide 16 affords, with moderate diastereoselectivity (78% de), the (f )-sulfoxide 17,24 designed as chiral ligand for catalytic asymmetric synthesis. 

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