Oxidants m-CPBA

Mn (TMPyP)] with a variety of oxidants, m-CPBA, HSOj, and C10 , has been shown to produce the same, short-lived intermediate. An oxoMn(V) porphyrin structure was assigned to this intermediate. The rate of formation of oxoMn(V) from Mn (TMPyP) followed second-order kinetics,... 

The rapid reaction rates of peroxides with metalloporphyrins and the detection of observable oxometalloporphyrin species, especially in the reactions of manganese porphyrins with various oxidants (m-CPBA, NaOCl, KHSOj), have also inspired the use of these porphyrins as detectors... 

The oxidative C-N bond formation by hypervalent iodine(III) species continued to be an efficient organic tool in the synthesis of various benzofused heterocycles. A catalytic amount of iodine(III) species was sufficient to drive tire reaction to yield various N-substituted benzimidazoles 159 (Scheme 38). Active I(IIl) was produced by the oxidation of a catalytic amount of iodobenzene using co-oxidant m-CPBA. The I(III) species reacted with amidines 158 to generate... 

Sharpless and Masumune have applied the AE reaction on chiral allylic alcohols to prepare all 8 of the L-hexoses. ° AE reaction on allylic alcohol 52 provides the epoxy alcohol 53 in 92% yield and in >95% ee. Base catalyze Payne rearrangement followed by ring opening with phenyl thiolate provides diol 54. Protection of the diol is followed by oxidation of the sulfide to the sulfoxide via m-CPBA, Pummerer rearrangement to give the gm-acetoxy sulfide intermediate and finally reduction using Dibal to yield the desired aldehyde 56. Homer-Emmons olefination followed by reduction sets up the second substrate for the AE reaction. The AE reaction on optically active 57 is reagent... 

Alkyl-1,4-dihydropyridines on reaction with peracids undergo either extensive decomposition or biomimetic oxidation to A-alkylpyridinum salts (98JOC10001). However, A-methoxycarbonyl derivatives of 1,4- and 1,2-dihydro-pyridines (74) and (8a) react with m-CPBA to give the methyl tmns-2- 2>-chlorobenzoyloxy)-3-hydroxy-1,2,3,4-tetrahydropyridine-l-carboxylate (75) and methyl rran.s-2-(3-chlorobenzoyloxy)-3-hydroxy-l,2,3,6-tetrahydropyridine-l-carboxylate (76) in 65% and 66% yield, respectively (nonbiomimetic oxidation). The reaction is related to the interaction of peracids with enol ethers and involves the initial formation of an aminoepoxide, which is opened in situ by m-chlorobenzoic acid regio- and stereoselectively (57JA3234, 93JA7593). 

An interesting oxidative ring-opening reaction is shown in Scheme 2.36. Oxidation of vinylaziridines 138 with m-CPBA gave 142 through [2,3] Meisenheimer... 

The phenomenon that early transition metals in combination with alkyl hydroperoxides could participate in olefin epoxidation was discovered in the early 1970s [30, 31]. While m-CPBA was known to oxidize more reactive isolated olefins, it was discovered that allylic alcohols were oxidized to the corresponding epoxides at the same rate or even faster than a simple double bond when Vv or MoVI catalysts were employed in the reaction [Eq. (2)] [30]. 

Cp = 7 -C5H5 m-CPBA = m-chloroperbenzoic acid Scheme 45 Oxidation of molybdenum polysulfido complexes... 

As mentioned in Sect. 2.2, phosphine oxides are air-stable compounds, making their use in the field of asymmetric catalysis convenient. Moreover, they present electronic properties very different from the corresponding free phosphines and thus may be employed in different types of enantioselective reactions, m-Chloroperbenzoic acid (m-CPBA) has been showed to be a powerful reagent for the stereospecific oxidation of enantiomerically pure P-chirogenic phos-phine-boranes [98], affording R,R)-97 from Ad-BisP 6 (Scheme 18) [99]. The synthesis of R,R)-98 and (S,S)-99, which possess a f-Bu substituent, differs from the precedent in that deboranation precedes oxidation with hydrogen peroxide to yield the corresponding enantiomerically pure diphosphine oxides (Scheme 18) [99]. 

Triazoline imino sugar derivatives 297 that are prospective glycosidase inhibitors have been prepared as single diastereomers in high yield via an lAOC reaction of in situ generated azido alkene 296 (Eq. 32) [78]. m-CPBA oxidation of the dithioacetal groups in the 0-acetylated 5-azido-5-deoxydibenzyl dithio-acetal of o-xylose or D-ribose 294 to the bis-sulfone 295, followed by loss of HOAc between C-1 and C-2 provided the lAOC precursor 296. 

Methods A oxidation with m-CPBA, B oxidation with (-l-)-MPCA. 

Figure 54.1. FT-IR spectra of catalyst (4a) used once on the diastereoselective epoxidation of (1) using different oxidants and recovered by reduced pressure (a.) fresh catalyst, (b.) DMD. (c.) 02/pivaladehyde. (d.)NaOCl/4-PPNO. (e.) m-CPBA/4-NMO.

Oxidation of oximes to nitro compounds with m-CPBA has been applied to the synthesis of dialkyl 1-nitroalkanephosphonates (Eq. 2.63),124 which are useful reagents for conversion of carbonyl compounds to nitroalkenes.125... 

The most effective and frequently used oxidant of secondary amines in organic solvents (CH2CI2, CH3CN, MeOH) is m-chloroperbenzoic acid (m-CPBA). Oxy-dation with m-CPBA of seco-curane type indoline alkaloids of strychnobrasiline (32), in deacetylated form, gives the corresponding nitrones (33), (34), and (35) (Scheme 2.12) (86). 

The synthesis of camphor-derived nitrones (87), of spin traps containing alkyl-phenylphosphoryl (36a,b) (88) and diethoxyphosphoryl substituents (37-39) requires m-CPBA as an oxidant (Fig. 2.3) (89, 90). 

In order to optimize oxidation conditions of diethyl(2-methylpyrrolidine-2-yl) phosphonate into the corresponding nitrone, a comparative analysis of the action of various oxidants such as H2O2, m-CPBA, Oxone, 2-phenylsulfonyl-3-phenyl-oxaziridine (PSPO), DMD, and A-methylrnorpholine /V-oxide in the presence of a catalytic quantity of tetrapropylammonium perruthenate (NMO/TPAP) has been made (92). 

The use of m-CPBA allows the formation of nitrones in the oxidation of tertiary amines. The resulting amines A-oxides are subject to either Cope or Meisenheimer rearrangements, providing formation of nitrones. Thus, the generated corresponding nitrones in the oxidation of bicyclic aziridines give nitrones as a result of a Meisenheimer rearrangement (Scheme 2.14) (93). 

Oxidations of a range of p-cyanoethyl tertiary amines (44) with m-CPBA in CH2CI2 give the corresponding A-oxides (45), which can be isolated or undergo Cope elimination affording hydroxylamines (46) in high yields (Scheme 2.16) (Table 2.1) (96). Hydroxylamines (46) can be easily oxidated into nitrones (see Section 2.2.1.3). 

Oxidative ring opening of isoxazolidines leads to nitrones. Thus, bicyclic isox-azolidines (50) and (51), treated with m-CPBA, afford nitrones (52), (53), (54), and (55) (Scheme 2.19). Conformational analysis has confirmed the key role of the nitrogen lone pair with respect to regioselectivity of the reaction and of the intramolecular kinetic deprotonation of the intermediate oxoammonium derivative (125). 

Similar oxidative ring opening occurs in other bi- and tricyclic isoxazolidines upon treatment with m-CPBA (126, 127). 

Oxidation with m-CPBA of monocyclic isoxazolidines (56) without H at a-C gives a tautomeric mixture of acyclic nitrones (57) and six-membered cyclic hydroxylamines (58), with their proportion depending on the substituents... 

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