Acids m-chloroperbenzoic

The other main illogical electrophiles are epoxides, easily made from an olefin and a per-acid, the usual one being m-chloroperbenzoic acid (MCPBA) a commercial product. A more detailed explanation comes later, in fiiames 276-7. 

The oxidation of 2- and 5-sulfides is usually performed in acetic acid and 30% hydrogen peroxide (213, 229, 263, 345-350) Or with m-chloroperbenzoic acid (341). Ary] (8, 272. 349, 351-353) and alkyl sulfones (129, 203, 214, 270, 274, 275) are thus obtained in good yields. Other oxidative reagents such as KMn04 (7, 273) or CrO (7) in acetic add have also been used. 

Fig. 5. Corey synthesis ofPGE2 and PGF2Q, where DiBAL-H = diisobutylaluminumhydride MCPBA = m — chloroperbenzoic acid py = pyridine ...

Fig. 6. Synthesis of prostaglandins via a bicyclo[3.1.0]hexane intermediate where MCPBA = m — chloroperbenzoic acid.

Furano(3,6)pyridazinophane gives with m-chloroperbenzoic acid the corresponding chiral mono-lV-oxide (91) (80JOC4584). 

The alkylthio group is replaceable by nucleophiles. The positions 7 and 4 react under mild conditions in that order the 2-alkylthio functions require more drastic treatment. Conversion of l-methyl-4-methylthiopteridin-2-one (157) into the 4-methylamino derivative (158) can be achieved by stirring with methylamine at room temperature (equation 48). The reactivity of an alkylthio group can often be further enhanced by oxidation to the corresponding sulfoxide and sulfone. Thus, reaction of l,3-dimethyl-7-methylthiolumazine (160) with m-chloroperbenzoic acid yields 7-methylsulfinyl- (161) and 7-methylsulfonyl-l,3-dimethyllumazine (162 equation 49) (82UP21601). 4-Amino-2-methylthio-7-... 

The replacement of rhodium from a wide range of rhodacycles to form condensed furans, thiophenes, selenophenes, tellurophenes and pyrroles has been widely explored and a range of examples is shown in Scheme 97. The rhodacycles are readily generated from the appropriate dialkyne and tris(triphenylphosphine)rhodium chloride. Replacement of the rhodium by sulfur, selenium or tellurium is effected by direct treatment with the element, replacement by oxygen using m-chloroperbenzoic acid and by nitrogen using nitrosobenzene. 

Oxidation of fused isoxazolidine (173) with one equivalent of m-chloroperbenzoic acid produced an oxazine. The mechanism of transformation involves formation of an A/-oxide... 

The most common method of epoxidation is the reaction of olefins with per-acids. For over twenty years, perbenzoic acid and monoperphthalic acid have been the most frequently used reagents. Recently, m-chloroperbenzoic acid has proved to be an equally efficient reagent which is commercially available (Aldrich Chemicals). The general electrophilic addition mechanism of the peracid-olefin reaction is currently believed to involve either an intra-molecularly bonded spiro species (1) or a 1,3-dipolar adduct of a carbonyl oxide, cf. (2). The electrophilic addition reaction is sensitive to steric effects. 

The advantages of m-chloroperbenzoic acid have already been emphasized it is commercially available, stable and highly selective when methylene dichloride is used as solvent, the m-chlorobenzoic acid precipitates from solution, thereby decreasing the danger of acid-catalyzed side reactions." ... 

In a typical Knof procedure, 3jS-hydroxyandrost-5-en-17-one acetate is epoxidized with perbenzoic acid (or m-chloroperbenzoic acid ) to a mixture of 5a,6a- and 5)5,6)5-epoxides (75) in 99 % yield. Subsequent oxidation with aqueous chromium trioxide in methyl ethyl ketone affords the 5a-hydroxy-6-ketone (76) in 89% yield. Baeyer-Villiger oxidation of the hydroxy ketone (76) with perbenzoic acid (or w-chloroperbenzoic acid ) gives keto acid (77) in 96% yield as a complex with benzoic acid. The benzoic acid can be removed by sublimation or, more conveniently, by treating the complex with benzoyl chloride and pyridine to give the easily isolated )5-lactone (70) in 40% yield. As described in section III-A, pyrolysis of j5-lactone (70) affords A -B-norsteroid (71). Knof used this reaction sequence to prepare 3)5-hydroxy-B-norandrost-5-en-17-one acetate, B-noran-... 

P-Acetoxy-5, l-diketo-5,6-seco-androstan-6-oic Acid (77). To a solution of dione (76) dissolved in 50 ml of chloroform in a water bath is added, in portions with stirring over 0.5 hr, 7.5 g of m-chloroperbenzoic acid - (assay 85%). The mixture is stirred at room temperature for about 18 hr and then evaporated in vacuo at 25° to give a mixture of m-chlorobenzoic acid and 3y5-acetoxy-5,17-diketo-5,6-seco-androstan-6-oic acid. The mixture can be used in the following step with only a small loss in overall yield. ... 

The parent indolo[2,3-fl]carbazole (1) has also been the subject of a study probing its reactivity toward oxidizing agents. One of the substrates involved, namely 85 (prepared from 1 and 2,5-dimethoxytetrahydrofuran in the presence of acid), was subjected to treatment with m-chloroperbenzoic acid, to give the dione 86 as the major product and a sensitive compound assigned the hydroxy structure 87. A cleaner reaction took place when 85 underwent oxidation with tert-butyl hydroperoxide assisted by VO(acac)2, to produce 86 exclusively in 86% yield. Likewise, A,N -dimethylindolo[2,3-fl]carbazole furnished the dione 88 on treatment with this combination of reagents (96J(X 413). 

The treatment of 1,2,4-triazines containing the camphor (168) or methylcyclo-pentane fragment (169) with m-chloroperbenzoic acid gives annelated 1,2,4-triazine 1-oxides 170 and 171, respectively (82JHC1201). 

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 a -halosulfone, required for the Ramberg-Backlund reaction, can for example be prepared from a sulfide by reaction with thionyl chloride (or with N-chlorosuccinimide) to give an a-chlorosulfide, followed by oxidation to the sulfone—e.g. using m-chloroperbenzoic acid. As base for the Ramberg-Backlund reaction have been used alkoxides—e.g. potassium t-butoxide in an etheral solvent, as well as aqueous alkali hydroxide. In the latter case the use of a phase-transfer catalyst may be of advantage. ... 

A 30 g (0.15 mol) quantity of 4-chloro-2.6-diaminopyrimidine is dissolved in 600 ml of hot 3A alcohol, the solution cooled to 0°C to 10°C and 41.8 g (0.24 mol) of m-chloroperbenzoic acid is added. The mixture is held at 0°C to 10°C for 4 hours and filtered. The solid is shaken for 2 hours in 0.24 mol of 10% sodium hydroxideand filtered. The solid is washed with water and dried to yield 19.3 g of crude product. This product Is extracted for 1 hour with 900 ml of boiling acetonitrile to yield 14.8 g (44.7% yield) of 6-amino-4-chloro-1,2-dihydro-1 -hy-droxy-2-iminopyrimidine, melting point 193°C. 

Hydroxychloroquine sulfate m-Chloroperbenzoic acid Alfacalcidol Minoxidil... 

The use of m-chloroperbenzoic acid and HC1 in an aprotic solvent was reported for preparing 2-chloropurine nucleosides (81JOC2819). 

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