Olefin oxidative cleavage

MALAPRAOE LEMIEUX JOHNSON Olefin (dfoO cleavage Oxidative cleavage of 1,2-glycols to two cart nyls (Malaprade) or direct oxidation o( olefins IO4 and OSO4 catalyst (Lenveux Johnson)... 

Glycol and o -hydroxy acid cleavage Oxidative decarboxylation Oxidative rearrangement of olefins... 

High-valent ruthenium oxides (e. g., Ru04) are powerful oxidants and react readily with olefins, mostly resulting in cleavage of the double bond [132]. If reactions are performed with very short reaction times (0.5 min.) at 0 °C it is possible to control the reactivity better and thereby to obtain ds-diols. On the other hand, the use of less reactive, low-valent ruthenium complexes in combination with various terminal oxidants for the preparation of epoxides from simple olefins has been described [133]. In the more successful earlier cases, ruthenium porphyrins were used as catalysts, especially in combination with N-oxides as terminal oxidants [134, 135, 136]. Two examples are shown in Scheme 6.20, terminal olefins being oxidized in the presence of catalytic amounts of Ru-porphyrins 25 and 26 with the sterically hindered 2,6-dichloropyridine N-oxide (2,6-DCPNO) as oxidant. The use... 

The periodate olefin cleavage generated large amounts of colloidal MnO2 waste and sodium iodate (NalOj). The process therefore involved multiple unit operations and suffered from poor volume productivity and oxidation efficiency (three out of four available oxygens in NalO4 are wasted). 

We therefore employed a similar combination of catalytic Ru , with NaOCl as oxidizing agent, to the intermediate 38 to effect endocylic olefin cleavage affording dioic acid 39 (or corresponding monomethyl ester) in comparable yield, as shown in Scheme 14.12. 

Similarly to oxidative olefin cleavage with periodate, the first intermediate formed is ester 35, here a perruthenate at the oxidation level +VI1 A -elimination releases ketone 6 and the mthenium(V) acid 36 /V-Methylmorpholine-N-oxide (NMO) serves in this case to regenerate the perruthenate(VII) speck s, and must therefore be introduced in stoichiometric quantity. 

The second step consists of an oxidative olefin cleavage. 

Whereas C-H bond cleavage has been used only rarely, e.g. in adamantane [103], C-C bond rupture is more common, but only in strained carbocycles [104-106]. C-N bond cleavage is observed in azoalkane + decomposition [106d], although little synthetic use has been elaborated [107]. In contrast, C-Sn bond cleavage in alkyl-staimanes has been developed into a novel alkylation of a, -unsaturated ketones [108] and a versatile alkylation of electron-poor olefins [109]. Oxidative Si-Si [110] and Ge Ge bond cleavage [102] have also found use. 

C 0 04 Treatment of poly (vinylpyiidine) with OsO..206 Bis-hydroxylation of alkyl- and arylsubstituted olefins, as well as of a,p-unsat. esters, ketones or aliylic alcohols. In the presence of a sec. oxidant catalytic amounts of polymer-bound OSO4 are needed. Aldehydes from olefins by oxidative cleavage using simultaneously polymer-bound OSO4 and NalQj. O ... 

Intermediate (61) has also been taken forward by a new procedure whereby the ethylene ketal, by olefin cleavage, esterification, Baeyer—Villiger oxidation and lactonisation, afforded (66a), of which the formyl derivative (66b) on ozonolysis and acetylation gave (67). PGEi then followed via olefin cleavage and Wittig elaboration [65]. 

The two-phase permanganate oxidation of olefins generally affords products of oxidative cleavage. Weber and Shepherd found that when benzyltriethylammonium chloride was used as catalyst and the temperature was maintained near 0°C, internal olefins were oxidized by basic permanganate in dichloromethane to the corresponding czs-glycols in moderate yields (Eq. 11.3) [6]. Cyclohexene, c/s-cyclooctene and trans-cyclododecene were dihydroxylated by this method in 15%, 50%, and 50% yields... 

Primary and secondary alcohols are oxidized to the corresponding carboxylic adds and ketones, respectively, [Eqs. (2) and (3)] [9j. Olefins undergo oxidative cleavage to afford the carbonyl compounds [Eqs. (4) and (5)] [10], while dx-dihydroxylation occurs selectively when the reaction is carried out in a short period of time (0.5 min) at 0°C in EtOAc-CHjCN-HiO [Eq. (6)] [lOg]. 

Oxidation of olefins and dienes provides the classic means for syntheses of 1,2- and 1,4-difunctional carbon compounds. The related cleavage of cyclohexene rings to produce 1,6-dioxo compounds has already been discussed in section 1.14. Many regio- and stereoselective oxidations have been developed within the enormously productive field of steroid syntheses. Our examples for regio- and stereoselective C C double bond oxidations as well as the examples for C C double bond cleavages (see p. 87f.) are largely selected from this area. 

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