Oppenhauer oxidation

In the case of the synthesis of cortisone, Oppenhauer oxidation of hydroxyl group at C(14) -after the necessary acetalisation of the unsaturated carbonyl group-leads to intermediate 16a. which, under the basic conditions of Oppenhauer oxidation, spontaneously isomerises to 17a. with the more stable trans-BIC junction. An additional advantage of this sequence is that the carbonyl group activates the C(13) vicinal position, and allows not only the introduction of the methyl group, but facilitates the construction of ring D of the cortisone molecule. 

Oppenhauer oxidation, 886, 887J, 888 Orange II, 621, 625, 745 Organocadmium compounds, syntheses with, 933-935... 

Intramolecular hydride transfer under MPV reduction conditions occurs in substrate (25) with complete stereospecificity to generate (26).275 A 2 1 mixture of product to reactant was observed, irrespective of reaction tune or relative excess of Al(0 Pr)3, indicative of an equilibrium, hitennolecular hydride transfer to give (27) does not occur and the absence of the epimer of (25) implies that complete stereodifferentiation also occurs in the reverse process (Oppenhauer oxidation). Stereodifferentiation under... 

S)-(+)-carvone. The key steps were Baeyer-Villiger oxidation, Oppenhauer oxidation, Meerwein-Ponndorf-Verley reduction, a stereospecific Grignard addition, and an intramolecular Sn2 reaction. 

Metals other than ruthenium also have the potential to produce diverse DKR methods. But although some rhodium, iridium and aluminium complexes are known to catalyse the racemisation of alcohols, only a few have proved to be compatible with enzymatic reactions. In 1996, Williams and colleagues demonstrated the compatibility of enzymes and rhodium complexes by reporting the first example of racemisation of a secondary alcohol through rhodium-catalysed Oppenhauer oxidation/Meerwein Ponndorf Verley reduction with concomitant acylation of one enantiomer with a lipase from Pseudomonas fluorescens (PFL) (Scheme 4.45). ... 

Also alcohols can be submitted as substrates to the decarbonylation with rhodium catalysts, provided an Oppenhauer oxidation precedes the reaction (Scheme 8.7) [9]. The tandem reaction with an iridium-based Oppenhauer catalyst was exemplified with 1-nonanol in benzophenone as solvent and gave M-octane in 63% yield. 

Scheme 8.7 Decarbonylation of 1-nonanol by a tandem (Oppenhauer oxidation)-decarbonylation sequence.

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