By Oppenauer oxidation

A carbonyl group cannot be protected as its ethylene ketal during the Birch reduction of an aromatic phenolic ether if one desires to regenerate the ketone and to retain the 1,4-dihydroaromatic system, since an enol ether is hydrolyzed by acid more rapidly than is an ethylene ketal. 1,4-Dihydro-estrone 3-methyl ether is usually prepared by the Birch reduction of estradiol 3-methyl ether followed by Oppenauer oxidation to reform the C-17 carbonyl function. However, the C-17 carbonyl group may be protected as its diethyl ketal and, following a Birch reduction of the A-ring, this ketal function may be hydrolyzed in preference to the 3-enol ether, provided carefully controlled conditions are employed. Conditions for such a selective hydrolysis are illustrated in Procedure 4. 

The orally active progestational agent 17a-ethynyltestosterone (56) was subsequently obtained by Oppenauer Oxidation. Similarly ethynyla-tion of 3-ethoxyandrosta-3,5-dien-17-one followed by acid hydrolysis afforded the 17a-ethynyl compound (56). ... 

Hydrolysis of the acetate (71) followed by Oppenauer oxidation gives B-norcholest-4-en-3-one in high yield. An analogous reaction sequence can be used to prepare B-norprogesterone and derivatives of B-nortestosterone from pregnenolone acetate and dehydroepiandrosterone acetate, respectively."" ... 

Rapoport, H., Naumann, R., Bissel, E.R., Bonner, R.M. The preparation of some dihydro ketones in the morphine series by Oppenauer oxidation, J. Org. Chem. 1950, 15, 1103-1107. 

Dehydrorotenone 1 can be readily transformed into rotenone 2 by reduction of the chromone to the chromanol followed by Oppenauer oxidation. Two elegant syntheses of dehydrorotenone 1 used DCC as a key reagent as follows (i) treatment of derrisic acid 3 with DCC/EtjN followed by reaction of the intermediate thus obtained with sodium propanoate in ethanol gave 1. (ii) Condensation of tubaic acid 4 with the pyrrolidine enamine derived from 5 in the presence of DCC also gave 1. 

The addition of a-deprotonated alkyl halides to alkenes or carbonyl compounds can, because of the good leaving-group properties of halides, also lead to formation of cyclopropanes [292] or epoxides [187, 304, 306, 310], respectively. Because of the inherent instability of a-halo organometallic compounds, these intermediates should be handled carefully and on a small scale only. The ketone produced by the last reaction in Scheme 5.34 is probably formed by Oppenauer oxidation of the intermediate alcohol by the excess benzaldehyde [310],... 

Cephalotaxinone (C18H19N04) was first isolated and characterized from C. harringtonia var. harringtonia (89) and later from C. fortunei (PS). In the IR spectrum of this material, the hydroxyl group of cephalotaxine was absent but a carbonyl absorbance at 1720 cm 1 was present. A shift in the olefinic absorbance from 1665 to 1625 cm 1 suggested an enone structure. Cephalotaxinone was found to be identical to the product 112 formed by Oppenauer oxidation of cephalotaxine (105a) (see Scheme 30). This also established the stereochemistry of 112 at C-4 and C-5. 

Cinchonine (CVI) can be transformed into dihydrocorynantheane (XV) by a series of reactions which first changes it into 9-benzoy]-2-oxyhexahydrocinchonine (CVII). The latter reacts with cyanogen bromide to give CVIII and this in turn under alkaline conditions suffers reduction and rearrangement to CIX, which on further reduction with lithium aluminum hydride followed finally by Oppenauer oxidation generates 3-epidihydrocorynantheane (CX). This can be isomerized by known means to dihydrocorynantheane (XV) (71). 

The diazepinol (40) is readily obtained from ketone (10) with sodium borohydride and is converted back into 10 with A -bromoacetamide or by Oppenauer oxidation.32 In a similar manner 32 and the AT-acetyl derivative of 10 can be reduced to carbinols. Acylation of 40 or treatment of the reduction product of 32 with acetic acid gave the trans-annular oxide (41). The carbinol (40), the acetyl carbinol from 10, the oxide (41), and the diacetyl analog of 41 all undergo rearrangement with mineral acid to give the four furfurylhydrazines (42).32... 

Thus it has been used as the first stage to obtain the starting material for the microbiological method with CSD-10 and simplified in more recent work leading to a synthesis of estrone in four steps from 3p-acetoxy-19-hydroxyandrost-5-en-17-one (ref. 116). Cholesteryl acetate was transformed by standard methods to the required androstane compound shown in the following scheme, which with hypobromous acid followed by lead tetraacetate and zinc reduction (cf. ref. 115) afforded the 19-hydroxy derivative. This with thallium nitrate in dioxan underwent loss of formaldehyde and hydration with water to afford the 19-nor-10p-alcohol in 70% yield. The diol obtained by saponification was converted by Oppenauer oxidation with N-methylpiperid-4-one as hydride aceptor (ref. 117) and afforded a 78% yield of the enone which was transformed almost quantitatively into... 

An informative and amusing background to that unique material, camphor, has appeared. Its preparation by Oppenauer oxidation of the epimeric borneols occurs without epimerization. Epimerization does not occur in the presence of potassium t-butoxide in t-butyl alcohol, but it does with potassium isopropoxide in propan-2-ol." The reaction of camphor with phosphoric acid yields a complex mixture of m- and p-cymenes, 3,4-dimethylethylbenzene, 1,2,3,4-and 1,2,3,5-tetramethylbenzene, fenchone, carvenone, and carvacrol. A very detailed examination of the metal-ammonia reduction has revealed an intermediate camphor analogue of pinacol formed by association of a camphor anion radical with the metal cation. This intermediate was isolated and characterized. Other effects are discussed, such as that of adding a large excess of metal salt (LiBr, KBr, or NH Cl)." ... 

Solanidine on hydrogenation in acetic acid in the presence of platinum oxide yields solanidan-3/3-ol (IX) in which the rings A and B are fused in the trans positions. Its epimer, solanidan-3a-ol (XI) is obtainable by reacting the p-toluenesulfonate of IX with potassium acetate. The ketone X, obtainable from IX by Oppenauer oxidation also yields XI when it is reduced catalytically in acetic acid containing hydrogen bromide in the presence of platinum oxide (6, 23, 40, 45). 

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