Modified Oppenauer

Nortricyclanone has been prepared by oxidation of nortri-cyclanol using chromic acid in acetic acid and using a modified Oppenauer reaction. The present procedure is based on the Jones modification of chromic acid oxidations. 

A modified Oppenauer oxidation, using activated neutral chromatographic alumina and chloral in CCI4 at room temperature, allows the oxidation of cyclobutanol in ... 

Aldol cyclization. Exposure of the hydroxy ketone 1 to excess potassium t-butoxide and benzophenone in refluxing benzene provides the o,/S-unsaturated ketone 2 directly/ This transformation involves a modified Oppenauer oxidation followed by aldol closure of the resulting keto aldehyde. The product serves as an intermediate in the synthesis of Elaeocarpus alkaloids. 

The modified Oppenauer oxidation was used in the synthesis of estrone by P. Kocovsiw et al. The tetracyclic did was exposed to aluminum isopropoxide and A/-methyl-piperidine-4-one (oxidizing agent) to obtain the corresponding enone in good yield. The formation of the enone involved the migration of the initial p,y-double bond. The treatment of this enone with TsOH overnight in ether led to the formation of estrone by aromatization. 

The approach previously outlined in Scheme 8 was used to generate numerous TV, d-disubstituted isoquinuclidines. Red-Al reduction of the lactam (83) and subsequent oxidation of the hydroxyl groups to ketones 134 was achieved via a modified Oppenauer procedure [108] using benzophenone and potassium butoxide and was accomplished in 90 minutes and in fair yields. 

In a preliminary study of caranine, it was found that a modified Oppenauer oxidation of the base gave the phenanthridinium compound XXX which was identical with one of the oxidation products of lycorine (102). From this oxidation it was postulated that caranine possesses the lycorine ring system with a hydroxyl group in the 1-position. Subsequent... 

Administration of loganin-8- H (153) 35) to G. ledgeriana plants afforded inactive cinchonine (99) and radioactive quinine (10) (Table I) 36) which contained all the tritium at C-8. The site of radioactivity was secured by chemical means. A modified Oppenauer oxidation of the quinine and workup with DgO-DCl gave radioinactive quinidinone... 

Although the traditional Oppenauer conditions utilized aluminum catalysts, alternative metal alkoxides, for example, chloromagnesium alkoxides, are competent in the transformation.3 In 1945, Woodward devised a new system, which involved the use of potassium r-butoxide, and benzophenone for the oxidation of quinine (29) to quinone (30).13 This was termed the modified Oppenauer oxidation. The traditional aluminum catalytic system failed in this case due to the complexation of the Lewis-basic nitrogen to the aluminum centre. The synthetic flexibility of this procedure was extended by the use of more potent hydride acceptors.46... 

Hydration of the double bond led to a mixture of alcohols, which were separated and heated with potassium hydroxide in diethylene glycol at 225°C in the presence of a trace of hydrazine (H2NNH2) to cause partial demethylation.That was followed by a modified Oppenauer (potassium t-butoxide-benzophenone) oxidation. Then, bromination of the arylketone produced a dibromide that formed a 2,4-dinitro-phenylhydrazone (DNPH) derivative identical to one obtained from 1-bromothe-... 

Potassium tert-butoxide Modified Oppenauer oxidation... 

The lithium aluminum hydride reduction of deacetyldeformopicraline (picrinine, VI) affords deformopicralinol (XXI R = H), whose structural relationship with picralinol (XXI R = CH20H) was confirmed by comparison of their mass spectra. When subjected to a modified Oppenauer oxidation deformopicralinol yielded two products. One was the indole-... 

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