Aluminum oxide stereochemistry

As shown in Scheme 6.13, if the catalyst for the reduction is changed from Pt to Pd, the stereochemistry of the reduction is apparently altered. However, once it is recognized that Pd on alumina (aluminum oxide [AI2O3]) causes isomerization—a rearrangement vide infra) from one alkene to another—faster than reduction occurs, the result is explicable. Thus, (Scheme 6.13) 1,2-dimethylcyclohexene... 

Final clarification of the structure of quinamine was accomplished on the one hand by the production of cinchonamine upon lithium aluminum hydride reduction of the base (6), and on the other hand by the reverse reaction brought about by peracid (18) (Chart I). The reduction is explicable via the ring chain tautomeric hydroxyindolenine (VIII), which is also the primary product of the peracid oxidation of cinchonamine [cf. oxidation of tetrahydrocarbazole (19)]. The oxidation is stereospecific, but the stereochemistry of the introduced C-7 hydroxyl is still unknown. 

Both cis- and tram-isomers were formed from 1-methylcyclohexene in trichloroethylene, as deduced from the complexity of the H-NMR spectrum of the isolated product (21 %)31. Different physical properties and stereochemistry were assigned to the adduct prepared from 1-phenylcyclohexene in the same conditions by different authors31,32, but the possibility that different dimers were isolated by homospecific and heterospecific dimerization should be considered, syn Addition was claimed in one of these reports, since the presumed cis adduct was converted to m-2-phenylcyclohexanamine by reduction with lithium aluminum hydride31. However, oxidation of the tram-adduct afforded the corresponding nitro derivative, whose dipole moment agreed with the value calculated for the tram-product32. 

In fact, a variation of this reaction has been utilized in the well-known Meerwein-Ponndorf-Verley reduction of carbonyl compounds (reverse of Oppenauer oxidation of alcohols) by aluminum isopropoxide The reaction involves a six-centered transition state, wherein the P-hydride is delivered into an incoming carbonyl group [Eq. (6.86)]. The stereochemistry of this reaction has been studied in detail. ... 

Reduction of the ketolactam 390 (having the newly assigned A/B trans stereochemistry) with sodium borohydride followed by reduction of the amide with lithium aluminum hydride gave an amino alcohol. Oxidation of this amino alcohol with chromic acid followed by rereduction with lithium aluminum hydride gave an amino alcohol different from that obtained previously. In the oxidation to the ketone 373, therefore, epimerization at C-9a must have occurred, and the two amine alcohols must have the configurations 391 and 392. Since in both compounds Bohlmann bonds were observed in the IR spectrum, the A/ ring juncture is trans. 

The trialdehyde 38 was obtained in four steps in 60-65% overall yield from trimesic acid (34, Scheme 3). Esterification of 34 with 1-propanol in excess, by refluxing with hydrogen chloride catalyst, leads to triester 35 in quantitative yield. Hydrogenation of 35 in acetic acid solvent (Pt catalyst) yields pure cij,ds-cyclohexane-l,3,5-tricarboxylate ester 36, also in quantitative yield. Reduction of ester 36 with lithium aluminum hydri in tetrahydrofuran solvent produces c ,cis-l,3,5-tris(hydroxymethyl)cyclo-hexane cis,cis-37) in 90-95% yields. Swern oxidation of triol 37 led to cij,c -l,3,5-triformylcyclohexane 38 in 70% yield. The stereochemistry of 38, as well as that of precursors 36 and 37, was established as ca,cis in each case by high resolution H NMR. 

Cyclohexene oxide reacts with azide ion to give an azido alcohol. Subsequent reduction by lithium aluminum hydride gives an amino alcohol. Write the structure of the product showing its stereochemistry. 

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