Ephedrine intramolecular

Metal alkoxides undergo alkoxide exchange with alcoholic compounds such as alcohols, hydro-xamic acids, and alkyl hydroperoxides. Alkyl hydroperoxides themselves do not epoxidize olefins. However, hydroperoxides coordinated to a metal ion are activated by coordination of the distal oxygen (O2) and undergo epoxidation (Scheme 1). When the olefin is an allylic alcohol, both hydroperoxide and olefin are coordinated to the metal ion and the epoxidation occurs swiftly in an intramolecular manner.22 Thus, the epoxidation of an allylic alcohol proceeds selectively in the presence of an isolated olefin.23,24 In this metal-mediated epoxidation of allylic alcohols, some alkoxide(s) (—OR) do not participate in the epoxidation. Therefore, if such bystander alkoxide(s) are replaced with optically active ones, the epoxidation is expected to be enantioselective. Indeed, Yamada et al.25 and Sharp less et al.26 independently reported the epoxidation of allylic alcohols using Mo02(acac)2 modified with V-methyl-ephedrine and VO (acac)2 modified with an optically active hydroxamic acid as the catalyst, respectively, albeit with modest enantioselectivity. 

The reaction of 1,2-allenyl sulfones with (-(-ephedrine led to enantiomerically pure 1,3-oxazolidines 216 via the formation of a conjugated enamine and subsequent intramolecular Michael addition [115]. 

The effect of temperature on the reduction of nitro-alkanes has been extensively exploited in the synthesis of cp-ephedrine analogues [i5,21,22] starting from 1-aryl-2-nitropropenes which are easily converted to the substrates 2. Reduction of these nitrocompounds below 20° C affords the hydroxylamine. The amine is formed above 55° C. Neutralisation of either reaction mixture causes rapid intramolecular migration of the acetyl group from oxygen to nitrogen, a reaction which implies a... 

It has recently been shown that when the tetrahedral intermediate of the reaction is cyclic, it is a better donor of nucleophilic CF3. These cyclic intermediates can be generated intramolecularly from trifluoroacetamides or trifluorosulfmamides derived from (9-silylated ephedrine. These reagents are able to trifluoromethylate aldehydes and ketones, even in the case of enolizable substrates, as a strong base is not required (Figure 2.34). However, while the source of CF3 is chiral, there is no chirality transfer to the addition product, and the replacement of ephedrine by other chiral amino alcohols did not show any improvement. " Similar to asymmetric trifluoromethylation with the Ruppert reagent, only the use of a fluoride salt of cinchonine can increase the enantioselectivity. " " ... 

In this enantiodifferentiating photoreduction, the chiral amine plays two roles, as a chiral inductor and as an electron donor. Irradiation of 25 (Scheme 10) in a hexane slurry of unmodified NaY zeolite gave only the intramolecular hydrogen abstraction product 26. However, photolysis of 25 coimmobilized with ephedrine, pseudoephedrine, or norephedrine in NaY supercages afforded the reduction product 27 along with 26. It is clear that the immobilized amine plays the decisive role in the photoinduced electron-transfer reduction of 25, since 27 was not formed in unmodified or (— )-diethyl tartrate-modified zeolites. Consequently, the ee of obtained 27 was independent of the loading level of the chiral inductor. 

Schreiber utilized oxazolidine 220, derived from ephedrine, as an auxiliary for asymmetric hetero-Diels-Alder reactions (Scheme 17.31) [113]. In an experiment that anticipates subsequent developments in organic catalysis, condensation of 220 with aldehyde 219 led to covalent attachment of the auxiliary to the substrate, generating enamine 221. The stage was thus set for intramolecular cycloaddition, which afforded 222 as a 17 1 mixture of diaster-eomers. The dihydropyran 222 served as a key intermediate in the synthesis of the macrolide antibiotic brefeldin C (223). 

The OH group in ephedrine can engage in intramolecular hydrogen bonding, even in dilute... 

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