Amine oxides, alkenes from chiral forms

Since alcohols are less effective as hydrogen donors than amines, a PET photoaddition can occur only when the oxidized component of the reaction is the alkene. Furthermore, if the photosensitizer is chiral, the polar addition would occur in an enantiodifferentiating manner to some degree. Thus, the photoaddition of 2-propanol to 1,1-diphenylpropene, when sensitized by chiral naphthalene(di)carbox-ylates, formed the anti-Markovnikov photoadduct with enantiomeric excesses of up to 58% [53]. Unfortunately, the reaction is far from attracting synthetic interest as the yields are still too low. 

Sharpless applied the same principle of using a central metal that can hold a chiral directing group proximal to an alkene substrate in an enantloselective version of the OSO4-catalyzed alkene dihydroxylation (Section 12-11). Here, the essence of the chiral auxiliary is an amine derived from the family of natural alkaloids called the cinchona (Section 25-8). One of these amines is dihydroquinine, which is added in the linked dimeric form shown on the right. Instead of H2O2 as the stoichiometric oxidant (Section 12-11), Fe ... 

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