Cinchonidine-derived catalysts hydrogenation with

For the hydrogenation of a-functionalized ketones, the Pt on alumina system, modified with cinchonidine or its simple derivative 10,11-dihydro-O-methyl-cinchonidine, is the best catalyst [43, 44, 46]. This so-called Orito system [47] is... 

In 2006, Ohkata and coworkers found that the natural cinchonidine (CD) functions as a Brans ted base catalyst (1 mol%) in the reaction between chloromethyl ketones 193 and (3-substituted methylidenemalononitriles 194 to furnish the corresponding tetrasubstituted trans-cyclopropanes 195 with enantioselectivities of up to 82% ee (Scheme 9.68) [62]. The 9-0H-protected derivatives provided almost no enantios-electivity, indicating that the hydrogen bonding is crucial for stereoinduction. 

As the cinchona alkaloids contain a nucleophilic nitrogen center, they can be alkylated at this position. Thus, cinchonidine reacts with benzyl chlorides to form quaternary salts, e.g., 9 and 108, which are useful as chiral phase-transfer catalysts (see Section D.1.5.2.4. for enantioselec-tive additions to azaenolates, and D.4.1. for the oxidation of enolates). Further modification by catalytic reduction of the double bond (hydrogen/platinum) leads to the corresponding dihydrocinchonidine derivatives. 

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