Cinchona alkaloids allylic substitution

Another type of Cinchona alkaloid catalyzed reactions that employs azodicarbo-xylates includes enantioselective allylic amination. Jprgensen [51-53] investigated the enantioselective electrophilic addition to aUyhc C-H bonds activated by a chiral Brpnsted base. Using Cinchona alkaloids, the first enantioselective, metal-free aUyhc amination was reported using alkylidene cyanoacetates with dialkyl azodi-carboxylates (Scheme 12). The product was further functionalized and used in subsequent tandem reactions to generate useful chiral building blocks (52, 53). Subsequent work was applied to other types of allylic nitriles in the addition to a,P-unsaturated aldehydes and P-substituted nitro-olefins (Scheme 13). 

Chen and coworkers published a formal [3 + 3]-type reaction to give highly substituted cyclohexenes 8. This domino process consists of an allylic-allylic alkylation of an a,a-dicyanoalkene derived from 1-indanone and Morita-Baylis-Hillman carbonates, following an intramolecular Michael addition, by employing dual orga-nocatalysis of commercially available modified cinchona alkaloid (DHQD)2AQN If (hydroquinidine (anthraquinone-l,4-diyl) diether) and (S)-BINOL. The cyclic adducts... 

High yields of 2-substituted chromans are readily attained from the asymmetric intramolecular oxa-Michael addition reaction of phenols bearing an (f -a,P-unsaturated ketone or thioester moiety mediated by a cinchona-alkaloid-urea-based bifunctional organocatalyst (140BC119). Molecular iodine-catalyzed reaction of phenols with a,P-unsaturated alcohols affords a wide range of 2,2-disubstituted chromans (14T5221). Chiral derivatives result from the intramolecular allylic alkylation of phenols bearing an... 

Chen et al. have found that commercially available modified cinchona alkaloids [(DHQD)2AQN] are outstanding catalysts for the asymmetric allylic alkylation (AAA) reaction of MBH carbonates with a,a-dicyanoolefins 268 or 3-substituted oxindoles 269. Enantioenriched compounds 270 and 271, respectively, with multifunctional frameworks bearing adjacent stereogenic centers were obtained in excellent stereoselectivities (Scheme 3.107). 

In 2008, Shibata et al. disclosed the first successful catalytic enantioselective fluorination based on the use of cinchona alkaloids. Therefore, it was demonstrated that allyl silanes and silyl enol ethers underwent efficient enantioselective fluorodesilylation with NFSI and a catalytic amount of a bis-cinchona alkaloid in the presence of an excess of base to provide the corresponding fluorinated compounds with an F-substituted quaternary carbon centre with enantioselectivities of up to 95% ee (Scheme 5.3). Furthermore, the authors showed that this catalytic system could be applied to the catalytic... 

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