Cinchona alkaloids cyclopropanation

The asymmetric cyclopropanation of a-bromocyclohexenone with cyanoacetate 31 has been achieved under phase-transfer conditions by the use of cinchona alkaloid-derived catalyst, which constructs chiral quaternary carbons on the cyclopropane... 

Enantioselective variants of these cyclopropanation reactions were achieved by replacing DABCO with cinchona alkaloid catalysts 53a-d [100-102]. 

In the same year, Connon and coworkers [63] reported that the chiral bifunctional cinchona alkaloid-based thiouea 81a is also able to catalyze the addition of dimethyl chloromalonate 196 to nitroolefins 124, leading to the Michael adduct that cyclizes to form the cyclopropane 197 in the presence of DBU. Almost single diastereomeric nitrocyclopropanes (>98% de) were obtained in good yields. However, the enantios-electivity obtained with this type of catalyst was poor (<47% ee) (Scheme 9.69). 

The potential of Cinchona alkaloids as nucleophilic catalysts was also demonstrated in Gaunl s cyclopropanation approach by reacting a-halo carbonyl compounds with Michael acceptors in the presence of catalytic amounts of 0-protected Cinchona alkaloids (468—470). This reaction is thought to proceed... 

Scheme 118 Cinchona alkaloid-catalyzed cyclopropanation in the synthesis of members of the oxylipin family...

Johansson CCC, Bremeyer N, Ley SV, Owen DR, Smith SC, Gaimt MJ (2006) Enantioselective Catalytic Intramolecular Cyclopropanation Using Modified Cinchona Alkaloid Organocatalysts. Angew Chem Int Ed 45 6024... 

An enantioselective organocatalytic cyclopropanation reaction via chiral ammonium ylides was also developed. The reaction operates under an 8 2 process of a-halocarbonyl compounds by means of cinchona alkaloid catalysts, allowing the... 

Johansson, C. C., Bremeyer, N., Ley, S. V., Owen, D. R., Smith, S. C., Gaunt, M. J. (2006). Enantioselective catalytic intramolecular cyclopropanation using modified cinchona alkaloid organocatalysts. Angewandte Chemie - International Edition, 45, 6024-6028. 

The simple C9 ethers derived from the natural cinchona alkaloids are infrequently applied in organocatalysis. A relatively recent example concerns an asymmetric cyclopropanation reaction with the C9 O-methyl derivatives of 1 and 4, respectively (Scheme 6.13) [35]. The functionalized cyclopropanes were obtained in excellent diastereo- and enantioselectivity as well as in high yields. 

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