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Cinchonidine catalyzed the cyclopropanation reaction between chloromethyl ketones and β-substituted methylidenemalononitriles to give trans-cyclopropanes with enantioselectivity up to 82% ee. Experimental evidence suggests that cinchonidine functions as a chiral Brønsted base catalyst in the reaction and hydrogen bonding is essential for inducing high enantioselectivity.
The reaction between an α-pyridinium acetamide bearing an 8-phenylmenthyl group as the chiral auxiliary and β-substituted methylidenemalononitriles gave rise to trans-cyclopropanes with diastereomeric ratios of up to 98:2. For most of the reactions, the absolute stereochemistry of the major product was found to be opposite of that of the major products of the reaction of the corresponding ester series,...
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