Both enantiomers of cis- and trans-fused 3,4,4a,8a-tetrahydro-2H,5H-pyrano[2,3-b]pyran-7-carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse-electron-demand hetero-Diels-Alder/oxa-Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self-assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives.
Enantioselective aldol reactions of acetophenone with β,γ-unsaturated α-ketoesters and cyclic ketones with phenylglyoxal hydrates were realized with cinchona alkaloid-derived thiourea catalysts. The corresponding aldol products were obtained in high yields and good to excellent diastereoselectivities and enantioselectivities (up to 95% ee).
Both enantiomers of cis‐ and trans‐fused 3,4,4a,8a‐tetrahydro‐2H,5H‐pyrano[2,3‐b]pyran‐7‐carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse‐electron‐demand hetero‐Diels–Alder/oxa‐Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self‐assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives.
A highly stereoselective method for achieving the anti-Mannich reaction of aldehydes and ketones with ethyl (4-methoxyphenylimino)acetate was realized using the modularly designed organocatalysts (MDOs) self-assembled from cinchona alkaloid derivatives and (A)-pyrrolidien-3-carboxylic acid in the reaction media. The desired anti-Mannich products were obtained in good to excellent yields (up to 93%), excellent diastereoselectivities (up to 99:1 dr), and good to high enantioselectivities (up to 99% ee).
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