- Harnessing Additional Capability from in Water Reaction Conditions: Aldol versus Knoevenagel Chemoselectivity
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Aldol reaction chemoselectivity, racemic or enantioselective, has not been previously demonstrated in the presence of Knoevenagel active functional groups. Here, we show that unhindered β-diketones remain unreacted while a ketone moiety undergoes a highly
- Ali El Damrany Hussein, Hussein,Debnath, Samarpita,Goswami, Falguni,Hussain, Ishtiaq,Karn, Alka,Nakka, Srinuvasu,Nugent, Thomas C.
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supporting information
p. 3539 - 3545
(2021/06/12)
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- Advances towards highly active and stereoselective simple and cheap proline-based organocatalysts
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Ten 4-acyloxy-L-prolines were screened as catalysts at loadings of 2-0.1 mol-% for the direct asymmetric aldol reaction in water by using variable amounts of water. Among them, a new catalyst, the L-proline carrying a trans-4-(2,2-diphenylacetoxy) group, and a catalyst previously synthesized by us, the L-proline carrying a trans-4-(4-phenylbutanoyloxy) group, were found to be excellent catalysts for the aldol reaction between cyclohexanone or cyclopentanone and substituted benzaldehydes when employed in only 1 and 0.5 mol-%,respectively, at room temperature without additives. For such catalysts, high turnover numbers were obtained, which are among the highest values obtained for enamine organocatalysis. Finally, these catalysts can be synthesized by direct O-acylation from inexpensive molecules and successfully used in scaled-up reactions. Highest activity and selectivity at minor expense! Simple and cheap 4-acyloxy-L-prolines were easily prepared and successfully employed in the direct asymmetric aldol reaction in water by using a loading of2-0.1 mol-%. Interestingly, high turnover numbers, among the highest values ever reported for enamine organocatalysis, were obtained.
- Giacalone, Francesco,Gruttadauria, Michelangelo,Agrigento, Paola,Lo Meo, Paolo,Noto, Renato
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experimental part
p. 5696 - 5704
(2010/12/25)
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