Direct asymmetric aldol reaction using MBHA resin-supported peptide containing L-proline unit

MBHA resin-supported tripeptide catalyst system containing L-proline unit has been developed for use in the direct asymmetric aldol reaction of acetone and aldehydes, which afford the corresponding products with satisfactory isolated yields and enantiomeric excesses. 2009 Hong Bin Zou. Published by E]sevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Highly Enantioselective Direct Asymmetric Aldol Reaction Catalyzed by 4,5-Methano-L-proline

The 4,5-methano-L-proline was used as chiral organocatalysts in direct asymmetric aldol reactions.Under the optimal conditions,excellent enantioselectivities(up to 99%ee)were obtained with high chemical yields(up to 95%)for a series of aldehydes using only 5 mol%catalyst loading.To show the practicality of the method,the reaction was tested at a large scale.The reaction was complete in 16 h,and the aldol product was obtained in 86%yield and 93%ee.

Tetrahydrobenzo[5]helicenediol derivatives as additives for efficient proline-catalyzed asymmetric List-Lerner-Barbas aldol reactions of bulky aldehyde substrates

Tetrahydrobenzo[5]helicenediol（THB-[5]HDIOL） derivatives as additives for the efficient prolinecatalyzed asymmetric List-Lerner-Barbas（LLB） aldol reactions of bulky aldehyde substrates was described. It was found that with dibromo-substituted helical diols P-4 a/M-4 a as additives, the prolinecatalyzed LLB aldol reaction of 9-anthraldehyde and acetone gave the product in 83% yield and 99% ee.Transition state models revealed an edge-to-face p-p stacking between the anthracenyl group in TS（R）and the phenyl group of the additive, which might result in the high enantioselectivity.

Asymmetric Direct Aldol Reaction of Cyclohexanone Catalyzed by （ N＇-BenzyI-N＇-D-prolyl）-trans-4- hydroxy-L-proline Hydrazide

A new proline catalyst, namely （N＇-benzyl-N＇-D-prolyl）-trans-4-hydroxy-L-proline hydrazide, has been prepared and proved to be a superior catalyst for the asymmetric aldol reaction of cyclohexanone and aromatic aldehydes, affording up to 98 ： 2 dr and 98% ee.

L-Proline catalyzed aldol reactions between acetone and aldehydes in supercritical fluids:An environmentally friendly reaction procedure

The direct asymmetric aldol reaction between various aldehydes and acetone catalyzed by L-proline catalyst was successfully carried out in supercritical CO_(2) (scCO_(2)) and 1,1,1,2-tetrafluoroethane (R-134a) fluids.The enantioselectivity of 84% ee to the targeted product was achieved under 20 MPa,40 °C,and 15 mol% of the catalyst in supercritical CO_(2) (scCO_(2)) fluid.The effects of reaction parameters,such as temperature,pressure,catalyst loading and different substituted aldehydes on both enantioselectivity and aldol yield were discussed.The titled reaction was also performed in 1,1,1,2-tetrafluoroethane,and the obtained results were compared with those in scCO2.This new reaction procedure provides an environmental asymmetric aldol reaction system as compared with that in organic solvents.