High acceleration of the direct aldol reaction cocatalyzed by BINAM-prolinamides and benzoic acid in aqueous media |
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| Institution: | 1. Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University, Houston, TX 77004, USA;2. Department of Biotechnology, Faculty of Engineering, Karpagam Academy of Higher Education, Coimbatore, India;3. Department of Pharmaceutical Sciences, Maharshi Dayanand University, Rohtak, India;4. Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India;1. Key Laboratory of Ion Beam Bio-engineering, Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, China;2. University of Science and Technology of China, Hefei 230029, Anhui, China;1. Department of Theoretical Physics, Faculty of Physics, Vilnius University, Saul?tekio 9-III, LT-10222 Vilnius, Lithuania;2. Institute of Physics, Center for Physical Sciences and Technology, Savanori? 231, LT-02300 Vilnius, Lithuania;1. State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China;2. Department of Obstetrics and Gynecology, Tongren Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200336, China;1. Department of Chemistry, Karamanoglu Mehmetbey University, 70100 Karaman, Turkey;2. Department of Chemistry, Necmettin Erbakan University, 42099 Meram, Konya, Turkey |
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| Abstract: | The enantioselective direct aldol reaction, organocatalyzed by recoverable BINAM-prolinamide derivatives can be highly accelerated by a catalytic amount of a carboxylic acid without a detrimental of the obtained enantioselectivities. From the study of suitable acids and reaction conditions, benzoic acid in aqueous DMF or in water was shown to give the best results with high yields and enantioselectivities. Thus, the reaction between p-nitrobenzaldehyde and acetone catalyzed by (Sa)-BINAM-l-Pro and benzoic acid can be carried out at ?20 °C in only 8.5 h to give the expected product with 86% ee. In the case of butan-2-one, the iso- and the anti-isomers are obtained in a 1:1 isomer ratio up to 99% ee. Cyclohexanone gives the anti-aldol in up to 99% dr and 97% ee in only 2 h. The opposite diastereoselectivity is obtained in the case of cyclopentanone with lower ee up to 65% for the syn and 85% for the anti-isomer. |
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