Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions |
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| Authors: | Tamás Nemcsok Zsolt Rapi György Keglevich Alajos Grün Péter Bakó |
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| Affiliation: | Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budapest, Hungary |
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| Abstract: | A few new d ‐mannitol‐based monoaza‐15‐crown‐5 type chiral lariat ethers and 18‐crown‐6 type macrocycles were synthesized. These crown compounds were used as phase transfer catalysts in asymmetric Michael addititons and in a Darzens condensation under mild conditions to afford the corresponding products in a few cases in good to excellent enantioselectivities. In the Michael addition of diethyl acetoxymalonate to trans‐chalcone, in the addition of diethyl acetamidomalonate to ß‐nitrostyrene, in the reaction of diethyl bromomalonate with benzylidene malononitriles, in the cyclopropanation reaction of diethyl bromomalonate and 2‐benzylidene‐1,3‐indandione, and in the Darzens condensation of α‐chloroacetophenone with benzaldehyde, maximum enantioselectivities of 39%, 65%, 99%, 56%, and 62%, respectively, were obtained in the presence of the d ‐mannitol‐based macrocycles as the catalysts. |
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| Keywords: | asymmetric Michael addition Darzens condensation phase transfer catalysis sugar‐based crown ethers |
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