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Enantioselective Synthesis of Quaternary Carbon Stereocenters: Addition of 3‐Substituted Oxindoles to Vinyl Sulfone Catalyzed by Pentanidiums 下载免费PDF全文
Dr. Lili Zong Shubo Du Kek Foo Chin Dr. Chao Wang Prof. Dr. Choon‐Hong Tan 《Angewandte Chemie (International ed. in English)》2015,54(32):9390-9393
A pentanidium‐catalyzed highly enantioselective conjugate addition of 3‐alkyloxindoles to phenyl vinyl sulfone has been demonstrated. This approach allows the construction of 3,3‐dialkyl‐substituted oxindole frameworks with high yield and excellent enantioselectivity (up to 99 %) under simple phase‐transfer conditions. A variety of oxindoles bearing all‐carbon quaternary stereogenic centers were obtained in the presence of 0.25 mol % pentanidium. Meanwhile, practicality was illustrated by a gram‐scale asymmetric synthesis of two 3,3‐dialkyl‐substituted oxindoles. The resulting adduct can be smoothly transformed to the natural product analogue in a short synthetic route. 相似文献
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Dr. Jingyun Ren Dr. Xu Ban Dr. Xin Zhang Dr. Siu Min Tan Dr. Richmond Lee Prof. Dr. Choon-Hong Tan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9140-9143
We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium-catalyzed kinetic resolution (KR) of racemic tertiary bromides under base-free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway. 相似文献
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Jingyun Ren Xu Ban Xin Zhang Siu Min Tan Richmond Lee Choon‐Hong Tan 《Angewandte Chemie (International ed. in English)》2020,59(23):9055-9058
We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium‐catalyzed kinetic resolution (KR) of racemic tertiary bromides under base‐free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway. 相似文献
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Catalytic Enantioselective Alkylation of Sulfenate Anions to Chiral Heterocyclic Sulfoxides Using Halogenated Pentanidium Salts 下载免费PDF全文
Lili Zong Xu Ban Choon Wee Kee Prof. Dr. Choon‐Hong Tan 《Angewandte Chemie (International ed. in English)》2014,53(44):11849-11853
We report halogenated pentanidiums as phase‐transfer catalysts for the asymmetric alkylation of sulfenate anions to various sulfoxides with high enantioselectivities (up to 99 % ee) and yields (up to 99 %). This approach gives access to enantioenriched heterocyclic sulfoxides that might not be compatible with strong oxidants or organometallic reagents. Computational studies have revealed that the multiple noncovalent interactions such as halogen bonds and nonclassical hydrogen bonds are involved. 相似文献
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