Direct Catalytic Asymmetric Mannich Reaction with Dithiomalonates as Excellent Mannich Donors: Organocatalytic Synthesis of (R)‐Sitagliptin |
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Authors: | Dr Han Yong Bae Mun Jong Kim Jae Hun Sim Prof?Dr Choong Eui Song |
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Institution: | 1. Department of Chemistry, Sungkyunkwan University, Jangan, Suwon, Korea;2. Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany |
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Abstract: | In this study, dithiomalonates (DTMs) were demonstrated to be exceptionally efficient Mannich donors in terms of reactivity and stereoselectivity in cinchona‐based‐squaramide‐catalyzed enantioselective Mannich reactions of diverse imines or α‐amidosulfones as imine surrogates. Owing to the superior reactivity of DTMs as compared to conventional malonates, the catalyst loading could be reduced to 0.1 mol % without the erosion of enantioselectivity (up to 99 % ee). Furthermore, by the use of a DTM, even some highly challenging primary alkyl α‐amidosulfones were smoothly converted into the desired adducts with excellent enantioselectivity (up to 97 % ee), whereas the use of a malonate or monothiomalonate resulted in no reaction under identical conditions. The synthetic utility of the chiral Mannich adducts obtained from primary alkyl substrates was highlighted by the organocatalytic, coupling‐reagent‐free synthesis of the antidiabetic drug (?)‐(R)‐sitagliptin. |
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Keywords: | β -amino thioesters asymmetric catalysis dithiomalonates Mannich reaction organocatalysis |
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