Stereoselective Dithiophosphorylation of Cinchona Alkaloids: Easy Approach to Prospective Chiral Ligands and Organocatalysts |
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Authors: | Mariola Zielińska-Błajet Jacek Skarżewski |
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Institution: | Department of Organic Chemistry, Faculty of Chemistry, Wroc?aw University of Technology, Wybrze?e Wyspiańskiego 27 , Wroc?aw , Poland |
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Abstract: | Abstract The 9-mesylates of Cinchona alkaloids reacted with HSP(S)(OEt)2 in benzene at 50°C to give the corresponding O,O-diethyl-dithiophosphates of the alkaloids with complete inversion of configuration at the 9-C stereogenic centers (3 examples, 42–45% yields). Also O-ethyl-dithiophosphoric acid derivative of 9-epi-quinine was obtained. The configuration of the stereogenic centers were established using homo- and hetero-NOE NMR techniques and comparing the experimental and calculated (GIAO/DFT) spectra. The dithiophosphates of alkaloids were tested as chiral ligands in the Pd-catalyzed allylic alkylation of dimethyl malonate with rac-1,3-diphenylprop-2-enyl acetate and in the Cu-catalyzed asymmetric Henry reaction and gave the respective product with up to 51% ee. Quinine O,O-diethyl-phosphorodithioate was also tested as a novel potential chiral solvating agent for amino acids (N-Boc-phenylglycine) in 31P and 1H NMR spectroscopy. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental files: Additional figures] |
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Keywords: | O O-diethyl-phosphorodithioates of alkaloids dithiophosphates asymmetric synthesis stereoselectivity |
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