Asymmetric hydrogenation of α,β-unsaturated phosphonates with Rh-BisP* and Rh-MiniPHOS catalysts: Scope and mechanism of the reaction
- †Department of Chemistry, Faculty of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan; ‡COE Laboratory, Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan; and ¶Department of Chemistry, Moscow State University, Moscow 119899, Russia
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Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved December 17, 2003 (received for review October 28, 2003)
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Scheme 1. -
Fig. 1.Section plots of the phase-sensitive 1H—1H NOESY spectrum of catalyst–substrate complex 3. (Left) Only negative (exchange) cross-peaks are shown. (Right) Only positive (NOE) cross-peaks are shown.
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Fig. 2.Operation of either unsaturated or dihydride pathway is possible on low-temperature hydrogenation of a catalyst–substrate complex.
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Fig. 3.Section plots of 1H (400 MHz, CD3OD), 13C (100 MHz, CD3OD; spectra obtained by using α-13C-labeled 1), and 31P (162 MHz, CD3OD) NMR spectra of intermediates observed in low-temperature experiments. (a) The sample obtained by mixing the CD3OD solutions of 1 and 2 at –100°C, spectrum taken at –95°C. (b) The same sample as in a after raising the temperature to –70°C. (c) The same sample as in a after raising the temperature to –30°C and recooling to –60°C. (d) The sample obtained by hydrogenation of the CD3OD solution of 4 for 10 min at –30°C, spectrum taken at –60°C.
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Fig. 4.Transformations taking place when 1 was reacted with 4 at –100°C.
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Fig. 5.Possible side process in the low-temperature reaction of 1 with 4.
Footnotes
- Copyright © 2004, The National Academy of Sciences
