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Whitehead, A.; Sieck, S. R.; Mukherjee, S.; Hanson, P. R., Science of Synthesis, (2005) 21, 923.
Cationic rhodium catalysts have been used for the asymmetric hydrogenation of enamido[52] and enol esters.[53] These catalysts, in conjunction with C2-symmetric diphosphine ligands (DuPHOS and BPE, see Scheme 19), can also asymmetrically hydrogenate acylphosphonate enolates in good ee and yield of the resulting α-hydroxy phosphonates.[54] O-Alkylation of acylphosphonates, formed from acid chlorides 60 and trimethyl phosphite, with benzoic anhydride and 1,8-diazabicyclo[5.4.0]undec-7-ene affords a number of benzoyl enol ethers 61 exclusively as the E-isomer in 43–86% yield (Scheme 19). Treatment of a benzoyl enol ether 61 with a rhodium catalyst under hydrogen pressure (4 atm) gives the desired product 62. Enantiomeric excess ranges from 60–96% and either enantiomer can be obtained depending on the configuration of the chiral rhodium ligand.
Meeeee 88 Meeeeeeee eee Meeeeeeeee Meeeeeeeeeeee ee Meeeeeeeeeeeeee Meeeeeee[88]
| M8 | Meeeee (M*) | Meeeee ee 88 | ee (%) ee 88 | Meeeeeeeee (%) ee 88 ee 88 | Mee |
|---|---|---|---|---|---|
| M | (M,M)-Me-MMM | (–)-(M) | 88 | 88 | [88] |
| M | (M,M)-Me-MeMMMM | (+)-(M) | 88 | 888 | [88] |
| M | (M,M)-Me-MeMMMM | (–)-(M) | 88 | 888 | [88] |
| M | (M,M)-Me-MeMMMM | (–)-(M) | 88 | 888 | [88] |
| M | (M,M)-eMe-MeMMMM | (+)-(M) | 88 | 88 | [88] |
| Me | (M,M)-Me-MMM | (+)-(M) | 88 | 88 | [88] |
| Me | (M,M)-Me-MeMMMM | (–)-(M) | 88 | 888 | [88] |
| Me | (M,M)-Me-MeMMMM | –e | –e | 888 | [88] |
e Meeeeeeeeeeeeee eee eeeeeeeeee.
Meeeeeeeeeee Meeeeeeee
α-Meeeeeeeee Meeeeeeeeeee 88; Meeeeee Meeeeeeee eee Meeeeeeeee Meeeeeeeeeeee:[88]
Meeee e M8 eeeeeeeeee, e Meeeee–Meeeee eeee eee eeeeeee eeee eee eeeeeee eeee eeeee 88 (ee. 8.888 e), eeeee, eeeeeeee MeMM, eee e eeeeeee eeeeeeee (8.888 e). Meeee eeee eeeeee/M8 eeeeee, eee eeee eee eeeeeeeeeee ee ee eeeeeee eeeeeeee ee 8–8 eee ee M8. Mee eeeeeee eee eeeeeee ee ee. Meeeeeeeee eee eeeeeeeeee ee 8M ee 88M MMM eeeeeeee. Mee eeeeeee eee eeeeeeeeeeee, eeee eeeeee eeeeeee e eeeeee eee eeee (MeMMe) ee eeeeee eeeeeeee. Mee ee eee eeeeeeeeee eeee ee eeeeeee ee eee eeeee eeeeeee, eeeeeee eeeeeee eeeeeeeeeeee, ee e eeeeeeeeee ee eeee eeeeeeeeeeeeeeee eeeeeeee eeeeeee-eeeeeeeee α-eeeeeee eeeeeeeeeee eeee eee eeeeeeeeeeeee eeeeeee eeeeeee eeeee eeeeee MMMM (Meeeee eeeeee, MM eeeeeeeee ee 888 ee). Meeeeeeee eeee eeeeeeee ee eeeeeeeeeeeee ee eee eeeeeeeeeeeee eeeeeee eeee eeeeee eeeee 88% Me/M.
References
| [52] | Meee, M. M.; Meeee, M. M.; Meeeeee, M. M., M. Me. Meee. Mee., (8888) 888, 888, eee eeeeeeeeee eeeee eeeeeee. |
| [53] | Meee, M. M.; Meeeeee, M. M.; Meeeeee, M., M. Me. Meee. Mee., (8888) 888, 8888. |
| [54] | Meee, M. M.; Meeeeeee, M. M.; Meeeee, M. M., Mee. Meee., (8888) 8, 888. |
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