Jacobsen Catalytic Assymetric Epoxide-Opening Reactions

Jacobsen Catalytic Assymetric Epoxide-Opening Reactions -...

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t -Bu t -Bu NN t -Bu t -Bu O O M H H t -Bu t -Bu t -Bu t -Bu O O Cr Cl H H M = Co(O 2 CCH 3 )(H 2 O) ( S , S )- 5 ( R , R )- 6 R OH OH R O R O R O R OH OH R R O R O H 2 O R O R OH OH O N O Fmoc H 3 C H 3 C O N 3 OH N Fmoc N 3 OH H 3 C H 3 CN 3 OH R CH 3 CH 2 Cl (CH 2 ) 3 CH 3 Ph CH=CH 2 R RN 3 OH Chem 2 15 Jacobsen Catalytic Asymmetric Epoxide-Opening Reactions Myers H 2 O ( R , R )- 5 R -epoxide S -epoxide S -1,2-diol R -1,2-diol ++ Hydrolytic Kinetic Resolution (HKR): (±) 5 (mol %) 0.2 0.3 0.42 0.8 0.64 water (equiv) 0.55 0.55 0.55 0.70 0.50 time (hours) 12 8 5 44 20 Epoxide ee (%) isolated yield (%) >98 98 98 98 84 44 44 46 38 44 Diol ee (%) isolated yield (%) 98 86 98 98 94 50 38 48 39 49 k rel >400 50 290 20 30 From: Tokunaga, M.; Larrow, J. F.; Kakiuchi, F.; Jacobsen, E. N. Science 1997 , 277 , 936-938. Enantioselective Opening of Meso Epoxides: Martínez, L. E.; Leighton, J. L.; Carsten, D. H.; Jacobsen, E. N. J. Am. Chem. Soc. 1995 , 117 , 5897-5898. 1. ( R , R )- 6 (2 mol%), Et 2 O, TMSN 3 2. CSA, CH 3 OH * Isolated yield of silyl ether. Epoxides fused to 5-membered rings show higher enantioselectivity than 6-membered-ring (±) H 2 O ( S , S )- 5 ( S , S )- 5 72 81 80 95 65 * 82 substrate product yield (%) ee (%) and acyclic substrates.
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Jacobsen Catalytic Assymetric Epoxide-Opening Reactions -...

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