A BMPD-yttrium isopropoxide complex: Highly efficient chiral Lewis acid catalyst for asymmetric silylcyanation

Journal of Organic Chemistry

Volumn 61, Issue 7, 1996, Pages 2264-2265

  Abiko, Atsushi ^a   Wang, Guo Qiang ^a  

^a KAO CORPORATION   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001701511     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960271l     Document Type: Article

References (19)

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11. 3 afforded the same results, but the complex formed rather slowly (14 h at room temperature).
12. 1NMR δ 6.20 (s, 3H).
13. North, M. Synlett 1993, 807.
14. One equivalent (to the catalyst) of the TMSCN was consumed to silylate the alcohol, which was produced upon complexation of yttrium isopropoxide with BMPD.
15. Enantiomeric purity was determined by HPLC analysis (μ-Porasil, Hex:EtOAc = 20:1) after conversion to the corresponding (R)-MTPA ester.
16. 2, 90% ee; toluene, 75% ee; ether, 70% ee, THF, 38% ee; EtCN, 0% ee.
17. Complexation in the presence of benzyl alcohol (2 equiv, rt, 1 h) or treatment (rt, 1 h) of the complex, prepared by the usual manner, with benzyl alcohol (2 equiv) followed by the addition of benzaldehyde and TMSCN at -78°C gave the cyanohydrin with 40 and 35% ee, respectively. However, complexation in the presence of benzyl alcohol (2 equiv, rt, 1 h) followed by the treatment with benzaldehyde at room temperature gave the cyanohydrin with 81% ee after the reaction with TMSCN at -78°C. The structure change might be accompanied by the MPV reaction and responsible for the high selectivity.
18. Weber, W. P. Silicon Reagents for Organic Synthesis; Springer-Verlag: Berlin, Heidelberg, New York, 1983; p 7.
19. Mikami, K.; Matsukawa, S. J. Am Chem. Soc. 1994, 116, 4077.