Rhodium-Catalyzed Asymmetric Ring Opening of Oxabicyclic Alkenes with Organoboronic Acids

Organic Letters

Volumn 4, Issue 8, 2002, Pages 1311-1314

  Lautens, Mark ^a   Dockendorff, Chris ^a   Fagnou, Keith ^a   Malicki, Adrianna ^a  

^a UNIVERSITY OF TORONTO   (Canada)

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ARTICLE;

EID: 0000299234     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0256062     Document Type: Article

References (21)

1. Review of asymmetric arylations: Bolm, C.; Hildebrand, J. P.; Muñiz, K.; Hermanns, N. Ang. Chem., Int. Ed. 2001, 40, 3284.
2. Sakai, M.; Hayashi, H.; Miyaura, N. Organometallics 1997, 16, 4229.
3. (a) Hayashi, T. Synlett 2001, 879.
4. (b) Senda, T.; Ogasawara, M.; Hayashi, T. J. Org. Chem. 2001, 66, 6852 and references therein.
5. For other examples of ARO reactions, see, for example: (a) Lautens, M.; Hiebert, S.; Renaud, J.-L. J. Am. Chem. Soc. 2001, 123, 6834. (b) Lautens, M.; Fagnou, K.; Taylor, M.; Rovis, T. J. Organomet. Chem. 2001, 624, 259. (c) Lautens, M.; Rovis, T. J. Am. Chem. Soc. 1997, 119, 11090.
6. For other examples of ARO reactions, see, for example: (a) Lautens, M.; Hiebert, S.; Renaud, J.-L. J. Am. Chem. Soc. 2001, 123, 6834. (b) Lautens, M.; Fagnou, K.; Taylor, M.; Rovis, T. J. Organomet. Chem. 2001, 624, 259. (c) Lautens, M.; Rovis, T. J. Am. Chem. Soc. 1997, 119, 11090.
7. For other examples of ARO reactions, see, for example: (a) Lautens, M.; Hiebert, S.; Renaud, J.-L. J. Am. Chem. Soc. 2001, 123, 6834. (b) Lautens, M.; Fagnou, K.; Taylor, M.; Rovis, T. J. Organomet. Chem. 2001, 624, 259. (c) Lautens, M.; Rovis, T. J. Am. Chem. Soc. 1997, 119, 11090.
8. Only a single diastereomer has ever been detected for any of the ring-opened products in this Letter.
9. Our initial efforts were inspired by a report by Kobayashi where boronates were found to show enhanced reactivity relative to the analagous boronic esters and acids: Kobayashi, Y.; Mizojiri, E.; Ikeda, E. J. Org. Chem. 1996, 61, 5391.
10. Other ligands giving worse reactivity and/or enantioselectivity were BINAP, tol-BINAP, and i-Pr-POX. See the Supporting Information for more details.
11. It is hypothesized that the use of base accelerates the transmetalation of the boronic acid to rhodium. This has been proposed in the Pd-catalyzed Suzuki reaction. See, for example: (a) Suzuki, A.; Miyaura, N. Chem. Rev. 1995, 95, 2457. (b) Wright, S. W.; Hageman, D. L.; McClure, L. D. J. Org. Chem. 1994, 59, 6095.
12. It is hypothesized that the use of base accelerates the transmetalation of the boronic acid to rhodium. This has been proposed in the Pd-catalyzed Suzuki reaction. See, for example: (a) Suzuki, A.; Miyaura, N. Chem. Rev. 1995, 95, 2457. (b) Wright, S. W.; Hageman, D. L.; McClure, L. D. J. Org. Chem. 1994, 59, 6095.
13. No reaction was observed in the presence of 4 A molecular sieves and no added water.
14. Lautens, M; Roy, A.; Fukuoka, K.; Fagnou, K.; Martín-Matute, B. J. Am. Chem. Soc. 2001, 123, 5358.
15. 3.
16. 3 was recently reported: Murakami, M.; Igawa, H. Chem. Commun. 2002, 390.
17. (b) Pd-catalyzed asymmetric arylation reactions of 1 have been reported: Fiaud, J.-C.; Moinet, C. Tetrahedron Lett. 1995, 36, 2051.
18. See the Supporting Information for details. Absolute configurations of the other compounds in this Letter have been tentatively assigned by analogy.
19. Additional catalyst and phenylboronic ester were added to both reactions (performed with 50 mg of oxabicycle) to push reactions to completion.
20. Studies to support this mechanism are underway.
21. See ref 4a for a discussion of this step in a Pd-catalyzed ARO.