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Monday, February 20, 2012
Douglass F. Taber
University of Delaware

Enantioselective Construction of Alkylated Centers: The Shishido Synthesis of (+)-Helianane

Teck-Peng Loh of Nanyang Technological University developed (Org. Lett. 2011, 13, 876. ) an organocatalyst for the enantioselective Michael addition of an aldehyde to the versatile acceptor 2, to give 3. Kirsten Zeitler of the Universitšt Regensburg employed (Angew. Chem. Int. Ed. 2011, 50, 951. ) a complementary strategy for the enantioselective coupling of 4 with 5. Clark R. Landis of the University of Wisconsin devised (Org. Lett. 2011, 13, 164. ) a Rh catalyst for the enantioselective formylation of the diene 7.

Don M. Coltart of Duke University alkylated (J. Am. Chem. Soc. 2011, 133, 8714. ) the chiral hydrazone of acetone to give 9, then alkylated again to give, after hydrolysis, the ketone 11 in high ee. Youming Wang and Zhenghong Zhou of Nankai University effected (J. Org. Chem. 2011, 76, 3872. ) the enantioselective addition of acetone to the nitroalkene 12. Takeshi Ohkuma of Hokkaido University achieved (Angew. Chem. Int. Ed. 2011, 50, 5541. ) high ee in the Ru catalyzed hydrocyanation of 15.

Gregory C. Fu, now at the California Institute of Technology, coupled (J. Am. Chem. Soc. 2011, 133, 8154. ) the 9-BBN borane 18 with the racemic chloride 17 to give 19 in high ee. Scott McN. Sieburth of Temple University optimized (Org. Lett. 2011, 13, 1787. ) a Rh catalyst for the enantioselective intramolecular hydrosilylation of 20 to 21.

Several general methods have been devised for the enantioselective assembly of quaternary alkylated centers. Sung Ho Kang of KAIST Daejon developed (J. Am. Chem. Soc. 2011, 133, 1772. ) a Cu catalyst for the enantioselective acylation of the prochiral diol 22. Hyeung-geun Park of Seoul National University established (J. Am. Chem. Soc. 2011, 133, 4924. ) a phase transfer catalyst for the enantioselective alkylation of 24. Peter R. Schreiner of Justus-Liebig University Giessen found (J. Am. Chem. Soc. 2011, 133, 7624. ) a silicon catalyst that efficiently rearranged the Shi-derived epoxide of 26 to the aldehyde 27. Amir H. Hoveyda of Boston College coupled (J. Am. Chem. Soc. 2011, 133, 4778. ) 28 with the alkynyl Al reagent 29 to give 30 in high ee.

Kozo Shishido of the University of Tokushima prepared (Synlett 2011, 1171. ) 31 by the Mitsunobu coupling of m-cresol with the enantiomerically-pure allylic alcohol. Stoichiometric AlMe3 mediated the Claisen rearrangement at room temperature, to deliver 32, the key intermediate for the synthesis of (+)-Helianane (33).

D. F. Taber, Org. Chem. Highlights 2012, February 20.