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Monday, April 9, 2012
Douglass F. Taber
University of Delaware

C-O Ring Construction: The Georg Synthesis of Oximidine II

Chun-Bao Miao and Hai-Tao Yang of Changzhou University constructed (J. Org. Chem. 2011, 76, 9809. ) the oxetane 2 by exposing the Michael adduct 1 to I2 and air. Huanfeng Jiang of the South China University of Science and Technology carboxylated (Org. Lett. 2011, 13, 5520. ) the alkyne 3 in the presence of a nitrile to give the three-component coupled product 4.

Alois Fürstner of the Max-Planck-Institut Mülheim cyclized (Angew. Chem. Int. Ed. 2011, 50, 7829. ) 5 with a Mo catalyst, released in situ from a stable precursor, to give 6 in high ee. Hiromichi Fujioka of Osaka University rearranged (Chem. Commun. 2011, 47, 9197. ) 7 to the cyclic aldehyde, largely as the less stable diastereomer 8. Edward A. Anderson of the University of Oxford cyclized (Angew. Chem. Int. Ed. 2011, 50, 11506. ) 9 to 10 with excellent stereochemical fidelity. Similarly, Andrei V. Malkov, now at Loughborough University, and Pavel Kocovsky of the University of Glasgow combined (J. Org. Chem. 2011, 76, 7781. ) the individual enantiomers of 11 and 12 to give 13 as single enantiomerically-pure diastereomers.

Daniel Romo of Texas A&M University cyclized (Angew. Chem. Int. Ed. 2011, 50, 7537. ) the bromo ester 14 to the lactone 15. Xin-Shan Ye of Peking University condensed (Synlett 2011, 2410. ) the sulfone 16 with 17 to give the sulfone 18, with high diastereocontrol.

Jiyong Hong of Duke University found (Org. Lett. 2011, 13, 5816. ) that 19 could be cyclized to either diastereomer of 20 by judicious optimization of the reaction conditions. Stacey E. Brenner-Moyer of Brooklyn College showed (Org. Lett. 2011, 13, 6460. ) that cyclization of racemic 21 in the presence of 22 and the Hayashi catalyst delivered a ~ 1:1 mixture of 23 and 24, each with good stereocontrol. Kyoko Nakagawa-Goto of the University of North Carolina showed (Synlett 2011, 1413. ) that the MOM ether 25, prepared in high de by Evans alkylation, cyclized efficiently to 26. Armen Zakarian of UC Santa Barbara cyclized (Org. Lett. 2011, 13, 3636. ) 27, readily prepared in high ee by asymmetric Henry addition, to the enone 28.

In the course of a synthesis of Oximidine II (31), Gunda I. Georg of the University of Minnesota planned (Angew. Chem. Int. Ed. 2011, 50, 7855. ) to cyclize the iodo alkyne 29. The anticipated E, Z product was too unstable to be isolated, but could be reduced in situ to the desired E, Z, Z triene 30.

D. F. Taber, Org. Chem. Highlights 2012, April 9.