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Monday, June 27, 2011
Douglass F. Taber
University of Delaware

Alkene and Alkyne Metathesis: (+)-Anamarine (Sabitha), (±)-Pseudotabersonine (Martin), Lactimidomycin (Fürstner)

AMasato Matsugi of Meijo University showed (J. Org. Chem. 2010, 75, 7905. ) that over five iterations, the fluorous-tagged Ru catalyst 1b was readily recovered and reused for the cyclization of 2 to 3. Hengquan Yang of Shanxi University reported (Chem. Commun. 2010, 46, 8659. ) that the Hoveyda catalyst 1a encapsulated in mesoporous SBA-1 could also be reused several times. Jean-Marie Basset of KAUST Catalysis Center, Régis M. Gauvin of Université Lille and Mostafa Taoufik of Université Lyon 1 described (Chem. Commun. 2010, 46, 8944. ) a tungsten catalyst on silica that was also active for alkene metathesis.

Reto Dorta of the University of Zurich, exploring (J. Am. Chem. Soc. 2010, 132, 15179. ) several alternatives, found that only 4c cyclized cleanly to 5. Karol Grela of the Polish Academy of Sciences showed (Synlett 2010, 2931. ) that 3-nitropropene (not illustrated) participated in cross metathesis when catalyst 1c was used. Shawn K. Collins of the Université de Montréal complexed (J. Am. Chem. Soc. 2010, 132, 12790. ) 6 with a quinolinium salt to direct paracyclophane formation. Min Shi of the Shanghai Institute of Organic Chemistry incorporated (Org. Lett. 2010, 12, 4462. ) the cyclopropene 8 in cross metathesis, to give 10. A. Srikrishna of the Indian Institute of Science, Bangalore constructed (Synlett 2010, 3015. ) the cyclooctenone 12 by ring-closing metathesis.

LuAnne McNulty of Butler University established (J. Org. Chem. 2010, 75, 6001. ) that a cyclic boronic half acid 15, prepared by ring-closing metathesis, coupled with an iodoalkene 16 to deliver the diene 17 with high geometric control.

Gowravaram Sabitha of the Indian Institute of Chemical Technology, Hyderabad, en route (Tetrahedron Lett. 2010, 51, 5736. ) to (+)-Anamarine (21), observed that the tetraacetate 18b would not participate in cross metathesis. Fortunately, 18a, an earlier intermediate in the synthesis, worked well. Stephen F. Martin of the University of Texas prepared (Org. Lett. 2010, 12, 3622. ) (±)-Pseudotabersonine 24 by way of a spectacular metathesis that converted 22 to 23.

Ring-closing alkyne metathesis was a key step in the total synthesis of Lactimidomycin (27) reported (J. Am. Chem. Soc. 2010, 132, 14064. ) by Alois Fürstner of the Max-Planck-Institut Mülheim. Both Professor Fürstner (J. Am. Chem. Soc. 2010, 132, 11045. ) and Jeffrey S. Moore of the University of Illinois (Chem. Commun. 2010, 46, 7939. ) have worked on optimizing these Mo catalysts.

D. F. Taber, Org. Chem. Highlights 2011, June 27.