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Monday, December 21, 2009
Douglass F. Taber
University of Delaware

Transition Metal-Mediated C-C Ring Construction: The Stoltz Synthesis of (-)-Cyanthiwigin F

X. Peter Zhang of the University of South Florida extended (Org. Lett. 2009, 11, 2273. ) Co-catalyzed asymmetric cyclopropanation to the activated ester 2. The product 3 readily coupled with amines. André B. Charette of the Université de Montréal showed (J. Am. Chem. Soc. 2009, 131, 6970. ) that even α-olefins such as 4 could be cyclopropanated in high ee with the diazo amide 5. Xue-Long Hou of the Shanghai Institute of Organic Chemistry established (J. Am. Chem. Soc. 2009, 131, 8734. ) conditions for the enantioselective coupling of 7 and 8 to give 9, in which sidechain chirality was also controlled. Tristan H. Lambert of Columbia University found (J. Am. Chem. Soc. 2009, 131, 7536. ) that “methylene” could be transferred in an intramolecular sense from the epoxide of 10 to the alkene, delivering the cyclopropane 11 in high ee.

Yuichi Kobayashi of the Tokyo Institute of Technology established (Org. Lett. 2009, 11, 1103. ) that the 2-picolinoxy leaving group worked well for the SN2' coupling with 13 to give 14. Chang Ho Oh of Hanyang University developed (J. Org. Chem. 2009, 74, 370. ) a new route to cyclopentenones such as 16, by gold-catalyzed cyclization of diynes such as 15. David J. Procter of the University of Manchester used (J. Am. Chem. Soc. 2009, 131, 7214, ; Tetrahedron Lett. 2009, 50, 3224, ) SmI2 to cyclize 17 to 18 and 19 to 20, each with high diastereocontrol.

Yoshiaki Nishibayashi of the University of Tokyo devised (Angew. Chem. Int. Ed. 2009, 48, 2534. Ru catalysts for the cyclization of an enyne such as 21 to the cyclohexadiene 22. Laurel L. Schafer of the University of British Columbia developed (J. Am. Chem. Soc. 2009, 131, 2116. a Zr catalyst for the diastereocontrolled cyclization of amino alkenes such as 23. Hongbin Zhai of the Shangahi Institute of Organic Chemistry showed (J. Org. Chem. 2009, 74, 2592. ) that the Mo-mediated cyclization of 25 also proceeded with high diastereocontrol. Even more impressive was the selectivity Kozo Shishido of the University of Tokushima demonstrated (Tetrahedron Lett. 2009, 50, 1279. ) for the cyclization of 27.

Professor Lambert established (J. Am. Chem. Soc. 2009, 131, 2496. ) that the rearrangement of the vinyl cyclopropane 29 to the cyclopentene 30, usually a high temperature process, could be effected with MgI2. We (J. Org. Chem. 2009, 74, 2433. ) found that Fe-mediated cyclocarbonylation of 31 led to the cyclohexenone 32.

Brian M. Stoltz of Caltech prepared (Nature 2008, 453, 1228. ) the diester 33 by dimerization of diallyl succinate followed by methylation. Pd-mediated rearrangement delivered 34, the central ring of (-)-Cyanthiwigin (35), in high de and ee..

D. F. Taber, Org. Chem. Highlights 2009, December 21