Metal-Mediated Ring Construction: The Hoveyda Synthesis of (-)-Nakadomarin A
John F. Hartwig of the University of California, Berkeley effected (J. Am. Chem. Soc. 2013, 135, 3375. ) selective borylation of the cyclopropane 1 to give 2. It would be particularly useful if this borylation could be made enantioselective. Eric M. Ferreira of Colorado State University showed (Org. Lett. 2013, 15, 1772. ) that the enantomeric excess of 3 was transferred to the highly substituted cyclopropane 4.
Antonio M. Echavarren of ICIQ Tarragona demonstrated (Org. Lett. 2013, 15, 1576. ) that Au-mediated cyclobutene construction could be used to form the medium ring of 6. Joseph M. Fox of the University of Delaware developed (J. Am. Chem. Soc. 2013, 135, 9283. ) what promises to be a general enantioselective route to cyclobutanes such as 8, by way of the intermediate bicyclobutane (not illustrated). Huw M. L. Davies of Emory University reported (Org. Lett. 2013, 15, 310. ) a preliminary investigation in this same direction.
Masahisa Nakada of Waseda University prepared (Org. Lett. 2013, 15, 1004. ) the cyclopentane 10 by enantioselective cyclization of 9 followed by reductive opening. Young-Ger Suh of Seoul National University cyclized (Org. Lett. 2013, 15, 531. ) the lactone 11 to the cyclopentane 12. Xavier Ariza and Jaume Farràs of the Universitat de Barcelona optimized (J. Org. Chem. 2013, 78, 5482. ) the Ti-mediated reductive cyclization of 13 to 14. The hydrogenation catalyst reduced the intermediate Ti-C bond without affecting the alkene.
Erick M. Carreira of ETH Zurich observed (Angew. Chem. Int. Ed. 2013, 52, 5382. ) that a sterically-demanding Rh catalyst mediated the highly diastereoselective cyclization of 15 to 16. The ketone 16 was the key intermediate in a synthesis of the epoxyisoprostanes.
Jianrong (Steve) Zhou of Nanyang Technological University used (Angew. Chem. Int. Ed. 2013, 52, 4906. ) a Pd catalyst to effect the coupling of 17 with the prochiral 18. Geum-Sook Hwang and Do Hyun Ryu of Sungkyunkwan University devised (J. Am. Chem. Soc. 2013, 135, 7126. ) a boron catalyst to effect the addition of the diazo ester 21 to 20. They showed that the sidechain stereocenter was effective in directing the subsequent hydrogenation of 22.
Luis A. Maldonado of the Universidad Nacional Autónoma de México found (J. Org. Chem. 2013, 78, 5282. ) conditions for aldol condensation of the Cu/Al enolate from the enantioselective addition of Me3Al to 23. David A. Evans of Harvard University observed (J. Org. Chem. 2013, 78, 175. ) that the Z-acceptor of 26 constrained the intramolecular Michael addition to proceed with high diastereocontrol.
Amir H. Hoveyda of Boston College developed (Chem. Eur. J. 2013, 19, 2726. ) W catalysts that effected kinetic ring-closing metathesis with high Z selectivity, as illustrated by the cyclization of 28 to 29. The catalyst was not sensitive to moisture, and worked well even in the presence of a basic N.