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Monday, April 27, 2009
Douglass F. Taber
University of Delaware

New Methods for C-N Ring Construction

Chaozhong Li of the Shanghai Institute of Organic Chemistry demonstrated (Org. Lett. 2008, 10, 4037 ) facile and selective Cu-catalyzed β-lactam formation, converting 1 to 2. Paul Helquist of the University of Notre Dame devised (Org. Lett. 2008, 10, 3903 ) an effective catalyst for intramolecular alkyne hydroamination, converting 3 into the imine 4. Six-membered ring construction worked well also.

Jon T. Njardarson of Cornell University found (Org. Lett. 2008, 10, 5023 ) a Cu catalyst for the rearrangement of alkenyl aziridines such as 5 to the pyrroline 6. Philippe Karoyan of the UPMC, Paris developed (J. Org. Chem. 2008, 73, 6706 ) an interesting chiral auxiliary directed cascade process, converting the simple precursor 7 into the complex pyrrolidine 9. Sherry R. Chemler of the State University of New York, Buffalo devised (J. Am. Chem. Soc. 2008, 130, 17638 ) a chiral Cu catalyst for the cyclization of 10, to give 12 with substantial enantiocontrol. Wei Wang of the University of New Mexico demonstrated (Chem. Commun. 2008, 5636 ) the organocatalyzed condensation of 13 and 14 to give 16 with high enantio- and diastereocontrol.

Two complementary routes to azepines/azepinones have appeared. F. Dean Toste of the University of California, Berkeley showed (J. Am. Chem. Soc. 2008, 130, 9244 ) that a gold complex catalyzed the condensation of 17 and 18 to give 19. Frederick G. West of the University of Alberta found (Org. Lett. 2008, 10, 3985 ) that lactams such as 20 could be ring-expanded by the addition of the propiolate anion 21.

Takeo Kawabata of Kyoto University extended (Org. Lett. 2008, 10, 3883 ) “memory of chirality” studies to the cyclization of 23, demonstrating that 24 was formed in high ee. Paul V. Murphy of University College Dublin took advantage (Org. Lett. 2008, 10, 3777 ) of the well-known intramolecular addition of azides to alkenes, showing that the intermediate could be intercepted with nucleophiles such as thiophenol, to give the cyclized product 26 with high diastereocontrol. Ryo Shintani and Tamio Hayashi, also of Kyoto University, found (J. Am. Chem. Soc. 2008, 130, 16174 ) that a chiral Pd catalyst effected condensation of racemic 27 with an aryl isocyanate to give, via decarboxylation, the lactam 28 in high ee. Ying-Chun Chen of Sichuan University optimized (Angew. Chem. Int. Ed. 2008, 47, 9971 ) the organocatalyst-mediated condensation of 29 with 30 to give 31 with high enantio- and diastereocontrol.

Guillaume Bélanger of the Université de Sherbrooke devised (Org. Lett. 2008, 10, 4939 ) an elegant cascade dipole formation and cycloaddition, converting 32 into 33 as a single diastereromer.

D. F. Taber, Org. Chem. Highlights 2009, April 27.