New Methods for C-N Ring Construction

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 foimd (Organic Lett. 2008,10, 3985) that lactams such as 20 could be ring-expanded by the addition of the propiolate anion 21. 

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

Diels-Alder cycUzation of a triene such as 31 would offer rapid access to polycyclic indole alkaloids. Christopher D. Vanderwal of the University of California, Irvine developed (J. Am. Chem. Soc. 2009,131, 3472) alkaline conditions for this powerful transformation. He then carried 32 on to the Strychnos alkaloid Norfluorocurarine 33. 

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