Synfacts 2009(11): 1207-1207  
DOI: 10.1055/s-0029-1218142
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Au(I)-Catalyzed Synthesis of Cycloalkene-Fused Pyrroles

Contributor(s): Victor Snieckus, Cédric Schneider
X. Zhao, E. Zhang, Y.-Q. Tu*, Y.-Q. Zhang, D.-Y. Yuan, K. Cao, C.-A. Fan, F.-M. Zhang
Lanzhou University, P. R. of China
Further Information

Publication History

Publication Date:
22 October 2009 (online)

Significance

Reported is an efficient synthesis of trisubstituted and cycloalkene-fused pyrroles via a Au(I)-catalyzed rearrangement of propargylic aziridines. Based on previous results (P. W. Davies, N. Martin Org. Lett. 2009, 11, 2293), the propargylic aziridines are converted into the 3-vinyl-2,3,5-trisubstituted pyrroles 2. A plausible mechanism is proposed which involves a unique sequential N-addition to a C-C triple bond (5-endo-dig cycli-zation) catalyzed by Au(I), ring opening of an aziridine, and Wagner-Meerwein-type C-to-C rearrangement (M. Saunders, H. A. Jimenez-Vazquez Chem. Rev. 1991, 91, 375). During the optimization of the reaction conditions using different gold/silver complexes and solvents, it was demonstrated that the hydroxyl group must be protected by TBSCl and that the reaction was tolerant of both R¹ = EWG-Ar or EDG-Ar as well as the acyclic and cyclic alkyl groups. Moreover, the reaction of five-membered ring substrates 1 proceeded much faster than those of the six-membered ring systems. The method was ­extended to substrate 3 to afford the expected ketone 4.