Journal of the American Chemical Society, Vol.133, No.14, 5500-5507, 2011
Phosphoramidite Gold(I)-Catalyzed Diastereo- and Enantioselective Synthesis of 3,4-Substituted Pyrrolidines
In this article the utility of phosphoramidite ligands in enantioselective Au-I catalysis was explored in the development of highly diastereo- and enantioselective Au-I-catalyzed cycloadditions of allenenes. A Au-I-catalyzed synthesis of 3,4-disubstituted pyrrolidines and gamma-lactams is described. This reaction proceeds through the enantioselective Au-I-catalyzed cyclization of allenenes to form a carbocationic intermediate that is trapped by an exogenous nucleophile, resulting in the highly diastereoselective construction of three contiguous stereogenic centers. A computational study (DFT) was also performed to gain some insight into the underlying mechanisms of these cycloadditions. The utility of this new methodology was demonstrated through the formal synthesis of (-)-isocynometrine.