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 γ-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.(Figure Presented)