Silver-mediated amination reaction

A silver-mediated amination reaction of benzoxazoles (100 134) (Scheme 65) was reported by Chang under relatively mild conditions (60 °C, 0.8—1.0 eq. amine) compared to earlier reports (140 °C, 4 eq. amine (Mori) and 120—140 °C, 5 eq. amine (Schreiber)) (2009AGE9127). 

Liu W, Jiang H, Huang L (2010) One-pot silver-catalyzed and PIDA-mediated sequential reactions Synthesis of polysubstituted pyrroles directly from alkynoates and amines. Org Lett 12(2) 312—315... 

The development of a silver-mediated Diels-Alder reaction to construct the pentacyclic intermediate 77a in which the two methylene groups were positioned trans to each other paved the way for the asymmetric total synthesis of (+)-perophoramidine. In our retrosynthetic analysis (Scheme 26), we planned to synthesize (+)-perophoramidine via late-stage regioselective N1 -methylation of the hexacycUc intermediate 100. We planned to constmct the B-ring in 100 via intramolecular amination of the imidate functional group in 101, which could be readily synthesized fi-om 77a via a series of functional group transformations. 

In a convenient one-pot process, easily accessed propargyl vinyl ethers and aromatic amines are effectively converted into tetra- and pentasubstituted 5-methylpyrroles, which can fnrther be transformed into 5-formylpyrroles via 2-iodoxybenzoic acid (IBX)-mediated oxidation (Binder and Kirsch 2006). The cascade reaction proceeds through a silver(l)-catalyzed propargyl Claisen rearrangement, an amine condensation, and a gold(l)-catalyzed 5-exo-dig heterocyclization, as shown in Schane 11.4. 

---