Cu(i)-carbenoid- and Ag(i)-Lewis acid-catalyzed asymmetric intermolecular insertion of α-diazo compounds into N–H bonds

Abstract

Chiral Cu(I)-bisoxazoline- and Cu(I)-PN-complexes were found to catalyze the intermolecular insertion of α-diazo compounds into N–H bonds. The insertion reactions proceed with enantioselectivities of up to 28% ee for the different α-diazo acetates into one of the N–H bonds of different amines. Analogous chiral Ag(I) complexes were found to give higher enantioselectivities of up to 48% ee, however, lower yields were obtained. There are indications, that the Ag(I)-mediated reactions follow a different reaction mechanism compared to the Cu(I)-catalyzed insertions. It is demonstrated that different α-amino acid derivatives can be obtained via this approach in good yields and with low to moderate enantioselectivities. However, the results obtained are the highest asymmetric inductions obtained for an intermolecular N–H insertion via chiral carbene complexes or chiral Lewis acid catalysis.