title: Asymmetric Catalysis with Organic Azides and Diazo Compounds Initiated by Photoinduced Electron Transfer.
abstract: Electron-acceptor-substituted aryl azides and α-diazo carboxylic esters are used as substrates for visible-light-activated asymmetric α-amination and α-alkylation, respectively, of 2-acyl imidazoles catalyzed by a chiral-at-metal rhodium-based Lewis acid in combination with a photoredox sensitizer. This novel proton- and redox-neutral method provides yields of up to 99% and excellent enantioselectivities of up to >99% ee with broad functional group compatibility. Mechanistic investigations suggest that an intermediate rhodium enolate complex acts as a reductive quencher to initiate a radical process with the aryl azides and α-diazo carboxylic esters serving as precursors for nitrogen and carbon-centered radicals, respectively. This is the first report on using aryl azides and α-diazo carboxylic esters as substrates for asymmetric catalysis under photoredox conditions. These reagents have the advantage that molecular nitrogen is the leaving group and sole byproduct in this reaction.
authors: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Strasse 4, 35043 Marburg, Germany.
authors: Xiaoqiang
authors: X
authors: Huang
authors: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
authors: Richard D
authors: RD
authors: Webster
authors: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Strasse 4, 35043 Marburg, Germany.
authors: Klaus
authors: K
authors: Harms
authors: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Strasse 4, 35043 Marburg, Germany.
authors: Eric
authors: E
authors: Meggers