Cu(I)/bis(azaferrocene)-catalyzed enantioselective synthesis of beta-lactams via couplings of alkynes with nitrones.
As a consequence of the wide-ranging significance of beta-lactams (e.g., use as drugs and as chiral building blocks), a great deal of effort has been dedicated to the development of methods for their stereoselective synthesis. Although considerable progress has been achieved, nearly all of the approaches that have been described are based on the use of chiral precursors; direct catalytic enantioselective routes to beta-lactams are rare as well as limited in scope. In this communication, we establish that, using a new C2-symmetric planar-chiral bis(azaferrocene) ligand, we can generate beta-lactams with very good enantiomeric excess and cis diastereoselection via catalytic enantioselective Kinugasa reactions (couplings of alkynes with nitrones). Appealing attributes of this process include the ready availability of the starting materials, the functional-group tolerance of the reaction, and the convergency of the approach.
Lo
Michael M-C
MM
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Fu
Gregory C
GC
D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D009589:Nitrogen Oxides / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D047090:beta-Lactams / Q000138:chemical synthesis*
D000480:Alkynes; D005296:Ferrous Compounds; D000075163:Metallocenes; D009589:Nitrogen Oxides; D009942:Organometallic Compounds; D047090:beta-Lactams; C459724:bis(azaferrocene); C015388:nitrones; D003300:Copper; C004998:ferrocene