On the Mechanism and Stereoselectivity of the Copper(I)-Catalyzed Cyclopropanation of Olefins − A Combined Experimental and Density Functional Study

✍ Scribed by Michael Bühl; Frank Terstegen; Frank Löffler; Bernd Meynhardt; Stefanie Kierse; Michael Müller; Christian Näther; Ulrich Lüning

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 420 KB
• Volume: 2001
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/1099-0690(200106)2001:11<2151::aid-ejoc2151>3.0.co;2-4

✦ Synopsis

The mechanism of copper(I)-catalyzed olefin cyclopropanation with diazomethanes has been studied at the BP86/AE1 level of density-functional theory. For the model system Cu(diazabutadiene) + + ethene + diazomethane, copper carbene complexes are confirmed as viable intermediates, with rate-determining barriers of the order of 25 kcal/mol (energies including zero-point corrections) or 14 kcal/mol (when entropic contributions are included). For another model system, Cu(2,9-dimethyl-1,10-phenanthroline) + + styrene + diazoacetate, very small anti/syn selectivities (resulting in trans/cis-cyclopropanes) have been found both computationally and experimentally. Cu(carbene) complexes with