Strong Electronic Effects in the cis-Selective Asymmetric Cyclopropanation of Olefins Catalyzed by [RuCl(PNNP)]+

✍ Scribed by Stephan Bachmann; Antonio Mezzetti

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: German
• Weight: 124 KB
• Volume: 84
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/1522-2675(20011017)84:10<3063::aid-hlca3063>3.0.co;2-r

✦ Synopsis

The cationic [RuCl(PNNP)] catalysts containing tetradentate ligands with a P 2 N 2 donor set (PNNP) show strong electronic effects in the cyclopropanation of para-substituted styrenes. The reactivity trend confirms that the carbene transfer to the olefin has electrophilic character. Linear free-energy relationships are observed for the relative reactivity, the cis/trans selectivity, and for the enantioselectivity (of the cis-cyclopropane). The linear correlation between log (k X /k H ) and s shows a large value of 1 (À 2.4), which is indicative of significant charge buildup in the transition state of the carbene transfer to the olefin. All the relevant parameters (reactivity, diastereoselectivity, and enantioselectivity) increase with the increasing electron density at the CC bond. To define the scope of the [RuCl(PNNP)] catalysts, 1-and 2-substituted styrenes, and oct-1-ene were also investigated.