Asymmetric inter- and intramolecular cyclopropanations of alkenes catalyzed by rhodium D4-porphyrin: a comparison of rhodium- and ruthenium-centred catalysts

✍ Scribed by Pang-Fei Teng; Tat-Shing Lai; Hoi-Lun Kwong; Chi-Ming Che

• Book ID: 104359672
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 199 KB
• Volume: 14
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/s0957-4166(03)00047-8

✦ Synopsis

Iodo-(5,10,15,20-tetrakis(1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl)porphyrinatorhodium(III), designated as [Rh(P*)(I)], was prepared and its catalytic activity in the asymmetric cyclopropanation of alkenes with ethyl diazoacetate (EDA) was examined. High catalyst turnovers (TON >10 3 ) and moderate enantioselectivities (up to 68% ee) were observed. However, the obtained trans/cis ratios are low. Competition experiments revealed that electron-donating substituents on styrene accelerate the cyclopropanations. The log(k X /k H ) versus | + plot for substituted styrenes exhibits a good linearity with a small negative z + value (-0.14). [Rh(P*)(I)] is also active in the intramolecular cyclopropanation of allyl diazoacetates. A comparison between rhodium and ruthenium porphyrin complexes was made.