60212-44-4Relevant academic research and scientific papers
Actuation of asymmetric cyclopropanation catalysts: Reversible single-crystal to single-crystal reduction of metal-organic frameworks
Falkowski, Joseph M.,Wang, Cheng,Liu, Sophie,Lin, Wenbin
, p. 8674 - 8678 (2011)
To and fro: Chiral metal-organic frameworks (CMOFs) derived from redox-active ruthenium/salen building blocks exhibited reversible single-crystal to single-crystal reduction and reoxidation. The catalytically inactive Ru III CMOFs (green; see picture) were reduced to RuII CMOFs (red) that were highly active for the asymmetric cyclopropanation of alkenes with very high diastereo- and enantioselectivities. Copyright
Chiral metal-organic frameworks with tunable open channels as single-site asymmetric cyclopropanation catalysts
Falkowski, Joseph M.,Liu, Sophie,Wang, Cheng,Lin, Wenbin
scheme or table, p. 6508 - 6510 (2012/08/14)
A pair of interpenetrated and non-interpenetrated chiral metal-organic frameworks with the same catalytic sites but different open channel sizes catalysed asymmetric cyclopropanation of substituted terminal alkenes with excellent diastereoselectivities (up to 9.6) and enantioselectivities (up to >99%).
Recyclable polymer- and silica-supported Ruthenium(II)-Salen bis-pyridine catalysts for the asymmetric cyclopropanation of olefins
Gill, Christopher S.,Venkatasubbaiah, Krishnan,Jones, Christopher W.
scheme or table, p. 1344 - 1354 (2009/12/22)
Homogeneous ruthenium(II)-salen bis-pyridine complexes are known to be highly active and selective catalysts for the asymmetric cyclopropanation of terminal olefins. Here, new methods of heterogenization of these Ru-salen catalysts on polymer and porous silica supports are demonstrated for the facile recovery and recycle of these expensive catalysts. Activities, selectivities, and recyclabilities are investigated and compared to the analogous homogeneous and other supported catalysts for asymmetric cyclopropanation reactions. The catalysts are characterized with a variety of methods including solid state cross-polarization magic-angle spinning (CP MAS) 13C and 29Si NMR, FT-IR, elemental analysis, and thermogravimetric analysis. Initial investigations produced catalysts possessing high selectivities but decreasing activities upon reuse. Addition of excess pyridine during the washing steps between cycles was observed to maintain high catalytic activities over multiple cycles with no impact on selectivity. Polymer-supported catalysts showed superior activity and selectivity compared to the porous silicasupported catalyst. Additionally, a longer, flexible linker between the Ru-salen catalyst and support was observed to increase enantioselectivity and diastereoselectivity, but had no effect on activity of the resin catalysts. Furthermore, the polymer-supported Ru-salen-Py2 catalysts were found to generate superior selectivities and yields compared to other leading heterogeneous asymmetric cyclopropanation catalysts.
