113428-57-2Relevant articles and documents
Chiral calix-salen cobalt complexes, catalysts for the enantioselective dynamic hydrolytic kinetic resolution of epibromohydrin
Dandachi, Hiba,Nasrallah, Houssein,Ibrahim, Farah,Hong, Xiang,Mellah, Mohamed,Jaber, Nada,Schulz, Emmanuelle
, p. 457 - 462 (2014)
New calix-salen cobalt (III) complexes were synthesized as a mixture and as pure trimer or tetramer complexes. These cyclic complexes were used as catalysts to promote the dynamic hydrolytic kinetic resolution (HKR) of epibromohydrin in order to evaluate the effect of the cyclic structures size on the cooperative bimetallic interactions. Since the obtained catalysts were easily recovered from the reaction mixture by simple filtration, their efficiency was evaluated in recycling procedures. It was found that both cyclic oligomer complexes (trimer and tetramer) and the mixture of calix-salen complexes delivered the expected diol with high enantioselectivity and yield. Tetramer calix-salen cobalt complex proved to be the most active and selective catalyst of the series. In this case, an optimal conformation to allow the formation of bimetallic species activating respectively both the epoxide and water as nucleophile is probably responsible for an efficient dual activation.
Mixing and matching chiral cobalt- and manganese-based calix-salen catalysts for the asymmetric hydrolytic ring opening of epoxides
Dandachi, Hiba,Zaborova, Elena,Kolodziej, Emilie,David, Olivier R.P.,Hannedouche, Jér?me,Mellah, Mohamed,Jaber, Nada,Schulz, Emmanuelle
, p. 246 - 253 (2017/03/01)
Homochiral oligomeric salen macrocycles possessing aromatic spacers have been prepared as new calix-salen derivatives. The corresponding cobalt and manganese complexes were synthesized and characterized, and their catalytic activities have been studied in the challenging hydrolysis of meso epoxides. While manganese calix-salen complexes were not active in the studied reactions, the dual heterobimetallic system, using an equimolar combination of cobalt and manganese calix-salen derivatives proved to be more enantioselective than the sole cobalt system. Furthermore, as heterogeneous complexes, the catalytic mixture could be easily recovered by simple filtration and successfully reengaged in subsequent catalytic runs. Interestingly, no need for cobalt reactivation was noticed to maintain maximum efficiency of this dual system. The matched Co/Mn dual catalyst was also used to promote the dynamic hydrolytic kinetic resolution of epibromohydrin.
Hydrolytic kinetic resolution of epoxides catalyzed by chromium(III)-endo, endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] complexes. Improved activity, low catalyst loading
Berkessel, Albrecht,Ertuerk, Erkan
, p. 2619 - 2625 (2007/10/03)
The hydrolytic kinetic resolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane) , was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol%) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99% ee). Besides monosubstituted epoxides, 2-methyl-2-n-pentyloxirane, which is an example for 2,2-disubstituted epoxides, could be ring-opened in an asymmetric fashion with water in the presence of an electronically tuned chromium-(III)-DIANANE complex.
