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Electronically Tuned Chiral Ruthenium Porphyrins: Extremely Stable and Selective Catalysts for Asymmetric Epoxidation and Cyclopropanation
Author(s) -
Berkessel Albrecht,
Kaiser Patrick,
Lex Johann
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305045
Subject(s) - cyclopropanation , ruthenium , porphyrin , ethyl diazoacetate , substituent , chemistry , catalysis , ligand (biochemistry) , medicinal chemistry , trifluoromethyl , stereochemistry , photochemistry , combinatorial chemistry , organic chemistry , biochemistry , alkyl , receptor
We report the use of three enantiomerically pure and electronically tuned ruthenium carbonyl porphyrin catalysts for the asymmetric cyclopropanation and epoxidation of a variety of olefinic substrates. The D 4 ‐symmetric ligands carry a methoxy, a methyl or a trifluoromethyl group at the 10‐position of each of the 9‐[ anti ‐(1,2,3,4,5,6,7,8‐octahydro‐1,4:5,8‐dimethanoanthracene)]‐substituents at the meso ‐positions of the porphyrin. Introduction of a CF 3 ‐substituent in this remote position resulted in greatly improved catalyst stability, and turnover numbers of up to 7 500 were achieved for cyclopropanation, and up to 14 200 for epoxidation, with ee values typically >90 % and ≈80 %, respectively. In one example, the axial CO ligand at the ruthenium was exchanged for PF 3 , resulting in the first chiral ruthenium porphyrin with a PF 3 ligand reported to date. In cyclopropanations with ethyl diazoacetate, the latter catalyst performed exceedingly well, and gave a 95 % ee in the case of 1,1‐diphenylethylene as substrate.