Chiral dirhodium catalysts derived from l-serine, l-threonine and l-cysteine: design, synthesis and application

Abstract

A series of dirhodium tetrakis((4S)-3-(arylsulfonyl)oxazolidine-4-carboxylate), dirhodium tetrakis((4S,5R)-5-methyl-3-(arylsulfonyl)oxazolidine-4-carboxylate) and dirhodium tetrakis((4R)-3-(arylsulfonyl)thiazolidine-4-carboxylate 1,1-dioxide) complexes with different para-substituted arylsulfonyl groups (e.g. -NO 2 , -F, -CF 3 , -Me, -t Bu, -OMe and -n C 12 H 25 ) derived from L-serine, L-threonine and L-cysteine, respectively, were prepared with yields in the range of 40-87% through refluxing ligands in water with Na 4 Rh 2 (CO 3 ) 4 . These chiral Rh(II) complexes have been fully characterized by EA, IR, UV-vis, NMR and specific rotation measurements. They are found to be effective chiral catalysts for asymmetric aziridination and cyclopropanation reactions in terms of reactivity and enantioselectivity. They are extremely stable and can be stored for a long period (at least 18 months) on the bench without adversely affecting their reactivity and selectivity. The heterocyclic rings as well as the substituents on the arylsulfonyl groups have critical effects on the degree of asymmetric induction. In general, a higher enantioselectivity was observed in the reactions catalyzed by the oxazolidine-4-carboxylate-derived catalysts than the thiazolidine-4-carboxylate 1,1-dioxide-based catalysts. Among these 21 new Rh(II) catalysts, the uses of dirhodium tetrakis((4S)-3-((4-dodecylphenyl)sulfonyl)oxazolidine-4-carboxylate) (Rh 2 (4S-DOSO) 4 ) and dirhodium tetrakis-((4S,5R)-5-methyl-3-((4-nitrophenyl)sulfonyl)oxazolidine-4-carboxylate) (Rh 2 (4S,5R-MNOSO) 4 ) resulted in the highest levels of enantioselectivity in aziridination (94% ee) and cyclopropanation (98% ee) of styrene, respectively. The successful design and syntheses of these novel Rh(II) complexes enlarged the scope of accessible chiral dirhodium(II) catalysts. † Electronic supplementary information (ESI) available: NMR spectra of the ligands and Rh(II) complexes; CIF files giving crystallographic data. CCDC 1055407 and 1038152. For ESI and crystallographic data in CIF or other electronic format see

Dirhodium(II,II) Paddlewheel Complexes

“… Dirhodium(II,II) complexes containing O , O '‐bridging ligands with structural motive OOCCHHetR; Het=nitrogen, R=alkyl or aryl (cyclic α‐amino acid derivatives): T1 , [182] T2 , [182] T3 , [232] T4 , [182] T5 , [223] T6 , [233] T7 , [233] T8 , [234] T9 , [234] T10 , [234] T11 , [234] T12 , [234] T13 , [234] T14 , [234] T15 , [234] T16 , [234] T17 , [234] T18 , [234] T19 , [234] T20 , [234] T21 , [234] T22 , [234] T23 , [234] T24 , [234] T25 , [234] T26 , [234] T27 , [234] T28 , [234] T29 , [235] T30 [235] …”

Novel Porous Rhodium Metal–Organic Aerogel for Efficient Removal of Organic Dyes and Catalysis of Si–H Insertion Reactions

“…In addition to iridium and ruthenium complexes, which are by far the most general catalysts for this purpose, dirhodium­(II) complexes have also garnered considerable attention as catalysts for Si–H insertion reactions. In these complexes, the bridging of the two rhodium centers by four ligands results in the formation of a paddle-wheel structure in which two axial positions of the metal ions remain uncoordinated and can act as active catalytic sites . However, most of the reported dirhodium­(II)-catalyzed processes have been carried out in homogeneous solution to ensure sufficient contact between substrates and catalysts, and thus the practical utility of the complexes is limited.…”

“…In these complexes, the bridging of the two rhodium centers by four ligands results in the formation of a paddle-wheel structure in which two axial positions of the metal ions remain uncoordinated and can act as active catalytic sites. 28 However, most of the reported dirhodium(II)-catalyzed processes have been carried out in homogeneous solution to ensure sufficient contact between substrates and catalysts, and thus the practical utility of the complexes is limited. To our knowledge, there have been only a few studies on heterogeneous dirhodium(II)catalyzed Si−H insertion reactions that occur under mild conditions.…”

Coptisine, a natural alkaloid from Coptidis Rhizoma, inhibits plasmodium falciparum dihydroorotate dehydrogenase

“…Therefore, it is still an unmet need to exploit novel and diverse PfDHODH inhibitors to evaluate their antimalaria activities. [14,15] In our continuous efforts to develop more natural product inspired antimalarial drugs, [16][17][18] we collected a library of active ingredients of TCM for the screening of PfDHODH inhibitors. [13] For instance, artemisinin, a miracle of TCM, is used worldwide as first-line treatment against confirmed or suspected plasmodium falciparum malaria.…”