Chiral Cyclopentadienyl Ligands: Design, Syntheses, and Applications in Asymmetric Catalysis

Abstract

Figure 5. An overview of the current families of Cp X ligands.

Ruthenium(II)/Chiral Carboxylic Acid Catalyzed Enantioselective C–H Functionalization of Sulfoximines

“…Thus, asymmetric catalytic systems efficiently employed with the group 9 catalysts 10 can also be used with Ru(II) catalysts, except for the introduction of chiral Cp x ligands. 10` b c It is worth noting that both the strategies mentioned above (Scheme 1a and 1b) have been successfully employed in Rh(III)- 11 and Co(III)-catalyzed 12 reactions to control the enantio-determining step that takes place after the cleavage of a C–H bond.…”

Theoretical Studies on the Mechanism of the Formation of Cyclopentadienes and Dihydropyridazines

“…Cyclopentadienes (Cps) are important, as synthetic intermediates, in the field of organic and organometallic chemistry. [1][2][3][4][5] Cps are well-known as precursors to build transition-metal complexes with Cp-type ligands in the field of coordination chemistry [6][7][8][9][10] and also as diene units to form cyclic heterocycles with the help of inter-and intramolecular Diels-Alder (DA) reactions. [11][12][13][14] Despite their importance, it is very difficult to synthesise substituted Cps, due to the instability of the parent Cp and the easy migration of the endocyclic double bonds.…”

Rhodium(III)‐Catalyzed Asymmetric [4+1] and [5+1] Annulation of Arenes and 1,3‐Enynes: A Distinct Mechanism of Allyl Formation and Allyl Functionalization

“…[13] With the powerful role of chiral cyclopentadienyl (Cp x )r hodium(III) catalysts in asymmetric CÀHa ctivation as pioneered by Cramer [15a] and Rovis, [15b] asymmetric Rh III catalysis has demonstrated increasing potential in construction of highly enantioenriched aromatics. [13][14][15][16][17][18] In previous asymmetric C À H activation systems,a lkenes, [15] alkynes, [16] and diazo [17] compounds are predominant coupling partners.I np articular, alkenes [15a-f] and alkynes [16] typically react as aC2component. On the other hand, in the very few reports of Cp x Rh(III)catalyzed asymmetric [4+ +1] annulation systems,o nly diazo compounds, [17a,b] difluoroalkynes, [18] allenes, [13] and alkene [19] have been employed as coupling reagents (Scheme 1b), which stays contrast to various reports of racemic [n+ +1] annulation reactions.…”