Chiral Dirhodium(II) Carboxylates and Carboxamidates as Effective Chemzymes in Asymmetric Synthesis of Three‐Membered Carbocycles

Abstract

In this review the recent advances in the utilization of two of the most important classes of dirhodium(II) paddlewheel complexes, dirhodium(II) carboxylates and carboxamidates, as chemzymes in inter- and intramolecular asymmetric cyclopropanation, as well as cyclopropenation reactions are discussed.

Chiral Dirhodium(II) Carboxylates: New Insights into the Effect of Ligand Stereo-Purity on Catalyst Structure and Enantioselectivity

“…X-ray quality crystals of the dirhodium(II) complexes were obtained by dissolving the pure complex in the relevant solvent (for [Rh 2 (S-PTTL) 4 2 ]. (MeOH) 3/2 green prismatic crystals from anhydrous MeOH).…”

“…Chiral dirhodium(II) complexes are currently renowned as catalysts that can effectively drive a broad spectrum of reactions with superior levels of chemo-, regio-and stereo-selectivity [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Their remarkable selectivity has reached a stage where they can function as a powerful tool in building up value added molecules with complex structures [7,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

On the Structure of Chiral Dirhodium(II) Carboxylate Catalysts: Stereoselectivity Relevance and Insights

“…It was also assumed that, the ligand's blocking group cannot be situated in the periphery of the dirhodium(II) core as it would bump into the neighboring ligand [36,53]. Thus, by taking into account the α-and β-arrangements for all four ligands, four possible conformations can be mainly considered: α,α,α,α (C4-symmetry), α,α,β,β (C2-symmetry), α,β,α,β (D2-symmetry) and α,α,α,β (C1-symmetry) ( Figure 1) [2,4,36,53,54]. …”

“…It was also assumed that, the ligand's blocking group cannot be situated in the periphery of the dirhodium(II) core as it would bump into the neighboring ligand [36,53]. Thus, by taking into account the α-and β-arrangements for all four ligands, four possible conformations can be mainly considered: α,α,α,α (C 4 -symmetry), α,α,β,β (C 2 -symmetry), α,β,α,β (D 2 -symmetry) and α,α,α,β (C 1 -symmetry) ( Figure 1) [2,4,36,53,54]. Main arrangements of ligand's blocking groups around the dirhodium(II) core and their point groups (the sterically blocking groups around the rhodium active sites are depicted as ovals) [2,4,36,53,54].…”

“…Chiral dirhodium(II) paddlewheel complexes are among the most attractive catalysts that found a widespread application in the fields of metal-nitrene and metal-carbene transformations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This immense interest originates from their exceptional ability to effectively catalyze a broad spectrum of reactions with high levels of chemo-, regio-and stereo-selectivity.…”