Chiral Amino Acids‐Derived Catalysts and Ligands

Abstract

Transforming amino acids into novel catalysts and ligands is a remarkable subset of new catalyst development in order to imitate enzymatic efficiencies. Their ability to perform a variety of asymmetric catalytic reactions is complimented by their ready availability, rich transformations, stability and easy procedure. Herein, we focused on describing our endeavor of developing new catalysts and ligands from primary and secondary amino acids. It includes C2‐symmetric N,N'‐dioxides, guanidine‐amides, bispidine‐based diamines, and other organic salts. The account covered a brief introduction about their discovery, representative applications and related mechanisms.

Bimetallic Rhodium(II)/Indium(III) Relay Catalysis for Tandem Insertion/Asymmetric Claisen Rearrangement

“…[c] With 5mol %c atalyst. Based on Xray structures,c ontrol experiments,a nd previous works, [9] possible transition state models were proposed to elucidate the origin of chiral induction. (20 mg), and toluene (0.2 m), 70 8 8C, 4h.The er value was detected by chiral-phase HPLC.…”

“…Therefore,w especulate that the active catalyst in the current system is mononuclear indium complex. Based on Xray structures,c ontrol experiments,a nd previous works, [9] possible transition state models were proposed to elucidate the origin of chiral induction. As shown in Figure 1b,the allyl vinyl ether intermediate binds to In III with oxygen atoms of both tosyl group and ester group in abidentate manner, while the Ph group prefers to point downwards to prevent the steric hindrance with the amide unit of the ligand.…”

“…Intrigued by the well-characterized platform of N,N'dioxide-metal complexes as chiral Lewis acid catalysts, [9] we became interested in expanding their utility through combining Lewis acid catalysis with transition metal catalysis.T his manifold provides anew avenue to chiral molecules which are difficult to access by conventional approaches. [10] In view of the reaction mechanism of N-sulfonyl-1,2,3-triazoles with allyl alcohol derivatives,w ee nvisioned that bimetallic relay catalytic systems are probably ag ood choice to address the challenging issue mentioned in the preceding paragraph.…”

Asymmetric Synthesis of Oxa‐Bridged Oxazocines through a Catalytic RhII/ZnII Relay [4+3] Cycloaddition Reaction

“…In prior synthesis,a midation, ketalization, and S N Ar reaction were applied as ak ey step to realize this construction. [13] Chiral N,N'-dioxide ligands have been proven to have good coordination ability with Lewis acids, [14] but not with transition metals,w hich means that the two catalysts have good compatibility in relay catalysis.B ased on our previous work, [15] we envisaged an achiral Rh II complex leading to isomünchnone from diazoimide,f ollowed by the application of aLewis acid combined with achiral N,N'-dioxide ligand to promote the subsequent asymmetric cycloaddition reaction in one pot, to realize ac atalytic bimetallic relay asymmetric [4+ +3]-cycloaddition of b,g-unsaturated a-ketoesters with isomünchnones.…”

“…Changing the ester group (R 1 )from methyl to abulkier aliphatic isopropyl, cyclopentyl, or benzyl group,the yields and ee values could still remain (entries 1-4). b,g-Unsaturated a-ketoesters with electron-withdrawing or electron-donating substituents at different positions of the phenyl group can react smoothly to afford the corresponding products in good yields (71-90 %y ield) and excellent ee values (97-99 % ee;e ntries [5][6][7][8][9][10][11][12][13][14][15][16]. It was worth mentioning that a-ketoester 1j,which contains ahydroxy group,was also compatible,p roducing the product 3ja in 88 %y ield with 97 % ee (entry 10).…”