Chiral Recognition and Photoreaction of β-Amino Acids with Iridium(III)Complexes

β-Amino acids(AAs),homologs ofα-AAs,are important building blocks of biological materials.Herein,chiral recognitions ofβ-AAs with Ir(III)complexes are reported,in favor of formation of the thermodynamically stableΛ-[Ir(pq)_(2)(D-β-AAs)]andΔ-[Ir(pq)_(2)(L-β-AAs)](pq is 2-phenylquinoline)diastereomers.The photoreactions of[Ir(pq)_(2)(β-AA)]complexes are observed in an EtOH solution in the presence of O_(2) at room temperature.The primaryβ-AAs complexes,such as rac-[Ir(pq)_(2)(β-ala)](β-ala isβ-alanine),Δ-[Ir(pq)_(2)(D-β-ma)]andΛ-[Ir(pq)_(2)(D-β-ma)](β-ma isβ-methylalanine),Δ-[Ir(pq)_(2)(D-β-pa)]andΛ-[Ir(pq)_(2)(D-β-pa)](β-pa isβ-phenylalanine),and rac-[Ir(pq)_(2)(β-dma)](β-dma is 3,3-dimethyl-β-alanine),are interligand C—N cross-coupling in situ between pq andβ-AAs ligands.The secondaryβ-AA complexesΔ-[Ir(pq)_(2)(L-β-pro)]andΛ-[Ir(pq)_(2)(L-β-pro)](β-pro isβ-proline,2-(pyrrolidin-2-yl)acetic acid)are dehydrogenatively oxidized into imino acid complexesΔ-[Ir(pq)_(2)(L-β-pro-2H^(β)’)]andΛ-[Ir(pq)_(2)(L-β-pro-2H^(β)’)](L-β-pro-2H^(β)’=2-(3,4-dihydro-2H-pyrrol-2-yl)acetic acid),respectively.Moreover,the dehydrogenative reaction inΔ-[Ir(pq)_(2)(L-β-pro)]diastereomer is regioselective depending on the reaction temperature,affordingΔ-[Ir(pq)_(2)(L-β-pro-2H^(β)’)]andΔ-[Ir(pq)_(2)(L-β-pro-2H^(β))](β-pro-2H^(β)=2-(3,4-dihydro-2H-pyrrol-5-yl)acetic acid)at low temperature.The chiral recognitions and photoreactions of Ir(III)-β-AAs complexes are much different from the previous observations in Ir(III)-α-AAs complexes.

Diastereoselective Photoreaction of Ir(III) Amine Complexes for Generation of New Multidentate Ligands in situ via a Postcoordinated Interligand-Coupling Strategy

The diastereoselective photoreactions of Ir(III)-amine and Ir(III)-diamine complexes are observed in the presence of O2.TheɅ-[Ir(pq)_(2)(R-mapy)](PF_(6))(pq is 2-phenylquinoline and mapy is 2-(1-aminoethyl)pyridine)diastereomer is dehydrogenatively oxidized into imine complexɅ-[Ir(pq)_(2)(mapy-2H)](PF_(6))at room temperature,while theɅ-[Ir(pq)_(2)(S-mapy)](PF_(6))diastereomer occurs interligand C—N cross-coupling reaction at 60℃,affording a new tetradentate complexɅ-[Ir(pq)(S-pqpe)](PF_(6))(pqpe is 2-phenyl-N-(1-pyridin-2-yl)ethyl-quinolin-8-amine).The identical cases are also observed in diamine complexesɅ-[Ir(pq)_(2)(R,R-chda)](PF_(6))(chda is 1,2-diaminocyclohexane),Ʌ-[Ir(pq)_(2)(R,S-chda)](PF_(6)),andɅ-[Ir(pq)_(2)(S,S-chda)](PF_(6)),where the R configuration ligand is dehydrogenatively oxidized into imine,while the S configuration is retentive and the bound nitrogen atom is coupling to the C8 of pq ligand,affordingɅ-[Ir(pq)_(2)(chdi)](PF_(6))(chdi is 1,2-diiminocyclohexane),Ʌ-[Ir(pq)(S-pqchim)](PF_(6))(pqchim is N-(2-iminocyclohexyl)-2-phenyl-quinolin-8-amine),andɅ-[Ir(S,S-pqchda)](PF_(6))(pqchda is N',N”-bis(2-phenylquinolin-8-yl)cyclohexane-1,2-diamine),respectively.These provide a new and useful protocol for the synthesis of multidentate ligands in situ via the postcoordinated interligand-coupling strategy under mild conditions.

Thermodynamic Resolution of Pharmaceutical Precursor Modafinil Acid on the Basis of Chiral-at-Metal Strategy

Chiral-at-metal strategy was developed to resolve the essential sulfoxide pharmaceutical intermediates R-modafinil acid and its ana-logues with high yields and ee values.The efficient resolution process was achieved based on the diastereoselective discrimination caused by hydrogen bond and intramolecular π-π interaction between chiral-at-metal center and the coordinated chiral sulfoxide ligands.Moreover,the chiral Ir(lll)receptor can be reused with complete retention of their configurations and without the loss of reaction activity and enantioselectivity.This work provides a new access to synthesize R-modafinil acid as well as its analogues and develops the application of chiral-at-metal strategy in chiral resolution.