Synthesis of novel planar chiral Ag and Rh N-heterocyclic carbene complexes derived from [2.2]paracyclophane and their application in ultrasound assisted asymmetric addition reactions of organoboronic acids to aldehydes

Duan, Wenzeng; Ma, Yudao; He, Fuyan; Zhao, Lei; Chen, Jianqiang; Song, Chun

doi:10.1016/j.tetasy.2013.01.017

Cited by 29 publications

(13 citation statements)

References 75 publications

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“…The pattern of results for the methylimidazole series was more complicated. Three alcohols (13)(14)(15), containing a para-substituted or unsubstituted aromatic ring, were formed in 0 %-70 % ee. Since the more electron-rich (OMe substituted) substrate gave the highest ee product, and the electron-poor (Cl substituted) the lowest, it is speculated that S-configuration products were formed, via an approach of substrate to catalyst in which the aromatic group is proximal to the η 6arene of the catalyst (Figure 6C).…”

Section: Resultsmentioning

confidence: 99%

“…This compound has been reported and fully characterized. [13,14] Furan-2-carbaldehyde (250 mg, 2.60 mmol) was added to a flask, followed by THF (2.5 mL) and the flask was placed into an ice bath and cooled to 0 °C, with stirring under a nitrogen atmosphere. Phenyl magnesium bromide (0.950 ml, 3.0 M in diethyl ether, 2.85 mmol) was added dropwise and the reaction was stirred under the nitrogen atmosphere at rt overnight.…”

Section: General Experimental Detailsmentioning

confidence: 99%

“…The reaction was also followed by HPLC ODH, 30 cm × 6 mm column, hexane:iPrOH 97 : 3, 1.0 mL/min, T = 25 °C); (R,R)-3C-tethered Ru(II)-TsDPEN catalyst: [α] D 23 + 2.35 (c 0.5 in CHCl 3 ) 99.9 % conversion (HPLC calibration: 1 : 1 furan-2-yl(phenyl)methanone: furan-2-yl-(phenyl)methanol gives 25.3 : 1 ratio of absorption at 254 nm); 47 % ee (R) (lit. [14] [α] D 20 À 1.4 (c 0.15 in CHCl 3 ) 20 % ee (S)).…”

Section: General Experimental Detailsmentioning

confidence: 99%

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Asymmetric Transfer Hydrogenation of Aryl Heteroaryl Ketones using Noyori‐Ikariya Catalysts

et al. 2021

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A range of ketones flanked by a combination of an aromatic and a heterocyclic ring (furan, thiophene, N-methylimidazole) were reduced under asymmetric transfer hydrogenation (ATH) conditions. Using a range of [(arene)Ru(TsDPEN)Cl] precatalysts, including tethered derivatives, the reduction enantioselectivity was high (up to 99 % ee) in cases where the aromatic ring contained an ortho-substituent. The enantioselectivity is influenced by a combination of steric and electronic factors which for the furan and thiophene series, follow literature precedents. In the case of the N-methylimidazole-containing ketones, an unexpected switch in enantioselectivity took place upon variation of the opposing aromatic group. Pyrrole-containing ketones were resistant to reduction. This study demonstrates the asymmetric transfer hydrogenation (ATH) of a range of hindered heterocyclic ketones, in high conversion and ee, using Noyori-Ikariya catalysts.

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Section: Resultsmentioning

confidence: 99%

Section: General Experimental Detailsmentioning

confidence: 99%

Section: General Experimental Detailsmentioning

confidence: 99%

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Asymmetric Transfer Hydrogenation of Aryl Heteroaryl Ketones using Noyori‐Ikariya Catalysts

et al. 2021

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“…A series of Ag complexes bearing planar chiral NHC ligands, 131 – 135 (Figure ) was reported by Ma and Song et al . A combination of complexes 131 – 135 and an appropriate Rh source served as an effective catalyst system for the asymmetric addition of organoboronic acids to aryl aldehydes.…”

Section: Ag(i)‐carbene Complexes Of Chiral Nhc Ligandsmentioning

confidence: 99%

Coinage Metal Complexes of Chiral N‐Heterocyclic Carbene Ligands: Syntheses and Applications in Asymmetric Catalysis

et al. 2020

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Chiral N‐heterocyclic carbenes (NHCs) have become ligands of choice due to their remarkable catalytic activity in organic transformation reactions. Combining the chiral NHC ligand family and coinage metals became a productive area of research. The organometallic chemistry of coinage metals with the chiral N‐heterocyclic carbene (NHC) ligands is reviewed, with a special emphasis on the synthesis, characterization and possible applications obtained. Significant sections are devoted to the various recently developed coinage metal‐chiral NHC complexes and a detailed comparison of their activities which aims to rationalize the structure–activity relationships. Various methods of preparations of coinage metal‐chiral NHC complexes along with some typical examples of reactivity and mechanisms are covered. Cu‐chiral NHC complexes involved in conjugated additions, allylic substitutions, boration of alkenes, hydrosilylation of ketones and formation of alkenes are covered, along with some remarkable examples and reactivity of Ag‐chiral NHC complexes. Finally, applications of Au‐chiral NHC complexes in the asymmetric cyclization of ester‐functionalized 1,6‐enynes, 1,6‐enyneamines and substituted propargyloxymethanes are also reviewed.

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“…[2.2]paracyclophane derivatives have been used in asymmetric synthesis as both chiral auxiliaries 28,29 and chiral ligands. 30,31 Current research has focused on the synthesis of new chiral ligands incorporating the [2.2]paracyclophane backbone.…”

Section: Cyclophanesmentioning

confidence: 99%

Tracking the Source of Enantioselectivity

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<p>Enantioselectivity remains one of synthetic chemistry’s most formidable problems. It arises due to the formation of diastereomeric species in a reaction, either in the form of diastereomeric intermediates or a set of diastereomeric transition states. Without control a racemic mixture is formed. A resolution method is then required to separate the enantiomers. Any given resolution method will rely on the differing energies of diastereomers to allow for their separation. Experimentally there are a myriad of different options that may be used to induce separation; for example chromatography and/or crystallisation. The actual process that occurs through- out this separation has not, however, been fully investigated in all cases. A better understanding of the process is able to provide an understanding of how resolution methods work i.e. when diastereomers occur and how great their energy differences are. This is vital in increasing the efficiency and effectiveness of any given resolution method. This theoretical study completed an investigation of the reaction pathway between the enantiomers of 2-formyl-3-hydroxyl[2.2]paracyclophane (FHPC) with (S)-valyl-(S)-valine. A subsequent investigation of an alternative resolution method, involving (R)-α-PEAM, was also conducted. This latter resolution method was proposed experimentally as a simpler method that could aid in improving the separation of the enantiomers. This investigation was carried out using Density Functional Theory (DFT) with the PBE0 functional and the triple-ζ TZVP basis set. The complete reaction profile was determined and diastereomeric intermediates and transition states for both resolution methods along two different pathways were determined; the ‘N-deprotonation Pathway’ and the ‘O-deprotonation Pathway’. The inadequacy of the first resolution method was found to be due to the presence of copper(II). Furthermore it was discovered that the re- action for both pathways would most likely proceed through the ‘O-deprotonation Pathway’ due to the barriers being lower in energy.</p>

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Synthesis of novel planar chiral Ag and Rh N-heterocyclic carbene complexes derived from [2.2]paracyclophane and their application in ultrasound assisted asymmetric addition reactions of organoboronic acids to aldehydes

Cited by 29 publications

References 75 publications

Asymmetric Transfer Hydrogenation of Aryl Heteroaryl Ketones using Noyori‐Ikariya Catalysts

Asymmetric Transfer Hydrogenation of Aryl Heteroaryl Ketones using Noyori‐Ikariya Catalysts

Coinage Metal Complexes of Chiral N‐Heterocyclic Carbene Ligands: Syntheses and Applications in Asymmetric Catalysis

Tracking the Source of Enantioselectivity

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