Recent Advances in Metal‐Catalyzed Asymmetric Hydroboration of Ketones

Wang, Ruibin; Park, Sehoon

doi:10.1002/cctc.202001947

Cited by 29 publications

(27 citation statements)

References 184 publications

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“…Upon activation with LiCH 2 SiMe 3 , both UiO-67-Fe and UiO-68-Fe became the active catalysts for the asymmetric hydroboration of aliphatic and aromatic ketones using pinacolborane (Table 2). 96,97 The reaction of ketones with 1.1 equiv of pinacolborane in the presence of 0.05 mol % Fe loading, vol-UiO-Fe for 12 min in THF at room temperature produced borate esters in excellent yields and enantiopurity. In most cases, the borate esters were obtained in quantitative yields by simple removal of the solid MOF-catalyst and volatiles.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Chiral Iron(II)-Catalysts within Valinol-Grafted Metal–Organic Frameworks for Enantioselective Reduction of Ketones

et al. 2021

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The development of highly efficient and enantioselective heterogeneous catalysts based on earth-abundant elements and inexpensive chiral ligands is essential for environment-friendly and economical production of optically active compounds. We report a strategy of synthesizing chiral amino alcohol-functionalized metal–organic frameworks (MOFs) to afford highly enantioselective single-site base-metal catalysts for asymmetric organic transformations. The chiral MOFs (vol-UiO) were prepared by grafting of chiral amino alcohol such as l-valinol within the pores of aldehyde-functionalized UiO-MOFs via formation of imine linkages. The metalation of vol-UiO with FeCl2 in THF gives amino alcohol coordinated octahedral FeII species of vol-FeCl(THF)3 within the MOFs as determined by X-ray absorption spectroscopy. Upon activation with LiCH2SiMe3, vol-UiO-Fe catalyzed hydrosilylation and hydroboration of a range of aliphatic and aromatic carbonyls to afford the corresponding chiral alcohols with enantiomeric excesses up to 99%. Vol-UiO-Fe catalysts have high turnover numbers of up to 15 000 and could be reused at least 10 times without any loss of activity and enantioselectivity. The spectroscopic, kinetic, and computational studies suggest iron-hydride as the catalytic species, which undergoes enantioselective 1,2-insertion of carbonyl to give an iron-alkoxide intermediate. The subsequent σ-bond metathesis between Fe–O bond and Si–H bond of silane produces chiral silyl ether. This work highlights the importance of MOFs as the tunable molecular material for designing chiral solid catalysts based on inexpensive natural feedstocks such as chiral amino acids and base-metals for asymmetric organic transformations.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Chiral Iron(II)-Catalysts within Valinol-Grafted Metal–Organic Frameworks for Enantioselective Reduction of Ketones

et al. 2021

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“…However, the progress in hydroboration of unsaturated C–hetero bonds by rare‐earth catalysts still remains limited, and many questions need to be addressed, such as the underlying mechanisms and stereoselectivity of prochiral substrates, for example, unsymmetrical epoxides and ketones. [ 52 ] Thus, there is still great unknown space to be explored in this field owing to the high Lewis acidity and flexible coordination geometries of rare‐earth metals, and the rapid emerging areas, such as photocatalysis, flow chemistry, and cooperative catalysis, will be significantly accelerated with the participation of rare‐earth metals. [ 53 ]…”

Section: Discussionmentioning

confidence: 99%

Rare‐earth metal‐catalyzed hydroboration of unsaturated compounds

Nie

Han

Wang

et al. 2021

Applied Organom Chemis

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The reduction of unsaturated compounds is one of the most widely applied transformations in organic synthesis. Aggressive reductants, highly pressurized hydrogen gas, and stoichiometric amount of metal salts used have greatly burdened the environment, stimulating the development of catalytic approaches with milder and greener conditions. In this context, the hydroboration has attracted great attention, and great progress has been achieved in the past decades. Due to the great performance of rare‐earth complexes in numerous organic transformations, such complexes are also employed as catalysts in the hydroboration of different unsaturated compounds. The current review summarized recent works of rare‐earth complexes catalyzed hydroboration of various unsaturated compounds, covering the publications mainly in past 5 years albeit with alkenes as exception. The transformations are mainly classified into two categories: hydroboration of C–C and C–hetero unsaturated compounds, and some closely related works are also discussed, such as rare‐earth catalyzed direct borylation of C–H bonds.

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“…Hence, we developed an improved PGB-0 through the synthesis of PGB-0-F (fructose) and PGB-0-Sor (sorbitol) complexes. [ 7 ] In the present study, we synthesized PGB-0-ol by a simple process using NaBH 4 as a reducing agent,[ 8 ] and purified the new compound using preparative layer chromatography (PLC). The final product was clarified by IR, NMR, and mass spectrometry.…”

Section: Introductionmentioning

confidence: 99%