Tris(cyclopentadienyl)lanthanide Complexes as Catalysts for Hydroboration Reaction toward Aldehydes and Ketones

Sufang, Chen; Yan, Dandan; Xue, Mingqiang; Hong, Yubiao; Yao, Yingming; Shen, Qi

doi:10.1021/acs.orglett.7b01335

Cited by 91 publications

(53 citation statements)

References 58 publications

(28 reference statements)

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“…[4][5][6][7][8] Lanthanide oxophilicity can also enable C-O bond cleavage in ethers or in transesterification reactions; however, reductive catalytic C-O bond cleavage processes are typically inhibited by the stabilization of intermediates containing Ln-O bonds (Ln = lanthanides and group 3). A few examples of hydroboration of ketones and aldehydes, using the homoleptic lanthanum catalysts La{N(SiMe3)2}3 and Cp3La, [9][10][11] or hydroboration and C-O bond cleavage of esters catalyzed by La{C(SiHMe2)3}3 or La{N(SiMe3)2}3, [12][13] suggest strategies for overcoming the Ln-O bond strength to make use of highly electrophilic lanthanide centers. In fact, La{C(SiHMe2)3}3 represents the most active and versatile catalyst for the ringopening hydroboration of epoxides to date.…”

Section: Introductionmentioning

confidence: 99%

“…Among the analytical techniques capable of probing the grafting process, as well as the structures and dynamics of surface-attached organometallic species, nuclear magnetic resonance (NMR) spectroscopy proved to be particularly powerful. 29,32,[35][36][37][38][39][40][41] Here, definite structural characterizations of the surfacegrafted alkyl lanthanum species were obtained from one-and two-dimensional (1D and 2D) solid-state (SS)NMR measurements on 1 H, 11 B, 13 C and 29 Si nuclei, performed in concert with solution-state NMR, elemental analysis and diffuse reflectance infrared spectroscopy (DRIFTS). Importantly, SSNMR experiments were used to understand and optimize the grafting reactions, to provide spectroscopic signatures of the secondary La↼H-Si interactions in the grafted ligands, and to propose the structures of the active catalytic centers generated by reacting pinacolborane (HBpin) with surface-attached alkyl lanthanum species.…”

Section: Introductionmentioning

confidence: 99%

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Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

et al. 2020

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Single-site organolanthanum complexes supported on mesoporous silica nanoparticles, La{C(SiHMe2)3}n@MSNs, catalyze the ring-opening hydroboration reaction of aliphatic and styrenic epoxides with pinacolborane (HBpin). The surface-bound complexes, synthesized by reaction of the homoleptic tris(alkyl)lanthanum La{C(SiHMe2)3}3 and SBA-type MSN treated at 700 °C (MSN700), are mostly monopodal ≡SiO-La{C(SiHMe2)3}2 and contain an average of one bridging La↼H-Si per alkyl ligand. This structure was established through a combination of solid-state NMR (SSNMR) experiments, including J-resolved SiH coupling and quantitative 29Si measurements, diffuse reflectance IR, and elemental analysis. These rigorous analyses also established that grafting reactions in pentane provide a preponderance of ≡SiO-La{C(SiHMe2)3}2 sites and are superior to those in benzene and THF, and that grafting onto MSN treated at 550 °C (MSN550) results in a mixture of surface species. The single-site supported catalysts are more selective and in most cases more active than the homogeneous analogue, allow easy purification of products from the catalyst, are strongly resistant to leaching into solution phase, and may be recycled for reuse at least five times. After reaction of La{C(SiHMe2)3}n@MSN and HBpin, species including ≡SiO-La{C(SiHMe2)3}(H2Bpin) and ≡SiO-La{C(SiHMe2)3}{κ2-pinB-O(CMe2)2OBH3} are identified by detailed 1D and 2D 11B SSNMR experiments.ABSTRACT: Single-site organolanthanum complexes supported on mesoporous silica nanoparticles, La{C(SiHMe2)3}n@MSNs, catalyze the ring-opening hydroboration reaction of aliphatic and styrenic epoxides with pinacolborane (HBpin). The surface-bound complexes, synthesized by reaction of the homoleptic tris(alkyl)lanthanum La{C(SiHMe2)3}3 and SBA-type MSNs treated at 700 °C (MSN700), are mostly monopodal ≡SiO-La{C(SiHMe2)3}2 and contain an average of one bridging La↼H-Si per alkyl ligand. This structure was established through a combination of solid-state NMR (SSNMR) experiments, including J-resolved SiH coupling and quantitative 29 Si measurements, diffuse reflectance IR, and elemental analysis. These rigorous analyses also established that grafting reactions in pentane provide a preponderance of ≡SiO-La{C(SiHMe2)3}2 sites and are superior to those in benzene and THF, and that grafting onto MSN treated at 550 °C (MSN550) results in a mixture of surface species. The single-site supported catalysts are more selective and in most cases more active as the homogeneous analogue, allow easy purification of products from the catalyst, are strongly resistant to leaching into solution phase, and may be recycled for reuse at least five times. After reaction of La{C(SiHMe2)3}n@MSN and HBpin, species including ≡SiO-La{C(SiHMe2)3}(H2Bpin) and ≡SiO-La{C(SiHMe2)3}{κ 2 -pinB-O(CMe2)2OBH3} are identified by detailed 1D and 2D 11 B SSNMR experiments. AUTHOR INFORMATION Corresponding Authors

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

et al. 2020

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“…[9][10][11][12][13][14] As a result, innumerable procedures have been evolved to accomplish the addition of boranes to nitriles. All these procedures require more or less effective catalysts based on transition-metal complexes such as Co, Fe, Ru, [15][16][17][18][19][20][21][22][23] alkaline earth metal (Mg), [24][25][26][27][28][29][30][31][32][33][34][35] but the processes culminate in frustrated Lewis pairs. [36][37][38] On the other hand, while the reduction of aryl and alkyl nitriles can be achieved using stoichiometric quantities of maingroup reducing agents such as LiAlH 4 and NaBH 4 , [39] the combustible nature of these reagents and large quantities of inorganic waste by-products they generate render the process unattractive, and hence reductive hydroboration is preferable in order to provide further functionality to the resultant amine.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Hydroboration of Organic Nitriles Promoted by Aluminum Complex

2018

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We demonstrate an efficient protocol for the chemoselective hydroboration of organic nitriles with pinacolborane (HBpin) and catecholborane (HBcat) using aluminum alkyl complex [k 2 -{2-FÀC 6 H 4 NP(Se)Ph 2 } 2 AlÀ(Me)] as a pre-catalyst to afford diboryl amines under solvent-free and mild conditions (60 8C) in high yield. The aluminum complex was prepared by the reaction of [2-FÀC 6 H 4 NHP(Se)Ph 2 ] and trimethylaluminum in toluene. The solid-state structure of Al complex is established. Nitriles with a wide array of electronwithdrawing and electron-donating functional groups were easily converted to the desired products through the formation of aluminum hydride as an active species. A kinetic study of the catalytic reaction is also reported.

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“…For example, some reported catalysts demonstrated high efficiency on aldehydes and ketones but proved to have no catalytic activity on esters at all . Viewing that the ester hydroboration has been reported sparingly, it is rewarding to extend our existed hydroboration work from aldehydes and ketones,[10a‐d] imines and alkynes[10e] as well as carboxylic acids[10f] to esters. Recently, Marks et al .…”

Section: Background and Originality Contentmentioning

confidence: 99%

La[N(SiMe₃)₂]₃‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups

Kang

Yan

et al. 2019

Chin. J. Chem.

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Summary of main observation and conclusion The commercially available homoleptic lanthanum amide La[N(SiMe3)2]3 (LaNTMS) is reported to enable the hydroboration of esters using pinacolborane (HBpin) as the reducing agent. A wide range of substrates including aromatic, aliphatic esters and lactones were applicable to afford corresponding boronic esters in excellent yields under mild and neat conditions with broad functional group compatibility and good chemoselectivity. Furthermore, LaNTMS is capable to realize the very challenging and rarely reported hydroboration of carbonate esters with low catalyst loading at room temperature. Both cyclic and linear carbonate esters can be easily converted to the corresponding products with satisfactory yields. Besides, the hydroboration of alkynes has been developed by using LaNTMS as a catalyst.

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Tris(cyclopentadienyl)lanthanide Complexes as Catalysts for Hydroboration Reaction toward Aldehydes and Ketones

Cited by 91 publications

References 58 publications

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

Catalytic Hydroboration of Organic Nitriles Promoted by Aluminum Complex

La[N(SiMe₃)₂]₃‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups

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Tris(cyclopentadienyl)lanthanide Complexes as Catalysts for Hydroboration Reaction toward Aldehydes and Ketones

Cited by 91 publications

References 58 publications

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

Catalytic Hydroboration of Organic Nitriles Promoted by Aluminum Complex

La[N(SiMe3)2]3‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups

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La[N(SiMe₃)₂]₃‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups