- Nucleophilic Addition and α-C-H Substitution Reactions of an Imine Mediated by Dibutylmagnesium and Organolithium Reagents
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A series of nucleophilic addition reactions and α-C-H substitution reactions of an imine-containing ligand 2-(2-((((1H-pyrrol-2-yl)methylene)amino)methyl)-1H-pyrrol-1-yl)-N,N-dimethylethan-1-amine (HL1) were reported. The reactions of HL1 with 0.5 and 2 equiv ofnBu2Mg, respectively, gave two complexes of compositions [Mg(L1)2] (1) and [Mg2(L2)2] (2) (H2L2 =N-((1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)methyl)-1-(1H-pyrrol-2-yl)pentan-1-amine). The nucleophilic addition ofnBu2Mg to the C═N bond of the HL1 ligand occurred in the process for the formation of2. Treatment of HL1 with 2 and 1 equiv ofnBuLi generated [Li2(L3)2] (3) (HL3 = 2-(2-(((1-(1H-pyrrol-2-yl)pentylidene)amino)methyl)-1H-pyrrol-1-yl)-N,N-dimethylethan-1-amine) and [Li2(L1)2] (4). An α-C-H substitution of the HC═NR moiety of the HL1 ligand triggered bynBuLi was discovered in the preparation of3. The formation of3demonstrates a new concept for the C-C coupling that involved inert C-H bond activation of HC═NR skeleton. The reactions of HL1 with MeLi,sec-BuLi, and tert-BuLi, respectively, were also examined. The products for both the nucleophilic addition of organolithium reagents to the C═N bond and α-C-H substitution of the HC═NR moiety of the HL1 ligand were determined. The mechanisms for the formations of2and3were rationalized by DFT calculations. The hydroboration reactions catalyzed by2were investigated, and these reactions characterize ample substrate scope, very good yields, and high selectivity.
- Dang, Yan,Jia, Chaohong,Li, Yafei,Li, Yahong,Lu, Yanhua,Wang, Yalan,Xia, Yuanzhi,Xu, Man,Zhang, Liang
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- Catalytic hydroboration of carbonyl derivatives by using phosphinimino amide ligated magnesium complexes
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Reduction of carbonyl derivatives by using Earth-abundant, cheap, and environmentally benign metal-based catalysts through an atom-efficient method is a challenging task. Herein, we report the synthesis and characterization of dinuclear magnesium complexes 1-3 chelated by a phosphinimino amide skeleton. In combination with pinacolborane (HBpin) as a reducing agent, complex 1 bearing an ortho-methyl substituent on the phenyl ring of the ligand showed excellent reduction capability for a broad range of carbonyl derivatives under mild reaction conditions. Aldehydes, ketones, and acrolein substrates were efficiently reduced to the corresponding alkoxy-borane products with a record high TOF. Besides, acrolein derivatives were exclusively reduced to 1,2-regioselective products. Using two equiv. of HBpin, ester substrates were reduced to two kinds of alkoxy-borane products. Carbonate reduction accomplished by using complex 1 and three equiv. of HBpin afforded diols and a methanol precursor, respectively. When chiral substrates such as (S)-1,2-propanediol carbonate and l-lactide or polymeric P(l-LA) were employed, the chirality was almost retained in their reductive products.
- Cui, Dongmei,Li, Min,Liu, Xinli
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supporting information
p. 13037 - 13041
(2021/10/12)
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- Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin-2-iminato) Hafnium Complexes
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Imidazolin-2-iminato hafnium complexes of the type [(ImRN)Hf(CH2Ph)3] were synthesized (ImtBuN = 1,3-di-tert-butylimidazolin-2-iminato); ImDippN = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-iminato.
- Khononov, Maxim,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
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supporting information
p. 3153 - 3160
(2020/02/28)
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- Catalytic regeneration of a Th-H bond from a Th-O bond through a mild and chemoselective carbonyl hydroboration
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Here we present an unprecedented chemoselective hydroboration for aldehydes and ketones catalysed by actinides. The reaction features a very low catalyst loading (0.1-0.004 mol%) and quantitative product formation in less than 15 minutes, at room temperature. Thermodynamic and kinetic studies including stoichiometric and labeling studies with deuterated pinacolborane allow us to propose a plausible mechanism for this remarkable catalytic regeneration of a Th-H bond via carbonyl hydroboration.
- Ghatak, Tapas,Makarov, Konstantin,Fridman, Natalia,Eisen, Moris S.
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supporting information
p. 11001 - 11004
(2018/10/08)
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- Rapid, Mild, and Selective Ketone and Aldehyde Hydroboration/Reduction Mediated by a Simple Lanthanide Catalyst
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Rapid, clean hydroboration of ketones and aldehydes with HBpin is achieved using the homoleptic rare-earth catalyst La[N(SiMe3)2]3 (LaNTMS). The reaction employs low catalyst loadings (0.01-1 mol % LaNTMS), proceeds rapidly (>99% in 5 min) at 25 °C, and is moderately air-tolerant. Additionally, this hydroboration has good functional group compatibility, including halides, nitro groups, and nitriles, and is exclusively carbonyl-selective in the presence of alkenes and alkynes.
- Weidner, Victoria L.,Barger, Christopher J.,Delferro, Massimiliano,Lohr, Tracy L.,Marks, Tobin J.
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p. 1244 - 1247
(2017/08/09)
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- Titanocene(II)-catalyzed hydroboration of carbonyl compounds
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Titanocene bis(catecholborane), [Cp2Ti(HBcat)2] (1), catalyzes the room-temperature hydroboration of carbonyl compounds by pinacolborane (HBpin) rapidly, cleanly, and chemoselectively. Aryl aldehydes and ketones produced alkoxypinacolboronate esters in moderate to high yields in 2 h, and facile hydrolysis of alkoxypinacolboronate esters over silica occurred cleanly to afford alcohols in good yields. Complex 1 demonstrated a preference for C=O bonds over C=C bonds in both conjugated and nonconjugated enones. Kinetic studies of the catalytic hydroboration of a series of acetophenones showed that electron-poor substrates undergo the reaction more quickly than electron-rich substrates. This result is consistent with the proposed mechanism, in which stronger π-acids should undergo C=O bond cleavage more readily. Computational studies using benzophenone and benzaldehyde showed that the hydroboration is spontaneous and likely proceeds via intermediates that are best described as Ti metallacycles whose structures are not significantly altered by substrate steric differences. This result indicates that similarities in the electronic properties of benzophenone and benzaldehyde supersede their steric differences in determining reaction outcomes.
- Oluyadi, Abdulafeez A.,Ma, Shuhua,Muhoro, Clare N.
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