95770-20-0Relevant articles and documents
Ir-Catalyzed ortho-Borylation of Phenols Directed by Substrate-Ligand Electrostatic Interactions: A Combined Experimental/in Silico Strategy for Optimizing Weak Interactions
Chattopadhyay, Buddhadeb,Dannatt, Jonathan E.,Andujar-De Sanctis, Ivonne L.,Gore, Kristin A.,Maleczka, Robert E.,Singleton, Daniel A.,Smith, Milton R.
, p. 7864 - 7871 (2017)
A strategy for affecting ortho versus meta/para selectivity in Ir-catalyzed C-H borylations (CHBs) of phenols is described. From selectivity observations with ArylOBpin (pin = pinacolate), it is hypothesized that an electrostatic interaction between the partial negatively charged OBpin group and the partial positively charged bipyridine ligand of the catalyst favors ortho selectivity. Experimental and computational studies designed to test this hypothesis support it. From further computational work a second generation, in silico designed catalyst emerged, where replacing Bpin with Beg (eg = ethylene glycolate) was predicted to significantly improve ortho selectivity. Experimentally, reactions employing B2eg2 gave ortho selectivities > 99%. Adding triethylamine significantly improved conversions. This ligand-substrate electrostatic interaction provides a unique control element for selective C-H functionalization.
Catalytic Hydroboration of Esters by Versatile Thorium and Uranium Amide Complexes
Makarov, Konstantin,Kaushansky, Alexander,Eisen, Moris S.
, p. 273 - 284 (2022/01/03)
The challenging hydroboration of esters is achieved using simple uranium and thorium amides, U[N(SiMe3)2]3 and [(Me3Si)2N]2An[κ2-(N,C)-CH2Si(CH3)2N(SiMe3)] (An = Th or U) acting as precatalysts in the reaction with pinacolborane (HBpin). All three complexes showed impressive catalytic activities, reaching excellent yields. A large scope of esters was investigated including aliphatic, aromatic, and heterocyclic esters that were transformed cleanly to the corresponding hydroborated alcohols, which readily hydrolyzed to the free alcohols. Moreover, the actinide catalysts demonstrated unexpected high functional tolerance toward nitro, halide, cyano, and heteroaromatic functional groups. The reaction exhibited excellent selectivity toward the ester when additional double and triple unsaturated C-C bonds were present. Lactones and poly caprolactone have been successfully cleaved to the monomeric units, showing a great promise toward polymer degradation and recycling. Detailed kinetic studies are provided in order to determine the rate dependence on the concentration of catalyst, HBpin, and ester. A plausible mechanism is proposed based on stoichiometric reactions, DFT calculations, thermodynamic measurements, and deuterium-labeling studies.
Hydroboration of Nitriles, Esters, and Carbonates Catalyzed by Simple Earth-Abundant Metal Triflate Salts
Thenarukandiyil, Ranjeesh,Satheesh, Vanaparthi,Shimon, Linda J. W.,de Ruiter, Graham
, p. 999 - 1006 (2021/03/30)
During the past decade earth-abundant metals have become increasingly important in homogeneous catalysis. One of the reactions in which earth-abundant metals have found important applications is the hydroboration of unsaturated C?C and C?X bonds (X=O or N). Within these set of transformations, the hydroboration of challenging substrates such as nitriles, carbonates and esters still remain difficult and often relies on elaborate ligand designs and highly reactive catalysts (e. g., metal alkyls/hydrides). Here we report an effective methodology for the hydroboration of challenging C≡N and C=O bonds that is simple and applicable to a wide set of substrates. The methodology is based on using a manganese(II) triflate salt that, in combination with commercially available potassium tert-butoxide and pinacolborane, catalyzes the hydroboration of nitriles, carbonates, and esters at room temperature and with near quantitative yields in less than three hours. Additional studies demonstrated that other earth-abundant metal triflate salts can facilitate this reaction as well, which is further discussed in this report.
Catalytic hydroboration of carbonyl derivatives by using phosphinimino amide ligated magnesium complexes
Cui, Dongmei,Li, Min,Liu, Xinli
supporting information, p. 13037 - 13041 (2021/10/12)
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.
Manganese-Catalyzed Hydroborations with Broad Scope
Ghosh, Pradip,Jacobi von Wangelin, Axel
supporting information, p. 16035 - 16043 (2021/06/16)
Reductive transformations of easily available oxidized matter are at the heart of synthetic manipulation and chemical valorization. The applications of catalytic hydrofunctionalization benefit from the use of liquid reducing agents and operationally facile setups. Metal-catalyzed hydroborations provide a highly prolific platform for reductive valorizations of stable C=X electrophiles. Here, we report an especially facile, broad-scope reduction of various functions including carbonyls, carboxylates, pyridines, carbodiimides, and carbonates under very mild conditions with the inexpensive pre-catalyst Mn(hmds)2. The reaction could be successfully applied to depolymerizations.
La(CH2C6H4NMe2-o)3-catalyzed reduction of esters to alcohols with pinacolborane
Gong, Mingliang,Luo, Yunjie,Xie, Hongzhen,Zhang, Fangcao
supporting information, p. 17654 - 17659 (2021/10/04)
Catalytic reduction of esters is a favourable synthetic strategy to obtain the corresponding alcohols. La(CH2C6H4NMe2-o)3, a simple and facilely accessible lanthanide complex, can serve as a highly efficient catalyst for the reduction of esters with pinacolborane (HBpin), selectively affording alcohols in good yields under mild conditions. This protocol exhibits good tolerance for many functional groups such as C-C double bond, nitro, halogen, furyl, and thienyl groups. A lanthanum hydride species like [La]-H·HBpin is supposed to play a crucial role in promoting the interaction of esters with HBpin.
Readily available lithium compounds as catalysts for the hydroboration of carbodiimides and esters
Bisai, Milan Kumar,Das, Tamal,Gour, Kritika,Sen, Sakya S.,Vanka, Kumar
supporting information, (2021/06/26)
Selective and efficient hydroboration of esters and carbodiimides to alcohols and amines by two well-defined and readily accessible lithium complexes, 2,6-di-tert-butyl phenolate lithium (1a) and 1,1’-dilithioferrocene (1b) are described. A range of aliphatic, aromatic, and cyclic esters with various functional groups were selectively converted into the corresponding boronate esters. Similarly, the single hydroboration of carbodiimides with aliphatic and aromatic substituents on the nitrogen atoms was studied. A possible mechanistic pathway of the hydroboration of carbodiimides with HBpin has been proposed using NMR studies and DFT calculations. These reactions are convenient alternatives to stoichiometric hydride reduction or hydrogenation. The employing of lithium complexes is also significant, because of the need to find cheap and green alternatives to noble metal complexes.
Ruthenium-catalyzed selective hydroboronolysis of ethers
Kaithal, Akash,Kalsi, Deepti,Krishnakumar, Varadhan,Pattanaik, Sandip,Bordet, Alexis,Leitner, Walter,Gunanathan, Chidambaram
, p. 14390 - 14397 (2020/12/21)
A ruthenium-catalyzed reaction of HBpin with substituted organic ethers leads to the activation of C?O bonds, resulting in the formation of alkanes and boronate esters via hydroboronolysis. A ruthenium precatalyst, [Ru (p-cymene)Cl]2Cl2 (1), is employed, and the reactions proceed under neat conditions at 135 °C and atmospheric pressure (ca. 1.5 bar at 135 °C). Unsymmetrical dibenzyl ethers undergo selective hydroboronolysis on relatively electron-poor C?O bonds. In arylbenzyl or alkylbenzyl ethers, C?O bond cleavage occurs selectively on CBn?OR bonds (Bn = benzyl); in alkylmethyl ethers, selective deconstruction of CMe?OR bonds leads to the formation of alkylboronate esters and methane. Cyclic ethers are also amenable to catalytic hydroboronolysis. Mechanistic studies indicated the immediate in situ formation of a mono-hydridobridged dinuclear ruthenium complex [{(η6-p-cymene)RuCl}2(μ?H?μ?Cl)] (2), which is highly active for hydroboronolysis of ethers. Over time, the dinuclear species decompose to produce ruthenium nanoparticles that are also active for this transformation. Using this catalytic system, hydroboronolysis could be applied effectively to a very large scope of ethers, demonstrating its great potential to cleave C?O bonds in ethers as an alternative to traditional hydrogenolysis.
Oxidative Addition of Water, Alcohols, and Amines in Palladium Catalysis
Grünwald, Annette,Heinemann, Frank W.,Munz, Dominik
supporting information, p. 21088 - 21095 (2020/10/02)
The homolytic cleavage of O?H and N?H or weak C?H bonds is a key elementary step in redox catalysis, but is thought to be unfeasible for palladium. In stark contrast, reported here is the room temperature and reversible oxidative addition of water, isopropanol, hexafluoroisopropanol, phenol, and aniline to a palladium(0) complex with a cyclic (alkyl)(amino)carbene (CAAC) and a labile pyridino ligand, as is also the case in popular N-heterocyclic carbene (NHC) palladium(II) precatalysts. The oxidative addition of protic solvents or adventitious water switches the chemoselectivity in catalysis with alkynes through activation of the terminal C?H bond. Most salient, the homolytic activation of alcohols and amines allows atom-efficient, additive-free cross-coupling and transfer hydrogenation under mild reaction conditions with usually unreactive, yet desirable reagents, including esters and bis(pinacolato)diboron.
Magnesium-catalyzed hydroboration of organic carbonates, carbon dioxide and esters
Cao, Xu,Lu, Kai,Ma, Mengtao,Wang, Weifan,Xue, Fei,Yao, Weiwei
supporting information, p. 2776 - 2780 (2020/03/13)
A low-valent magnesium(i) complex [(XylNacnac)Mg]2 was employed as a highly efficient precatalyst for the hydroboration of a variety of cyclic and linear organic carbonates, polycarbonates, CO2 and esters with HBpin under mild conditions. The resultant boronates can be used for the preparation of the corresponding value-added diols, triols or alcohols through hydrolysis.
