1875-88-3Relevant academic research and scientific papers
Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey
, p. 235 - 246 (2022/01/03)
The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.
Borane evolution and its application to organic synthesis using the phase-vanishing method
Soga, Nene,Yoshiki, Tomo,Sato, Aoi,Kawamoto, Takuji,Ryu, Ilhyong,Matsubara, Hiroshi
supporting information, (2021/03/26)
Although borane is a useful reagent, it is difficult to handle. In this study, borane was generated in situ from NaBH4 or nBu4NBH4 with several oxidants using a phase-vanishing (PV) method. The borane generated was directly reacted with alkenes, affording the desired alcohols in good yields after oxidation with H2O2 under basic conditions. The selective reduction of carboxylic acids with the evolved borane was examined. The organoboranes generated by the PV method successfully underwent Suzuki–Miyaura coupling. Using this PV system, reactions with borane can be carried out easily and safely in a common test tube.
Chemoselective Cleavage of Si-C(sp3) Bonds in Unactivated Tetraalkylsilanes Using Iodine Tris(trifluoroacetate)
Matsuoka, Keitaro,Komami, Narumi,Kojima, Masahiro,Mita, Tsuyoshi,Suzuki, Kimichi,Maeda, Satoshi,Yoshino, Tatsuhiko,Matsunaga, Shigeki
supporting information, p. 103 - 108 (2021/01/13)
Organosilanes are synthetically useful reagents and precursors in organic chemistry. However, the typical inertness of unactivated Si-C(sp3) bonds under conventional reaction conditions has hampered the application of simple tetraalkylsilanes in organic synthesis. Herein we report the chemoselective cleavage of Si-C(sp3) bonds of unactivated tetraalkylsilanes using iodine tris(trifluoroacetate). The reaction proceeds smoothly under mild conditions (-50 °C to room temperature) and tolerates various polar functional groups, thus enabling subsequent Tamao-Fleming oxidation to provide the corresponding alcohols. NMR experiments and density functional theory calculations on the reaction indicate that the transfer of alkyl groups from Si to the I(III) center and the formation of the Si-O bond proceed concertedly to afford an alkyl-λ3-iodane and silyl trifluoroacetate. The developed method enables the use of unactivated tetraalkylsilanes as highly stable synthetic precursors.
A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
, p. 5019 - 5026 (2020/05/01)
A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
, p. 13659 - 13667 (2020/11/30)
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
Diaminodiphosphine tetradentate ligand and ruthenium complex thereof, and preparation methods and applications of ligand and complex
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Paragraph 0301-0303; 0305, (2019/11/04)
The invention discloses a diaminodiphosphine tetradentate ligand and a ruthenium complex thereof, and preparation methods and applications of the ligand and the complex, and provides a ruthenium complex represented by a formula I, wherein L is a diaminodiphosphine tetradentate ligand represented by a formula II, and X and Y are respectively and independently chlorine ion, bromine ion, iodine ion,hydrogen negative ion or BH4. According to the present invention, the ruthenium complex exhibits excellent catalytic activity in the catalytic hydrogenation reactions of ester compounds, has high yield and high chemical selectivity, is compatible with conjugated and non-conjugated carbon-carbon double bond, carbon-carbon triple bond, epoxy, halogen, carbonyl and other functional groups, and hasgreat application prospects.
Synthetic method for 2-(4-chlorophenyl)ethanol
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Paragraph 0016; 0035-0058, (2019/10/01)
The invention discloses a synthetic method for 2-(4-chlorophenyl)ethanol. The method comprises the following steps: using ethyl (4-chlorophenyl)acetate as a starting material, firstly, placing the ethyl (4-chlorophenyl)acetate, isopropanol and an appropriate amount of tetrahydrofuran solvent into a reactor, performing heating under stirring, adding sodium borohydride in batches at a reflux temperature, performing a reaction for 28-30 h (or extending the reaction time at room temperature), stopping the reaction, performing cooling to room temperature, performing acidification treatment (to be about neutral), allowing the acidified material to stand for layering, retaining an organic layer, performing extraction on an aqueous layer by using ethyl acetate, merging organic layers, performing washing by using a saturated salt solution, performing rotary evaporation at 40-60 DEG C to remove a solvent, and performing filtration on a crude product by using a silica gel column to obtain the higher-purity 2-(4-chlorophenyl)ethanol.
Control of Homocoupling Versus Reduction in Titanium(III)-Mediated Radical Opening of Styrene Oxides
González-Delgado, José A.,Arteaga, Jesús F.
, p. 7864 - 7869 (2019/12/27)
We describe the use of titanocene monochloride in the implementation of an experimental procedure that enables control of the homolytic opening of styrene oxides in a chemoselectively controlled manner. This leads either to homocoupling products or to phenethyl alcohol derivatives. The process occurs via the generation of benzyl radicals, which may undergo a) recombination or b) reduction, yielding benzyl-Ti(IV) species upon subsequent addition of H2O to the corresponding hydroxylated compounds. The main goal of this work is the study of the reactivity pattern of styrene oxides towards the formation of the mentioned products, thereby adding value to this interesting building block.
Photochemical Homologation for the Preparation of Aliphatic Aldehydes in Flow
Chen, Yiding,Leonardi, Marco,Dingwall, Paul,Labes, Ricardo,Pasau, Patrick,Blakemore, David C.,Ley, Steven V.
, p. 15558 - 15568 (2019/01/04)
Cheap and readily available aqueous formaldehyde was used as a formylating reagent in a homologation reaction with nonstabilized diazo compounds, enabled by UV photolysis of bench-stable oxadiazolines in a flow photoreactor. Various aliphatic aldehydes were synthesized along with the corresponding derivatized alcohols and benzimidazoles. No transition-metal catalyst or additive was required to affect the reaction, which proceeded at room temperature in 80 min.
Synthesis method of p-chlorophenethyl alcohol
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Paragraph 0021-0032, (2018/05/15)
The invention discloses a synthesis method of p-chlorophenethyl alcohol. The synthesis method comprises the following steps of enabling paradichlorobenzene and a magnesium chip to generate a Grignardreaction in an ether solvent to generate a Grignard reagent, then enabling the Grignard reagent to generate an addition reaction with epoxy ethane, depressurizing after the reaction is completed, recovering the ether solvent, subsequently, quenching through acid water, adding a solvent, extracting, separating liquid, water scrubbing, drying and filtering an organic phase, depressurizing, recovering an extracting solvent, finally, distilling and collecting a fraction, so that the target-product p-chlorophenethyl alcohol can be obtained. According to the synthesis method, the paradichlorobenzeneis used; chlorine atoms are 1,4-orientating groups; isomeric impurities with other substitution positions are difficultly produced; a product is easily separated and purified and the synthesis methodhas advantages that the comprehensive raw-material cost is low, the safety coefficient is high, the three wastes are easily treated, steps are a few and the yield is high, and the like.
