- Matteson Reaction under Flow Conditions: Iterative Homologations of Terpenes
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The Matteson reaction is ideally suited for flow chemistry since it allows iterative homologation of boronate esters. The present study provides accurate data on reaction times of the individual steps of the Matteson reaction, which occurs in less than 10 s in total. The protocol allows terpenes to be (per-)homologated in a controlled manner to yield homo-, bishomo-, and trishomo-terpenols after oxidative workup. The new terpene alcohols are validated with respect to their olfactoric properties.
- Kuhwald, Conrad,Kirschning, Andreas
-
supporting information
p. 4300 - 4304
(2021/05/26)
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- Selective hydroboration of equilibrating allylic azides
-
The iridium(i)-catalyzed hydroboration of equilibrating allylic azides is reported to provide only the anti-Markovnikov product of alk-1-ene isomers in good yields and with good functional group tolerance.
- Liu, Ruzhang,Xu, Jun,Zhang, Yuanyuan
-
supporting information
p. 8913 - 8916
(2021/09/13)
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- Access to Trisubstituted Fluoroalkenes by Ruthenium-Catalyzed Cross-Metathesis
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Although the olefin metathesis reaction is a well-known and powerful strategy to get alkenes, this reaction remained highly challenging with fluororalkenes, especially the Cross-Metathesis (CM) process. Our thought was to find an easy accessible, convenient, reactive and post-functionalizable source of fluoroalkene, that we found as the methyl 2-fluoroacrylate. We reported herein the efficient ruthenium-catalyzed CM reaction of various terminal and internal alkenes with methyl 2-fluoroacrylate giving access, for the first time, to trisubstituted fluoroalkenes stereoselectively. Unprecedent TON for CM involving fluoroalkene, up to 175, have been obtained and the reaction proved to be tolerant and effective with a large range of olefin partners giving fair to high yields in metathesis products. (Figure presented.).
- Nouaille, Augustin,Pannecoucke, Xavier,Poisson, Thomas,Couve-Bonnaire, Samuel
-
supporting information
p. 2140 - 2147
(2021/03/06)
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- Redox-active ligand based Mn(i)-catalyst for hydrosilylative ester reduction
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Herein a Mn(i) catalyst bearing a redox-active phenalenyl (PLY) based ligand is reported for the efficient hydrosilylation of esters to alcohols using the inexpensive silane source polymethylhydrosiloxane (PMHS) under mild conditions. Mechanistic investigations suggest a strong ligand-metal cooperation where a ligand-based single electron transfer (SET) process initiates the reaction through Si-H bond activation.
- Chakraborty, Soumi,Das, Arpan,Mandal, Swadhin K.
-
supporting information
p. 12671 - 12674
(2021/12/04)
-
- Nickel-Catalyzed 1,2-Carboamination of Alkenyl Alcohols
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An alcohol-directed, nickel-catalyzed three-component umpolung carboamination of unactivated alkenes with aryl/alkenylboronic esters and electrophilic aminating reagents is reported. This transformation is enabled by specifically tailored O-(2,6-dimethoxybenzoyl)hydroxylamine electrophiles that suppress competitive processes, including undesired β-hydride elimination and transesterification between the alcohol substrate and electrophile. The reaction delivers the desired 1,2-carboaminated products with generally high regio- and syn-diastereoselectivity and exhibits a broad scope of coupling partners and alkenes, including complex natural products. Various mechanistic experiments and analysis of the stereochemical outcome with a cyclic alkene substrate, as confirmed by X-ray crystallographic analysis, support alcohol-directed syn-insertion of an organonickel(I) species.
- Cheng, Peter T.,Engle, Keary M.,Foo, Klement,Kang, Taeho,Kim, Nana,Zhang, Hao
-
supporting information
p. 13962 - 13970
(2021/09/11)
-
- Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides
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We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated in situ. The combination of an isophthalonitrile photocatalyst and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.,Williams, Oliver P.,Yeung, Charles S.
-
supporting information
p. 10882 - 10889
(2021/07/31)
-
- Alcohol Etherification via Alkoxy Radicals Generated by Visible-Light Photoredox Catalysis
-
A mechanistically divergent method is described that, employing a commercially available hypervalent iodine(III) reagent, generates alkoxy radicals from 1°, 2°, and 3° alcohols and allows their use in the functionalization of C(sp3)-H and C(sp2)-H bonds. This visible-light photoredox catalysis produces alkyl ethers via 1,5/6-hydrogen atom transfer or aryl ethers via 1,5-addition. This mild methodology provides a practical strategy for the synthesis of acetals, orthoesters, tetrahydrofurans, and chromanes.
- Rivero, Alexandra R.,Fodran, Peter,Ondrejková, Alica,Wallentin, Carl-Johan
-
supporting information
p. 8436 - 8440
(2020/11/03)
-
- Design, organocatalytic synthesis, and bioactivity evaluation of enantiopure fluorinated LpxC inhibitors
-
Enantiopure compounds with a strategically incorporated fluorine atom intended to enhance LpxC inhibition have been synthesized using an organocascade fluorination reaction as the key step. These are the first low molecular weight LpxC inhibitors to contain a fluorine atom on a critically important chiral center that is substituted with two pharmacophoric moieties, and were thusly designed to provide new SAR data for this class of compounds. Fluorinated compounds were evaluated against ESKAPE pathogens and exhibited MICs of ≤12.5 μg mL-1 against Pseudomonas aeruginosa.
- Brenner-Moyer, Stacey E.,Connell, Nancy D.,Rodríguez-Alvarado, Melanie,Russo, Riccardo
-
p. 5867 - 5878
(2020/08/19)
-
- Preparation method of p-phenylbutoxybenzoic acid
-
The invention discloses a preparation method of p-phenylbutoxybenzoic acid. The preparation method comprises the following steps: using tetrahydrofuran as an initial raw material; carrying out a catalytic reaction with benzoyl chloride to prepare 4-chlorobutanol benzoate; carrying out a Friedel-Crafts alkylation reaction and hydrolysis on 4-chlorobutanol benzoate and benzene to obtain 4-phenylbutanol, carrying out a reaction on the 4-phenylbutanol and thionyl chloride to obtain 4-phenylchlorobutane, carrying out an alkylation reaction on the 4-phenylchlorobutane and methyl p-hydroxybenzoate under the action of potassium carbonate to obtain methyl p-phenylbutoxybenzoate. The raw materials used in the invention are cheap and easily available, the process is easy to realize industrialization,and the obtained final product has the advantages of high purity, novel route, short synthesis route, no dangerous process and simple equipment.
- -
-
Paragraph 0047-0048
(2020/07/24)
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- Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups
-
The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate-attached benzene, such as the methoxy group a
- Fujiki, Katsumasa,Tanaka, Katsunori
-
supporting information
p. 4616 - 4620
(2020/07/06)
-
- Manganese-Catalyzed Stereospecific Hydroxymethylation of Alkyl Tosylates
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The development of a stereospecific hydroxymethylation of alkyl tosylates using an inexpensive, first-row catalyst is described. The transformation proceeds under mild conditions with low pressure to deliver homologated alcohols as products. Chiral, nonracemic β-branched primary alcohols are obtained with high enantiospecificity from easily accessed secondary alkyl substrates. Simple modification of the reaction system also permits access to α-d2 alcohols. These studies use anionic metal carbonyl catalysis to access a synthetic equivalent of the challenging hydroxymethyl anion from carbon monoxide.
- Shenouda, Hannah,Alexanian, Erik J.
-
supporting information
p. 9268 - 9271
(2019/11/19)
-
- CO-Free Enantioselective Hydroformylation of Functionalised Alkenes: Using a Dual Catalyst System to Give Improved Selectivity and Yield
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The scope of carbon monoxide-free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2-bis-((2,5)-diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. (Figure presented.).
- Pittaway, Rachael,Dingwall, Paul,Fuentes, José. A.,Clarke, Matthew. L.
-
supporting information
p. 4334 - 4341
(2019/08/21)
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- Acid-Promoted Hydroformylative Synthesis of Alcohol with Carbon Dioxide by Heterobimetallic Ruthenium-Cobalt Catalytic System
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The acid-aided heterobimetallic ruthenium-cobalt catalytic system for the reductive hydroformylation with carbon dioxide was established. Various alkenes, including waste from biomass and petroleum industry, could be upgraded to valuable alcohols with this protocol. Acid-promoted reverse water-gas shift (RWGS), thereby accelerating the hydroformylative synthesis of alcohol. The theoretical computations revealed that acid promoted RWGS by facilitating the dehydroxylation of ruthenium hydroxy carbonyl intermediate.
- Zhang, Xuehua,Tian, Xinxin,Shen, Chaoren,Xia, Chungu,He, Lin
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p. 1986 - 1992
(2019/03/17)
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- Dual Photoredox/Copper Catalysis for the Remote C(sp3)?H Functionalization of Alcohols and Alkyl Halides by N-Alkoxypyridinium Salts
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Under mild dual photoredox/copper catalysis, the reaction of N-alkoxypyridinium salts with readily available silyl reagents (TMSN3, TMSCN, TMSNCS) afforded δ-azido, δ-cyano, and δ-thiocyanato alcohols in high yields. The reaction went through a domino process involving alkoxy radical generation, 1,5-hydrogen atom transfer (1,5-HAT) and copper-catalyzed functionalization of the resulting C-centered radical. Conditions for catalytic enantioselective δ-C(sp3)?H cyanation were also documented.
- Bao, Xu,Wang, Qian,Zhu, Jieping
-
supporting information
p. 2139 - 2143
(2019/01/25)
-
- Synthetic method of 4-phenyl-1-butanol as intermediate
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The invention discloses a synthetic method of 4-phenyl-1-butanol as an intermediate. The synthetic method takes ferrous sulfate, I2, NaBH4, Fe-N/C, tetrapyridophenazine and 4-phenylbutyric acid as main raw materials, wherein the proportions of the used raw materials are as follows: the mass ratio of the 4-phenylbutyric acid to the I2 is 5 : 4, the mass ratio of the Fe-N/C to the NaBH4 is 5 : 8, and the molar ratio of the tetrapyridophenazine to the ferrous sulfate is 5 : 7. According to the synthetic technology provided by the invention, the 4-phenylbutyric acid and a sodium borohydride systemof iodine are adopted to be subjected to reduction reaction under the effect of the Fe-N/C as a catalyst to obtain the 4-phenyl-1-butanol; compared with the traditional synthetic method, the catalystis liable to separate and recover; and through a great amount of experiments, the temperatures, the dosages, the proportions and the technological processes of the experiments are continuously optimized, so that reaction operation is convenient, the time is short, the yield of a product is greatly increased, and the purity of the quality is greatly improved.
- -
-
Page/Page column 4-7
(2018/10/11)
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- Synthesis method of N-benzyl-alpha-methylbenzylamine
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The invention discloses a synthesis method of N-benzyl-alpha-methylbenzylamine. According to the method, phenylethylamine, benzaldehyde, KBH4, (NH4)2Mo7O24, Ni(NO3)2, 4,4'-dipyridyl, urea formaldehyderesin and H3PMo12O40 are used as main raw materials. The synthesis method is used for carrying out nucleophilic addition through phenylethylamine and benzaldehyde under the action of a catalyst whichis P-Mo2Ni/NC and then further reducing to obtain N-benzyl-alpha-methylbenzylamine. Compared with the conventional synthesis method, the synthesis method has the advantages that limited carbonizationof polyacids is capable of effectively avoiding excessive growth of metal carbide particles; nano-sized monodispersed catalyst particles can be obtained; racemization is not generated when KBH4 is used as a reducing agent for reducing intermediate products which are imine materials; and phenylethylamine with two configurations and extremely high optical purity can be easily obtained.
- -
-
Paragraph 0008
(2018/11/03)
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- Substrate and Catalyst Effects in the Enantioselective Copper-Catalysed C–H Insertion Reactions of α-Diazo-β-oxo Sulfones
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Excellent enantioselectivities of up to 98 % ee are achieved by employing the copper-bis(oxazoline)-NaBARF catalyst system in the C–H insertion reactions of α-diazo-β-oxo sulfones. The influence of variation of the bis(oxazoline) ligand, copper salt, additive and substrate on both the efficiency and the enantioselectivities of these intramolecular C–H insertion reactions has been explored. Optimum enantioselectivities are achieved with phenyl and diphenyl ligands across the substrate series.
- Shiely, Amy E.,Clarke, Leslie-Ann,Flynn, Christopher J.,Buckley, Aoife M.,Ford, Alan,Lawrence, Simon E.,Maguire, Anita R.
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supporting information
p. 2277 - 2289
(2018/06/04)
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- Robust cobalt oxide catalysts for controllable hydrogenation of carboxylic acids to alcohols
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The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production, while efficient heterogeneous catalyst systems are still being explored. Here, we report the selective hydrogenation of carboxylic acids using earth-abundant cobalt oxides through a reaction-controlled catalysis process. The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system. The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples. A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large-scale production. Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.
- Song, Song,Wang, Dong,Di, Lu,Wang, Chuanming,Dai, Weili,Wu, Guangjun,Guan, Naijia,Li, Landong
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p. 250 - 257
(2018/02/20)
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- Practical Intermolecular Hydroarylation of Diverse Alkenes via Reductive Heck Coupling
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The hydroarylation of alkenes is an attractive approach to construct carbon-carbon (C-C) bonds from abundant and structurally diverse starting materials. Herein we report a palladium-catalyzed reductive Heck hydroarylation of aliphatic and heteroatom-substituted terminal alkenes and select internal alkenes with an array of (hetero)aryl iodides. The reaction is anti-Markovnikov selective with terminal alkenes and tolerates a wide variety of functional groups on both the alkene and (hetero)aryl coupling partners. Additionally, applications of this method to complex molecule diversifications are demonstrated. Mechanistic experiments are consistent with a mechanism in which the key alkylpalladium(II) intermediate is intercepted with formate and undergoes a decarboxylation/C-H reductive elimination cascade to afford the saturated product and turn over the cycle.
- Gurak, John A.,Engle, Keary M.
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p. 8987 - 8992
(2018/09/11)
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- Dual Rh?Ru Catalysts for Reductive Hydroformylation of Olefins to Alcohols
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An active and selective dual catalytic system to promote domino hydroformylation–reduction reactions is described. Apart from terminal, di- and trisubstituted olefins, for the first time the less active internal C?C double bond of tetrasubstituted alkenes can also be utilized. As an example, 2,3-dimethylbut-2-ene is converted into the corresponding n-alcohol with high yield (90 %) as well as regio- and chemoselectivity (>97 %). Key for this development is the use of a combination of Rh complexes with bulky monophosphite ligands and the Ru-based Shvo's complex. A variety of aromatic and aliphatic alkenes can be directly used to obtain mainly linear alcohols.
- Rodrigues, Fábio M. S.,Kucmierczyk, Peter K.,Pineiro, Marta,Jackstell, Ralf,Franke, Robert,Pereira, Mariette M.,Beller, Matthias
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p. 2310 - 2314
(2018/07/31)
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- Cu-Catalyzed Hydroxymethylation of Unactivated Alkyl Iodides with CO To Provide One-Carbon-Extended Alcohols
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We have developed a reductive carbonylation method by which unactivated alkyl iodides can be hydroxymethylated to provide one-carbon-extended alcohol products under Cu-catalyzed conditions. The method is tolerant of alkyl β-hydrogen atoms, is robust towards a wide variety of functional groups, and was applied to primary, secondary, and tertiary alkyl iodide substrates. Mechanistic experiments indicate that the transformation proceeds by atom-transfer carbonylation (ATC) of the alkyl iodide followed in tandem by two CuH-mediated reductions in rapid succession. This radical mechanism renders the Cu-catalyzed system complementary to precious-metal-catalyzed reductive carbonylation reactions.
- Zhao, Siling,Mankad, Neal P.
-
supporting information
p. 5867 - 5870
(2018/04/17)
-
- Pd-Catalyzed debenzylation and deallylation of ethers and esters with sodium hydride
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Herein we demonstrate simply that the addition of Pd(OAc)2 as a promotor switches the reactivity of a commonly used base NaH to a nucleophilic reductant. The reactivity is engineered into a palladium-catalyzed reductive debenzylation and deallylation of aryl ethers and esters. This operationally simple, mild protocol displays a broad substrate scope and a broad spectrum of functional group tolerance (>50 examples) and high chemoselectivity toward aryl ethers over aliphatic structures. Moreover, the dual reactivity of NaH as a base and a reductant is demonstrated in efficient synthetic elaboration.
- Mao, Yujian,Liu, Ye,Hu, Yanwei,Wang, Liang,Zhang, Shilei,Wang, Wei
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p. 3016 - 3020
(2018/04/14)
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- Enantioselective copper catalysed intramolecular C-H insertion reactions of α-diazo-β-keto sulfones, α-diazo-β-keto phosphine oxides and 2-diazo-1,3-diketones; the influence of the carbene substituent
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Enantioselectivities in C-H insertion reactions, employing the copper-bis(oxazoline)-NaBARF catalyst system, leading to cyclopentanones are highest with sulfonyl substituents on the carbene carbon, and furthermore, the impact is enhanced by increased steric demand on the sulfonyl substituent (up to 91%ee). Enantioselective intramolecular C-H insertion reactions of α-diazo-β-keto phosphine oxides and 2-diazo-1,3-diketones are reported for the first time.
- Shiely, Amy E.,Slattery, Catherine N.,Ford, Alan,Eccles, Kevin S.,Lawrence, Simon E.,Maguire, Anita R.
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supporting information
p. 2609 - 2628
(2017/04/01)
-
- Enantioselective organocatalytic α-sulfamidation of aldehydes using sulfonyl azides
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Enantioselective organocatalytic α-sulfamidation of unbranched aldehydes is described using MacMillan's second-generation imidazolidinone catalyst and o-nitrobenzenesulfonyl azide. The reactions are highly stereoselective (89.9–96.3% ee) with yields up to 71%. A strong correlation between aldehyde structure and product yield was found to exist, with 3-arylpropanals providing the best results. Application to functionalized amino acid synthesis is presented.
- McGorry, Raymond J.,Allen, Stacey K.,Pitzen, Micha D.,Coombs, Thomas C.
-
supporting information
p. 4623 - 4627
(2017/11/15)
-
- Harnessing open-source technology for low-cost automation in synthesis: Flow chemical deprotection of silyl ethers using a homemade autosampling system
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An inexpensive homemade 3-axis autosampler was used to facilitate the automation of an acid catalysed flow chemical desilylation reaction. Harnessing open-source software technologies (Python, OpenCV), an automated computer-vision controlled liquid-liquid extraction step was used to provide effective inline purification. A Raspberry Pi single-board computer was employed to interface with the motors used in the autosampler and actuated fluidic valves.
- O'Brien, Matthew,Konings, Lisette,Martin, Matthew,Heap, Jordan
-
supporting information
p. 2409 - 2413
(2017/06/01)
-
- N-Heterocyclic Olefin Catalyzed Silylation and Hydrosilylation Reactions of Hydroxyl and Carbonyl Compounds
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N-Heterocyclic olefins (NHOs), the alkylidene derivatives of N-heterocyclic carbenes (NHCs), have recently emerged as a new family of promising organocatalysts with strong nucleophilicity and Br?nsted basicity. The development of a novel method is shown using NHOs as efficient promoters for the direct dehydrogenative silylation of alcohols or hydrosilylation of carbonyl compounds. Preliminary results of the first NHO-promoted asymmetric synthesis are also discussed.
- Kaya, U?ur,Tran, Uyen P.N.,Enders, Dieter,Ho, Junming,Nguyen, Thanh V.
-
supporting information
p. 1398 - 1401
(2017/03/23)
-
- Chelating Bis(1,2,3-triazol-5-ylidene) Rhodium Complexes: Versatile Catalysts for Hydrosilylation Reactions
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NHC-rhodium complexes (NHC=N-heterocyclic carbenes) have been widely used as efficient catalysts for hydrosilylation reactions. However, the substrates were mostly limited to reactive carbonyl compounds (aldehydes and ketones) or carbon-carbon multiple bonds. Here, we describe the application of newly-developed chelating bis(tzNHC)-rhodium complexes (tz=1,2,3-triazol-5-ylidene) for several reductive transformations. With these catalysts, the formal reductive methylation of amines using carbon dioxide, the hydrosilylation of amides and carboxylic acids, and the reductive alkylation of amines using carboxylic acids have been achieved under mild reaction conditions.
- Nguyen, Thanh V. Q.,Yoo, Woo-Jin,Kobayashi, Shu
-
supporting information
p. 452 - 458
(2016/02/12)
-
- Markovnikov-Selective, Activator-Free Iron-Catalyzed Vinylarene Hydroboration
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Two series of structurally related alkoxy-tethered NHC iron(II) complexes have been developed as catalysts for the regioselective hydroboration of alkenes. Significantly, Markonikov-selective alkene hydroboration with HBpin has been controllably achieved using an iron catalyst (11 examples, 35-90% isolated yield) with up to 37:1 branched:linear selectivity. anti-Markovnikov-selective alkene hydroboration was also achieved using HBcat and modification of the ligand backbone (6 examples, 44-71% yields). In both cases, ligand design has enabled activator-free low-oxidation-state iron catalysis.
- Macnair, Alistair J.,Millet, Clément R. P.,Nichol, Gary S.,Ironmonger, Alan,Thomas, Stephen P.
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p. 7217 - 7221
(2016/10/14)
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- MONONUCLEAR IRON COMPLEX AND ORGANIC SYNTHESIS REACTION USING SAME
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Provided is a mononuclear iron complex that comprises an iron-silicon bond that is represented by formula (1) and that exhibits excellent catalyst activity in each of a hydrosilylation reaction, a hydrogenation reaction, and reduction of a carbonyl compound. In formula (1), R1-R6 either independently represent an alkyl group, an aryl group, an aralkyl group or the like that may be substituted with a hydrogen atom or X, or represent a crosslinking substituent in which at least one pair comprising one of R1-R3 and one of R4-R6 is combined. X represents a halogen atom, an organoxy group, or the like. L represents a two-electron ligand other than CO. When a plurality of L are present, the plurality of L may be the same as or different from each other. When two L are present, the two L may be bonded to each other. n and m independently represent an integer of 1 to 3 with the stipulation that n+m equals 3 or 4.
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- METHOD FOR MANUFACTURING ALCOHOL BY HYDROGENATION OF CARBOXYLIC ACID COMPOUND AND ESTER COMPOUND
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PROBLEM TO BE SOLVED: To provide a method for obtaining alcohol by hydrogenation of carboxylic acid compound efficiently by using a homogeneous system catalyst, especially a method for obtaining alcohol by hydrogenation of various carboxylic acid compound and ester compound by the homogeneous system catalyst efficiently even under alleviation condition. SOLUTION: A carboxylic acid compound and/or an ester compound is hydrogenated in a presence of a rhenium complex represented by ReXmYnZp, where X is a halogen atom, Y is same or different and each a ligand containing one or more phosphorus atom, Z is a ligand other than X and Y, m is an integer of 1 to 6, p is an integer of 0 to 2 and the sum of m, n and p is an integer of 2 to 6, and a specific alkali metal salt. COPYRIGHT: (C)2015,JPOandINPIT
- -
-
Paragraph 0117; 0118; 0127; 0129; 0130
(2016/10/10)
-
- Visible-light-promoted conversion of alkyl benzyl ether to alkyl ester or alcohol via O-α-sp3 C-H cleavage
-
A mild and high-yielding visible-light-promoted conversion of alkyl benzyl ethers to the alkyl esters or alkyl alcohols was developed. Mechanistic studies provided evidence for a radical chain reaction involving the homolytic cleavage of O-α-sp3 C-H bonds in the substrate as one of the propagation steps. We propose that α-bromoethers are key intermediates in the transformation.
- Lu, Ping,Hou, Tianyuan,Gu, Xiangyong,Li, Pixu
-
supporting information
p. 1954 - 1957
(2015/04/27)
-
- From alkenes to alcohols by cobalt-catalyzed hydroformylation-reduction
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The cobalt-catalyzed hydroformylation of alkenes in the presence of a range of novel cyclic phosphine ligands was investigated. The effect of various parameters such as solvents, additives, cobalt/phosphine ratio, CO/H2 (1:2), and nature of the alkenes was examined. The results revealed that both terminal and internal alkenes are hydroformylated in high yields to give mainly linear products at moderate temperature and syn gas pressure. The linearity ranges from 43 to 85%, with Lim-10 giving the highest proportion of linear product.
- Achonduh, George,Yang, Qian,Alper, Howard
-
supporting information
p. 1241 - 1246
(2015/03/05)
-
- One-Carbon Homologation of Primary Alcohols and the Reductive Homologation of Aldehydes Involving a Jocic-Type Reaction
-
(Trichloromethyl)carbinols, which are formed in one operation from either alcohols or aldehydes, can be converted into primary alcohols in a Jocic-type reaction involving LiBH4. The net result is a convenient two-step, one-carbon homologation of primary alcohols or a reductive one-carbon homologation of aldehydes featuring a broad substrate scope. The method is step-economical, and it nicely complements established one-carbon homologation strategies. (Trichloromethyl)carbinols, which are formed in one operation from either alcohols or aldehydes, can be converted into primary alcohols in a Jocic-type reaction involving LiBH4. The net result is a convenient two-step, one-carbon homologation of primary alcohols or a reductive one-carbon homologation of aldehydes featuring a broad substrate scope.
- Li, Zhexi,Gupta, Manoj K.,Snowden, Timothy S.
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p. 7009 - 7019
(2015/11/16)
-
- Unexpectedly fast catalytic transfer hydrogenation of aldehydes by formate in 2-propanol-water mixtures under mild conditions
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Unsaturated aldehydes were efficiently reduced by transfer hydrogenation from sodium formate in water-2-propanol mixtures using a water-soluble Ru(II)-tertiary phosphine catalyst. The reaction yielded unsaturated alcohols with complete selectivity and without hydrogenation or isomerization of CC bonds of the substrates. Very high reaction rate was observed in the transfer hydrogenation of cinnamaldehyde already at 30 °C with turnover frequency of 160 h-1 and this increased to 3800 h-1 at 70 °C. Consequently, the method is applicable to the synthesis of unsaturated alcohols in case of heat sensitive or highly volatile aldehydes, too. Based on multinuclear NMR investigations, trans-[RuH2(H2O)(mtppms)3] is suggested as the key catalytic species.
- Szatmári, Imre,Papp, Gábor,Joó, Ferenc,Kathó, ágnes
-
-
- Facile and selective deprotection of PMB ethers and esters using oxalyl chloride
-
Oxalyl chloride, (0.5 equiv) was found to cleave the PMB group from alkyl, aryl PMB ethers, and esters to give corresponding alcohol and acid in good yields. This method offers simple and efficient protocol for the selective deprotection of PMB ether and ester in DCE at ambient temperature.
- Ilangovan, Andivelu,Anandhan, Karnambaram,Kaushik, Mahabir Prasad
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p. 1081 - 1084
(2015/02/19)
-
- Enantioselective copper catalysed C-H insertion reaction of 2-sulfonyl-2-diazoacetamides to form γ-lactams
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The first examples of asymmetric copper-catalysed intramolecular C-H insertion reactions of 2-sulfonyl-2-diazoacetamides are described; trans γ-lactams with up to 82% ee are achieved with the CuCl2-bisoxazoline-NaBARF catalyst system. The reactions generally display high efficiency and high trans selectivity, and also a strong regiochemical preference for insertion to lead to the formation of 5-membered rings over 4-membered rings. In cases where there are competing C-H insertion pathways available, to form sulfolanes or thiopyrans, only the insertion into the amide chain to form γ-lactams is observed. With phenylsulfonyl derivatives, a minor competing C-H insertion pathway leading to β-lactams is seen; interestingly, changing the identity of the copper ligand changes the product ratio of β/γ-lactams. The copper catalysed reactions compare favorably in terms of efficiency and enantioselectivity to the corresponding reactions catalysed by commercially available chiral rhodium catalysts.
- Clarke, Leslie Ann,Ring, Aoife,Ford, Alan,Sinha, Abhijeet S.,Lawrence, Simon E.,Maguire, Anita R.
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p. 7612 - 7628
(2015/02/18)
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- Highly chemoselective reduction of amides (primary, secondary, tertiary) to alcohols using SmI2/amine/H2O under mild conditions
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Highly chemoselective direct reduction of primary, secondary, and tertiary amides to alcohols using SmI2/amine/H2O is reported. The reaction proceeds with C-N bond cleavage in the carbinolamine intermediate, shows excellent functional group tolerance, and delivers the alcohol products in very high yields. The expected C-O cleavage products are not formed under the reaction conditions. The observed reactivity is opposite to the electrophilicity of polar carbonyl groups resulting from the nX → πC=O (X = O, N) conjugation. Mechanistic studies suggest that coordination of Sm to the carbonyl and then to Lewis basic nitrogen in the tetrahedral intermediate facilitate electron transfer and control the selectivity of the C-N/C-O cleavage. Notably, the method provides direct access to acyl-type radicals from unactivated amides under mild electron transfer conditions.
- Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
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supporting information
p. 2268 - 2271
(2014/03/21)
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- Mechanism of SmI2/amine/H2O-promoted chemoselective reductions of carboxylic acid derivatives (esters, acids, and amides) to alcohols
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Samarium(II) iodide-water-amine reagents have emerged as some of the most powerful reagents (E° = -2.8 V) for the reduction of unactivated carboxylic acid derivatives to primary alcohols under single electron transfer conditions, a transformation that had been considered to lie outside the scope of the classic SmI2 reductant for more than 30 years. In this article, we present a detailed mechanistic investigation of the reduction of unactivated esters, carboxylic acids, and amides using SmI2-water-amine reagents, in which we compare the reactivity of three functional groups. The mechanism has been studied using the following: (i) kinetic, (ii) reactivity, (iii) radical clock, and (iv) isotopic labeling experiments. The kinetic data indicate that for the three functional groups all reaction components (SmI2, amine, water) are involved in the rate equation and that the rate of electron transfer is facilitated by base assisted deprotonation of water. Notably, the mechanistic details presented herein indicate that complexation between SmI2, water, and amines can result in a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to a variety of carboxylic acid derivatives. These observations will have important implications for the design and optimization of new processes involving Sm(II)-reduction of ketyl radicals. (Chemical Equation Presented).
- Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
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p. 11988 - 12003
(2015/01/16)
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- Ketyl-type radicals from cyclic and acyclic esters are stabilized by SmI2(H2O)n: the role of SmI2(H 2O)n in post-electron transfer steps
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Mechanistic details pertaining to the SmI2-H2O- mediated reduction and reductive coupling of 6-membered lactones, the first class of simple unactivated carboxylic acid derivatives that had long been thought to lie outside the reducing range of SmI2, have been elucidated. Our results provide new experimental evidence that water enables the productive electron transfer from Sm(II) by stabilization of the radical anion intermediate rather than by solely promoting the first electron transfer as originally proposed. Notably, these studies suggest that all reactions involving the generation of ketyl-type radicals with SmI2 occur under a unified mechanism based on the thermodynamic control of the second electron transfer step, thus providing a blueprint for the development of a broad range of novel chemoselective transformations via open-shell electron pathways.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information
p. 8459 - 8466
(2014/06/24)
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- Mn-catalyzed three-component reactions of imines/nitriles, grignard reagents, and tetrahydrofuran: An expedient access to 1,5-amino/keto alcohols
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An expedient Mn-catalyzed three-component synthesis of 1,5-amino/keto alcohols from Grignard reagents, imines/nitriles, and tetrahydrofuran (THF) is described, which deviates from the classic Grignard addition to imines/nitriles in THF solvent. THF is split and sewn in an unprecedented manner in the reaction, leading to the formation of two geminal C-C bonds via C-H and C-O cleavage. Mechanistic experiments and DFT calculations reveal radical and organo-Mn intermediates in the catalytic cycle and the α-arylative ring-opening of THF as the key reaction step.
- He, Ruoyu,Jin, Xiqing,Chen, Hui,Huang, Zhi-Tang,Zheng, Qi-Yu,Wang, Congyang
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supporting information
p. 6558 - 6561
(2014/05/20)
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- On the role of pre- and post-electron-transfer steps in the SmI 2/Amine/H2O-mediated reduction of esters: New mechanistic insights and kinetic studies
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The mechanism of the SmI2-mediated reduction of unactivated esters has been studied using a combination of kinetic, radical clocks and reactivity experiments. The kinetic data indicate that all reaction components (SmI2, amine, H2O) are involved in the rate equation and that electron transfer is facilitated by Bronsted base assisted deprotonation of water in the transition state. The use of validated cyclopropyl-containing radical clocks demonstrates that the reaction occurs via fast, reversible first electron transfer, and that the electron transfer from simple Sm(II) complexes to aliphatic esters is rapid. Notably, the mechanistic details presented herein indicate that complexation between SmI2, H2O and amines affords a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride-mediated reductions and as a source of acyl-radical equivalents for C-C bond forming processes. Electron donors: The mechanism of the SmI 2-mediated reduction of unactivated esters has been studied by using a combination of kinetic, radical clock, and reactivity experiments. Notably, the mechanistic details presented herein indicate that complexation between SmI2, H2O, and amines gives a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride-mediated reductions and as a source of acyl-radical equivalents for C-C bond-forming processes (see scheme).
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information
p. 4222 - 4226
(2014/05/06)
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- Iron-catalyzed arene alkylation reactions with unactivated secondary alcohols
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A simple, iron-based catalytic system allows for the inter- and intramolecular arylation of unactivated secondary alcohols. This transformation expands the substrate scope beyond the previously required activated alcohols and proceeds under mild reaction conditions, tolerating air and moisture. Furthermore, the use of an enantioenriched secondary alcohol provides an enantioenriched product for the intramolecular reaction, thereby offering a convenient approach to nonracemic products.
- Jefferies, Latisha R.,Cook, Silas P.
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p. 2026 - 2029
(2014/05/06)
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- Temporal separation of catalytic activities allows anti-Markovnikov reductive functionalization of terminal alkynes
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There is currently great interest in the development of multistep catalytic processes in which one or several catalysts act sequentially to rapidly build complex molecular structures. Many enzymes - often the inspiration for new synthetic transformations - are capable of processing a single substrate through a chain of discrete, mechanistically distinct catalytic steps. Here, we describe an approach to emulate the efficiency of these natural reaction cascades within a synthetic catalyst by the temporal separation of catalytic activities. In this approach, a single catalyst exhibits multiple catalytic activities sequentially, allowing for the efficient processing of a substrate through a cascade pathway. Application of this design strategy has led to the development of a method to effect the anti-Markovnikov (linear-selective) reductive functionalization of terminal alkynes. The strategy of temporal separation may facilitate the development of other efficient synthetic reaction cascades.
- Li, Le,Herzon, Seth B.
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- A highly active and air-stable ruthenium complex for the ambient temperature anti-markovnikov reductive hydration of terminal alkynes
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The conversion of terminal alkynes to functionalized products by the direct addition of heteroatom-based nucleophiles is an important aim in catalysis. We report the design, synthesis, and mechanistic studies of the half-sandwich ruthenium complex 12, which is a highly active catalyst for the anti-Markovnikov reductive hydration of alkynes. The key design element of 12 involves a tridentate nitrogen-based ligand that contains a hemilabile 3-(dimethylamino) propyl substituent. Under neutral conditions, the dimethylamino substituent coordinates to the ruthenium center to generate an air-stable, 18-electron, κ3-complex. Mechanistic studies show that the dimethylamino substituent is partially dissociated from the ruthenium center (by protonation) in the reaction media, thereby generating a vacant coordination site for catalysis. These studies also show that this substituent increases hydrogenation activity by promoting activation of the reductant. At least three catalytic cycles, involving the decarboxylation of formic acid, hydration of the alkyne, and hydrogenation of the intermediate aldehyde, operate concurrently in reactions mediated by 12. A wide array of terminal alkynes are efficiently processed to linear alcohols using as little as 2 mol % of 12 at ambient temperature, and the complex 12 is stable for at least two weeks under air. The studies outlined herein establish 12 as the most active and practical catalyst for anti-Markovnikov reductive hydration discovered to date, define the structural parameters of 12 underlying its activity and stability, and delineate design strategies for synthesis of other multifunctional catalysts.
- Zeng, Mingshuo,Li, Le,Herzon, Seth B.
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supporting information
p. 7058 - 7067
(2014/06/09)
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- Ruthenium-catalyzed hydroformylation/reduction of olefins to alcohols: Extending the scope to internal alkenes
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In the presence of 2-phosphino-substituted imidazole ligands and Ru 3(CO)12 or Ru(methylallyl)2(COD) direct hydroformylation and hydrogenation of alkenes to alcohols takes place. In addition to terminal alkenes, also more challenging internal olefins are converted preferentially to industrially important linear alcohols in high yield (up to 88%) and regioselectivity (n:iso up to 99:1).
- Wu, Lipeng,Fleischer, Ivana,Jackstell, Ralf,Profir, Irina,Franke, Robert,Beller, Matthias
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supporting information
p. 14306 - 14312
(2013/10/21)
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- From olefins to alcohols: Efficient and regioselective ruthenium-catalyzed domino hydroformylation/reduction sequence
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Exploring the alternatives: Ruthenium imidazoyl phosphine complexes catalyze the domino hydroformylation/reduction of alkenes to alcohols in good yields and with good selectivities (see scheme). Linear aliphatic alcohols are synthesized under reaction conditions typically used in industrial hydroformylations. Copyright
- Fleischer, Ivana,Dyballa, Katrin Marie,Jennerjahn, Reiko,Jackstell, Ralf,Franke, Robert,Spannenberg, Anke,Beller, Matthias
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supporting information
p. 2949 - 2953
(2013/04/10)
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- Formic acid: A promising bio-renewable feedstock for fine chemicals
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In light of the growing scarcity of petroleum-based raw materials, carbon dioxide (CO2) is becoming increasing attractive as organic carbon source. In this perspective, formic acid (HCOOH) might be an interesting bio-renewable solution to store, transport, and activate carbon dioxide for the synthesis of value-added chemicals. Herein, HCOOH has been successfully used as C1 building block for the synthesis of a library of alcohols via a catalysed oxo-synthesis, under green experimental conditions. Copyright
- Mura, Manuel G.,Luca, Lidia De,Giacomelli, Giampaolo,Porcheddu, Andrea
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supporting information
p. 3180 - 3186
(2013/01/15)
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- Regioselective reductive hydration of alkynes to form branched or linear alcohols
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The regioselective reductive hydration of terminal alkynes using two complementary dual catalytic systems is described. Branched or linear alcohols are obtained in 75-96% yield with ?25:1 regioselectivity from the same starting materials. The method is compatible with terminal, di-, and trisubstituted alkenes. This reductive hydration constitutes a strategic surrogate to alkene oxyfunctionalization and may be of utility in multistep settings.
- Li, Le,Herzon, Seth B.
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supporting information
p. 17376 - 17379,4
(2020/09/16)
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- A general electron transfer reduction of lactones using SmI 2-H2O
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Herein we describe a strategy for the selective, electron transfer reduction of lactones of all ring sizes and topologies using SmI 2-H2O and a Lewis base to tune the redox properties of the complex. The current protocol permits instantaneous reduction of lactones to the corresponding diols in excellent yields, under mild reaction conditions and with useful chemoselectivity. We demonstrate the broad utility of this transformation through the reduction of complex lactones and sensitive drug-like molecules. Sequential electron transfer reactions and syntheses of deuterated diols are also described.
- Szostak, Michal,Collins, Karl D.,Fazakerley, Neal J.,Spain, Malcolm,Procter, David J.
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supporting information; experimental part
p. 5820 - 5824
(2012/08/28)
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