- Cluster Catalysed Selective Transfer Hydrogenation of α,β-Unsaturated Aldehydes
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H4Ru4(CO)8L4 (L=PBun3) catalyses selective transfer hydrogenation of α,β-unsaturated aldehydes to α,β-unsaturated alcohols; kinetic and deuterium labelling studies indicate involvement of cluster intermediates and no participation by the cluster hydrides.
- Bhaduri, Sumit,Sharma, Krishna
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- Novel C-C bond cleavage under mild, neutral conditions: Conversion of electron-deficient aryl alkyl ketones to aryl carboxylic esters
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A novel, unique way to cleave the carbon-carbon bond in aryl alkyl ketones under mild, neutral conditions is described. Treatment of aryl alkyl ketones in a refluxing mixture of N,N-dimethylformamide dimethyl acetal and methanol for 16 h provided aryl car
- Zhang, Nan,Vozzolo, Joseph
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- Oxidative deprotection of tetrahydropyranyl and trimethylsilyl ethers in water using 1,4-dichloro-1,4-diazoniabicyclo[2,2,2]octane bis-chloride under neutral conditions
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The oxidative deprotection of trimethylsilyl and tetrahydropyranyl ethers in water using 1,4-dichloro-1,4-diazonia-bicyclo[2,2,2]octane bis-chloride as a new efficient reagent under neutral conditions is described. The DABCO was regenerated, rechlorinated and reused several times.
- Tajbakhsh, Mahmood,Habibzadeh, Setareh
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- Synthesis and fungicidal activity study of novel daphneolone analogs with 2,6-dimethylmorpholine
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A series of novel daphneolone analogs was designed and synthesized on the basis of natural product 1,5-diphenyl-2-penten-1-one (I) from Stellera chamaejasme L. as lead compound, whereby 2,6-dimethylmorpholine moiety was introduced to replace 1-phenyl group. Their structures were confirmed by IR, 1H NMR, and HRMS (ESI) or elemental analysis, 13C NMR for some representative compounds. The two isomers of target compounds were separated and identified by NOESY technique and chemical method. All of the synthesized compounds have been evaluated for anti-plant pathogenic fungi activities. The results showed that some compounds exhibited moderate to good antifungal activities against tested fungi at the concentration of 50 mg/L. Among them, compound 7d, with a 4-bromine-substituted phenyl group and cis-2,6-dimethylmorpholine moiety, displayed best activity with an EC50 of 23.87 μmol/L against Valsa Mali, superior to lead compound I. In addition, preliminary structure-activity relationship analysis indicated that, between two isomers of target compounds, the antifungal activities of the isomer with cis-2,6-dimethylmorpholine were better than the trans-isomer.
- Xu, Gao-Fei,Yang, Xin-Ling,Lei, Peng,Liu, Xi-Li,Zhang, Xue-Bo,Ling, Yun
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- Microwave-assisted fast fabrication of a nanosized Pt3Co alloy on reduced graphene oxides
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Ultrafine and homogenously dispersed Pt3Co alloy nanoparticles were fabricated on reduced graphene oxide (RGO) in a few minutes under microwave irradiation. Characterization results confirmed that microwave irradiation was important for higher metal utilization, the easy control of alloy composition, improved dispersion of the Pt3Co particles and minimizing the re-graphitization of the parent RGO by comparison with conventional solvent-thermal and impregnation methods. This Pt3Co/RGO-MW catalyst was extremely active and selective during the hydrogenation of cinnamaldehyde to cinnamyl alcohol. The calculated specific activity of each Pt atom in the Pt3Co/RGO-MW at 70 °C was 23.8 min-1.
- Shi, Juanjuan,Nie, Renfeng,Zhang, Mengyuan,Zhao, Mengsi,Hou, Zhaoyin
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- Simple and efficient water soluble thioligands for rhodium and iridium catalyzed biphasic hydrogenation
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The activity of catalytic systems derived from the interaction between Rh(CO)2acac and [Ir(COD)Cl]2, respectively, with the water soluble thioligands (L)-Cysteine (1) and (S)-Captopril (2), was tested in the aqueous biphasic hydrogenation of some representative α,β-unsaturated compounds as 2-cyclohexen-1-one (I), trans-cinnamaldehyde (V) and [3-(1,3-benzodioxol-5-yl)-2-methylpropenal] (X), precursor of the fragrance Helional (XI). The precatalyst Rh/Cap was able to hydrogenate cyclohexenone even at low pressure at 60 °C in a neutral medium while Rh/Cy required either higher pressure and temperature or an alkaline medium. The iridium based catalysts, Ir/Cy and Ir/Cap, showed an analogous trend though their activities were lower than those of the related rhodium catalysts. All the catalysts were easily recycled without significant loss of activity. The rhodium catalysts were also used in the hydrogenation of the above aldehydes V and X and their activity was strongly enhanced when ethylene glycol was used as organic solvent or co-solvent.
- Di Dio, Sabrina,Marchetti, Mauro,Paganelli, Stefano,Piccolo, Oreste
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- A hybrid polyketone-SiO2 support for palladium catalysts and their applications in cinnamaldehyde hydrogenation and in 1-phenylethanol oxidation
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An organic-inorganic hybrid material, PK-SiO2 (PK = polyketone), was employed as support for Pd catalysts. Their synthesis was carried out by MW irradiation of an ethanol solution of Pd(OAc)2 in the presence of the support. The obtai
- Antonetti, Claudia,Toniolo, Luigi,Cavinato, Gianni,Forte, Claudia,Ghignoli, Chiara,Ishak, Randa,Cavani, Fabrizio,Raspolli Galletti, Anna Maria
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- Nanosized transition metals in controlled environments of phyllosilicate-mesoporous silica composites as highly thermostable and active catalysts
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Stabilization of transition metals in nano-phyllosilicate phases generated by digestion of mesoporous silica is reported as an efficient route for the formation of highly dispersed metallic nanoparticles with outstanding catalytic activity. The Royal Society of Chemistry.
- Ciotonea, Carmen,Dragoi, Brindusa,Ungureanu, Adrian,Chirieac, Alexandru,Petit, Sabine,Royer, Sebastien,Dumitriu, Emil
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- Asymmetric hydroformylation of styrene catalyzed by carbohydrate diphosphite-Rh(I) complexes
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A series of new chelating diphosphite ligands with a furanoside backbone and axially chiral biphenyl or binaphthyl moieties have been synthesized. Their Rh(I) complexes have been tested as catalyst precursors for the asymmetric hydroformylation of styrene. Systematic variation in chirality at both chiral sugar backbone stereocenters (C-3 and C-5) and either the axial chiral biphenyl or binaphthyl substituents revealed a remarkable effect on the selectivity of the hydroformylation catalysts. In this way, by judicious choice of these elements, both regio- and enantioselectivities can be optimized. Thus, both high enantioselectivity (up to 93% S) and regioselectivity in 2-phenylpropanal (up to 98.8%) were found under mild reaction conditions (15-40°C, 10 bar of syngas) for the ligand with a glucofuranoside backbone and bis(trimethylsilyl)-2,2′-biphenyl moiety. The solution structures of HRh(L-L)(CO)2 complexes have been studied by high pressure NMR and IR. Varying the configuration of the binaphthyl moieties revealed a remarkable effect on the diphosphite coordination modes on the intermediate HRh(L-L)(CO)2 species and, therefore, on enantioselectivity. Enantioselectivity was highest for ligands with a strong bis-equatorial coordination preference.
- Dieguez, Montserrat,Pamies, Oscar,Ruiz, Aurora,Claver, Carmen
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- Dendritic nanoreactor encapsulating Rh complex catalyst for hydroformylation
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A Rh phosphine complex was encapsulated within the surface alkylated poly(propylene imine) dendrimers through ionic interactions. The resulting dendrimer complexes functioned as nanoreactors for hydroformylation of olefins. The congested surface of dendrimers with long alkyl chains favored hydroformylation of higher olefins. One-pot three reactions composed of hydroformylation, the Knoevenagel reaction, and hydrogenation proceeded within the dendritic nanoreactor. Copyright
- Mizugaki, Tomoo,Miyauchi, Yasuaki,Murata, Makoto,Ebitani, Kohki,Kaneda, Kiyotomi
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- Perchloric acid adsorbed on silica gel (HClO4-SiO2) as an inexpensive, extremely efficient, and reusable dual catalyst system for acetal/ketal formation and their deprotection to aldehydes/ketones
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Perchloric acid adsorbed on silica gel (HClO4-SiO2) is reported as extremely efficient, inexpensive, and reusable catalyst for dual role for protection of aldehydes/ketones (with trialkyl orthoformates) as acetals/ketals and deprotection (with water-alcohol) to regenerate the carbonyl compounds in high yields at room temperature and in short times. Acetalization/ketalization of electrophilic aldehydes/ketones was carried out under solvent-free conditions. Weakly electrophilic aldehydes/ketones and aldehydes having a substituent that can coordinate with the catalyst, required the corresponding alcohol as solvent. Georg Thieme Verlag Stuttgart.
- Kumar, Raj,Kumar, Dinesh,Chakraborti, Asit K.
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- High catalytic activity of - for hydroformylation of olefins
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Comparison of the catalytic activity of - with those of the known catalyst systems (- and Ru3(CO)12) has revealed that - is an active catalyst for hydroformylation of 1-pentene, styrene, and ethyl acrylate. - partly reduces the aldehydes initially formed into their corresponding alcohols.In the reaction of ethyl acrylate catalyzed by - or -, significant amounts of carbonylative dimers (diethyl 2-formyl-2-methylglutarate and 4-ethoxycarbonyl-4-methyl-δ-valerolactone) were also formed.
- Hayashi, Teruyuki,Gu, Zheng Hui,Sakakura, Toshiyasu,Tanaka, Masato
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- DABCO-bromine complex: A novel oxidizing agent for oxidative deprotection of THP and silyl ethers and semicarbazones to corresponding carbonyl compounds
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A tetrameric DABCO-bromine complex was synthesized, characterized, and utilized as a novel active bromine complex for the oxidative deprotection of THP and silyl ethers and semicarbazones to carbonyl compounds. Copyright Taylor & Francis Group, LLC.
- Tajbakhsh, Mahmood,Heravi, Majid M.,Habibzadeh, Setareh
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- Rhodium-catalysed isomerisation of allylic alcohols in water at ambient temperature
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An environmentally benign method for the transformation of allylic alcohols into carbonyl compounds is described. Using [Rh(COD(CH3CN) 2]BF4 (2) in combination with 1,3,5-triaza-7- phosphaadamantane (PTA, 1) as the catalytic system in water results in a very fast redox isomerisation of a variety of secondary allylic alcohols at ambient temperature. Also, some primary allylic alcohols can be isomerised into the corresponding aldehydes. The active complex, which in some cases can be used in catalyst loadings as low as 0.5 mol%, is formed in situ from commercially available reagents. Based on deuterium labelling studies, a tentative mechanism involving metal-enone intermediates is presented.
- Ahlsten, Nanna,Lundberg, Helena,Martin-Matute, Belen
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- SYNTHESIS AND PHOTOCHEMISTRY OF 2,3,8,9-TETRAHYDROINDENONE-1
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The novel β,γ,δ,ε-unsaturated ketone (2) was prepared and all its photoproducts were identified, following wavelength dependent, irradiation-induced transformations.
- Abramson, Sarah,Fuchs, Benzion
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- Novel cleavage of (E)-allyl vic-diols to aldehydes using the 2nd-generation Grubbs catalyst
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Secondary (E)-allyl vic-diol cleavage in the presence of the 2nd-generation Grubbs catalyst has been developed. The position of a vic-diol adjacent to C{double bond, long}C plays a crucial role in the cleavage reaction compared to an alkyl vic-diol based on a model compound.
- Han, Chunguang,Uemura, Daisuke
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- Selective hydrogenations on heterogenized ruthenium complexes
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The heterogenized versions of [RuCl2(PPh3) 3] and [{RuCl2(TPPMS)2}2] were prepared and applied in the selective hydrogenation of α, β-unsaturated aldehydes. Depending on the conditions the above heterogenized catalysts could hydrogenate selectively either the C=O or the C=C bonds, similar to the results obtained in aqueous biphasic systems. Meanwhile the heterogenized catalysts show all the advantages that we can expect from a heterogeneous catalyst: good performance, easy separation, and the possibility of recycling. The effect of H2 pressure on the selectivity was also studied.
- Zsigmond, Agnes,Balatoni, Istvan,Bogar, Krisztian,Notheisz, Ferenc,Joo, Ferenc
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- Synthesis of aldehydes from carboxylic acids via N-methoxyimidoyl bromides: Deoximation of O-methyloximes
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Aldehydes are synthesized by hydrogenation and subsequent deoximation of substituted N-methoxyalkanimidoyl bromides, which are prepared in one pot by reaction of the corresponding carboxylic acids with methoxyamine and triphenylphosphine carbon tetrabromide. Regeneration of aldehydes and ketones from O-methyloximes under mild conditions is also described.
- Sakamoto,Kikugawa
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- A Low Rhodium Content Smart Catalyst for Hydrogenation and Hydroformylation Reactions
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Abstract: This paper describes the preparation, broad characterization and study of activity in hydrogenation and hydroformylation reactions of an easily produced 0.18% Rh/Al2O3. Analytical studies on fresh and recycled samples shed light on the smart properties of such catalyst. Results showed high activity as well as fine/excellent chemoselectivity or regioselectivity, characteristics that may suggest a wide range of applicability. Graphic Abstract: The low metal content catalyst 0.18% Rh/Al2O3 was very active in both hydrogenation and hydroformylation reactions so providing intermediates for valuable APIs, as Nabumetone and Eletriptan, and a fragrance with a fresh, green-floral smell, that recalls scent of lily of the valley.[Figure not available: see fulltext.]
- Paganelli, Stefano,Tassini, Riccardo,Rathod, Vikas D.,Onida, Barbara,Fiorilli, Sonia,Piccolo, Oreste
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- Platinum nanocrystals supported on CoAl mixed metal oxide nanosheets derived from layered double hydroxides as catalysts for selective hydrogenation of cinnamaldehyde
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Pt nanoparticles supported on sheetlike mixed metal oxides (MMO) derived from layered double hydroxides are found to be highly efficient catalysts for the selective hydrogenation of cinnamaldehyde. A series of characterizations are employed to investigate the structure and composition of the support and catalyst. Divalent species have a significant influence on the activity and selectivity. CoAl MMO-supported catalysts achieve an increase in both conversion and selectivity to cinnamyl alcohol through the formation of PtCo alloy on the surfaces of catalysts during preparation. A possible reaction path is proposed. The effects of Co/Al ratio and calcination temperature on catalytic performance are researched in this work.
- Tian, Zhengbin,Li, Qingyang,Hou, Juying,Pei, Lei,Li, Yan,Ai, Shiyun
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- Dual Catalytic Activity of Palladium Doped with a Rhodium Complex in a One-pot, Four Step Process
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The extraction of the two competing reactions from the same catalyst - a composite catalytic-complex@catalytic-metal - is reported. A Wilkinson rhodium based catalyst entrapped within metallic palladium catalyst is shown to perform both hydroformylation and hydrogenation with a ratio that depends on H2 and CO pressures. Here we demonstrate this special reactivity in a one-pot, four step sequence, which include hydroformylations of phenyl acetylenes, reduction of nitrobenzene to aniline, carbonyl-amine condensations forming imines; and imine reductions.
- Shapiro, Leora,Driess, Matthias,Avnir, David
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- Chemoselective flow hydrogenation of Α,Β – Unsaturated aldehyde with nano-nickel
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Herein, it is presented a novel catalytic system for the continuous-flow chemoselective hydrogenation of α,β – unsaturated aldehydes used in the production of high-value cosmetics and pharmaceuticals precursors. The reaction was catalyzed by nano-nickel particles grafted on polymeric support, synthesized via a simple, adaptable and green methodology. The system was highly active and very selective to C[dbnd]C bond saturation.
- Giziński, Damian,Goszewska, Ilona,Zieliński, Maciej,Lisovytskiy, Dmytro,Nikiforov, Kostiantyn,Masternak, Joanna,Zienkiewicz-Machnik, Ma?gorzata,?r?bowata, Anna,Sá, Jacinto
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- Composites based on modified clay assembled Rh(III)–heteropolymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde
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New composites based on the [RhMo6O24H6]3? (RhMo6) heteropolyanion supported on pillared (PILC), heterostructured (PCH) and functionalized(PILC-F) and (PCH-F) systems based on clays were prepared, characterized and tested as catalysts in the liquid-phase hydrogenation of cinnamaldehyde. The original phases and supported systems were characterized using several techniques such as powder X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM–EDS), Raman microprobe studies, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analyses (TG-DSC), temperature programmed reduction (TPR), and textural analysis (BET method), which confirmed their functionalization, physicochemical modification and the nature of Mo adsorbed species. Active acidic, basic and redox sites were determined by temperature programmed surface reaction (TPSR). Mo loading reached 7?wt% for the system RhMo6/PCH-F and 3?wt% for the system RhMo6/PILC-F, while unfunctionalized clay systems showed a value of 1?wt% of Mo. The catalytic performance showed that PCH-based composites were the most active and reached up to 56% conversion at 360?min of reaction when tested in liquid-phase cinnamaldehyde hydrogenation. The selectivity for all the systems was mainly toward hydrocinnamic aldehyde (HCAL) and reached 77% for the RhMo6/PCH-F catalyst at 25% conversion.
- Bertolini, Guillermo R.,Vetere, Virginia,Gallo, María A.,Mu?oz, Mercedes,Casella, Mónica L.,Gambaro, Luís,Cabello, Carmen I.
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- Heavy-Metal-Free Fischer-Tropsch Type Reaction: Sequential Homologation of Alkylborane Using a Combination of CO and Hydrides as Methylene Source
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Carbon homologation reactions occur within the well-known Fischer-Tropsch process, usually mediated by transition metal catalysts at high temperature. Here we report the low-temperature, heavy-metal-free homologation of a carbon chain using CO as a C1-source showing for the first time that transition-metal catalysts are not required for Fischer-Tropsch-type reactivity. Reaction of an alkylborane in the presence of either LiHBEt3 or LiAlH4 resulted in multiple CO insertion/reduction events to afford elongated chains by more than two methylene (-CH2-) units, affording aldehyde products upon oxidative aqueous workup. Theoretical and experimental mechanistic studies indicate that the boron terminus is responsible for CO incorporation as well as sequential hydride delivery leading to reduction of acylborane intermediates to alkylboranes.
- Phanopoulos, Andreas,Pal, Shrinwantu,Kawakami, Takafumi,Nozaki, Kyoko
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- Monophosphanylcalix[6]arene ligands: Synthesis characterization, complexation, and their use in catalysis
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Novel phosphanylcalix[6]arenes having mono-O-diphenylphosphanylmethyl (3) and mono-O-(4-diphenylphosphanylphenyl)methyl substituents (5) have been synthesized. The structures of these monophosphanylcalix[6]arenes were determined by NMR spectroscopy, mass spectrometry, and X-ray crystal structure analysis. The X-ray structure reveals that 3 adopts a flattened 1,2,3-alternate conformation in the crystalline state, while the NMR spectra show that 3 and 5 have a cone conformation in solution. Structure optimization and energy calculations for 3 and 5 at the B3LYP/LANL2DZ-CONFLEX5/MMFF94s level of theory show that the cone conformation is slightly more stable than the 1,2,3-alternate conformation by 0.36 kcal mol-1 for 3 and 0.96 kcal mol-1 for 5. Complexation of 3 with [PtCl2(COD)] and [Rh(COD) 2]BF4 gives cis-coordinated [PtCl2(3) 2] and [Rh(COD)(3)2]BF4, respectively. The X-ray analysis of [PtCl2(3)2] shows that 3 adopts a cone conformation upon complexation. Combination of 3 and 5 with [Rh(COD) 2]BF4 provides an active catalyst for the hydroformylation of a variety of terminal alkenes. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Obora, Yasushi,Yun, Kui Liu,Kubouchi, Sho,Tokunaga, Makoto,Tsuji, Yasushi
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- Cofactor-Free, Direct Photoactivation of Enoate Reductases for the Asymmetric Reduction of C=C Bonds
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Enoate reductases from the family of old yellow enzymes (OYEs) can catalyze stereoselective trans-hydrogenation of activated C=C bonds. Their application is limited by the necessity for a continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Visible light-driven activation of OYEs through NAD(P)H-free, direct transfer of photoexcited electrons from xanthene dyes to the prosthetic flavin moiety is reported. Spectroscopic and electrochemical analyses verified spontaneous association of rose bengal and its derivatives with OYEs. Illumination of a white light-emitting-diode triggered photoreduction of OYEs by xanthene dyes, which facilitated the enantioselective reduction of C=C bonds in the absence of NADH. The photoenzymatic conversion of 2-methylcyclohexenone resulted in enantiopure (ee>99 %) (R)-2-methylcyclohexanone with conversion yields as high as 80–90 %. The turnover frequency was significantly affected by the substitution of halogen atoms in xanthene dyes.
- Lee, Sahng Ha,Choi, Da Som,Pesic, Milja,Lee, Yang Woo,Paul, Caroline E.,Hollmann, Frank,Park, Chan Beum
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- Dimethyl sulfoxide pivaloyl chloride: A new reagent for oxidation of alcohols to carbonyls
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An efficient procedure for conversion of alcohols to the corresponding carbonyl compounds, an alternative to the classical Swern oxidation, is described. Pivaloyl chloride is employed as a mild and inexpensive electrophile. A possible reaction mechanism is proposed. Copyright Taylor & Francis Group, LLC.
- Dubey, Abhishek,Kandula, Subba Rao V.,Kumar, Pradeep
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- Efficient preparation and application of monodisperse palladium loaded graphene oxide as a reusable and effective heterogeneous catalyst for suzuki cross-coupling reaction
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A homogeneously dispersed graphene oxide supported palladium nanomaterial (Pd?GO) has been successfully synthesized and used as a catalyst in cross-coupling reactions at room temperature. Various analytical techniques such as X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) were used to characterize the monodisperse Pd?GO. Monodisperse Pd?GO nanomaterials were used for the cross-coupling reactions which brought together organic molecules with functional significance. This catalyst showed superior catalytic activity and stability for these coupling reactions. High product yields, short reaction times and mild reaction conditions, obtained by the using of developed catalysts. Importantly, the catalyst can be used at least five experiments successfully without losing its efficiency.
- Diler, Fatma,Burhan, Hakan,Genc, Hayriye,Kuyuldar, Esra,Zengin, Mustafa,Cellat, Kemal,Sen, Fatih
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- Pt supported nitrogen doped hollow carbon spheres for the catalysed reduction of cinnamaldehyde
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Carbon and nitrogen coated St?ber silica spheres were prepared by a standard procedure using acetonitrile at different CVD temperatures (800-1000 °C) and as a function of time (1-4 h). HF treatment was used to remove the silica from the carbon coated silica to give monodispersed nitrogen doped hollow carbon spheres (N-HCSs; shell thickness = 50 nm). The surface areas of the N-CSs increased significantly after removal of the SiO2 core (N-HCS = 47 m2/g). Platinum nanoparticles, prepared by a [Pt(COD)Cl2] deposition method were dispersed (d = 2.8 ± 0.4 nm) on the N-HCS supports. Thermal treatment of the Pt/N-HCS900-4 (prepared at 900°C for 4 h) in a 5% H2/Ar atmosphere at 120 °C (Pt/N-HCS900-4-120) and 300 °C (Pt/N-HCS900-4-300) gave metallic Pt (2.48%) which was confirmed by XRD and XPS studies. The XPS N1s spectra of Pt/N-HCS900-4-120 showed the presence of quaternary, pyridinic and pyrollic nitrogen atoms. These nitrogen doped carbon supported Pt nanoparticle catalysts were observed to reduce cinnamaldehyde to the unsaturated alcohol, cinnamyl alcohol (isopropanol/30 bar H2/80 °C) with >99% conversion and selectivity. The catalyst used in the reduction of cinnamaldehyde to cinnamyl alcohol could be recycled 12 times with minimal loss in conversion and this correlated with the small amount of Pt leaching or physical loss of catalyst (2%). The corresponding Pt/catalyst made on undoped HCSs showed a much greater loss of activity with recycling. It is seen that N doping of carbon is an effective method to bind Pt to carbon.
- Nongwe, Isaac,Ravat, Vilas,Meijboom, Reinout,Coville, Neil J.
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- Pd cluster nanowires as highly efficient catalysts for selective hydrogenation reactions
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Palladium is a key catalyst invaluable to many industrial processes and fine-chemical synthesis. Although recent progress has allowed the synthesis of Pd nanoparticles with various shapes by using different techniques, the facile synthesis of Pd nanocrystals and turning them into a highly active, selective, and stable catalyst systems still remain challenging. Herein, we report the highly selective one-pot synthesis of monodisperse Pd cluster nanowires in aqueous solution; these consist of interconnected nanoparticles and may serve as highly active catalysts because of the enrichment of high index facets on the surface, including {443}, {331}, and {221} steps. For the first time, carbon nanotube and I3-Al2O3 immobilized Pd cluster nanowires showed highly enhanced catalytic performance in the liquid-phase selective hydrogenation of cinnamaldehyde and gas-phase hydrogenation of 1,3butadiene relative to immobilized Pd icosahedra and nanocubes, as well as commercial Pd catalysts. Power in the cluster: Monodisperse Pd cluster nanowires, which consist of interconnected nanoparticles (see figure), have been synthesized in aqueous solution and may serve as highly active catalysts due to the enrichment of high index facets on the surface. Carbon nanotube and I3-Al2O3 immobilized Pd cluster nanowires showed enhanced catalytic performance in hydrogenations reactions. Copyright
- Zhang, Zhi-Cheng,Zhang, Xin,Yu, Qi-Yu,Liu, Zhi-Chang,Xu, Chun-Ming,Gao, Jin-Sen,Zhuang, Jing,Wang, Xun
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- Highly Networked Platinum–Tin Nanowires as Highly Active and Selective Catalysts towards the Semihydrogenation of Unsaturated Aldehydes
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The selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols is an important process for many industrial applications, whereas the realization of excellent conversion efficiency and selectivity remains a significant challenge. Herein, we report the preparation of a class of networked Pt–Sn nanowires (Pt–Sn NWs) for the selective hydrogenation of unsaturated aldehydes to the desired unsaturated alcohols. The optimized Pt1.5Sn NWs delivered a high conversion efficiency (98.1 %) for the hydrogenation of cinnamaldehyde (CAL) and excellent selectivity to cinnamyl alcohol (COL) (90.6 %); thus, they outperformed Pt1.5Sn nanoparticles (NPs) as well as Pt NPs. The high performance of the Pt1.5Sn NWs was expanded to the hydrogenation of other α,β-unsaturated aldehydes. X-ray photoelectron spectroscopy revealed that a high ratio of metallic Pt in the Pt1.5Sn NWs boosted the conversion of CAL and that a high Sn content favored the hydrogenation of the C=O bond, both of which lead to excellent activity and selectivity.
- Zhu, Meiwu,Huang, Bin,Shao, Qi,Pi, Yecan,Qian, Yong,Huang, Xiaoqing
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- Facile synthesis of highly stable heterogeneous catalysts by entrapping metal nanoparticles within mesoporous carbon
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Cycling instability is a persisting problem in heterogeneous catalysis. Here we report an efficient strategy to enhance the recyclability of the heterogeneous catalysts by in situ entrapment of active nanoparticles in mesoporous carbon. A hard template method was used to fabricate the desired catalyst, where Al2O3 was employed as the template and polyphenols were used as carbon source as well as the stabilizing agent. Based on N2 adsorption/desorption analysis, the catalysts adopt the high surface area of the Al2O3 template and feature mesoporous pores. Additionally, the noble metal nanoparticles (Pd) were found to be well entrapped inside the carbon matrix with good dispersion. The as-prepared catalysts were highly active in various heterogeneous hydrogenations of C=C containing substrates (quinoline, cinnamaldehyde, etc.) and exhibited excellent cycling stability without any significant loss of activity for 10 recycles, which is superior to that of the commercial Pd/C catalyst. the Partner Organisations 2014.
- Mao, Hui,Peng, Shengjie,Yu, Hong,Chen, Jing,Zhao, Shilin,Huo, Fengwei
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- Nitrogen- and oxygen-functionalized carbon nanotubes supported Pt-based catalyst for the selective hydrogenation of cinnamaldehyde
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Carbon nanotubes (CNTs) supported Pt catalysts were employed to study the influence of nitrogen- and oxygen-functionalized surface on catalytic performance in the liquid-phase hydrogenation of cinnamaldehyde. Nitrogen- and oxygen-functionalized CNTs were simply treated with the hydrothermal method using ammonia and hydrogen peroxide, respectively, and the metal catalyst was prepared using an impregnation-reduction-deposition method. Here, we studied and gave some insights into the influence of the functionalization on CNTs surface chemistry environment and Pt nanoparticles using XRD, Raman spectroscopy, TEM, XPS, and nitrogen sorption techniques. It was shown that the functionalization lead to the small size distribution of Pt particles and promoted the conversion from ca. 75% to ca. 95%. To obtain the high selectivity, transition metals, cobalt and nickel, were doped into the Pt catalyst and the 99.7% conversion with the 87.9% selectivity was achieved over the nitrogen-functionalized CNTs supported PtCo catalysts. The PtCo/N-CNTs remained high activity even at 40°C and achieved 94.2% conversion and 90.3% selectivity.
- Tian, Zhengbin,Liu, Chao,Li, Qingyang,Hou, Juying,Li, Yan,Ai, Shiyun
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- A metal-free transfer hydrogenation: Organocatalytic conjugate reduction of α,β-unsaturated aldehydes
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Impressive tolerance is displayed in the efficient and chemoselective organocatalytic transfer hydrogenation of α,β-unsaturated aldehydes in the presence of a Hantzsch dihydropyridine and a catalytic amount of dibenzylammonium trifluoroacetate (see scheme). Various sensitive functional groups such as the nitro, cyano, alkenyl, and benzyloxy groups survive these reaction conditions.
- Yang, Jung Woon,Hechavarria Fonseca, Maria T.,List, Benjamin
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- Conglomerated system of Ag nanoparticles decorated Al2O3 supported cobalt and copper complexes with enhanced catalytic activity for oxidation reactions
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In this study, our aim is to increase the effectiveness of heterogeneous catalysts by reducing its drawback. For this purpose we have developed a new method to synthesize heterogeneous catalyst by dispersion of Silver nanoparticles onto Alumina supported cobalt and copper Schiff base complexes (AgNPs-Al2O3@ML).Initially Schiff base and its corresponding Co (III) complex, (CoL) and Cu (II) complex, (CuL)(L = Schiff base) were synthesized. Both the complexes were immobilized on Al2O3 to generate Al2O3@CoL (HT1) and Al2O3@CuL (HT2). Finally, Silver was dispersed onto both the heterogeneous complexes to generate our desired heterogeneous catalyst Ag NPs-Al2O3@CoL (AgHT1) and Ag NPs-Al2O3@CuL (AgHT2).A hike in BET surface area from HT1 to AgHT1 highlighted the fruitfulness of decoration of Ag NPs onto HT1. FESEM studies of AgHT1 and AgHT2 reveal the formation of pyramidal type silver nanoparticle onto HT1 and HT2. The catalytic ability of CoL, CuL (homogeneous catalyst), HT1, HT2 and AgHT1, AgHT2 (heterogeneous catalyst) were investigated by enrolling it on oxidation of alcohols, alkanes and epoxidation of alkenes using H2O2 as oxidant. Among the four heterogeneous catalysts AgHT1 showed highest activity. Finally a plausible mechanism has been put forward to elucidate the role of each substituent of the catalytic system. The heterogeneous catalysts HT1, HT2, AgHT1 and AgHT2 can be reused up to six times without any significant loss in its catalytic activity.
- Chakraborty, Tonmoy,Chakraborty, Aratrika,Maity, Suvendu,Das, Debasis,Chattopadhyay, Tanmay
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- Anaerobic nitroxide-catalyzed oxidation of alcohols using the NO +/NO· redox pair
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A new method for alcohol oxidation using TEMPO or AZADO in conjunction with BF3·OEt2 or LiBF4 as precatalysts and tert-butyl nitrite as a stoichiometric oxidant has been developed. The system is based on a NO+/NO· pair for nitroxide reoxidation under anaerobic conditions. This allows the simple, high-yielding conversion of various achiral and chiral alcohols to carbonyl compounds without epimerization and no formation of nonvolatile byproducts.
- Holan, Martin,Jahn, Ullrich
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- Synthesis and reactivity of heteroditopic dicarbene rhodium(i) and iridium(i) complexes bearing chelating 1,2,3-triazolylidene-imidazolylidene ligands
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1,2,3-Triazol-5-ylidenes (tzNHC) have become a popular class of NHC ligands in homogeneous catalysis. Herein, we introduce chelate monovalent Rh- and Ir(cod) complexes bearing bidentate ligands that combine this tzNHC and an Arduengo-type NHC motif. The reactivity of these complexes with H2 and CO gas has been investigated, leading to an interesting octahedral [Ir(tzNHC-CH2-NHC)(CO)2(H)2]OTf complex and [M(tzNHC-CH2-NHC)(CO)2]OTf complexes. The carbonyl stretching frequencies of the latter indicate that the ligand has stronger electron-donating properties than classic di-NHC ligands. The square planar rhodium and iridium NHC-tzNHC complexes have been applied in transfer hydrogenation employing isopropyl alcohol as the hydrogen donor, in which they show moderate activity (Ir > Rh) toward a range of ketones as well as for an aldehyde, an imine, and a diene. The new dicarbene complexes proved to be more active for this reaction than the analogues in which the triazolyl moiety coordinates through a nitrogen donor.
- Sluijter, Soraya N.,Elsevier, Cornelis J.
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- THE DIMESITYLBORON GROUP IN ORGANIC SYNTHESIS. 3. REACTIONS OF ALLYLDIMESITYLBORANE
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Allyldimesitylborane readily yields an anion that is attacked by electrophiles in a regio- and stereospecific fashion.Alkylation is at the γ-position to give trans-vinylboranes that can be oxidised to aldehydes.Reaction with trimethylsilyl chloride gives the new, highly differentiated three carbon synthon, Mes2BCHt:CHCH2SiMe3 also by γ-attack and reaction with benzaldehyde proceeds similarly to give rise to a novel γ-lactol synthesis.
- Pelter, Andrew,Singaram, Bakthan,Wilson, John W.
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- RHODIUM- AND PLATINUM-CATALYZED ASYMMETRIC HYDROFORMYLATION WITH (2S,3R)-2,3-BIS(DIPHENYLPHOSPHINO)BUTANE AS THE CHIRAL LIGAND
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Some mono- and disubstituted ethenes have been asymmetrically hydroformylated with rhodium and platinum catalysts using (2S,3S)-2,3-bis(diphenylphosphino)butane (Chiraphos) as the chiral ligand (maximum optical yield ca 45percent).The results are compared with those obtained when the chiral ligand is (4R,5R)-2,2-dimethyl-4,5-bis(diphenylphosphinomethyl)-1,3-dioxolane (Diop).The Chiraphos ligand causes a decrease of the catalytic activity with respect to Diop.Optical yields for rhodium catalysts are always higher with Chiraphos, whereas scattered results were obtained with platinum catalysts.Since for the catalytic systems examined asymmetric induction takes place before or during the formation of the intermediate diastereomeric metal alkyl complexes, the results are tentatively rationalized on the basis of a stereochemical model for the transition state leading to the above metal alkyl complexes intermediate.
- Consiglio, Giambattista,Morandini, Franco,Scalone, Michelangelo,Pino, Piero
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- Mild and Selective Catalytic Hydrogenation of the C=C Bond in α,β-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles
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Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2: 1) nano-Pd on a metal-organic framework (MOF: Pd0-MIL-101-NH2(Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd0-AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd0-MIL-101-NH2(Cr) and Pd0-AmP-MCF were capable of delivering the desired products in very short reaction times (10-90 min) with low loadings of Pd (0.5-1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.
- Nagendiran, Anuja,Pascanu, Vlad,Bermejo Gómez, Antonio,González Miera, Greco,Tai, Cheuk-Wai,Verho, Oscar,Martín-Matute, Belén,B?ckvall, Jan-E.
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- Hydrogenation of cinnamaldehyde using catalysts prepared from supported palladium phosphine complexes
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The liquid phase hydrogenation of cinnamaldehyde has been studied using catalysts prepared from the binuclear palladium complexes [Pd2X4(PR3)2] (X=Cl, Br, or I; R=Me, Et, and Pri or Bu for X=Br only) on silica, and the results have been compared with the performance of a standard Pd/SiO2 catalyst prepared from Pd(NO3)2 and with that of the unsupported molecular complexes. When X=Br, cinnamaldehyde is rapidly hydrogenated selectively to hydrocinnamaldehyde and no further reaction occurs. When X=I, the reactions are extremely slow but are again limited to hydrocinnamaldehyde formation. The catalysts prepared from the chloride-containing precursors behave differently, and some phenyl propanol is formed along with hydrocinnamaldehyde. However, the reaction mechanisms are different from that which operates with the silica-supported palladium catalyst. The rates of the reactions are dependent on the nature of the phosphine substituent, but the selectivities are dependent primarily on the halide. Hydrogenation reactions on all of the catalysts prepared from the binuclear complexes proceed only after an induction period during which partial reduction and/or surface reconstruction of the supported complexes occur. This contrasts with the performance of the standard Pd/SiO2 catalysts for cinnamaldehyde hydrogenation, which proceeds without any induction period. The reactions of all of these catalysts are thought to take place on a hydrocarbonaceous overlayer which is formed rapidly from unsaturated aldehydes and alcohols. Hydrogenations of cinnamaldehyde using the unsupported complexes in solution proceed at much lower rates, but reveal the same selectivities observed with their silica-supported counterparts.
- Cairns, Graham R.,Cross, Ronald J.,Stirling, Diane
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- Enhancing the catalytic performance of Pt/ZnO in the selective hydrogenation of cinnamaldehyde by Cr addition to the support
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An enhancement of the catalytic performance of platinum in the liquid phase hydrogenation of cinnamaldehyde has been achieved by modifying a ZnO support by addition of Cr(III) cations. The addition of chromium improves the structural properties of the support (larger surface area) and increases its reducibility, and resulted in a better Pt dispersion. The presence of chromium in the support enhanced the overall catalytic activity, and improved the high selectivity towards the unsaturated alcohol. The increase of the reduction temperature from 473 K to 623 K produces an impressive decrease in the turnover frequency for Pt/ZnO, whereas this value remains practically unmodified for Pt/Cr-Zn. The higher reduction temperature reduces the overall activity in both catalysts, but improves selectivity towards the unsaturated alcohol. The present 5 wt% Pt/Cr-ZnO catalyst showed the best results (in terms of selectivity) published until now without use of reaction promoters. The improved performance of this catalyst is ascribed to an adequate metal-support interaction and to the higher reducibility of the support that opens the possibility of alloy formation.
- Ramos-Fernandez,Ferreira,Sepulveda-Escribano,Kapteijn,Rodriguez-Reinoso
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- Separate deposition of gold and palladium nanoparticles on ordered mesoporous carbon and evaluation of their catalytic activity for cinnamaldehyde hydrogenation under atmospheric condition
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We report here, for the first time, a simple method to prepare ordered mesoporous carbon containing separate gold, and palladium nanoparticles (AuPd-OMC). Furthermore, the new catalysts were evaluated in the selective hydrogenation of cinnamaldehyde under atmospheric conditions. In comparison with the monometallic catalysts, the AuPd-OMC exhibited excellent catalytic activity (96.2% selectivity for hydro cinnamaldehyde). The observed synergistic effects were ascribed to hydrogen spillover. The Pd nanoparticles possess the main active sites that formed the active hydrogen species, while the Au nanoparticles served as active hydrogen acceptors and diluted the Pd active sites in order to suppress the deep hydrogenation.
- Gu, Huizi,Xu, Xiangsheng,Chen, Ao-Ang,Ao, Ping,Yan, Xinhuan
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- Aqueous biphasic hydrogenations catalyzed by rhodium and iridium complexes modified with human serum albumin
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Water soluble complexes derived from the interaction between Rh(CO)2(acac) and [Ir(COD)Cl]2, respectively, with human serum albumin (HSA), were employed in the aqueous biphasic hydrogenation of α,β-unsaturated compounds as 2-cyclohexen-1-one (I), 2-butenal (V), 3-phenyl-2-propenal (IX) and 3-aryl-2-methyl-2-propenals (XIII and XVII). Both catalytic systems Rh/HSA and Ir/HSA showed to be very active in the hydrogenation of ketone I even at low temperature and hydrogen pressure; in particular, the rhodium based catalyst showed to be very selective affording exclusively cyclohexanone (II). The α,β-unsaturated aldehydes investigated required higher temperature (up to 60 °C) and pressure (5 MPa) to obtain good conversions. In this case Rh/HSA resulted to be more active than Ir based catalyst. In all cases both Rh/HSA and Ir/HSA were easily recycled without significant loss of activity.
- Marchetti, Mauro,Minello, Fabiola,Paganelli, Stefano,Piccolo, Oreste
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- Tetronics/cyclodextrin-based hydrogels as catalyst-containing media for the hydroformylation of higher olefins
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The rhodium-catalyzed hydroformylation of alkenes has been investigated under biphasic conditions using combinations of α-cyclodextrin (α-CD) and poloxamines (Tetronics). Thermo-responsive hydrogels containing the Rh-catalyst are formed under well-defined conditions of concentration. Hydrogels consisting of the reverse-sequential Tetronic 90R4 prove to be more effective than those containing the conventional sequential Tetronic 701. The presence of α-CD is crucial to provoke the decantation of the multiphasic system once the reaction is complete. Optimized conditions (CO/H2 pressure, Rh-precursors, phosphanes, etc.) show that the catalytic system is especially applicable to the hydroformylation of terminal alkenes. The catalytic performance remains unchanged upon recycling as the hydrogel matrix prevents the oxidation of the phosphane.
- Chevry,Vanbésien,Menuel,Monflier,Hapiot
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- An insight into the Meerwein-Ponndorf-Verley reduction of α,β-unsaturated carbonyl compounds: Tuning the acid-base properties of modified zirconia catalysts
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A series of catalysts consisting of ZrO2 in pure form or modified by doping with boron or an alkaline-earth metal to enhance their acid and basic properties, respectively, were prepared and used in the Meerwein-Ponndorf-Verley reduction of cinnamaldehyde with 2-propanol, where they exhibited moderate activity and a high selectivity (up to 98%) towards cinnamyl alcohol. The catalyst preparation procedure and its modification (viz. doping with boron or an alkaline-earth metal) were found to delay crystallization and increase the number of hydroxyl groups present on the catalyst surface, and hence its catalytic activity. The surface acid and basic properties of the catalysts were determined by pyridine and carbon dioxide chemisorption, respectively. The most active sites in the studied reaction are seemingly proton (Bronsted) acid sites of medium-high strength formed by modification of the ZrO2 with boron; however, the increased activity thus obtained is accompanied by a loss of selectivity towards cinnamyl alcohol. Modifying ZrO2 with an alkaline-earth metal enhances its basicity, thereby reducing its catalytic activity and increasing its selectivity for the unsaturated alcohol.
- Urbano, Francisco J.,Aramendía, María A.,Marinas, Alberto,Marinas, José M.
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- Fine-tuning ligands for catalysis using supramolecular strategies
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Coordinative bonds have been used to prepare supramolecular ligands leading to well-defined catalysts formed by assembly. The construction of these ligands is based on selective metal-ligand interactions between nitrogen donor atoms of phosphorus-nitrogen building blocks and various zinc(II) porphyrins. The major advantage of this supramolecular approach of catalyst preparation is the simplification of ligand variation enabling straightforward modification of steric, electronic and chiral properties of the supramolecular ligand. A large number of new ligands becomes accessible by this modular variation of the building blocks. The ligand assembly based on pyridyl phosphites and zinc(II) porphyrin with electron-withdrawing substituents led to a twelve-fold increase in activity and an increase in enantioselectjvity from 17 to 50% in the rhodium-catalyzed hydrogenation of dimethyl itaconate. The first examples of assemblies based on non-chiral ligands and chiral zinc(II) porphyrin template molecules show, as proof of principle, an enantiomeric excess up to 18 % in the asymmetric palladium-catalyzed allylic alkylation. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Slagt, Vincent F.,Kaiser, Patrick,Berkessel, Albrecht,Kuil, Mark,Kluwer, Alexander M.,Van Leeuwen, Piet W. N. M.,Reek, Joost N. H.
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- Functionalized-1,3,4-oxadiazole ligands for the ruthenium-catalyzed Lemieux-Johnson type oxidation of olefins and alkynes in water
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Three arene-ruthenium(II) complexes bearing alkyloxy(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-trifluoromethylphenyl)methyl ligands were quantitatively obtained through the reaction of (E)-1-(4-trifluoromethylphenyl)-N-(5-phenyl-1,3,4-oxadiazol-2-yl)-methanimine with the ruthenium precursor [RuCl2(η6-p-cymene)]2 in a mixture of the corresponding alcohol and CH2Cl2 at 50 °C. The obtained complexes were fully characterized by elemental analysis, infrared, NMR and mass spectrometry. Solid-state structures confirmed the coordination of the 1,3,4-oxadiazole moiety to the ruthenium center via their electronically enriched nitrogen atom at position 3 in the aromatic ring. These complexes were evaluated as precatalysts in the Lemieux-Johnson type oxidative cleavage of olefins and alkynes in water at room temperature with NaIO4 as oxidizing agent. Good to full conversions of olefins into the corresponding aldehydes were measured, but low catalytic activity was observed in the case of alkynes. In order to get more insight into the mechanism, three analogue arene-ruthenium complexes were synthesized and tested in the oxidative cleavage of styrene. The latter tests clearly demonstrated the importance of the hemilabile alkyloxy groups, which may form more stable (N,O)-chelate intermediates and increase the efficiency of the cis-dioxo-ruthenium(VI) catalyst.
- Hkiri, Shaima,Touil, Soufiane,Samarat, Ali,Sémeril, David
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- Synthesis of rac-ɑ-aryl propionaldehydes via branched-selective hydroformylation of terminal arylalkenes using water-soluble Rh-PNP catalyst
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This work detailed the preparation of a class of water-soluble PNP ligands that differed by the nature of the substitute on phenyl ring of ligands. These ligands were incorporated into water-soluble rhodium-PNP complex catalysts that were used to regioselective hydroformylation of a series of terminal arylalkenes, providing efficient access to rac-α-aryl propionaldehydes in good to excellent yield (up to 97%) and branched-regioselectivity (up to 40:1 b/l ratio). Furthermore, gram-scale and diverse synthetic transformation demonstrated synthetic application of this methodology for non-steroidal antiinflammatory drugs.
- Gao, Peng,Ke, Miaolin,Ru, Tong,Liang, Guanfeng,Chen, Fen-Er
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p. 830 - 834
(2021/08/26)
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- Rh-Catalyzed Regio- and Enantioselective Allylic Phosphinylation
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Transition-metal-catalyzed branched and enantioselective allylic substitution of monosubstituted precursors with carbon, nitrogen, oxygen, sulfur, and fluoride nucleophiles has been well-established. However, such a selective carbon-phosphorus bond formation has not been realized probably due to the catalyst deactivation by the strong coordinating nature of phosphinylating reagents. Herein, we report a Rh-catalyzed highly regio- and enantioselective synthesis of allylic phosphine oxides in the presence of a chiral bisoxazoline-phosphine ligand. The application of α-hydroxylalkylphosphine oxides to keep the low concentration of the secondary phosphine oxides is essential for the high yields. The addition of diphenyl phosphoric acid was found to not only activate allylic alcohols but also accelerate the carbon-phosphorus bond formation.
- Li, Bing,Li, Changkun,Liu, Min,Rehman, Sajid Ur
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supporting information
p. 2893 - 2898
(2022/03/02)
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- Copper(i) pyrimidine-2-thiolate cluster-based polymers as bifunctional visible-light-photocatalysts for chemoselective transfer hydrogenation of α,β-unsaturated carbonyls
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The photoinduced chemoselective transfer hydrogenation of unsaturated carbonyls to allylic alcohols has been accomplished using cluster-based MOFs as bifunctional visible photocatalysts. Assemblies of hexanuclear clusters [Cu6(dmpymt)6] (1, Hdmpymt = 4,6-dimethylpyrimidine-2-thione) as metalloligands with CuI or (Ph3P)CuI yielded cluster-based metal organic frameworks (MOFs) {[Cu6(dmpymt)6]2[Cu2(μ-I)2]4(CuI)2}n (2), {[Cu6(dmpymt)6]2[Cu2(μ-I)2]4}n (3), respectively. Nanoparticles (NPs) of 2 and 3 served both as photosensitizers and photocatalysts for the highly chemoselective reduction of unsaturated carbonyl compounds to unsaturated alcohols with high catalytic activity under blue LED irradiation. The photocatalytic system could be reused for several cycles without any obvious loss of efficiency.
- Zhang, Meng Juan,Young, David James,Ma, Ji Long,Shao, Guo Quan
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p. 14899 - 14904
(2021/05/19)
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- Carbon molecular sieve supported pd catalyzed hydrogenation of cinnamaldehyde in alkaline medium
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Synthesis of various fine chemicals and pharmaceuticals are regulated through selective hydrogenation of α,β-unsaturated aldehydes. Hydrocinnamaldehyde is one of the important compounds in perfumery and flavouring industries. It is highly precarious and challenging to control the product selectivity as well as conversion in cinnamaldehyde hydrogenation. In this study, an effective hydrogenation of cinnamaldehyde was attained in presence of aqueous-protic organic medium by utilizing Pd/CMS and other additives of alkali such as K2CO3. The Pd/CMS catalyst along with alkali media catalyzed the hydrogenation of C=C selectively in cinnamaldehyde in order to form hydrocinnamaldehyde with 100% conversion rate. Additionally, the parallel hydrogenation of C=O and C=C bonds in cinnamaldehyde takes place in absence of media. The C=O bond reduction in cinnamaldehyde can be restricted through K2CO3 addition to aqueous-protic solution. The active sites of palladium were found to be uniform and analyzed using HRTEM data. Based on the mechanism involved in micropores of carbon molecular sieves, the key role of promoter is associated with hydrogenation of cinnamaldehyde. The catalytic criterion was appropriate with the acquired activity data.
- Krishna, Racharla,Ramakrishna, Chowdam,Saini, Bijendra,Gopi, Thakkallapalli,Swetha, Gujarathi,Shekar, Sridara Chandra,Srinivas, Ankanagari
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p. 846 - 852
(2021/04/09)
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- A Cationic Ru(II) Complex Intercalated into Zirconium Phosphate Layers Catalyzes Selective Hydrogenation via Heterolytic Hydrogen Activation
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Catalytic hydrogenations constitute economic and clean transformations to produce pharmaceutical and a multitude of fine chemicals in chemical industry. Herein, we report a cationic Ru(II) complex intercalated into zirconium phosphate (ZrP) layers that enables the efficient catalytic conversion of furfural and other biomass-derived carbonyl compounds into the corresponding alcohols through selective hydrogenation of C=O group. The ZrP layers acted not only as a support for the Ru-complex, but also as the new ligands to tune the Ru(II) center via forming Ru?O bond. The resulting catalysts exhibit excellent catalytic performance and can be easily recycled for six times without significant loss of activity and selectivity. The Ru(II) complex-intercalated catalysts have been characterized by XRD, SEM, HRTEM, HAADF-STEM, XPS, FT-IR, DR-UV/Vis, EXAFS and XANES. Especially, it is observed that the appropriate interlayer spacing between ZrP layers is favorable to stabilize the Ru(II) complex. Notably, on the basis of the further characterization and density functional theory (DFT) calculation, it is identified that the interaction of cationic Ru(II) complex and P?OH group within ZrP layers leads to the high catalytic performance in selective hydrogenation, and the newly formed Ru?O?P species plays a crucial role in the heterolytic hydrogen activation and selective hydrogenation of biomass-derived compounds containing a carbonyl group.
- Chen, Manyu,Xia, Jie,Li, Huan,Zhao, Xiuge,Peng, Qingpo,Wang, Jiajia,Gong, Honghui,Dai, Sheng,An, Pengfei,Wang, Haifeng,Hou, Zhenshan
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p. 3801 - 3814
(2021/08/03)
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- Ir nanoclusters confined within hollow MIL-101(Fe) for selective hydrogenation of α,β-unsaturated aldehyde
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Although the selective hydrogenation of α,β-unsaturated aldehyde to unsaturated alcohol (UOL) is an extremely important transformation, it is still a great challenge to achieve high selectivity to UOL due to thermodynamic favoring of the C[dbnd]C hydrogenation over the C[dbnd]O hydrogenation. Herein, we report that iridium nanoclusters (Ir NCs) confined within hollow MIL-101(Fe) expresses satisfied reaction activity (93.9%) and high selectivity (96.2%) for the hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) under 1 bar H2 atmosphere and room temperature. The unique hollow structure of MIL-101(Fe) benefits for the fast transport of reactant, ensuring the comparable reaction activity and better recyclability of Ir@MIL-101(Fe) than the counterparts which Ir NCs were on the surface of MIL-101(Fe). Furthermore, The X-ray photoelectron spectroscopy data indicates the electropositive Ir NCs, owing to the electron transfer from Ir to MIL-101(Fe), can interact with oxygen lone pairs, and Fourier transform infrared spectrum shows the Lewis acid sites in MIL-101(Fe) can strongly interact with C[dbnd]O bond, which contributes to a high selectivity for COL. This work suggests the considerable potential of synergetic effect between hollow MOFs and metal nanoclusters for selective hydrogenation reactions.
- Chen, Yurong,Li, Guangqin,Li, Yinle,Liu, Qian,Liu, Qinghua,Liu, Qinglin,Su, Hui
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supporting information
(2021/08/13)
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- Chemoselective hydrogenation of cinnamaldehyde over a tailored oxygen-vacancy-rich Pd@ZrO2catalyst
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Selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde is captivating due to its industrial relevance. Herein, a two-step synthesis method was adopted to develop oxygen vacancies in Pd@ZrO2catalysts. The oxygen vacancies were developed in Pd@ZrO2catalysts during impregnation of Pd which was confirmed by XPS and HR-TEM analyses. The characterization results revealed that there was a synergistic role of oxygen vacancies and nano-sized active Pd metals in Pd@ZrO2catalysts that assisted in achieving selectivity for hydrocinnamaldehyde which has been discussed in this study. We also studied the effects of different reaction parameters which revealed that 4 wt% Pd loading in a Pd@ZrO2catalyst provided enough active sites for complete conversion of CAL. Additionally, 100 °C temperature and 10 bar H2pressure provided enough energy for effective collisions and activation of reactants and catalysts to form the desired product in a reaction time of 9 h. Therefore, a defect-rich 4-Pd@ZrO2catalyst demonstrated complete CAL conversion with 86% yield towards HCAL which is the best result amongst various Pd@ZrO2catalysts with different Pd loading investigated for the hydrogenation of cinnamaldehyde. Moreover, a plausible mechanism was proposed to support the chemoselective hydrogenation of cinnamaldehyde over a 4-Pd@ZrO2catalyst. Along with high catalytic performance, the 4-Pd@ZrO2catalyst also showed impressive recyclability performance for up to six recycles. Thus, the oxygen-vacancy-rich Pd@ZrO2can be considered as an efficient catalyst for the chemoselective hydrogenation of cinnamaldehyde.
- Patil, Komal N.,Prasad, Divya,Bhanushali, Jayesh T.,Kakade, Bhalchandra,Jadhav, Arvind H.,Nagaraja, Bhari Mallanna
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p. 5659 - 5681
(2021/04/06)
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- Micellar Catalysis for Sustainable Hydroformylation
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It is here reported a fully sustainable and generally applicable protocol for the regioselective hydroformylation of terminal alkenes, using cheap commercially available catalysts and ligands, in mild reaction conditions (70 °C, 9 bar, 40 min). The process can take advantages from both micellar catalysis and microwave irradiation to obtain the linear aldehydes as the major or sole regioisomers in good to high yields. The substrate scope is largely explored as well as the application of hydroformylation in tandem with intramolecular hemiacetalization thus demonstrating the compatibility with a broad variety of functional groups. The reaction is efficient even in large scale and the catalyst and micellar water phase can be reused at least 5 times without any impact in reaction yields. The efficiency and sustainability of this protocol is strictly related to the in situ transformation of the aldehyde into the corresponding Bertagnini's salt that precipitates in the reaction mixture avoiding organic solvent mediated purification steps to obtain the final aldehydes as pure compounds.
- Calamante, Massimo,Dei, Filippo,Maramai, Samuele,Migliorini, Francesca,Petricci, Elena
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p. 2794 - 2806
(2021/05/03)
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- Atomically dispersed Rh on hydroxyapatite as an effective catalyst for tandem hydroaminomethylation of olefins
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Tandem hydroaminomethylation is an efficient and green route for one-pot synthesis of amines directly from olefins. Herein, heterogeneous hydroxyapatite (HAP) supported single-atom Rh catalyst was prepared and used for tandem hydroaminomethylation of olefins. Characterization techniques confirmed the atomic dispersion of Rh species on HAP. Up to 99% conversion of 1-hexene with high selectivity to the desired amines (93.2%) was obtained over 0.5Rh1/HAP catalyst. Mechanism study demonstrated that the first hydroformylation step during the tandem catalytic process was rate-determining. Compared with the Rh nanoparticles on other oxide supports (Mg3Al, MgO and Al2O3), the atomically dispersed Rh sites on HAP ensured the high hydroformylation activity, thereby guaranteed the outstanding catalytic performance for the total tandem process. Furthermore, various corresponding amines can be obtained with satisfactory yields over 0.5Rh1/HAP catalyst from a wide scope of olefins or amines substrates.
- Gun, Gong,Li, Liusha,Li, Xiao,Lin, Tiejun,Qin, Tingting,Zhong, Liangshu
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- A stable well-defined copper hydride cluster consolidated with hemilabile phosphines
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Copper hydrides are very useful in hydrogenation reactions. We report a stable Stryker-type copper hydride reagent protected by hemilabile phosphines: [Cu8H6(dppy)6](OTf)2(Cu8-H, dppy = diphenylphosphino-2-pyridine). The metal core of this cluster has a bicapped octahedral configuration, and the copper-bound hydrides each triply bridges over a triangular face of the octahedron. This cluster is attractive due to its facile preparation and excellent stability under ambient conditions. The comparable activity and selectivity both in the stoichiometric and catalytic reactions makeCu8-Ha promising alternative to Stryker's reagent.
- Yuan, Shang-Fu,Luyang, Heng-Wang,Lei, Zhen,Wan, Xian-Kai,Li, Jiao-Jiao,Wang, Quan-Ming
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p. 4315 - 4318
(2021/05/05)
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- Designing of Highly Active and Sustainable Encapsulated Stabilized Palladium Nanoclusters as well as Real Exploitation for Catalytic Hydrogenation in Water
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Abstract: Encapsulated nanoclusters based on palladium, 12-tunstophosphoric acid and silica was designed by simple wet impregnation methodology. The catalyst was found to be very efficient towards cyclohexene hydrogenation up to five catalytic runs with substrate/catalyst ratio of 4377/1 at 50?°C as well as for alkene, aldehyde, nitro and halogen compounds. Graphic Abstract: Silica encapsulated Pd nanoclusters stabilized by 12-tungstophosphoric acid is proved to be sustainable and excellent for water mediated hydrogenation reaction with very high catalyst to substrate ratio as well as TON.[Figure not available: see fulltext.]
- Patel, Anish,Patel, Anjali
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p. 803 - 820
(2020/08/12)
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- A TEMPO-Functionalized Ordered Mesoporous Polymer as a Highly Active and Reusable Organocatalyst
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The properties of high stability, periodic porosity, and tunable nature of ordered mesoporous polymers make these materials ideal catalytic nanoreactors. However, their application in organocatalysis has been rarely explored. We report herein for the first time the incorporation of a versatile organocatalyst, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), into the pores of an FDU-type mesoporous polymer via a pore surface engineering strategy. The resulting FDU-15-TEMPO possesses a highly ordered mesoporous organic framework and enhanced stability, and shows excellent catalytic activity in the selective oxidation of alcohols and aerobic oxidative synthesis of 2-substituted benzoxazoles, benzimidazoles and benzothiazoles. Moreover, the catalyst can be easily recovered and reused for up to 7 consecutive cycles.
- Guo, Ying,Wang, Wei David,Li, Shengyu,Zhu, Yin,Wang, Xiaoyu,Liu, Xiao,Zhang, Yuan
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supporting information
p. 3689 - 3694
(2021/09/29)
-
- Catalytic study of the copper-based magnetic nanocatalyst on the aerobic oxidation of alcohols in water
-
A copper-based magnetic nanocatalyst has been prepared by co-precipitation method and characterized by FESEM, EDS, TEM, XRD, XRF, ICP–OES, FTIR, and BET analysis. This new nanocatalyst displays a good activity toward the aerobic oxidation of a wide range of alcohols in water. Moreover, it is recyclable up to five following runs by simple filtration without any significant loss of its catalytic activity.
- Dehkordi, S. Saeid Saei,Albadi, Jalal,Jafari, Abbas Ali,Samimi, Heshmat Allah
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p. 2527 - 2538
(2021/03/24)
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- Integration of Earth-Abundant Photosensitizers and Catalysts in Metal-Organic Frameworks Enhances Photocatalytic Aerobic Oxidation
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We report here the construction of two metal-organic frameworks (MOFs), Zr6-Cu/Fe-1 and Zr6-Cu/Fe-2, by integrating earth-abundant cuprous photosensitizers (Cu-PSs) and Fe catalysts for photocatalytic aerobic oxidation. Site isolation and pore confinement stabilize both Cu-PSs and Fe catalysts, while the proximity between active centers facilitates electron and mass transfer. Upon visible light irradiation and using O2 as the only oxidant, Zr6-Cu/Fe-1 and Zr6-Cu/Fe-2 efficiently oxidize alcohols and benzylic compounds to afford corresponding carbonyl products with broad substrate scopes, high turnover numbers of up to 500 with a 9.4-fold enhancement over homogeneous analogues, and excellent recyclability in four consecutive runs. Control experiments, spectroscopic evidence, and computational studies revealed the photo-oxidation mechanism: Oxidative quenching of [Cu-PS]? by O2 affords [CuII-PS], which efficiently oxidizes FeIII-OH to generate a hydroxyl radical for substrate oxidation. This work highlights the potential of MOFs in promoting earth-abundant metal-based photocatalysis.
- Feng, Xuanyu,Pi, Yunhong,Song, Yang,Xu, Ziwan,Li, Zhong,Lin, Wenbin
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p. 1024 - 1032
(2021/01/26)
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- New method for promoting photosensitive oxidation to remove 1, 2-mercaptoethanol acetal protecting group by utilizing visible light irradiation
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The invention discloses a new method for removing a 1, 2-mercaptoethanol acetal protecting group, and belongs to the field of organic synthetic chemistry. The method comprises the following steps of:under a room-temperature open system, adding a substrate 2-substituted-1, 3-oxo-thio-cyclopentane and a catalytic amount of a photosensitizer Eosin Y into a proper amount of acetonitrile; and performing irradiating with a blue LED lamp for 3 hours while stirring to obtain the corresponding aldehyde compound with favorable yield. The method has the advantages of mild operation conditions, greenness, environmental protection, no harsh water and oxygen removal operation and device, realization of the reaction at room temperature, high substrate conversion rate, simple and easy post-treatment, andprovides a good method for removing the 1, 2-mercaptoethanol acetal protecting group at present.
- -
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Paragraph 0014-0016
(2021/01/30)
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- Differentiation of Pt?Fe and Pt?Ni3 Surface Catalytic Mechanisms towards Contrasting Products in Chemoselective Hydrogenation of α,β-Unsaturated Aldehydes
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Noble-metal catalysts serve as an irreplaceable role in pharmaceutical, perfume and fine chemicals fields. However, there still remains a grand challenge in controlling chemoselectivity. Herein, we have synthesized a bimetallic nanostructure supported on porous metal-organic frameworks (Pt?Fe/UiO-66, Pt-Ni3/UiO-66), in which Pt nanoparticles was modified with non-noble metal (Fe or Ni) directly. The as-synthesized catalysts can function as a switch for selective hydrogenation of α,β-unsaturated aldehydes to afford the potential products on-demand. In comparison with the conventional Pt-based catalysts, Pt?Fe/UiO-66 and Pt-Ni3/UiO-66 catalysts exhibit excellently catalytic activity, enhanced selectivity and improved stability for selectivity hydrogenation. The partial charge reconfiguration and electronic coupling effect existing in such distinctive bicomponent nanocatalysts was confirmed by some comprehensive characterization and density functional theory (DFT) calculations. The developed method for precisely modification the composition and interaction between the noble metal and non-noble metal provides a feasible avenue to design the advanced catalysts.
- Ning, Liangmin,Zhang, Mingtao,Liao, Shengyun,Zhang, Yuting,Jia, Dandan,Yan, Yunfang,Gu, Wen,Liu, Xin
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p. 704 - 711
(2020/12/07)
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- Platinum and cobalt intermetallic nanoparticles confined within MIL-101(Cr) for enhanced selective hydrogenation of the carbonyl bond in a,?-unsaturated aldehydes: synergistic effects of electronically modified Pt sites and Lewis acid sites
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Precious metals have been shown to play a vital role in the selective hydrogenation of a,?-unsaturated aldehydes, but still suffer from challenges to control selectivity. Herein, we have advanced the design of catalysts made out of Pt-Co intermetallic nanoparticles (IMNs) supported on a MIL-101(Cr) MOF (3%Pty%Co/MIL-101(Cr)), prepared by using a polyol reduction method, as an effective approach to enhance selectivity toward the production of a,?-unsaturated alcohol, the desired product. XRD, N2adsorption-desorption, FTIR spectroscopy, SEM, TEM, XPS, CO adsorption, NH3-TPD, XANES and EXAFS measurements were used to investigate the structure and surface properties of our 3%Pty%Co/MIL-101(Cr) catalysts. It was found that the Co-modified 3%Pty%Co/MIL-101(Cr) catalysts can indeed improve the hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL), reaching a higher selectivity under mild conditions than the monometallic Pt/MIL-101(Cr) catalysts: 95% conversion of CAL with 91% selectivity to COL can be reached with 3%Pt3%Co/MIL-101(Cr). Additionally, high conversion of furfural (97%) along with high selectivity to furfural alcohol (94%) was also attained with the 3%Pt3%Co/MIL-101(Cr) catalyst. The enhanced activity and selectivity toward the unsaturated alcohols are attributed to the electronic and geometric effects derived from the partial charge transfer between Co and Pt through the formation of uniformly dispersed Pt-Co IMNs. Moreover, various characterization results revealed that the addition of Co to the IMPs can promote the Lewis acid sites that facilitate the polarization of the charge-rich C?O bonds and their adsorptionviatheir oxygen atom, and also generate new interfacial acid sites.
- Zahid, Muhammad,Li, Jiang,Ismail, Ahmed,Zaera, Francisco,Zhu, Yujun
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p. 2433 - 2445
(2021/04/22)
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- Platinum Nanosheets Intercalated into Natural and Artificial Graphite Powders
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Insertion of sheet-type platinum particles (platinum nanosheets) between graphite layers was achieved by a thermal treatment of a mixture of platinum chloride (IV) and graphite powder (natural graphite or artificial graphite) under 0.3 MPa of chlorine at 723 K, followed by the treatment under 40 kPa of hydrogen pressure. Similar platinum nanosheets, which were 1–3 nm in thickness and 100–500 nm in width and had a number of hexagonal holes and edges with 120° angle, were formed between the layers of both natural graphite or artificial graphite; however, their location in the graphite layers depended on the type of graphite used. A number of platinum nanosheets were observed in the edge region of natural graphite particles which have flat surface. On the other hand, a number of platinum nanosheets were found inside and away from the edge of the artificial graphite particles especially in the vicinity of the cracks. Both the platinum nanosheet-containing artificial and natural graphite samples showed high selectivity to cinnamyl alcohol in cinnamaldehyde hydrogenation under supercritical carbon dioxide conditions, while spherical platinum particles, which were located on the surface of natural and artificial graphite, showed lower selectivity.
- Shirai, Masayuki,Kubo, Kohei,Sodeno, Mika,Nanao, Hidetaka
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p. 2035 - 2040
(2021/06/25)
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- Supported silver catalysts prepared via melt infiltration: Synthesis, characterization and performance in selective hydrogenation
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Heterogeneous supported catalysts are often synthesized by impregnation or precipitation methods. Recently, melt infiltration has emerged as an alternative method that allows high metal loadings and eliminates the need for a solvent, but challenges arise regarding control over the particle size and distribution. In this work, melt infiltration for the synthesis of supported silver catalysts is explored. The narrow pore size distribution of the chosen ordered mesoporous silica support, SBA-15, allowed in depth in-situ and ex-situ characterization of the infiltration of the precursor, molten silver nitrate, into the support and its subsequent decomposition to form metallic silver nanowires or nanoparticles. The heat treatment parameters during decomposition played a key role in determining whether nanowires or nanoparticles were formed. The supported silver catalysts containing high silver weight loadings were investigated in the selective hydrogenation of cinnamaldehyde, where the silver nanowires showed superior activity and selectivity over the nanoparticles. Hence, melt infiltration shows great promise for the synthesis of supported silver catalysts containing high silver weight loadings, which are applicable in, e.g., selective oxidation or hydrogenation reactions.
- Keijzer,Donoeva,de Jong,de Jongh
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p. 393 - 400
(2020/04/01)
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- Lewis Acidic Telluronium Cations: Enhanced Chalcogen-Bond Donor Properties and Application to Transfer Hydrogenation Catalysis
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We describe the synthesis and structures of o-C6F4(TeMes)2 (1) and o-C6F4(TeArF)2 (2, ArF = 3,5-(CF3)2C6H3)), two new bifunctional tellurides featuring an electron-withdrawing backbone. While 2 resisted methylation, 1 reacted with Me3O·BF4 in CH2Cl2 to afford o-C6F4(TeMes)(TeMeMes) ([3]+), a mixed-valent telluride/telluronium cation isolated as a tetrafluoroborate salt. Although attempts to methylate the second telluride have been unsuccessful, [3]+ readily catalyzes the hydrogenation of 2-phenyl-quinoline with Hantzsch ester. Comparison with simple telluronium cations including [ArF2TeMe]+ and [MesArFTeMe]+ confirms that the catalytic activity of these compounds originates from the presence of a tetravalent, cationic tellurium center.
- Gabba?, Fran?ois P.,Zhou, Benyu
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supporting information
p. 2371 - 2374
(2021/07/26)
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- Methyl-modified cage-type phosphorus ligand and preparation method thereof Preparation method and application thereof
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The invention discloses a methyl-modified cage-type phosphorus ligand, a preparation method and application thereof, in particular to a synthesis design, wherein methyl is further introduced on a phenyl ring of triphenylphosphine, and a methyl-modified cage-type phosphorus ligand is synthesized, and when a methyl meta-substituted cage-type phosphorus ligand is used as a hydroformylation reaction catalyst the proportion of n-structural aldehyde and isomeric aldehyde is 2.6. TOF-1 The methyl-substituted cage-type phosphorus ligand is excellent in performance, stable in property and recyclable, has excellent substrate applicability in the hydroformylation catalytic reaction, has a good industrial application prospect, and has very important significance in metal organic catalysis.
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-
Paragraph 0075-0084; 0087-0088
(2021/09/15)
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- Method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and diphosphine ligand used in method
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The invention discloses a method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and a diphosphine ligand used in the method. According to the invention, indole-substituted phosphoramidite diphosphine ligand which is stable in air and insensitive to light is synthesized by utilizing a continuous one-pot method, and the indole-substituted phosphoramidite diphosphine ligand and a rhodium catalyst are used for jointly catalyzing to successfully achieve a hydroformylation reaction of aromatic terminal alkyne and terminal conjugated eneyne under the condition of synthesis gas for the first time, so that an olefine aldehyde structure compound can be rapidly and massively prepared, and particularly, a polyolefine aldehyde structure compound which is more difficult to synthesize in the prior art can be easily prepared and synthesized, and a novel method is provided for synthesis and modification of drug molecules, intermediates and chemical products.
- -
-
Paragraph 0121-0124
(2021/05/29)
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- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
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The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
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supporting information
p. 6067 - 6072
(2021/08/16)
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- B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of: In situ -formed enamines
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A highly efficient B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of in situ-formed enamines in the presence of water and pinacolborane was developed. Regioselective β-deuteration of tertiary amines was achieved with high chemo- and regioselectivity. D2O was used as a readily available and cheap source of deuterium. Mechanistic studies indicated that B(C6F5)3 could activate water to promote the protonation and reduction of enamines. This journal is
- Wu, Rongpei,Gao, Ke
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p. 4032 - 4036
(2021/05/19)
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- Tetradentate nitrogen phosphine ligand and preparation method and application thereof
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The invention provides a novel tetradentate nitrogen phosphine ligand as well as a preparation method and an application thereof in an unsaturated olefin hydroformylation reaction. The tetradentate nitrogen phosphine ligand is used for the hydroformylation reaction of olefin, so that the catalyst is more stable in the reaction, is not easy to inactivate at high temperature (more than 200 DEG C), the pressure of synthesis gas required by the reaction is lower, the reaction positive-to-negative ratio is improved, and the selectivity of a main product can be effectively improved.
- -
-
Paragraph 0067-0069
(2021/04/07)
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- On the role of bismuth as modifier in AuPdBi catalysts: Effects on liquid-phase oxidation and hydrogenation reactions
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There is much about the action of bismuth within heterogeneous catalysis that still require a deeper understanding. We observed that, when Bi was added to AuPd bimetallic nanoparticles (NPs) supported on activated carbon, Bi affected the activity and significantly alters the selectivity in two model liquid phase reactions, namely the oxidation of cinnamyl alcohol and the hydrogenation of cinnamaldehyde. A combination of transmission electron microscopy and X-ray absorption spectroscopy provided a detailed characterization of trimetallic AuPdBi systems. We propose that the introduction of bismuth on AuPd NPs results in a partial blockage of most active sites, limiting the occurrence of consecutive reactions.
- Campisi, Sebastiano,Capelli, Sofia,Dann, Ellie,Dimitratos, Nikolaos,Ferri, Michele,Villa, Alberto,Wade, Austin,Wells, Peter P.
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- Chemo- And regioselective hydroformylation of alkenes with CO2/H2over a bifunctional catalyst
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As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway.
- Hua, Kaimin,Liu, Xiaofang,Wei, Baiyin,Shao, Zilong,Deng, Yuchao,Zhong, Liangshu,Wang, Hui,Sun, Yuhan
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supporting information
p. 8040 - 8046
(2021/11/01)
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- Insight into decomposition of formic acid to syngas required for Rh-catalyzed hydroformylation of olefins
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Formic acid (FA) is one kind of important bulk chemicals, which is recognized as a sustainable and eco-friendly energy carrier to transport H2 via dehydrogenation or CO via decarbonylation. Expectantly, FA upon decomposition into H2 and CO could be used as the syngas alternative for hydroformylation. In this paper, the behaviors of FA to release H2 as well as CO following the distinct pathways were carefully investigated for the first time, and then established a new hydroformylation protocol free of syngas. It was found that the atmospheric hydroformylation of olefins with formic acid (FA) as syngas alternative was smoothly fulfilled over Xantphos (L1) modified Rh-catalyst under mild conditions (80 °C, Rh concentration 1 mol %, 14 h), resulting in >90% conversion of the olefins along with the high selectivity to the target aldehydes (>93%). By using FA as syngas source, the side-reaction of olefin-hydrogenation was greatly depressed. The in situ FT-IR and the high-pressure 1H NMR spectroscopic analyses were applied to reveal how FA behaves dually as CO surrogate and hydrogen source over L1-Rh(acac)(CO)2 catalytic system, based on which the deeply insight into the catalytic mechanism of hydroformylation of olefins with FA as syngas alternative was offered.
- Liu, Lei,Chen, Xiao-Chao,Yang, Shu-Qing,Yao, Yin-Qing,Lu, Yong,Liu, Ye
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p. 406 - 415
(2020/12/07)
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- Selective Production of Linear Aldehydes and Alcohols from Alkenes using Formic Acid as Syngas Surrogate
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Performing carbonylation without the use of carbon monoxide for high-value-added products is an attractive yet challenging topic in sustainable chemistry. Herein, effective methods for producing linear aldehydes or alcohols selectively with formic acid as both carbon monoxide and hydrogen source have been described. Linear-selective hydroformylation of alkenes proceeds smoothly with up to 88 % yield and >30 regioselectivity in the presence of single Rh catalyst. Strikingly, introducing Ru into the system, the dual Rh/Ru catalysts accomplish efficient and regioselective hydroxymethylation in one pot. The present processes utilizing formic acid as syngas surrogate operate simply under mild condition, which opens a sustainable way for production of linear aldehydes and alcohols without the need for gas cylinders and autoclaves. As formic acid can be readily produced via CO2 hydrogenation, the protocols represent indirect approaches for chemical valorization of CO2.
- Chen, Junjun,Hua, Kaimin,Liu, Xiaofang,Deng, Yuchao,Wei, Baiyin,Wang, Hui,Sun, Yuhan
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p. 9919 - 9924
(2021/05/31)
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- Expanding the Biocatalytic Toolbox with a New Type of ene/yne-Reductase from Cyclocybe aegerita
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This study introduces a new type of ene/yne-reductase from Cyclocybe aegerita with a broad substrate scope including aliphatic and aromatic alkenes/alkynes from which aliphatic C8-alkenones, C8-alkenals and aromatic nitroalkenes were the preferred substrates. By comparing alkenes and alkynes, a ～2-fold lower conversion towards alkynes was observed. Furthermore, it could be shown that the alkyne reduction proceeds via a slow reduction of the alkyne to the alkene followed by a rapid reduction to the corresponding alkane. An accumulation of the alkene was not observed. Moreover, a regioselective reduction of the double bond in α,β-position of α,β,γ,δ-unsaturated alkenals took place. This as well as the first biocatalytic reduction of different aliphatic and aromatic alkynes to alkanes underlines the novelty of this biocatalyst. Thus with this study on the new ene-reductase CaeEnR1, a promising substrate scope is disclosed that describes conceivably a broad occurrence of such reactions within the chemical landscape.
- Karrer, Dominik,Gand, Martin,Rühl, Martin
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p. 2191 - 2199
(2021/02/26)
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- Aerobic epoxidation of styrene over Zr-based metal-organic framework encapsulated transition metal substituted phosphomolybdic acid
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Catalytic epoxidation of styrene with molecular oxygen is regarded as an eco-friendly alternative to producing industrially important chemical of styrene oxide (STO). Recent efforts have been focused on developing highly active and stable heterogeneous catalysts with high STO selectivity for the aerobic epoxidation of styrene. Herein, a series of transition metal monosubstituted heteropolyacid compounds (TM-HPAs), such as Fe, Co, Ni or Cu-monosubstituted HPA, were encapsulated in UiO-66 frameworks (denoted as TM-HPA@UiO-66) by direct solvothermal method, and their catalytic properties were investigated for the aerobic epoxidation of styrene with aldehydes as co-reductants. Among them, Co-HPA@UiO-66 showed relatively high catalytic activity, stability and epoxidation selectivity at very mild conditions (313 K, ambient pressure), that can achieve 82 % selectivity to STO under a styrene conversion of 96 % with air as oxidant and pivalaldehyde (PIA) as co-reductant. In addition, the hybrid composite catalyst can also efficiently catalyze the aerobic epoxidation of a variety of styrene derivatives. The monosubstituted Co atoms in Co-HPA@UiO-66 are the main active sites for the aerobic epoxidation of styrene with O2/PIA, which can efficiently converting styrene to the corresponding epoxide through the activation of the in-situ generated acylperoxy radical intermediate.
- Hu, Dianwen,Song, Xiaojing,Zhang, Hao,Chang, Xinyu,Zhao, Chen,Jia, Mingjun
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- Sulfonium ion-promoted traceless Schmidt reaction of alkyl azides
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Schmidt reaction by sulfonium ions is described. General primary, secondary, and tertiary alkyl azides were converted to the corresponding carbonyl or imine compounds without any trace of the activators. This bond scission reaction through 1,2-migration of C-H and C-C bonds was accessible to the one-pot substitution reaction.
- Ardiansah, Bayu,Kakiuchi, Kiyomi,Morimoto, Tsumoru,Tanimoto, Hiroki,Tomohiro, Takenori
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supporting information
p. 8738 - 8741
(2021/09/08)
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- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
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The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture.
- Martyanov, Oleg N.,Philippov, Alexey A.
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- One-pot, oxidative and selective conversion of benzylic silyl and tetrahydropyranyl ethers to gem-dichlorides using trichloroisocyanuric acid and triphenylphosphine as an efficient and neutral system
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A one-pot and oxidative method is described for the first time for the conversion of benzylic trimethylsilyl (TMS) and tetrahydropyranyl (THP) ethers to gem-dichlorides using trichloroisocyanuric acid (TCCA) and triphenylphosphine (PPh3) in neutral media. Various theses substrates containing electron withdrawing or donating groups can be efficiently converted to their corresponding gem-dichlorides in good to excellent yields. The present method shows a high degree of chemoselectivity, and due to its one-pot nature is in accordance with green chemistry.
- Khadem Moghaddam, Roqayeh,Aghapour, Ghasem
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p. 398 - 406
(2020/11/19)
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- Rational Localization of Metal Nanoparticles in Yolk–Shell MOFs for Enhancing Catalytic Performance in Selective Hydrogenation of Cinnamaldehyde
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The development of sustainable catalysts to simultaneously improve activity and selectivity remains a challenge. Herein, it is demonstrated that metal nanoparticles (MNPs) can be encapsulated into a yolk–shell metal–organic framework (MOF) with controllable spatial localization to optimize catalytic performance. When the MNPs are located in the void space between the shell and the core of the MOF, the resulting MNPs@MOF composites show both high catalytic activity and selectivity toward the hydrogenation of α,β-unsaturated aldehydes. In particular, the easily recoverable and stable Ptvoid@MOF(Y) shows an exceptionally high selectivity of 98.2 % for cinnamyl alcohol at a high conversion of 97 %. The excellent performance can be attributed to easy diffusion of the reactants to access highly exposed MNPs in the MOF support, as well as the improved adsorption of the reactant and desorption of the product due to the appropriate metal–support interaction and rich void space between core and shell.
- Zhou, Awu,Dou, Yibo,Zhou, Jian,Li, Jian-Rong
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p. 205 - 211
(2019/11/03)
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- Amorphous Nickel Phosphide Nanoparticles for Selective Hydrogenation of Cinnamaldehyde
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Abstract: The selective hydrogenation of α,β-unsaturated aldehydes plays a crucial role in industrial production, and an efficient non-noble metal catalyst for it has been pursued to reduce the cost. Herein, we report an amorphous nickel phosphide for the selective hydrogenation of cinnamaldehyde. Compared to crystalline nickel phosphide, amorphous nickel phosphide showed both high activity and high selectivity to target products. Its catalytic performance was also better than that of commercial Pd/C catalyst. In addition, initial P/Ni ratio was found to be an important factor to affect the activity of amorphous nickel phosphide. High initial P/Ni ratio led to high activity owing to small particles, high surface area and strong metallicity of as-synthesized catalyst. Moreover, excellent catalytic performances of amorphous nickel phosphide were observed in the selective hydrogenation of different α,β-unsaturated aldehydes and ketones. Graphic Abstract: [Figure not available: see fulltext.].
- Liu, Ping,Zhu, Ya-Lu,Zhou, Lei,Zhang, Wei-Hong,Li, Yong-Xin
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p. 2695 - 2702
(2020/03/23)
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- Ruthenium (II) quinoline-azoimine complex: Synthesis, crystalline structures spectroelectrochemistry and catalytic properties
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An octahedral ruthenium(II) complex with the general formula [RuII(Y)(bpy)Cl](ClO4) {Y= C6H5N=C(COCH3)-N=NC9H6N and bpy = 2,2′-bipyrdine} (1) was synthesized. The new ligand (Y) is coordinated to ruthenium via quinoline-N, imine-N and azo-N atoms. Both the novel complex 1 and the new ligand H2Y were structurally characterized by X-ray crystallography, spectroscopic (IR, UV–Vis and NMR spectroscopy) and electrochemical (cyclic voltammetry) techniques. The bonding in 1 and its published skeletal isomer [RuII(L1)(bpy)Cl](PF6) {L1 = C6H5N=N-C(COCH3) = NC9H6N5} (1A) has been analyzed using molecular orbital theory. The novel tridentate ligand (Y) stabilizes the Ru(II) oxidation state showing the Ru(III/II) couple at 1.05 V vs. Cp2Fe/Cp2Fe+. The potential use of 1 as a catalyst for hydrogenation of α, β-unsaturated aldehyde has been investigated. UV/Vis and IR-spectroelectrochemistry on complex 1 were performed.
- Abdel-Rahman, Obadah S.,Al-Noaimi, Mousa,Alwahsh, Manal I.,Awwadi, Firas F.,Hammoudeh, Ayman
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- Pd nanoparticles confined in mesoporous N-doped carbon silica supports: A synergistic effect between catalyst and support
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Palladium nanoparticles of similar size were deposited on different supports, layers of carbon materials (with and without nitrogen doping) on the surface of a MCF (mesocellular foam) silica. For the generation of the N-doped carbon coatings, three different N sources were used to also investigate a possible influence of the N-doped carbon precursor and thus the structure of the N-doped carbons on their performance as catalyst support. These catalysts were tested for the Suzuki coupling and hydrogenation reactions. For the Suzuki reaction, the carbon coatings showed to increase dramatically the stability of the MCF material. Furthermore, when N-doped carbon coatings were applied, strong improvement of the stability of the catalysts was observed due to an enhanced interaction between metal nanoparticles and the support, preventing metal particle growth. In hydrogenation reactions, the presence of the N-doped carbon coating on the silica support increases the adsorption of aromatic compounds causing an enhancement of the catalytic activity of Pd NPs when compared to the non-doped supports.
- Kerstien, Julius,Oliveira, Rafael L.,Schom?cker, Reinhard,Thomas, Arne
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p. 1385 - 1394
(2020/03/26)
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- Chemoselective hydrogenation of α,β-unsaturated aldehydes over Rh nanoclusters confined in a metal-organic framework
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Selective hydrogenation of α,β-unsaturated aldehydes to achieve high selectivity towards a desirable product is still a great challenge mainly because of the complex conjugate system. Herein, Rh nanoclusters encapsulated in MIL-101 (Cr), synthesized by the double solvent method, are able to selectively hydrogenate C-C of cinnamaldehyde, an α,β-unsaturated aldehyde and achieve over 98percent selectivity with a conversion of 98percent to a saturated aldehyde under mild conditions. Fourier transform infrared spectroscopy confirms that MIL-101 acts as an aldehyde protector to suppress the reactivity of C-O, and the X-ray photoelectron spectroscopy (XPS) data indicate that the electropositive Rh, owing to the electron transfer from Rh to MIL-101, preferentially absorbs C-C rather than C-O leading to -improvement of the selectivity towards saturated aldehydes. In addition, Rh@MIL-101 can also efficiently catalyse hydrodefluorination of aryl fluorides with good stability. This work provides a basic strategy to develop other selective heterogeneous catalystsviastructural modulation for synergetic catalysis.
- Liu, Qinglin,Li, Yinle,Fan, Yanan,Su, Cheng-Yong,Li, Guangqin
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supporting information
p. 11442 - 11447
(2020/06/29)
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- Producing of cinnamyl alcohol from cinnamaldehyde over supported gold nanocatalyst
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Chemoselective hydrogenation of unsaturated aldehyde to unsaturated alcohol has attracted growing interests in recent years due to its widespread applications in fine chemicals. However, the hydrogenation of the C=O bond was thermodynamically and kinetically unfavorable over the hydrogenation of the C=C bond. Thus, to obtain the unsaturated alcohol from the unsaturated aldehyde is very difficult in most of the catalytic systems. In this work, ZnAl-hydrotalcite-supported cysteine-capped Au25 nanoclusters were used as the precatalysts for chemoselective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The catalyst showed stable high selectivity (~ 95percent) at prolonged reaction time and complete conversion of the substrate. According to the results of the control experiments, the in-situ DRIFTS of the substrate under high pressure of hydrogen and the 27Al MAS-NMR spectroscopy, we proposed that the difference of the preferential adsorption of the C=O bond to that of the C=C bond was derived from the nature of the support of the gold catalysts.
- Liu, Fei,Liu, Xiaoyan,Tan, Yuan,Wang, Aiqin,Zhang, Leilei,Zhang, Tao
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p. 470 - 481
(2020/07/31)
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- Porous-Organic-Polymer-Triggered Advancement of Sustainable Magnetic Efficient Catalyst for Chemoselective Hydrogenation of Cinnamaldehyde
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In this study, we adopted a cost-effective, facile and metal & template-free strategy for the successful synthesis of hydroxyl enriched POP (denoted as TPT). An integrated catalyst, Pd?Fe3O4@TPT, has been developed for the liquid phase selective hydrogenation cinnamaldehyde (CAL). Pd?Fe3O4@TPT exhibited excellent catalytic performance, providing 100 % selectivity towards hydrocinnamaldehyde (HCAL) under mild reaction conditions (with relatively low hydrogen pressure and very short reaction time), whereas Fe2O3@TPT appeared inert. Compared with the conventional catalytic systems, our newly designed catalyst was superior in many aspects, owing to the rigid nature of TPT-POP, which prevents aggregation and leaching of the metal nanoparticles.
- Paul, Ratul,Sarkar, Chitra,Yan, Yong,Trinh, Quang Thang,Rao, Bolla Srinivasa,Pao, Chih-Wen,Lee, Jyh-Fu,Liu, Wen,Mondal, John
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p. 3687 - 3704
(2020/06/08)
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- Selective hydrogenation of cinnamaldehyde over magnetic flower-like carbonaceous Pd catalysts
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Synthesis of an easily separable and efficient catalyst is of great significance for selective hydrogenation of unsaturated functional groups. In this work, novel magnetic flower-like carbonaceous Pd catalysts are constructed for the selective reduction of the CC bond. According to the characterization results, a flower-like architecture is observed in the catalysts containing both Fe3O4 and Pd NPs, which is constructed by the secondary self-assembly in the preparation process due to the interaction between Pd and magnetic nitrogen-doped graphene (Fe3O4-NG). More flower-like structures are formed by increasing the Pd loading amount, further enhancing the specific surface area of the catalyst. The specific surface area of Pd-FONG-3 is the highest (521.17 m2 g-1). Combining the results of characterization and experiments, it is found that the catalytic activity is positively related to the flower-like architecture and the interaction between Pd NPs (6.0 nm) and Fe3O4 NPs (6.7 nm). Fe3O4 is not only beneficial to the magnetic recovery of the catalyst, but also acts as a cocatalyst, which can significantly improve the reactant conversion. Moreover, N species play an important role in protecting the CO bond, resulting in the selective hydrogenation of the CC group. Herein, Pd-FONG-3 exhibits excellent activity in the selective hydrogenation of cinnamaldehyde (CAL) with 99.5% conversion and 96.5% hydrocinnamaldehyde (HCAL) selectivity, and its catalytic performance is much better than that of the commercial 5% Pd/C catalyst (100% conversion and 69.1% HCAL selectivity). This work provides a new strategy to construct highly active catalysts with magnetic recovery properties for selective hydrogenation of CC bonds, and Pd-FONG-3 shows tremendous application foreground. This journal is
- Zhang, Dan,Wang, Bowei,Yan, Lijuan,Gao, Ruixiao,Liu, Lu,Xia, Ziyi,Yan, Xilong,Li, Yang,Chen, Ligong
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p. 20367 - 20374
(2020/12/21)
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- Transition-Metal-Free Synthesis of Electron Rich 1,3-Dienes via Base Promoted Isomerization of Propargylic Ethers
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Herein, a novel and scalable synthesis of electron rich 1,3-dienes based on KOtBu mediated isomerization of propargylic ether derivatives was developed. This new process features easy handling reaction conditions, transition-metal-free isomerization, high isolated yields, and most of all, it could be used for modification of natural products at late stage functionalizations.
- Liu, Chunxiang,Deng, Guogang,Li, Xin,Xu, Yiren,Yu, Kaili,Chen, Wen,Zhang, Hongbin,Yang, Xiaodong
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supporting information
p. 483 - 487
(2020/01/25)
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- Mild Deprotection of Dithioacetals by TMSCl/NaI Association in CH3CN
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A mild process using a combination of TMSCl and NaI in acetonitrile is used to regenerate carbonyl compounds from a variety of dithiane and dithiolane derivatives. This easy to handle and inexpensive protocol is also efficient to deprotect oxygenated and mixed acetals as 1,3-dioxanes, 1,3-dioxolanes and 1,3-oxathianes quantitatively. As a possible extension of this method, it was also shown that nitrogenated substrates such as hydrazones, N-tosylhydrazones, and ketimines reacted well under these conditions to give the expected ketones in high yields. The methodology proposed herein is a good alternative to the existing methods since it does not use metals, oxidants, reducing agents, acidic or basic media, and keto-products were obtained in high to excellent yields.
- Yao, Yunxin,Zhao, Guangkuan,Hamze, Abdallah,Alami, Mouad,Provot, Olivier
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p. 5775 - 5779
(2020/08/17)
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- Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis
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A small library of diaza-crown ether-bridged chiral diphosphoramidite ligands was prepared. In the rhodium-catalyzed asymmetric hydrogenation and hydroformylation reactions, these ligands exhibited distinct properties in catalytic activity and/or enantioselectivity. Hydrogenated products with opposite absolute configurations could be obtained in high yields with excellent ee values by utilizing (S,S)-L1 and (S,S)-L3, respectively. Meanwhile, the addition of alkali metal cations caused variations in catalytic outcomes, showing the supramolecular tunability of these Rh/diphosphoramidite catalytic systems.
- Luo, Yier,Ouyang, Guanghui,Tang, Yuping,He, Yan-Mei,Fan, Qing-Hua
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p. 8176 - 8184
(2020/07/15)
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- Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts
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The potential of oxide-supported rhodium single atom catalysts (SACs) for heterogeneous hydroformylation was investigated both theoretically and experimentally. Using high-level domain-based local-pair natural orbital coupled cluster singles doubles with
- Amsler, Jonas,Sarma, Bidyut B.,Agostini, Giovanni,Prieto, Gonzalo,Plessow, Philipp N.,Studt, Felix
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p. 5087 - 5096
(2020/03/16)
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