98-85-1Relevant articles and documents
A Convenient and Stable Heterogeneous Nickel Catalyst for Hydrodehalogenation of Aryl Halides Using Molecular Hydrogen
Anwar, Muhammad,Beller, Matthias,Dastgir, Sarim,Junge, Kathrin,Leonard, David K.,Ryabchuk, Pavel
, (2022/02/03)
Hydrodehalogenation is an effective strategy for transforming persistent and potentially toxic organohalides into their more benign congeners. Common methods utilize Pd/C or Raney-nickel as catalysts, which are either expensive or have safety concerns. In this study, a nickel-based catalyst supported on titania (Ni-phen@TiO2-800) is used as a safe alternative to pyrophoric Raney-nickel. The catalyst is prepared in a straightforward fashion by deposition of nickel(II)/1,10-phenanthroline on titania, followed by pyrolysis. The catalytic material, which was characterized by SEM, TEM, XRD, and XPS, consists of nickel nanoparticles covered with N-doped carbon layers. By using design of experiments (DoE), this nanostructured catalyst is found to be proficient for the facile and selective hydrodehalogenation of a diverse range of substrates bearing C?I, C?Br, or C?Cl bonds (>30 examples). The practicality of this catalyst system is demonstrated by the dehalogenation of environmentally hazardous and polyhalogenated substrates atrazine, tetrabromobisphenol A, tetrachlorobenzene, and a polybrominated diphenyl ether (PBDE).
Borane evolution and its application to organic synthesis using the phase-vanishing method
Soga, Nene,Yoshiki, Tomo,Sato, Aoi,Kawamoto, Takuji,Ryu, Ilhyong,Matsubara, Hiroshi
supporting information, (2021/03/26)
Although borane is a useful reagent, it is difficult to handle. In this study, borane was generated in situ from NaBH4 or nBu4NBH4 with several oxidants using a phase-vanishing (PV) method. The borane generated was directly reacted with alkenes, affording the desired alcohols in good yields after oxidation with H2O2 under basic conditions. The selective reduction of carboxylic acids with the evolved borane was examined. The organoboranes generated by the PV method successfully underwent Suzuki–Miyaura coupling. Using this PV system, reactions with borane can be carried out easily and safely in a common test tube.
Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
supporting information, p. 8313 - 8320 (2021/03/08)
Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
Direct use of the solid waste from oxytetracycline fermentation broth to construct Hf-containing catalysts for Meerwein-Ponndorf-Verley reactions
Chen, Yuxin,Yao, Xuefeng,Wang, Xiaolu,Zhang, Xuefeng,Zhou, Huacong,He, Runxia,Liu, Quansheng
, p. 13970 - 13979 (2021/04/22)
The oxytetracycline fermentation broth residue (OFR) is an abundant solid waste in the fermentation industry, which is hazardous but tricky to treat. The resource utilization of the waste OFR is still challenging. In this study, a novel route of using OFR was proposed that OFR was used as the organic ligands to construct a new hafnium based catalyst (Hf-OFR) for Meerwein-Ponndorf-Verley (MPV) reactions of biomass-derived platforms. The acidic groups in OFR were used to coordinate with Hf4+, and the carbon skeleton structures in OFR were used to form the spatial network structures of the Hf-OFR catalyst. The results showed that the synthesized Hf-OFR catalyst could catalyze the MPV reduction of various carbonyl compounds under relatively mild reaction conditions, with high conversions and yields. Besides, the Hf-OFR catalyst could be recycled at least 5 times with excellent stability in activity and structures. The prepared Hf-OFR catalyst possesses the advantages of high efficiency, a simple preparation process, and low cost in ligands. The proposed strategy of constructing catalysts using OFR may provide new routes for both valuable utilization of the OFR solid waste in the fermentation industry and the construction of efficient catalysts for biomass conversion.
Cascade Reductive Friedel-Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand
Albrecht, Martin,Alshakova, Iryna D.
, p. 8999 - 9007 (2021/07/31)
The synthesis of complex molecules like active pharmaceutical ingredients typically requires multiple single-step reactions, in series or in a modular fashion, with laborious purification and potentially unstable intermediates. Cascade processes offer attractive synthetic remediation as they reduce time, energy, and waste associated with multistep syntheses. For example, triarylmethanes are traditionally prepared via several synthetic steps, and only a handful of cascade routes are known with limitations due to high catalyst loadings. Here, we present an expedient catalytic cascade process to produce triarylmethanes. For this purpose, we have developed a bifunctional iridium system as the efficient catalyst to build heterotriaryl synthons via reductive Friedel-Crafts alkylation from ketones, arenes, and hydrogen. The catalytically active species were generated in situ from a robust triazolyl iridium(III) hydride complex and acid and is composed of a metal-bound hydride and a proximal ligand-bound proton for reversible dihydrogen release. These complexes catalyze the direct hydrogenation of ketones at slow rates followed by dehydration. Appropriate adjustment of the conditions successfully intercepts this dehydration and leads instead to efficient C-C coupling and Friedel-Crafts alkylation. The scope of this cascade process includes a variety of carbonyl substrates such as aldehydes, (alkyl)(aryl)ketones, and diaryl ketones as precursor electrophiles with arenes and heteroarenes for Friedel-Crafts coupling. The reported method has been validated in a swift one-step synthesis of the core structure of a potent antibacterial agent. Excellent yields and exquisite selectivities were achieved for this cascade process with unprecedentedly low iridium loadings (0.02 mol %). Moreover, the catalytic activity of the protic system is significantly higher than that of an N-methylated analogue, confirming the benefit of the Ir-H/N-H hydride-proton system for high catalytic performance.
Effect of solvent in the hydrogenation of acetophenone catalyzed by Pd/S-DVB
Bereta, Tomasz,Mieczyńska, Ewa,Ronka, Sylwia,Tylus, W?odzimierz,Trzeciak, Anna M.
, p. 5023 - 5028 (2021/03/26)
A solvent effect was found in the hydrogenation of acetophenone catalyzed by a new Pd/S-DVB catalyst, immobilized on a styrene (S)/divinylbenzene (DVB) copolymer containing phosphinic groups. The porous structure of the catalyst was characterized by a specific surface area of 94.7 m2g?1. The presence of Pd(ii) and Pd(0) in Pd/S-DVB was evidenced by XPS and TEM. Pd/S-DVB catalyzes the hydrogenation of acetophenone (APh) to 1-phenylethanol (PhE) and ethylbenzene (EtB). The highest conversion of APh was obtained in methanol (MeOH) and in 2-propanol (2-PrOH), while in water it was lower. The conversion of APh correlates well with the hydrogen-bond-acceptance (HBA) capacity of the solvent. However, in all binary mixtures of alcohol and water the APh conversion and the yield of products significantly decreased. The observed inhibiting effect can be explained by the microheterogeneity of these mixtures and the blocking of the catalyst surface restricting access of the substrates to the Pd centers.
Highly selective hydrogenation of aromatic ketones to alcohols in water: effect of PdO and ZrO2
Alsalahi, W.,Trzeciak, A. M.,Tylus, W.
, p. 10386 - 10393 (2021/08/09)
Pd/ZrO2and PdO/ZrO2composites, containing Pd or PdO nanoparticles, were prepared using an original one-step methodology. These nanocomposites catalyze the hydrogenation of acetophenone (AP) at 1 bar and 10 bar of H2in an aqueous solution. Compared to unsupported Pd or PdO nanoparticles, a remarkable increase in their activity was achieved as a result of interaction with zirconia. An unsupported PdO hydrogenated AP mainly to ethylbenzene (EB), while excellent regioselectivity towards 1-phenylethanol (PE) was obtained with PdO/ZrO2and it was preserved during recycling. Similarly, regioselectivity to PE was higher with Pd/ZrO2compared to unsupported Pd NPs. PdO and zirconia resulted in high selectivity to alcohols in the hydrogenation of substituted acetophenones.
Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
Martyanov, Oleg N.,Philippov, Alexey A.
, (2021/10/19)
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.
Me3SI-promoted chemoselective deacetylation: a general and mild protocol
Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
, p. 19310 - 19315 (2021/06/03)
A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
Insight into the chemoselective aromatic: Vs. side-chain hydroxylation of alkylaromatics with H2O2catalyzed by a non-heme imine-based iron complex
Ticconi, Barbara,Capocasa, Giorgio,Cerrato, Andrea,Di Stefano, Stefano,Lapi, Andrea,Marincioni, Beatrice,Olivo, Giorgio,Lanzalunga, Osvaldo
, p. 171 - 178 (2021/01/28)
The oxidation of a series of alkylaromatic compounds with H2O2 catalyzed by an imine-based non-heme iron complex prepared in situ by reaction of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2?:?2?:?1 ratio leads to a marked chemoselectivity for aromatic ring hydroxylation over side-chain oxidation. This selectivity is herein investigated in detail. Side-chain/ring oxygenated product ratio was found to increase upon decreasing the bond dissociation energy (BDE) of the benzylic C-H bond in line with expectation. Evidence for competitive reactions leading either to aromatic hydroxylation via electrophilic aromatic substitution or side-chain oxidation via benzylic hydrogen atom abstraction, promoted by a metal-based oxidant, has been provided by kinetic isotope effect analysis. This journal is
