538-93-2Relevant academic research and scientific papers
Synthesis of 1-(3-tert-butyldimethylsiloxy)phenyl-5,5-dimethyl-2,7,8-trioxabicyclo[4.2.0] octanes: New dioxetanes giving high chemiexcitation yields in thermolysis and in fluoride-induced CIEEL-decay
Matsumoto, Masakatsu,Murayama, Junko,Nishiyama, Masao,Mizoguchi, Yasuko,Sakuma, Toshimitsu,Watanabe, Nobuko
, p. 1523 - 1527 (2002)
Dioxetanes with annelated six-membered ring, 1-(3-tert-butyldimethylsiloxy)phenyl-5,5-dimethyl-2,7,8-trioxabicyclo[4.2.0] octanes (2a-2c) were synthesized by singlet oxygenation of the corresponding aryl-substituted dihydropyrans (3). Thermolysis of 2a-2c gave the corresponding ketoesters (5a-5c) as a normal decomposition product together with a considerable amount (23-26%) of ester (6) derived from Norrish type I reaction of the triplet-excited ester (5). On the other hand, treatment with tetrabutylammonium fluoride (TBAF) in DMSO induced rapid decomposition of 2 to emit blue light in high chemiexcitation yield (72-75%) of the oxyanion of a ketoester (10). These results show that the chemiexcitation efficiency of dioxetanes (2) was higher than that of their five-membered ring analog (1) not only for thermolysis and but also for the base-induced CIEEL.
Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
supporting information, p. 9029 - 9039 (2021/06/28)
Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
Bartfield, Noah M.,Frederich, James H.,Law, James A.
supporting information, p. 14360 - 14364 (2021/05/27)
Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
Zn-Mediated Hydrodeoxygenation of Tertiary Alkyl Oxalates
Ye, Yang,Ma, Guobin,Yao, Ken,Gong, Hegui
supporting information, p. 1625 - 1628 (2021/01/18)
Herein we describe a general, mild, and scalable method for hydrodeoxygenation of readily accessible tertiary alkyl oxalates by Zn/silane under Ni-catalyzed conditions. The reduction method is suitable for an array of structural motifs derived from tertiary alcohols that bear diverse functional groups, including the synthesis of a key intermediate en route to estrone.
Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
, p. 3802 - 3808 (2020/07/09)
A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
ISOBUTYL BENZENE AND A PROCESS FOR SYNTHESIS OF ISOBUTYL BENZENE BY USING A CATALYST
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Page/Page column 13; 16-17, (2020/12/11)
The present disclosure provides a process for the synthesis of isobutyl benzene by side chain alkylation of toluene in the presence of a catalyst. The catalyst used ub the process of present disclosure provides maximum conversion of toluene with high selectivity towards isobutyl benzene.
Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
Fang, Huaquan,Oestreich, Martin
supporting information, p. 11394 - 11398 (2020/05/25)
The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
Activation of C-C Bonds via σ-Bond Metathesis: Hydroborenium-Catalyzed Hydrogenolysis of Cyclopropanes
Su, Bo,Li, Yawei,Li, Zhen Hua,Hou, Jun-Li,Wang, Huadong
supporting information, p. 4159 - 4163 (2020/04/10)
High-valent transition metal or main group complex mediated σ-bond metathesis plays an important role in the activation of covalent H-E bonds. However, its involvement in the activation of C-C bonds has remained elusive. Here we describe direct hydroboration of the C-C bonds of cyclopropanes by a hydroborenium complex. Our mechanism study suggests this reaction operates through a σ-bond metathesis pathway. With this hydroborenium complex as a catalyst, hydrogenolysis of unfunctionalized cyclopropanes was achieved, which is unprecedented for homogeneous catalysts and provides an unconventional approach for C-C bond functionalization in the absence of metals.
Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
supporting information, p. 5599 - 5602 (2019/05/21)
The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes
Argouarch, Gilles
supporting information, p. 11041 - 11044 (2019/07/31)
A new and simple method for the deoxygenation of ketones to alkanes is presented. Most substrates are reduced under mild conditions by triethylsilane in the presence of catalytic amounts of [Rh(μ-Cl)(CO)2]2. This system selectively provides the methylene hydrocarbons in good to excellent yields starting from acetophenones and diaryl ketones. A rapid examination of the reaction pathway suggests that the ketone is first converted into an alcohol, which then undergoes hydrogenolysis to give the alkane.
