69112-21-6Relevant articles and documents
Ni-Catalyzed 1,2-Diarylation of Alkenyl Ketones: A Comparative Study of Carbonyl-Directed Reaction Systems
Apolinar, Omar,Derosa, Joseph,Engle, Keary M.,Karunananda, Malkanthi K.,Kleinmans, Roman,Li, Zi-Qi,Tran, Van T.,Wisniewski, Steven R.
supporting information, p. 5311 - 5316 (2021/07/26)
A nickel-catalyzed 1,2-diarylation of alkenyl ketones with aryl iodides and arylboronic esters is reported. Ketones with a variety of substituents serve as effective directing groups, offering high levels of regiocontrol. A representative product is diversified into a wide range of useful products that are not readily accessible via existing 1,2-diarylation reactions. Preliminary mechanistic studies shed light on the binding mode of the substrate, and Hammett analysis reveals the effect of electronic factors on initial rates.
Quantitative Analysis on Two-Point Ligand Modulation of Iridium Catalysts for Chemodivergent C-H Amidation
Hwang, Yeongyu,Jung, Hoimin,Lee, Euijae,Kim, Dongwook,Chang, Sukbok
supporting information, p. 8880 - 8889 (2020/12/23)
The transition-metal-catalyzed nitrenoid transfer reaction is one of the most attractive methods for installing a new C-N bond into diverse reactive units. While numerous selective aminations are known, understanding complex structural effects of the key intermediates on the observed chemoselectivity is still elusive in most cases. Herein, we report a designing approach to enable selective nitrenoid transfer leading to sp2 spirocyclization and sp3 C-H insertion by cooperative two-point modulation of ligands in the CpXIr(III)(κ2-chelate) catalyst system. Computational analysis led us to interrogate structural motifs that can be attributed to the desired mechanistic dichotomy. Multivariate linear regression analysis on the perturbation on the η5-cyclopentadienyl ancillary (CpX) and LX coligand, wherein we prepared over than 40 new catalysts for screening, allowed for construction of an intuitive yet robust statistical model that predicts a large set of chemoselective outcomes, implying that the catalysts' structural effects play a critical role on the chemoselective nitrenoid transfer. On the basis of this quantitative analysis, a new catalytic platform is now established for the unique lactam formation, leading to the unprecedented chemoselective reactivity (up to >20:1) toward a diverse array of competing sites, such as tertiary, secondary, benzylic, allylic C-H bonds, and aromatic πsystem.
Harnessing Secondary Coordination Sphere Interactions That Enable the Selective Amidation of Benzylic C-H Bonds
Jung, Hoimin,Schrader, Malte,Kim, Dongwook,Baik, Mu-Hyun,Park, Yoonsu,Chang, Sukbok
supporting information, p. 15356 - 15366 (2019/10/22)
Engineering site-selectivity is highly desirable especially in C-H functionalization reactions. We report a new catalyst platform that is highly selective for the amidation of benzylic C-H bonds controlled by π-πinteractions in the secondary coordination sphere. Mechanistic understanding of the previously developed iridium catalysts that showed poor regioselectivity gave rise to the recognition that the π-cloud of an aromatic fragment on the substrate can act as a formal directing group through an attractive noncovalent interaction with the bidentate ligand of the catalyst. On the basis of this mechanism-driven strategy, we developed a cationic (ν5-C5H5)Ru(II) catalyst with a neutral polypyridyl ligand to obtain record-setting benzylic selectivity in an intramolecular C-H lactamization in the presence of tertiary C-H bonds at the same distance. Experimental and computational techniques were integrated to identify the origin of this unprecedented benzylic selectivity, and robust linear free energy relationship between solvent polarity index and the measured site-selectivity was found to clearly corroborate that the solvophobic effect drives the selectivity. Generality of the reaction scope and applicability toward versatile γ-lactam synthesis were demonstrated.
New molybdenum(II) complexes with α-diimine ligands: Synthesis, structure, and catalytic activity in olefin epoxidation
Vasconcellos-Dias, Maria,Marreiros, Jo?o,Sales, Rita,Félix, Vitor,Brand?o, Paula,Nunes, Carla D.,José Calhorda, Maria
, (2019/02/10)
Three new complexes [Mo(η3-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR,13C- and29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.
Hydroformylation of piperylene and efficient catalyst recycling in propylene carbonate
Neubert, Peter,Fuchs, Sarah,Behr, Arno
, p. 4045 - 4052 (2015/07/15)
In contrast to monoolefins, diene hydroformylation is still a demanding task. Some dienes like butadiene and isoprene have been investigated more intensively, however, 1,3-pentadiene (piperylene) has been rarely investigated. Here, we present a systematic investigation of the hydroformylation of piperylene, using Rh(CO)2acac/Xantphos as an active catalyst which can be easily recycled in the green solvent propylene carbonate. Under the chosen conditions aldehyde yields of up to 82% have been obtained, while catalyst recycling was possible for up to six runs.
Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
Lorber, Katja,Schieberle, Peter,Buettner, Andrea
, p. 1025 - 1031 (2014/03/21)
Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
Lorber, Katja,Schieberle, Peter,Buettner, Andrea
, p. 1025 - 1031 (2015/04/22)
Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
Selective reduction of carboxylic acids to aldehydes catalyzed by B(C 6F5)3
Bezier, David,Park, Sehoon,Brookhart, Maurice
, p. 496 - 499 (2013/03/29)
B(C6F5)3 efficiently catalyzes hydrosilylation of aliphatic and aromatic carboxylic acids to produce disilyl acetals under mild conditions. Catalyst loadings can be as low as 0.05 mol %, and bulky tertiary silanes are favored to give selectively the acetals. Acidic workup of the disilyl acetals results in the formation of aldehydes in good to excellent yields.
Total syntheses of the gregatins A-D and aspertetronin A: Structure revisions of these compounds and of aspertetronin B, together with plausible structure revisions of gregatin E, cyclogregatin, graminin A, the penicilliols A and B, and the huaspenones A and B
Burghart-Stoll, Heike,Brueckner, Reinhard
experimental part, p. 3978 - 4017 (2012/10/18)
Comprehensive comparisons of 1H and 13C NMR chemical shift values in the furanone cores a, b, and c provide plausible support for a reassessment of the furanone nuclei of the title compounds from b to c. Total syntheses via enantiomerically pure lactic esters were based on the Seebach-Frater "self-reproduction of stereocenters" methodology. Attachment of the hexadienyl side-chain in a trans,trans-selective manner was achieved by addition of the Seebach-Frater enolate to trans-hex-4-en-1-al rather than to trans-hex-3-en-1-al. The type-c furanone cores of the synthetic materials were reached by single or double acylation of a model γ-hydroxy-β-oxo ester (compound 50) and its hexadiene-containing counterpart 29. Our syntheses confirmed the novel connectivities in six compounds. In addition, they required revision of the configuration of a quaternary carbon atom in five cases. Moreover, they allowed elucidation of the configurations of four previously unassigned stereocenters. Hindsight analyses of why the furanone cores of the title compounds had been misinterpreted as a and/or b instead of c are given. Why the stereocenters in the heterocycles had been incorrectly configured, on the bases (a) of relay studies in the 1960s, and (b) of a 1984 total synthesis of gregatin B, is also discussed.
Aerobic oxidation of primary aliphatic alcohols to aldehydes catalyzed by a palladium(II) polyoxometalate catalyst
Barats, Delina,Neumann, Ronny
scheme or table, p. 293 - 298 (2010/04/28)
A hexadecyltrimethylammonium salt of a "sandwich" type polyoxometalate has been used as a ligand to attach a palladium(II) center. This Pd-POM compound was an active catalyst for the fast aerobic oxidation of alcohols. The unique property of this catalyst is its significant preference for the oxidation of primary versus secondary aliphatic alcohols. Since no kinetic isotope effect was observed for the dehydrogenation step, this may be the result of the intrinsically higher probability for oxidation of primary alcohols attenuated by steric factors as borne out by the higher reactivity of 1-octanol versus 2-ethyl-1-hexanol. The reaction is highly selective to aldehyde with little formation of carboxylic acid; autooxidation is inhibited. No base is required to activate the alcohol. The fast reactions appear to be related to the electron-acceptor nature of the polyoxometalate ligand that may also facilitate alcohol dehydrogenation in the absence of base.
