23058-81-3Relevant academic research and scientific papers
Introducing NacNac-Like Bis(4,6-isopropylbenzoxazol-2-yl)methanide in s-Block Metal Coordination
Koehne, Ingo,Graw, Nico,Teuteberg, Thorsten,Herbst-Irmer, Regine,Stalke, Dietmar
, p. 14968 - 14978 (2017)
Within this work, the field of bulky methanides in metal coordination is exceeded by the synthesis of the versatile and promising bis(4,6-isopropylbenzoxazol-2-yl)methane (7) ligand platform. As an enhancement in this class of ligands, isopropyl (iPr) substituents as steric-demanding groups have been successfully introduced in proximity to the coordination pocket, mimicking the shielding abilities of the ubiquitous NacNac ligand scaffold to improve the steric protection of a coordinated s-block metal cation. A percent buried volume (% Vbur) calculation as well as an electronic structure analysis shades light onto the shielding and electronic abilities of the ligand in comparison to other selected methanides and diketiminates. Upon deprotonation with a variety of different group 1 and 2 metalation agents, a row of novel s-block metal complexes of the parent deprotonated monoanionic ligand 7 was obtained and structurally, as well as spectroscopically, characterized. In particular, in this context, the alkali-metal precursor complexes [Li(THF)2{(4,6-iPr-NCOC6H2)2CH}] (8) and [K{μ-(4,6-iPr-NCOC6H2)2CH}]∞ (9) as well as the alkaline-earth-metal compounds [MgCl(THF)2{(4,6-iPr-NCOC6H2)2CH}] (10) and [M(THF)n{(4,6-iPr-NCOC6H2)2CH}2] [M = Mg, n = 0 (11); M = Ca, n = 1 (12); M = Sr, n = 1 (13); M = Ba, n = 1 (14)] were successfully synthesized. Especially, the latter four exhibit interesting trends in the solid state as well as in solution within the metal series.
London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
, p. 4823 - 4832 (2021/02/01)
The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
Development of effective bidentate diphosphine ligands of ruthenium catalysts toward practical hydrogenation of carboxylic acids
Saito, Susumu,Wen, Ke,Yoshioka, Shota
, p. 1510 - 1524 (2021/06/18)
Hydrogenation of carboxylic acids (CAs) to alcohols represents one of the most ideal reduction methods for utilizing abundant CAs as alternative carbon and energy sources. However, systematic studies on the effects of metal-to-ligand relationships on the catalytic activity of metal complex catalysts are scarce. We previously demonstrated a rational methodology for CA hydrogenation, in which CA-derived cationic metal carboxylate [(PP)M(OCOR)]+ (M = Ru and Re; P = one P coordination) served as the catalyst prototype for CA self-induced CA hydrogenation. Herein, we report systematic trial- and-error studies on how we could achieve higher catalytic activity by modifying the structure of bidentate diphosphine (PP) ligands of molecular Ru catalysts. Carbon chains connecting two P atoms as well as Ar groups substituted on the P atoms of PP ligands were intensively varied, and the induction of active Ru catalysts from precatalyst Ru(acac)3 was surveyed extensively. As a result, the activity and durability of the (PP)Ru catalyst substantially increased compared to those of other molecular Ru catalyst systems, including our original Ru catalysts. The results validate our approach for improving the catalyst performance, which would benefit further advancement of CA self-induced CA hydrogenation.
Linear Hydroaminoalkylation Products from Alkyl-Substituted Alkenes
Warsitz, Michael,Doye, Sven
, p. 15121 - 15125 (2020/10/23)
The regioselective conversion of alkyl-substituted alkenes into linear hydroaminoalkylation products represents a strongly desirable synthetic transformation. In particular, such conversions of N-methylamine derivatives are of great scientific interest, because they would give direct access to important amines with unbranched alkyl chains. Herein, we present a new one-pot procedure that includes an initial alkene hydroaminoalkylation with an α-silylated amine substrate and a subsequent protodesilylation reaction that delivers linear hydroaminoalkylation products with high selectivity from simple alkyl-substituted alkenes. For that purpose, new titanium catalysts have been developed, which are able to activate the α-C?H bond of more challenging α-silylated amine substrates. In addition, a direct relationship between the ligand structure of the new catalysts and the obtained regioselectivity is described.
SULFONAMIDE DERIVATIVES AND USES THEREOF
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, (2020/12/30)
The present disclosure relates to compounds of Formula (I) or (II): and to their prodrugs, pharmaceutically acceptable salts, pharmaceutical compositions, methods of use, and methods for their preparation. The compounds disclosed herein are useful for inhibiting the maturation of cytokines of the IL-1 family by inhibiting inflammasomes and may be used in the treatment of disorders in which inflammasome activity is implicated, such as inflammatory, autoinflammatory and autoimmune diseases and cancers.
Monofunctional hyperbranched ethylene oligomers
Wiedemann, Thomas,Voit, Gregor,Tchernook, Alexandra,Roesle, Philipp,Goettker-Schnetmann, Inigo,Mecking, Stefan
, p. 2078 - 2085 (2014/03/21)
The neutral κ2N,O-salicylaldiminato Ni(II) complexes [κ2N,O-{(2,6-(3′,5′-R2C 6H3)2C6H3-Ni -C(H)-(3,5-I2-2-O-C6H2)}]NiCH 3(pyridine)] (1a-pyr, R = Me; 1b-pyr, R = Et; 1c-pyr, R = iPr) convert ethylene to hyperbranched low-molecular-weight oligomers (Mn ca. 1000 g mol-1) with high productivities. While all three catalysts are capable of generating hyperbranched structures, branching densities decrease significantly with the nature of the remote substituent along Me > Et > iPr and oligomer molecular weights increase. Consequently, only 1a-pyr forms hyperbranched structures over a wide range of reaction conditions (ethylene pressure 5-30 atm and 20-70 C). An in situ catalyst system achieves similar activities and identical highly branched oligomer microstructures, eliminating the bottleneck given by the preparation and isolation of Ni-Me catalyst precursor species. Selective introduction of one primary carboxylic acid ester functional group per highly branched oligoethylene molecule was achieved by isomerizing ethoxycarbonylation and alternatively cross metathesis with ethyl acrylate followed by hydrogenation. The latter approach results in complete functionalization and no essential loss of branched oligomer material and molecular weight, as the reacting double bonds are close to a chain end. Reduction yielded a monoalcohol-functionalized oligomer. Introduction of one reactive epoxide group per branched oligomer occurs completely and selectively under mild conditions. All reaction steps involved in oligomerization and monofunctionalization are efficient and readily scalable.
ARGININE METHYLTRANSFERASE INHIBITORS AND USES THEREOF
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, (2014/11/11)
Described herein are compounds of Formula (I), pharmaceutically acceptable salts thereof, and pharmaceutical compositions thereof. Compounds described herein are useful for inhibiting arginine methyltransferase activity. Methods of using the compounds for treating arginine methyltransferase-mediated disorders are also described.
Scope and mechanism of the Pt-catalyzed enantioselective diboration of monosubstituted alkenes
Coombs, John R.,Haeffner, Fredrik,Kliman, Laura T.,Morken, James P.
, p. 11222 - 11231 (2013/08/23)
The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and kinetic isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion into a Pt-B bond. Density functional theory analysis, combined with other experimental data, suggests that the insertion reaction positions platinum at the internal carbon of the substrate. A stereochemical model for this reaction is advanced that is in line both with these features and with the crystal structure of a Pt-ligand complex.
Catalytic enantioselective 1,2-diboration of 1,3-dienes: Versatile reagents for stereoselective allylation
Kliman, Laura T.,Mlynarski, Scott N.,Ferris, Grace E.,Morken, James P.
, p. 521 - 524 (2012/03/11)
More with boron: The development of catalytic enantioselective 1,2-diboration of 1,3-dienes enables a new strategy for enantioselective carbonyl allylation reactions (see scheme). These reactions occur with outstanding levels of stereoselection and can be applied to both monosubstituted and 1,1-disubstituted dienes. The carbonyl allylation reactions provide enantiomerically enriched functionalized homoallylic alcohol products. Copyright
