19550-30-2Relevant articles and documents
Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions
Mitra, Mainak,Nimir, Hassan,Demeshko, Serhiy,Bhat, Satish S.,Malinkin, Sergey O.,Haukka, Matti,Lloret-Fillol, Julio,Lisensky, George C.,Meyer, Franc,Shteinman, Albert A.,Browne, Wesley R.,Hrovat, David A.,Richmond, Michael G.,Costas, Miquel,Nordlander, Ebbe
, p. 7152 - 7164 (2015)
Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L1) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [FeII(CH3CN)(L)]2+ (L = L1 (1); L2 (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [FeIV(O)(L)]2+ (L = L1 (3); L2 (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and M?ssbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L1) and 2.5 h (L = L2). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([FeIV(O)(N4Py)]2+), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [FeIV(O)(L2)]2+ exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.
A novel chemiluminescence from the reaction of dioxiranes with alkanes. Proposed mechanism of oxygen-transfer chemiluminescence
Kazakov,Barzilova,Kazakov
, p. 191 - 192 (2001)
Oxidation of adamantane and 2,3-dimethylbutane by methyl(trifluoromethyl)dioxirane is accompanied by chemiluminescence (CL); formation of the emitter of CL, triplet excited trifluoropropanone, is proposed to occur via a concerted oxenoid mechanism of oxygen insertion into C-H bond of the hydrocarbons.
OH Radical Induced Oxidation of 2,3-Dimethylbutane in Air
Heimann, Gerald,Warneck, Peter
, p. 8403 - 8409 (1992)
The product distribution resulting from the OH induced oxidation of 2,3-dimethylbutane in air was measured and compared with predictions based on a general reaction mechanism.Relative rates derived for the abstraction of primary and tertiary hydrogen atoms by OH radicals from the parent compound are 17percent and 83percent, respectively.The branching ratio for the alcohol versus alkoxyl radical producing pathsways of the self-reaction of 2-propylperoxy radicals was determined to be (0.61 +/- 0.08):(0.39 +/- 0.08); the corresponding ratio for the self-reaction of primary 2,3-dimethylbutylperoxy radicals is (0.56 +/- 0.07): 0.44 +/- 0.07).Large amounts of 2,3-dimethyl-2-hydroperoxybutane and small amounts of 2,3-dimethyl-2-butanol were found, the latter as a product of the cross combination reactions of 2,3-dimethyl-2-butylperoxy with 2-propylperoxy and 2,3-dimethyl-1-butylperoxy radicals.Rate constants of 3.5 * 10-17 and 2 * 10-16 cm-3/(molecule s), respectively, were estimated for these reactions with the help of computer simulations.
A crystalline, internally-coordinated chloroborane for asymmetric hydroboration
von Dollen, Breanna,Wood, John L.,Savage, Quentin R.,Jones, Andrew J.,Garner, Charles M.
supporting information, (2022/02/01)
Asymmetric hydroboration is an important method in the preparation of enantiomerically-enriched compounds that are necessary in many areas of chemistry. Here is reported the preparation of a unique chiral chloroborane-internal ether complex and its applic
3-PHENYL-4-HEXYNOIC ACID DERIVATIVES AS GPR40 AGONISTS
-
Page/Page column 47; 48, (2019/07/23)
A compound of the formula (I)wherein R represents a straight or branched, primary or secondary acyclic hydrocarbyl C3–C15 group, which can be saturated or unsaturated, or a straight or branched, primary or secondary acyclic hydrocarbyl C3–C15 group, which can be saturated or unsaturated and wherein one or more of hydrogen atoms is replaced with fluorine atom; X represents hydrogen atom or halogen atom,and* denotes chiral center, and salts thereof. The compound is useful for the treatment of diseases mediated by GPR40, in particular type II diabetes. (I)
Ligand-Controlled Direct Hydroformylation of Trisubstituted Olefins
Shin, Taeil,Kim, Hyungsoo,Kim, Sungmin,Lee, Ansoo,Seo, Min-Seob,Choi, Jonghoon,Kim, Hyungjun,Kim, Hyunwoo
, p. 5789 - 5792 (2019/06/24)
The direct hydroformylation of trisubstituted olefins has been achieved with a combination of a Rh(I) catalyst and a π-acceptor phosphorus (briphos) ligand. A sterically bulky briphos ligand with a large cone angle that forms a 1:1 complex with Rh(I) is found to be reactive for the hydroformylation of trisubstituted olefins. The aldehyde products were obtained with high diastereoselectivity (>99:1) and regioselectivity (49%-81%).
Copper-catalyzed enantioselective hydroboration of unactivated 1, 1-disubstituted alkenes
Jang, Won Jun,Song, Seung Min,Moon, Jong Hun,Lee, Jin Yong,Yun, Jaesook
supporting information, p. 13660 - 13663 (2017/11/07)
We report an efficient and highly enantioselective hydroboration of aliphatic 1, 1-disubstituted alkenes with pinacolborane using a phosphine-Cu catalyst. The method allows facile preparation of enantiomerically enriched β-chiral alkyl pinacolboronates from a range of 1, 1-disubstituted alkenes with high enantioselectivity up to 99% ee. Unprecedented enantiodiscrimination between the geminal alkyl substituents was observed with functional group compatibility in the hydroboration. Furthermore, a catalyst loading as low as 1 mol % furnished the desired product without a decrease in yield or selectivity, demonstrating its efficiency in gram scale synthesis.
Rational Design of Thermodynamic and Kinetic Binding Profiles by Optimizing Surface Water Networks Coating Protein-Bound Ligands
Krimmer, Stefan G.,Cramer, Jonathan,Betz, Michael,Fridh, Veronica,Karlsson, Robert,Heine, Andreas,Klebe, Gerhard
, p. 10530 - 10548 (2016/12/16)
A previously studied congeneric series of thermolysin inhibitors addressing the solvent-accessible S2′ pocket with different hydrophobic substituents showed modulations of the surface water layers coating the protein-bound inhibitors. Increasing stabilization of water molecules resulted in an enthalpically more favorable binding signature, overall enhancing affinity. Based on this observation, we optimized the series by designing tailored P2′ substituents to improve and further stabilize the surface water network. MD simulations were applied to predict the putative water pattern around the bound ligands. Subsequently, the inhibitors were synthesized and characterized by high-resolution crystallography, microcalorimetry, and surface plasmon resonance. One of the designed inhibitors established the most pronounced water network of all inhibitors tested so far, composed of several fused water polygons, and showed 50-fold affinity enhancement with respect to the original methylated parent ligand. Notably, the inhibitor forming the most perfect water network also showed significantly prolonged residence time compared to the other tested inhibitors.
Sensing remote chirality: Stereochemical determination of β-, γ-, and δ-chiral carboxylic acids
Tanasova, Marina,Anyika, Mercy,Borhan, Babak
supporting information, p. 4274 - 4278 (2015/04/14)
Determining the absolute stereochemisty of small molecules bearing remote nonfunctionalizable stereocenters is a challenging task. Presented is a solution in which appropriately substituted bis(porphyrin) tweezers are used. Complexation of a suitably derivatized β-, γ-, or δ-chiral carboxylic acid to the tweezer induces a predictable helicity of the bis(porphyrin), which is detected as a bisignate Cotton Effect (ECCD). The sign of the ECCD curve is correlated with the absolute stereochemistry of the substrate based on the derived working mnemonics in a predictable manner.
Chiral propargylic cations as intermediates in SN1-type reactions: Substitution pattern, nuclear magnetic resonance studies, and origin of the diastereoselectivity
Nitsch, Dominik,Huber, Stefan M.,Poethig, Alexander,Narayanan, Arjun,Olah, George A.,Prakash, G. K. Surya,Bach, Thorsten
supporting information, p. 2851 - 2857 (2014/03/21)
Nine propargylic acetates, bearing a stereogenic center (-C*HXR 2) adjacent to the electrophilic carbon atom, were prepared and subjected to SN1-type substitution reactions with various silyl nucleophiles employing bismuth trifluoromethanesulfonate [Bi(OTf)3] as the Lewis acid. The diastereoselectivity of the reactions was high when the alkyl group R2 was tertiary (tert-butyl), irrespective of the substituent X. Products were formed consistently with a diastereomeric ratio larger than 95:5 in favor of the anti-diastereoisomer. If the alkyl substitutent R2 was secondary, the diastereoselectivity decreased to 80:20. The reaction was shown to proceed stereoconvergently, and the relative product configuration was elucidated. The reaction outcome is explained by invoking a chiral propargylic cation as an intermediate, which is preferentially attacked by the nucleophile from one of its two diastereotopic faces. Density functional theory (DFT) calculations suggest a preferred conformation in which the group R2 is almost perpendicular to the plane defined by the three substituents at the cationic center, with the nucleophile approaching the electrophilic center opposite to R2. Transition states calculated for the reaction of allyltrimethylsilane with two representative cations support this hypothesis. Tertiary propargylic cations with a stereogenic center (-C* HXR2) in the α position were generated by ionization of the respective alcohol precursors with FSO3H in SO2ClF at -80 C. Nuclear magnetic resonance (NMR) spectra were obtained for five cations, and the chemical shifts could be unambiguously assigned. The preferred conformation of the cations as extracted from nuclear Overhauser experiments is in line with the preferred conformation responsible for the reaction of the secondary propargylic cations.
