2425-28-7Relevant academic research and scientific papers
An 18O-Labeling Study of the β-(Nitroxy)alkyl and β-(Trifluoroacetoxy)alkyl Radical Migrations: Further Examples of a 1,2-Shift Mechanism
Crich, David,Filzen, G. Frederick
, p. 4834 - 4837 (1995)
The results of an 18O labeling study of the β-(nitroxy)alkyl and β-(trifluoroacetoxy)alkyl radical migrations are presented.Phenacyl bromide dimethyl acetal was hydrolyzed with H2(18)O water to give labelled phenacyl bromide and, following borohydride reduction, 18O labeled styrene bromohydrin.Nitration and trifluoroacetylation gave the radical precursors which were allowed to react with tributyltin hydride and AIBN in benzene at reflux.After cleavage to 2-phenylethanol, the rearrangement products were examined by GC-MS.The β-(nitroxy)alkyl migration is found to occur, in benzene to the extent of 64percent through a 1,2-, as opposed to a 2,3-shift, mechanism.The β-(trifluoroacetoxy)alkyl migration occurs 7percent by the 1,2-pathway.It is suggested that, in general, faster ester migrations occur to a greater extent through the 1,2-shift pathway.
Metalated Ir–CNP Complexes Containing Imidazolin-2-ylidene and Imidazolidin-2-ylidene Donors – Synthesis, Structure, Luminescence, and Metal–Ligand Cooperative Reactivity
Hernández-Juárez, Martín,Sánchez, Práxedes,López-Serrano, Joaquín,Lara, Patricia,González-Herrero, Pablo,Rendón, Nuria,álvarez, Eleuterio,Paneque, Margarita,Suárez, Andrés
, p. 3944 - 3953 (2020)
The iridium complex 1 based on a metalated CNP ligand containing an imidazolin-2-ylidene fragment has been prepared by treatment of the ligand precursor 4 with Ag2O followed by reaction with [IrCl(COE)2]2. The chlorohydride imidazolidin-2-ylidene complex 6, which is isostructural to 1, was synthetized by reaction of the previously reported dihydride derivative 3 with CH2Cl2. Complexes 1 and 6 exhibit luminescence arising from a 3MLCT/ILCT state involving the metalated CNP ligand, which is particularly intense for 1 in the solid state at 298 K. Furthermore, the reactivity of complexes 1 and 6 towards bases was compared. Deprotonation of 1 with KOtBu produced the selective formation of the dinuclear complex 7; meanwhile, the reaction of 6 led to a complex mixture of products. The same reactions carried out in the presence of PPh3 produced the selective deprotonation of the P-bonded methylene bridges of 1 and 6, yielding the isostructural derivatives 9 and 10. DFT calculations performed on the uNHC-containing tautomers I and II, and the sNHC-based isomers III and IV, showed that the NHC-deprotonated derivatives II and IV are more stable by 3.20 and 2.73 kcal mol–1, respectively, than their P-deprotonated counterparts (I and III). However, a reverse stability order was observed for hexacoordinated tautomers I·L and II·L, and III·L and IV·L (L = PPh3, CO, MeCN). Finally, the catalytic activity of complex 3 in the transfer hydrogenation of ketones has been assessed.
A vanadium-dependent bromoperoxidase in the marine red alga Kappaphycus alvarezii (Doty) Doty displays clear substrate specificity
Kamenarska, Zornitsa,Taniguchi, Tomokazu,Ohsawa, Noboru,Hiraoka, Masanori,Itoh, Nobuya
, p. 1358 - 1366 (2007)
Bromoperoxidase activity was initially detected in marine macroalgae belonging to the Solieriaceae family (Gigartinales, Rhodophyta), including Solieria robusta (Greville) Kylin, Eucheuma serra J. Agardh and Kappaphycus alvarezii (Doty) Doty, which are important industrial sources of the polysaccharide carrageenan. Notably, the purification of bromoperoxidase was difficult because due to the coexistence of viscoid polysaccharides. The activity of the partially purified enzyme was dependent on the vanadate ion, and displayed a distinct substrate spectrum from that of previously reported vanadium-dependent bromoperoxidases of marine macroalgae. The enzyme was specific for Br- and I- ions and inactive toward F- and Cl-. The Km values for Br- and H2O2 were 2.5 × 10-3 M and 8.5 × 10-5 M, respectively. The halogenated product, dibromoacetaldehyde, that accumulated in K. alvarezii was additionally determined.
In situ NMR study of asymmetric borane reduction reaction - An abnormal factor in the temperature effect on the bis-oxazaborolidine catalyst and the relationship between the catalyst structure and selectivity
Zhao, Jinkai,Bao, Xinhe,Liu, Xiumei,Wan, Boshun,Han, Xiuwen,Yang, Caiguang,Hang, Jiangfeng,Feng, Yan,Jiang, Biao
, p. 3351 - 3359 (2000)
The relationship between the structure of the catalyst and the selectivity in the asymmetric borane reduction reaction of prochiral ketones is discussed. The variation of the catalyst itself at low temperature is observed by the in situ NMR method and the origin of the temperature effect of the reaction is proposed. It is concluded that the amount of the effective component of the catalyst present has an important effect on the enantioselectivity. Copyright (C) 2000 Elsevier Science Ltd.
A highly regio- and chemoselective synthesis of vicinal bromohydrins by ring opening of terminal epoxides with dibromoborane-dimethyl sulfide
Roy, Chandra D.,Brown, Herbert C.
, p. 1608 - 1613 (2007)
Dibromoborane-dimethyl sulfide (BHBr2-SMe2) displays high degrees of chemo- and regioselectivity during the brominative cleavage of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydroborating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have been successfully accommodated during the epoxide opening process.
New chiral borohydride based reducing agent: Asymmetric reduction of 9-anthryl trifluoromethyl ketone and other carbonyl compounds
Maiti, Dilip K.,Bhattacharya, Pranab K.
, p. 99 - 108 (1998)
(S)-(+)-2-(α-Hydroxybenzyl)benzimidazole and (S)-(-)-2-benzimidazole-1-ethanol were synthesised and converted to chiral borohydrides which reduced prochiral ketones to the corresponding chiral alcohols in high yields (80 to 100%, e.e. 42 to 95%). This is the first report of sodium borohydride modified by 1,2-amino alcohol.
Enantioselective borane reduction of aromatic ketones catalyzed by chiral aluminum alkoxides
Fu, I.-Pin,Uang, Biing-Jiun
, p. 45 - 48 (2001)
The asymmetric borane reduction of prochiral ketones with an alkoxide catalyst prepared in situ from aluminum tri-iso-propoxide and (R)-binaphthol was examined. Using these conditions, alcohols were obtained in high yield and e.e.'s of up to 83%.
Regio- and stereoselective synthesis of bromoalkenes by homolytic hydrobromination of alkynes with hydrogen bromide
Kumaki, Wataru,Kinoshita, Hidenori,Miura, Katsukiyo
supporting information, (2022/03/07)
Homolytic hydrobromination of terminal and internal alkynes with a commercially available solution of hydrogen bromide in acetic acid has been investigated for regio- and stereoselective synthesis of bromoalkenes. Under an aerobic atmosphere at room temperature, the reaction of ethynylarenes with a small excess of HBr efficiently gave (2-bromoethenyl)arenes with good to high E-selectivity. (Alk-1-ynyl)arenes, or internal alkynes bearing both phenyl and alkyl groups at the sp-carbons also underwent the air-initiated hydrobromination to exhibit high Z-selectivity under kinetic conditions using a half equivalent of HBr.
Unmasking the Hidden Carbonyl Group Using Gold(I) Catalysts and Alcohol Dehydrogenases: Design of a Thermodynamically-Driven Cascade toward Optically Active Halohydrins
Escot, Lorena,González-Granda, Sergio,Gotor-Fernández, Vicente,Lavandera, Iván
, p. 2552 - 2560 (2022/02/16)
A concurrent cascade combining the use of a gold(I) N-heterocyclic carbene (NHC) and an alcohol dehydrogenase (ADH) is disclosed for the synthesis of highly valuable enantiopure halohydrins in an aqueous medium and under mild reaction conditions. The meth
Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast
Shukla, Meenakshi,Barick,Salunke,Chandra, Sudeshna
, (2021/02/05)
Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.
