4013-72-3Relevant articles and documents
Synthesis of: N -methylated amines from acyl azides using methanol
Chakrabarti, Kaushik,Dutta, Kuheli,Kundu, Sabuj
supporting information, p. 5891 - 5896 (2020/08/21)
The transformation of acyl azide derivatives into N-methylamines was developed using methanol as the C1 source via the one-pot Curtius rearrangement and borrowing hydrogen methodology. Following this protocol, various functionalised N-methylated amines were synthesized using the (NNN)Ru(ii) complex from carboxylic acids via an acyl azide intermediate. Several kinetic studies and DFT calculations were carried out to support the mechanism and also to determine the role of the Ru(ii) complex and base in this transformation.
Assaying RNA solvent accessibility in living cells with LASER
Feng, Chao,Spitale, Robert C.
, p. 401 - 411 (2020/06/23)
RNA molecules perform a wide variety of functions to control many cellular pathways. Critical to these roles is the ability of an RNA to fold into complex three-dimensional structures. As part of this folding, unique elements of RNA structure become more exposed or hidden to solvent and these properties are important to understand an RNAs final fold. Characterizing solvent accessibility can enable researchers to better understand the overall fold of an RNA and how it interacts with trans acting factors, such as proteins. Herein we describe the methods toward using light activated structural evaluation of RNA, or LASER, which measures purine nucleobase solvent accessibility. To date, LASER has been used inside and outside of cells to measure RNA solvent accessibility and RNA interactions with proteins.
Deoxygenative Amination of Azine-N-oxides with Acyl Azides via [3 + 2] Cycloaddition
Ghosh, Prithwish,Han, Sang Hoon,Han, Sangil,Kim, Dongeun,Kim, In Su,Kim, Saegun,Kwon, Na Yeon,Mishra, Neeraj Kumar
, p. 2476 - 2485 (2020/03/13)
A transition-metal-free deoxygenative C-H amination reaction of azine-N-oxides with acyl azides is described. The initial formation of an isocyanate from the starting acyl azide via a Curtius rearrangement can trigger a [3 + 2] dipolar cycloaddition of polar N-oxide fragments to generate the aminated azine derivative. The applicability of this method is highlighted by the late-stage and sequential amination reactions of complex bioactive compounds, including quinidine and fasudil. Moreover, the direct transformation of aminated azines into various bioactive N-heterocycles illustrates the significance of this newly developed protocol.
Spectroscopic Characterization of Nicotinoyl and Isonicotinoyl Nitrenes and the Photointerconversion of 4-Pyridylnitrene with Diazacycloheptatetraene
Liu, Qian,Qin, Yuanyuan,Lu, Yan,Wentrup, Curt,Zeng, Xiaoqing
, p. 3793 - 3801 (2019/05/10)
Recently, nicotinoyl nitrene (2) has been generated from the photodecomposition of nicotinoyl azide (1) and used as the key intermediate in probing nucleobase solvent accessibility inside cells. Following the 266 nm laser photolysis of nicotinoyl azide (1) and isonicotinoyl azide (5) in solid N2 matrices at 15 K, nicotinoyl nitrene (2) and isonicotinoyl nitrene (6) have now been identified by matrix-isolation infrared (IR) spectroscopy. Both aroyl nitrenes 2 and 6 adopt closed-shell singlet ground states stabilized by significant Nnitrene···O interactions, which is consistent with the spectroscopic analysis and calculations at the CBS-QB3 level of theory. Upon subsequent visible light irradiations, 2 (400 ± 20 nm) and 6 (532 nm) undergo rearrangement to pyridyl isocyanates 3 and 7. Further dissociation of 3 and 7 under 193 nm laser irradiation results in CO elimination and formation of ketenimines 12 and 13 via the ring opening of elusive pyridyl nitrenes 4 and 8, respectively. In addition to the IR spectroscopic identification of 8 in the triplet ground state, its reversible photointerconversion with ring expansion to diazacycloheptatetraene 9 has been observed directly. The spectroscopic identification of the nitrene intermediates was aided by calculations at the B3LYP/6-311++G(3df,3pd) level, and the mechanism for their generation in stepwise decompositions of the azides is discussed in the light of CBS-QB3 calculations.
Visible Light-Induced Regioselective Cycloaddition of Benzoyl Azides and Alkenes to Yield Oxazolines
Bellotti, Peter,Brocus, Julien,El Orf, Fatima,Selkti, Mohamed,K?nig, Burkhard,Belmont, Philippe,Brachet, Etienne
supporting information, p. 6278 - 6285 (2019/05/24)
Visible light catalysis allows the regioselective synthesis of oxazolines in high yields. The mild photosensitized manifold leverages the intermolecular formation of oxazolines with a wide functional group tolerance on both benzoyl azides and alkenes part
Ligand Isomerism in Coordination Cages
Dasary, Hareesha,Jagan, Rajamony,Chand, Dillip Kumar
, p. 12222 - 12231 (2018/10/02)
Complexation reactions of palladium(II) nitrate with a set of 3-pyridyl appended nonchelating bidentate ligands possessing regioisomeric phenylene-diurea functionalities as spacers were carried out. The ligands utilized in this study are 1,1′-(1,2-phenylene)bis(3-(pyridin-3-yl)urea), L1; 1,1′-(1,3-phenylene)bis(3-(pyridin-3-yl)urea), L2; and 1,1′-(1,4-phenylene)bis(3-(pyridin-3-yl)urea), L3. The complexation reactions of the ligands (L1, L2, and L3) with palladium(II) produced single discrete isomeric cages (1, 2, and 3) of Pd2L4 formulation in each case and thereby illustrated ligand-isomerism in coordination cages. All 16 hydrogen atoms of eight urea moieties present in four ligand strands are delineated completely endohedrally in cage 1 and completely exohedrally in cage 3, whereas cage 2 exhibited half of the urea hydrogens in exohedral locations and the remaining half in endohedral locations. In addition to the variable number of solvent molecules, the cavities of cages 1 and 2 lodged four and two nitrate ions, respectively, using the endohedral (H)urea atoms (i.e., NH groups) as binding sites, whereas the cavity of 3 remained anion free. The abilities of the complexes 1-3 for adsorption of CO2 gas are demonstrated, and their behaviors are compared.
Titanium-Promoted Cross-Coupling for the Selective Synthesis of Polysubstituted, Conjugated Amides
Chenniappan, Vinoth Kumar,Rahaim, Ronald J.
supporting information, p. 5090 - 5093 (2016/10/14)
α,β-Unsaturated amides are important building blocks and are key structural elements in a number of biologically active natural products. Despite their importance and prevalence, few methods exist to prepare conjugated amides directly and modularly. To address this gap, a titanium-promoted coupling of alkynes and isocyanates has been developed. The method is highly stereoselective, producing only the E isomer with good chemoselectivity and regioselectivity (>95/5), for unsymmetrical internal alkynes that contain a steric bias. The reactive titanacyclopentene intermediate formed from the coupling of the alkyne and isocyanate was additionally reacted with various electrophiles to access tetrasubstituted enamides.
Synthesis and biological evaluation of novel hydrogen sulfide releasing nicotinic acid derivatives
Sun, Yinxing,Zhang, Yusuo,Li, Yuyao,Cheng, Jian,Chen, Shiyu,Xiao, Yunqi,Ao, Guizhen
, p. 5368 - 5373 (2016/10/24)
Twelve novel hybrids of slowly releasing hydrogen sulfide donor ADT-OH combined with nicotinic acid were synthesized. All of their structures had been confirmed by1H NMR,13C NMR and MS spectra. The target compounds were evaluated for their neuroprotective effects on hippocampal neuron HT22 cells against glutamate-induced injury at the concentrations of 1–100?μM with MTT assay, and their toxicity on HT22 cells untreated by glutamine at the concentration of 100?μM. The active compound was further investigated for its effect on ischemic infarct volume by intraperitoneal injection at 3?h after ischemia in mice models of permanent middle cerebral artery occlusion (pMCAO). The results showed that all the compounds significantly protected HT22 cells from glutamate-induced damage at most of the experimental concentrations, and had no or little neurotoxicity on normal HT22 cells at the high concentration. More importantly, compound A6 significantly reduced infarct volume in the pMCAO model. These results suggested that compound A6 may be promising for further evaluation for the intervention of cerebral ischemic injury.
The challenge of palladium-catalyzed aromatic azidocarbonylation: From mechanistic and catalyst deactivation studies to a highly efficient process
Miloserdov, Fedor M.,McMullin, Claire L.,Belmonte, Marta Martinez,Benet-Buchholz, Jordi,Bakhmutov, Vladimir I.,Macgregor, Stuart A.,Grushin, Vladimir V.
supporting information, p. 736 - 752 (2014/03/21)
Azidocarbonylation of iodoarenes with CO and NaN3, a novel Heck-type carbonylation reaction, readily occurs in an organic solvent-H 2O biphasic system to furnish aroyl azides at room temperature and 1 atm. The reaction is catalyzed by Xantphos-Pd and exhibits high functional group tolerance. The catalyst deactivation product, [(Xantphos)PdI2], can be reduced in situ with PMHS to Pd(0) to regain catalytic activity. In this way, the catalyst loading has been lowered to 0.2% without any losses in selectivity at nearly 100% conversion to synthesize a series of aroyl azides in 80-90% isolated yield on a gram scale. Alternatively, the ArCON3 product can be used without isolation for further transformations in situ, e.g., to isocyanates, ureas, benzamides, and iminophosphoranes. A detailed experimental and computational study has identified two main reaction pathways for the reaction. For both routes, Ar-I oxidative addition to Pd(0) is the rate-determining step. In the presence of CO in excess, the Ar-I bond is activated by the less electron-rich Pd center of a mixed carbonyl phosphine complex. Under CO-deficient conditions, a slightly lower energy barrier pathway is followed that involves Ar-I oxidative addition to a more reactive carbonyl-free (Xantphos)Pd0 species. Mass transfer in the triphasic liquid-liquid-gas system employed for the reaction plays an important role in the competition between these two reaction channels, uniformly leading to a common aroyl azido intermediate that undergoes exceedingly facile ArCO-N 3 reductive elimination. Safety aspects of the method have been investigated.
