Search results for "Medicinal Chemistry"
showing 10 items of 2264 documents
Half-sandwich complexes of molybdenum-(III), -(IV) and -(V) with P–O and P–N bifunctional ligands Ph2PCH2X (X = 2-oxazolinyl, or C(O)NPh2)
2000
International audience; The reaction of the ligands Ph2PCH2X (X = 2-oxazolinyl, I; or C(O)NPh2, II) with the half-sandwich molybdenum(III) precursors [Mo(η-C5R5)(μ-Cl)2]2 (R = H or Me) has been investigated. Ligand I reacts with both complexes to form the corresponding adducts [Mo(η-C5R5)Cl2(Ph2PCH2C3H4NO)] (R = H, 1; or Me, 2). The reaction between I and [MoCp*Cl4] (Cp* = η-C5Me5) affords [MoCp*Cl4(Ph2PCH2C3H4NO-κ1P)] as a kinetic isomer, which then transforms quantitatively to [MoCp*Cl3(Ph2PCH2C3H4NO-κ2P,N)]+Cl−, 3. Ligand II reacts with [MoCp(μ-Cl)2]2 (Cp = η-C5H5) to afford the adduct [CpMoCl2{Ph2PCH2C(O)NPh2-κ2P,O}], 4, as an equilibrium mixture of two isomers. Longer reaction times in…
Arene C−H Activation at Aluminium(I): meta Selectivity Driven by the Electronics of S N Ar Chemistry
2020
The reactivity of the electron-rich anionic Al(I) ('aluminyl') compound K 2 [(NON)Al] 2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di- tert -butyl-9,9-dimethylxanthene) towards mono- and disubstituted arenes is reported. C-H activation chemistry with n -butylbenzene gives exclusively the product of activation at the arene meta position. Mechanistically, this transformation proceeds in a single step via a concerted Meisenheimer-type transition state. Selectivity is therefore based on similar electronic factors to classical S N Ar chemistry, which implies the destabilization of transition states featuring electron-donating groups in either the ortho or the para positions. In the cases of tolu…
Structurally characterized dipalladium(ii)-oxamate metallacyclophanes as efficient catalysts for sustainable Heck and Suzuki reactions in ionic liqui…
2018
A new generation of dipalladium-oxamate metallacyclophanes of formulas (n-NBu4)4 [Pd2(ppba)2] (1), (n-NBu4)4[Pd2(dpvba)2] (2), (n-NBu4)4[Pd2(dpazba)2] (3), (n-NBu4)4[Pd2(dpeba)2] (4) and (n-NBu4)4[Pd2(tpeba)2] (5) [n-NBu4+ = tetra-n-butylammonium cation, H4ppba = N,N′-1,4-phenylenebis(oxamic acid), H4dpvba = N,N′-4,4′-diphenylethenebis(oxamic acid), H4dpazba = N,N′-4,4′-diphenylazobis(oxamic acid), H4dpeba = N,N′-4,4′-diphenylethynebis(oxamic acid) and H4tpeba = N,N′-1,4-di(4-phenylethynyl)phenylenebis(oxamic acid)] was prepared. The crystal structure of the solvated species of 2–4, namely (n-NBu4)4[Pd2(dpvba)2]·6MeOH·2Et2O (2a), (n-NBu4)4[Pd2(dpazba)2]·8MeOH (3a), and (n-NBu4)2[Pd2(dpeba)2…
Cis- and trans molybdenum oxo complexes of a prochiral tetradentate aminophenolate ligand : Synthesis, characterization and oxotransfer activity
2020
Abstract Reaction of [MoO2Cl2(dmso)2] with the tetradentate O2N2 donor ligand papy [H2papy = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine] leads to formation of the dioxomolybdenum(VI) complex [MoO2(papy)] (1) as a mixture of cis and trans isomers. Recrystallization from methanol furnishes solid cis-1, whereas the use of a dichloromethane-hexane mixture allows for the isolation of the trans-1 isomer. Both isomers have been structurally characterized by X-ray crystallography and the energy difference between the isomeric pair has been investigated by electronic structure calculations. Optimization of two configurational isomers in the gas phase predicts the trans isomer to lie 2.5 kcal/mol lower…
Squaramide-Catalyzed Asymmetric aza-Friedel-Crafts/N,O-Acetalization Domino Reactions Between 2-Naphthols and Pyrazolinone Ketimines
2017
N-Boc ketimines derived from pyrazolin-5-ones were explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98 %) and stereoselectivity (>99:1 d.r. and 97-98 % ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98 % yield and 47-98 % ee.
New crystal structures of fluorinated α-aminophosphonic acid analogues of phenylglycine
2020
The four novel phosphonic acid analogues of phenylglycine with various substituents in phenyl ring (mostly fluorine atoms) have been synthesized by using procedure of amidoalkylation of phosphorus trichloride with aromatic aldehydes and acetamide. The NMR, ESI-MS spectroscopy, and single-crystal X-Ray diffraction methods were used to characterize unusual structures: the amino-(4-trifluoromethylbenzyl)-(1), amino-(3,4-difluorobenzyl)-(2), amino-(2,4,6-trifluorobenzyl)-(3), and amino-(2-fluoro-4-hydroxybenzyl)-(4) phosphonic acids. Since the α-aminophosphonates have a potential for biological activity and could be used as building blocks in medicinal chemistry, it is important to know their d…
Mono‐ and Bis(imidazolidinium ethynyl) Cations and Reduction of the Latter To Give an Extended Bis‐1,4‐([3]Cumulene)‐ p ‐carboquinoid System
2018
An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs.
Tetracationic and Tetraanionic Manganese Porphyrins: Electrochemical and Spectroelectrochemical Characterization
2017
International audience; The electrochemistry and spectroelectrochemistry of four tetrapositively charged and two tetranegatively charged porphyrins were characterized in two nonaqueous solvents (dimethyl sulfoxide and N,N-dimethylformamide) containing 0.1 M tetra-n-butylammonium perchlorate. The tetrapositively charged compounds are represented by the tetrapyridylporphyrins [TRPyPM]4+(X-)4, where R is a methyl or [2-[2-(2-methoxy)ethoxy]ethoxy]ethyl group, M = MnIIII, MnIIICl, CuII, or PdII, and X = I- or Cl-. The tetranegatively charged porphyrins are represented by the tetrasulfonato derivatives [TPPSMn(OAc)]4-(NH4+)4 and [TArPSMn(OAc)]4-(NH4+)4, where Ar = 4-O-[2-[2-(2-methoxy)ethoxy]eth…
Photolysis of Tertiary Amines in the Presence of CO2: The Paths to Formic Acid, α-Amino Acids, and 1,2-Diamines
2017
The photolysis of triethylamine (1a) in the presence of carbon dioxide leads to the hydrogenation of CO2, the α-C-C coupling of triethylamine (1a), and the CO2-insertion into the α-C-H σ-bond of amine 1a. This reaction is proposed to proceed through the radical ion pair [R3N·+·CO2·-] generated by the photoionization of amine 1a and the electron capture by CO2. The presence of lithium tetrafluoroborate in the reaction medium promotes the efficient and stereoselective α-C-C coupling of 1a by enhancing the production of α-dialkylamino radicals and the isomerization of N,N,N',N'-tetraethylbutane-2,3-diamine (4a).