Search results for "Medicinal chemistry"
showing 10 items of 2264 documents
Homoleptic heavy alkaline Earth and europium triazenides.
2009
The sigma-bond metathesis reaction between PhSiH(3) and the heteroleptic metal pentafluorophenyl compounds [Dmp(Tph)N(3)MC(6)F(5)(thf)(n)] (Dmp = 2,6-Mes(2)C(6)H(3) with Mes = 2,4,6-Me(3)C(6)H(2); Tph = 2-TripC(6)H(4) with Trip = 2,4,6-(i)Pr(3)C(6)H(2); n = 1, 2; M = Sr, Ba, Eu) supported by sterically crowded, biphenyl- and terphenyl-substituented triazenido ligands afforded the first homoleptic stontium, barium, and europium triazenides [M{N(3)Dmp(Tph)}(2)] {M = Sr (2), Ba (4), Eu (5)}. Crystallization of 2 from an n-heptane/1,2-dimethoxyethane mixture gave the complex [Sr{N(3)Dmp(Tph)}(2)(dme)] (3). All new compounds have been characterized by (1)H and (13)C NMR spectroscopy (not 5), ele…
Measuring the Relative Reactivity of the Carbon-Hydrogen Bonds of Alkanes as Nucleophiles
2018
We report quantitative measurements of the relative reactivities of a series of C-H bonds of gaseous or liquid CnH2n+2 alkanes (n = 1-8, 29 different C-H bonds) towards insitu generated electrophiles (copper, silver, and rhodium carbenes), with methane as the reference. This strategy surpasses the drawback of previous model reactions of alkanes with strong electrophiles suffering from C-C cleavage processes, which precluded direct comparison of the relative reactivities of alkane C-H bonds.
Bis(3,5-dimethylpyrazol-1-ato) zirconium complexes as precursors for ethylene polymerisation upon activation with MAO: Syntheses, characterisation an…
2007
Abstract The bis(3,5-dimethylpyrazol-1-ato) zirconium complex [Zr(η2-3,5-Me2Pz)2(NMe2)2(NHMe2)2] (2) is obtained by treatment of [Zr(NMe2)4] with 2 equiv. of 3,5-dimethylpyrazole 1. The reaction of the [ZrCl4(THF)2] adduct with 2 equiv. of the potassium salt of 1 affords the dichloro derivative [Zr(η2-3,5-Me2Pz)2Cl2]n (3), while reaction with 4.1 equiv. of 1 in the presence of 2.1 equiv. of NEt3 affords the dichloro pyrazole adduct [Zr(η2-3,5-Me2Pz)2Cl2(η1-3,5-Me2PzH)2] (4). Treatment of [Zr(CH2Ph)4] with 2 equiv. of 1 gives the dibenzyl complex [Zr(η2-3,5-Me2Pz)2(CH2Ph)2] (5) via alkane elimination. Compound 4 presents fluxional behaviour in CDCl3 solution, which was studied and quantified…
Comparative chemistry of 18-electron Mo(II) and 17-electron Mo(III) compounds containing only carbon-based ligands
1998
International audience; The chemical reactivity of various kinetically stable isomers of compound CpMo(η3-C3H5)(η4-C4H6), 1, and its oxidation product [1]+, as well as the bis-allyl Mo(III) complex CpMo(η3-C3H5)2, 2, and the bis-diene Mo(II) complex [CpMo(η4-C4H6)2]+, 3, is reviewed. The inertness toward isomerization processes of the allyl and butadiene ligands in the Mo(II) complexes has allowed a study of the relative reactivity toward both electrophilic and nucleophilic addition processes as a function of coordination mode. The dependence of various reaction pathways on the metal oxidation state has also been investigated. Of particular interest is the discovery that the electronically …
Synthesis of borylindenides. Complexes with iron and rhenium moieties
1999
Abstract Borylation of lithium indenide with BBrMe 2 gives the allylic 1-indenyl derivative (1-Ind)BMe 2 ( 1c ) together with the bis-allylic connected species (1-Ind) 2 BMe ( 3 ) and with BCl i Pr 2 , the allylic 1-indenyl (1-Ind)B i Pr 2 ( 1d ); the latter, with Et 3 N or Py added, rearranges to the vinylic 3-indenyl isomer (3-Ind)B i Pr 2 ( 2d ). The disubstituted indene C 9 H 6 Ind(SiMe 3 )B(O 2 C 2 Me 4 ) ( 5 ) was prepared from Li[C 9 H 6 B(O 2 C 2 Me 4 )] ( 4b ) and Me 3 SiCl. Both (1-Ind)BMe 2 and (1-Ind)B i Pr 2 readily undergo metalation when treated with LiTMP or LiInd to give pure 1-borylindenides Li(C 9 H 6 BMe 2 ) ( 4c ) and Li(C 9 H 6 B i Pr 2 ) ( 4d ). A barrier to internal …
Mechanism of oxidative allyl transfer from allylic ammonium cations to palladium(0) α-diimine complexes
1996
Abstract The palladium(0) complex [Pd(η2-fn)(NN′)] (1, fn = fumaronitrile; NN′ = C5H4N-2-CH=NC6H4OME-4) reacts slowly and reversibly with A + CH 2 CH=CH 2 (2a, A = NEt 3 ; 2 b , A = C 5 H 5 N ) to yield the cationic η3-allypalladium(II) derivative [ Pd (η[ 3 - C 3 H 5 )( N N ′)] + (3) the free amine A and fn. The equilibrium constant Ke is (2.6 ± 0.1) × 10−3 for 2a and 1.0 ± 0.4 for 2b. Kinetic studies of these oxidative allyl-transfer reactions show that the rates increase with increasing concentration of 2 and with decreasing concentration of fn. A stepwise mechanism is proposed which involves slow and reversible displacement of fn by 2 to give a labile intermediate [ Pd (η 2 - CH…
Design of P-Chirogenic Aminophosphine-Phosphinite Ligands at Both Phosphorus Centers: Origin of Enantioselectivities in Pd-Catalyzed Allylic Reaction…
2020
International audience; We have recently patented an unprecedented stereospecific N→O phosphinyl migration process which transforms P-chirogenic aminophosphines into phosphinites. A fine design of aminophosphine phosphinite ligands (AMPP*) derived from ephedrine and bearing a P-chirogenic center either at the aminophosphine or phosphinite moiety, was performed. The synthesis of AMPP* ligands with P-chirogenic aminophosphine moiety was based on the well-established stereospecific reaction of oxazaphospholidine-borane with organolithium reagents, followed by trapping with a chlorophosphine and borane decomplexation. Concurrently, the preparation of AMPP* ligands with P-chirogenic phosphinite …
A joint experimental and ab initio study on the reactivity of several hydroxy selenides. Stereoselective synthesis of cis-disubstituted tetrahydrofur…
2001
Abstract The reactivity of several hydroxy selenides bearing an ethereal chain with catalytic amounts of perchloric acid in dichloromethane was investigated. Results showed that the position of the oxygen atom with respect to the seleniranium ring was crucial in order to get a good yield of the cyclized product. The factors on which yields of the 5- endo cyclization of the seleniranium ions depend were analysed by ab initio (HF/3-21G ∗ ) studies. An explanation of the different coordinating ability, towards the positively charged selenium atom, of the allylic OMe and homoallylic OH-2 groups was given.
P-Chirogenic Phosphines Supported by Calix[4]arene: New Insight into Palladium-Catalyzed Asymmetric Allylic Substitution
2013
The first P-chirogenic mono- and diphosphine ligands supported on the upper rim of a calix[4]arene moiety were synthesized using the ephedrine methodology. The lithiated calix[4]arene mono- and dianions both react with the oxazaphospholidine–borane, prepared from ephedrine, to afford regio- and stereoselectively the corresponding calix[4]arenyl aminophosphine–boranes, by cleavage of the heterocyclic ring at the P–O bond position. Subsequent reactions with HCl and then organolithium reagent and finally decomplexation with DABCO lead to the corresponding calix[4]arenyl mono- or diphosphines. Both enantiomers of the calix[4]arenyl phosphines were obtained either by using (+)- or (−)-ephedrine …
A Simple Procedure for Oxidation of Alcohols using [Bis(acetoxy)iodo]benzene and a Catalytic Amount of Bromide Ions in Ethyl Acetate
2015
Primary and secondary benzylic alcohols and secondary aliphatic alcohols were oxidized to the corresponding aldehydes and ketones by using [bis(acetoxy)iodo]benzene (BAIB) and a catalytic amount of bromide ions, from tetrabutylammonium bromide or KBr, in ethyl acetate. The catalytic role of the bromide ions was also highlighted in the oxidation of primary aliphatic alcohols and secondary allylic alcohols carried out in the presence of 1 mol% TEMPO.