13C NMR studies on tricarbonylchromium complexes of dimethylaminofulvene and diphenylfulvene

The ¹³C NMR spectra of tricarbonylchromium complexes of dimethylaminofulvene diphenylfulvene have been studied. Comparison of the ¹³C NMR spectra of these complexes with those of the corresponding non-coordinated fulvenes shows that the contribution from the ylidic structure of the π-ligand in the first complex increases when the Cr atom becomes coordinated, while in the second complex this coordination does not favour a formation of the ylidic structure of the π-ligand.     

Pishchimuka's Intramolecular Rearrangement. The General Method for the Synthesis of 2-Oxo-1,2λ5-thiaphoapholanes and Thiaphosphorinanes

A new method is developed for the synthesis of 2-substituted 2-oxo-1,2⁵-thiaphospholanes and thiaphosphorinanes (thiolphostones) on the basis of intramolecular Pishchimuka rearrangement of thiophosphonic and thiophosphinic esters with -chloroalkyl substituents at the phosphorus atom. Intermediate compound in the Pishchimuka rearrangement, 2-ethyl-2-ethoxy-1,2⁴-thiaphospholanium perchlorate, was isolated.     

Synthesis and characterization of fluorophenylpalladium pincer complexes: electronic properties of some pincer ligands evaluated by multinuclear NMR spectroscopy and electrochemical studies

Palladium fluorophenyl complexes with different pincer ligands Pd(Ar)[2,6-(tBu(2)PCH(2))(2)C(6)H(3)] (13), Pd(Ar)[2,6-(tBu(2)PO)(2)C(6)H(3)] (14), Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))] (15), and Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Ru(C(5)H(5))] (16) were synthesized by the reaction of LiAr (Ar = C(6)H(4)F-4) with the respective trifluoroacetate palladium pincer complexes 9-12. The molecular structures of 14 and 16 were determined by an X-ray crystallographic method. Complexes 13-16 and {Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))]}PF(6) (17) were studied by multinuclear NMR spectroscopy and cyclic voltammetry. On the basis of (19)F NMR chemical shifts and (1)J((13)C-(19)F) coupling constants, as well as Pd(II)/Pd(IV) oxidation potentials, electronic characteristics of the corresponding pincer ligands were elucidated.     

Rh-Catalyzed asymmetric hydrogenation of (Z)-ethyl 3-acetamido-2-butenoate in supercritical carbon dioxide: the effect of cosolvents

Rh-Catalyzed asymmetric hydrogenation (up to 85% ee) of (Z)-ethyl 3-acetamido-2-butenoate was carried out for the first time in supercritical CO₂ using protic cosolvents. The activity of the Rh catalyst bearing the amidophosphite ligand increases with an increase in acidity of the protic cosolvents and with hydrogen pressure.     

Cyclotrimerization of alkynes catalyzed by the naphthalene ruthenium complex [CpRu(C10H8)]+

The naphthalene ruthenium complex [CpRu(C₁₀H₈)]⁺ (in the presence of Cl^? ions) catalyzes the cyclotrimerization of 2,2-dimethyl-5,5-dipropargyl-1,3-dioxane-4,6-dione with alkynes (acetylene, hex-1-yne, hex-3-yne, oct-1-yne, phenylacetylene, trimetylsilylacetylene, octa-1,7-diyne, pent-1-yn-5-ol, methyl propargyl ether, and propargyl acetate) giving tricyclic aromatic compounds in 55–85% yields.     

Synthesis and Intramolecular Cyclization of ω-Haloalkyl Dithiophosporus Acid Esters

y -Haloalkyl dithiophosphorus acid esters undergo the thermal rearrangement resulting in the corresponding 2-oxo-1,3,2-dithiaphosphacyclanes.     

Investigation of Bis(α-Phenylethylamido)Methylphosphonates by NMR Spectroscopy

Abstract

The influence of the relative location of chiral carbon and phosphorus atoms and the position of the aryl-group on diastereomeric anisochronity in non-racemic mixtures of enantiomers has been examined. The optical isomers of methanephosphonic acid bis(α-phenylethylamide) (I), which contain pro-chiral phosphorus atom, were synthesized by the reaction of methanephosphonic acid dichloride(II) with (+)- or (-) -α-phenylethylamine (III). The extent of chemical shift nonequivalence in ³¹P and ¹H NMR spectra of non-racemic mixtures of RR- and SS-I was negligible. It can be explained by the absence of aryl-amino group, favouring intermolecular association, effect of SCADA¹, and the long distance between the chiral center and pro-chiral phosphorus. Phosphonylation of non-racemic mixtures of (+)- and (-)-III by II proceeds stereospecifically giving mixture of RR-, SS-I, and two meso-compounds analyzed by ³¹P ¹H NMR.     

Synthesis and some properties of Nd(B11H14)3 · 4Dg (Dg is diglyme)

The reaction of Nd(BH₄)₃ · 3THF with decaborane-14 in diglyme at 85–90°C yields Nd(B₁₁H₁₄)₃ · 4Dg. The duration of the reaction is 20 h. The molar ratio of Nd(BH₄)₃ · 3THF to B₁₀H₁₄ is is 1 :3.5. The product is precipitated with heptane from a diglyme solution. The yield is 70%. In an inert atmosphere, Nd(B₁₁H₁₄)₃ · 4Dg is stable to 150°C and decomposes with an exotherm at 160–190°C. The IR spectrum of Nd(B₁₁H₁₄)₃ · 4Dg in the region of B-H stretching vibrations contains an intense band at 2530 cm^?1. The ¹¹B {¹H} NMR spectra of the synthesized compound in diglyme solutions contain signals of the tetradecahydro-nido-undecaborate anion B₁₁H ₁₄ ^? (δ = -14.0, -15.6, and -16.5 ppm).     

Synthesis and photophysical properties of polyphenylquinoxalines with thiophene and benzothiophene units in side chains

New bis(α-diketones) with thiophene and benzothiophene moieties were synthesized. A series of new polyphenylquinoxalines containing these moieties in side chains was prepared via polycondensation of these diketones with different aromatic tetramines. The polymers are soluble in a variety of organic solvents, and their solutions form transparent films having a tensile strength of σ = 80–100 MPa and an elongation at break of ? = 5–12%. The polymers exhibit fluorescence in solution in trifluoroacetic acid and in films with a maximum at 430–570 and 460–480 nm. The 10% mass loss temperature in air ranges within 440–490°C.     

Diastereomeric P*-mono- and P*,P*-bidentate diamidophosphite ligands based on 1,4:3,6-dianhydro-d-mannitol in asymmetric metallocomplex catalysis

Synthesis of diastereomeric mono- and bidentate diamidophosphites bearing P*-stereo-centers and phosphabicyclo[3.3.0]octane backbone and their coordination with rhodium(i) and palladium(ii) are considered. Their use in Rh-catalyzed asymmetric allylation allowed one to achieve 87% ee values and the use in Rh-catalyzed asymmetric hydrogenation gave up to 98% ee.