Aryl Naphthoates: A Conformational Analysis Supported by Single-Crystal X-Ray Diffraction

The conformational study by X-ray diffraction of 12 aroyl esters of ortho-acetyl phenols is reported. The data are supported by theoretical calculations and described in terms of co-planarity, intramolecular steric interference, and intermolecular contacts. The observed hindrance was correlated with the C=O stretching vibration values in infrared spectroscopy.

Modes of Xanthine Complexation to Dirhodium Tetrakis[(R)-α-methoxy-α- (trifluoromethyl)-phenylacetate] in Solution and in the Solid State

It is show n by IR and NMR studies that the xanthines 1-5 prefer a side-on com plexation to the chiral dirhodium tetrakis[(R)-α-methoxy-α-(trifluoromethyl)phenylacetatel (Rh*) in solution whereas carbonyl groups are involved in the solid state. For 6, at least the carbonyl group C-6 contributes to complexation in solution as well. A lternating strands of 6 and Rh* exist in the solid state as revealed by X-ray diffraction analysis described in detail. The determination of enantiomeric excess of the chiral xanthine 6 can easily be accomplished by the “dirhodium method ” (1H and 13C NMR in the presence of Rh*).

Die Kristallstruktur der orientierungsfehlgeordneten kubischen Hochtemperaturphase des Natriumperchlorats NaClO4 / The Crystal Structure of the Orientationally Disordered, Cubic High-temperature Phase of Sodium Perchlorate NaClO4

The crystal structure of the orientationally disordered, cubic high-temperature phase of NaC104 has been investigated using single crystal X-ray diffraction data. Space group Fm3m-O5 h, Z = 4, sodium and chlorine as in NaCl, oxygen in position 96 j (occupation factor 1/6).

Quassinoids and Other Constituents from Picrasma crenata

16-β-O-methylneoquassin and 16-β-O-ethylneoquassin, and four known quassi­ noids have been isolated together with coniferyl aldehyde, coniferin, cantin-6-one, 4,5-di-methoxycantin-6-one and (+)-neo-olivil from the wood of Picrasma crenata. Their structures were determined on basis of spectroscopic and X-ray analysis.

Chemischer Transport fester Lösungen, 26 [1]. Untersuchungen zur Mischphasenbildung und zum chemischen Transport in den Systemen TiS2/NbS2, TiSe2/NbSe2, NbS2/TaS2 und NbSe2/TaSe2 / Chemical Vapour Transport of Solid Solutions, 26 [1]. Formation of Mixed Phases and Chemical Vapour Transport in the Systems TiS2/NbS2, TiSe2/NbSe2, NbS2/TaS2 and NbSe2/TaSe2

In the systems TiS2/NbS2, TiSe2/NbSe2, NbS2/TaS2 und NbSe2/TaSe2 complete miscibility in the solid state has been observed by powder X-ray investigations. Mixed crystals as well as the binary compounds can be prepared by chemical vapour transport reactions using iodine as transport agent in the temperature gradient 1000→900 °C. The gaseous species TiI3(g), TiI4(g), NbI4(g) and TaI4(g) are responsible for the transport effect.

The First Cyclopentadienylalkylphosphane Nickel Chelates: Synthesis, Structures, and Reactions

The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta-4,6-diene with lithium di-tert-butylphosphide was treated with NiCl2 to yield [eta(5):kappa(1)-(di-tert-butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile-stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl- and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper-mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X-ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.

Syntheses and Structures of Sterically Congested Linear and Branched Cobalta[n]triangulanes

Treatment of {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}cobalt(I) chloride (5) with methylenecyclopropane (3) or bicyclopropylidene (4), as well as with their spirocyclopropanated analogues methylenespiropentane (7), cyclopropylidenespiropentane (10), or 7,7'-bi(dispiro[2.0.2.1]heptylidene) (15) in the presence of sodium amalgam at -50 degrees C, furnished the stable cobalt complexes 6, 9, 8, 11, and 16, respectively, in 72, 83, 84, 86, and 54 % isolated yield, respectively. The complexes 14 and 16 were also obtained by ligand exchange of the ethene complex {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}(eta(2)-ethene)cobalt(I) (12) with 13 and 15 in 79 and 52 % yield, respectively. The X-ray crystal-structure analyses of complexes 9, 14, and 16, as well as the NMR-spectroscopic data of all complexes, reveal that they can be regarded as linear and branched cobalta[n]triangulanes. The thermal stability of complexes 6, 8, and 9 up to 109, 145, and 160 degrees C was determined by differential thermal analysis-thermogravimetry (DTA-TG) analysis.

Oxazatricyclic noradamantanes: stereocontrolled synthesis of functionalized scopolines, related cage molecules, and drug leads

Scopolines 4 and the noradamantane scaffold are accessible from 8-oxabicyclo[3.2.1]oct-6-en-3-ones such as 6 by a concise route involving introduction of an axial amino nitrogen at C3, epoxidation, and cyclization. The resulting cage molecules are versatile drug leads.

Unanticipated formation of ortho-sulfone substituted phenols by anionic thia-Fries rearrangement of (aryl triflate)tricarbonylchromium complexes

Tricarbonylchromium complexes of aryl triflates undergo base-mediated anionic thia-Fries rearrangements to generate push-pull substituted [ortho-hydroxyaryl(trifluoromethylsulfonyl)phenol]tricarbonylchromium complexes under very mild reaction conditions.

2-Pyridinealdoxime, a new ligand for a Pd-precatalyst: Application in solid-phase-assisted Suzuki–Miyaura reaction

The preparation of a new palladium(II) complex with a 2-pyridinealdoxime ligand and its use as a Pd(0) precatalyst in the cross-coupling Suzuki-Miyaura reaction is described. Several concepts for the immobilization of this catalytic system are presented and compared in order to develop an efficient catalytic tool for high-throughput synthesis.

Homoleptic, sigma-bonded octahedral [M(CO)(6)](2+) cations of iron(II), ruthenium(II), and osmium(II). Part 1: Syntheses, thermochemical and vibrational characterizations, and molecular structures as [Sb(2)F(11)](-) and [SbF(6)](-) salts. A comprehensive, comparative study

Homoleptic octahedral, superelectrophilic sigma-bonded metal carbonyl cations of the type [M(CO)(6)](2+) (M = Ru, Os) are generated in the Bronsted-Lewis conjugate superacid HF/SbF(5) by reductive carbonylation of M(SO(3)F)(3) (M = Ru, Os) or OsF(6). Thermally stable salts form with either [Sb(2)F(11)](-) or [SbF(6)](-) as anion, just as for the previously reported [Fe(CO)(6)](2+) cation. The latter salts are generated by oxidative (XeF(2)) carbonylation of Fe(CO)(5) in HF/SbF(5). A rationale for the two diverging synthetic approaches is provided. The thermal stabilities of [M(CO)(6)][SbF(6)](2) salts, studied by DSC, range from 180 degrees C for M = Fe to 350 degrees C for M = Os before decarbonylation occurs. The two triads [M(CO)(6)][SbF(6)](2) and [M(CO)(6)][Sb(2)F(11)](2) (M = Fe, Ru, Os) are extensively characterized by single-crystal X-ray diffraction and vibrational and (13)C NMR spectroscopy, aided by computational studies of the cations. The three [M(CO)(6)][SbF(6)](2) salts (M = Fe, Ru, Os) crystallize in the tetragonal space group P4/mnc (No. 128), whereas the corresponding [Sb(2)F(11)](-) salts are monoclinic, crystallizing in space group P2(1)/n (No. 14). In both triads, the unit cell parameters are nearly invariant of the metal. Bond parameters for the anions [SbF(6)](-) and [Sb(2)F(11)](-) and their vibrational properties in the two triads are completely identical. In all six salts, the structural and vibrational properties of the [M(CO)(6)](2+) cations (M = Fe, Ru, Os) are independent of the counteranion and for the most part independent of M and nearly identical. Interionic C...F contacts are similarly weak in all six salts. Metal dependency is noted only in the (13)C NMR spectra, in the skeletal M-C vibrations, and to a much smaller extent in some of the C-O stretching fundamentals (A(1g) and T(1u)). The findings reported here are unprecedented among metal carbonyl cations and their salts.

The first and second cinchona rearrangement. Two fundamental transformations of alkaloid chemistry

Stereochemistry, products, and driving forces of the "first and second Cinchona rearrangement" have been investigated and a unified theory is presented. The first cage expansion affords [3.2.2]azabicyclic alpha-amino ether and is formulated via a configurationally stable bridgehead iminium ion and quasiequatorial nucleophilic attack. The second cage expansion affords beta-functionalized [3.2.2]azabicycles. In this case a nonclassical nitrogen-bridged cation is postulated to account for retention of configuration and potential reversibility of the cage expansion. The second rearrangement is favored for the so-called cinch bases (6'-R = H) in trifluoroethanol. Stereoelectronic factors, electron demand at C9, ground state conformation, and solvent type are crucial in all cases. A two-step protocol for preparing 9-epi-configured Cinchona alkaloids from 9-nat precursors is described.

Crystal structure of manganese gallium germanium silicon oxide (garnet type), Mn3(Ga2–yMny)(Ge3–zSiz)O12 (y = 0.6, z = 0.14; y = 0.44, z = 0), and of manganese gallium germanium silicon oxide (braunite type), Mn(Mn6–yGay)(Si1–zGez)O12 (y = 0.7, z = 0.4)

Ga1.4Ge2.86Mn3.6O12Si0.14 (1), cubic, Ia3̅d (No. 230), a = 12.043(3) Å, V = 1746.6 Å3, Z = 8, Rgt(F) = 0.028, wRref(F2) = 0.062, T = 300 K.

Ga1.56Ge3Mn3.44O12 (2), cubic, Ia3̅d (No. 230), a = 12.049(3) Å, V = 1749.3 Å3, Z = 8, Rgt(F) = 0.023, wRref(F2) = 0.052, T = 300 K.

Ga0.7Ge0.4Mn6.3O12Si0.6 (3), tetragonal, I41/acd (No. 142), a = 9.464(4) Å, c = 18.78(3) Å, V = 1682.1 Å3, Z = 8, Rgt(F) = 0.023, wRref(F2) = 0.053, T = 300 K.

High-pressure selectivity studies--a simple route to a homochiral wistarin precursor

The cycloaddition of spirobutenolide 3 to the homochiral cyclopentadiene 1 at 6.5 kbar leads exclusively to cycloadduct 5. Subsequent Diels-Alder or Michael additions again favour the cyclohexenone double bond; this perfect chemo- regio- and face selectivity was employed for a short and efficient approach to the wistarin framework.

Fused triazoles via tandem reactions of activated Cinchona alkaloids with azide ion. Second Cinchona rearrangement exemplified

[reaction: see text] Intramolecular 1,3-dipolar cycloadditions of cinchona azides to the C10-C11 alkyne and C10-C11 olefin unit of the alkaloid have been designed via tandem strategy. A variety of fused triazoles and triazolines with a bis-azahomotwistane skeleton have been prepared. In trifluoroethanol, O-mesylcinchonidine 7-OMs and NaN(3) furnish triazole 8 as well as cage-expanded 1,5-diazatricyclo[4.4.1.0(3,8)]undecane derivative 10. Both fused triazoles 8 and 10 are formed with retention of configuration at C9 and C3, respectively. 1-Azabicyclo[3.2.2]cage expansion is shown to be reversible.

Preparation of enantiopure 1-azabicyclo[3.2.2]nonanes functionalized at carbon C3, from cinchonine and cinchonidine. stereoselective solvolysis and an easily enolizable ketone

Solvolysis of C9 mesylated cinchonidine 1-OMs and cinchonine 2-OMs in solvent MeOH, EtOH, and CF(3)CH(2)OH affords ring-expanded 1-azabicyclo[3.2.2]nonanes oxygenated at carbon C3 ("second Cinchona rearrangement"). The newly introduced substituents at C3 and the neighboring quinolyl group Q' at C2 adopt quasiequatorial positions. The derived 1-azabicyclo[3.2.2]nonan-3-ones 5 and 6 are easily equilibrated. On contact with MeOD uptake of deuterium takes place at room temperature.

S(N)1-like reactions of bicyclic alpha-amino ethers with sulfur, nitrogen, and carbon nucleophiles. Synthesis of 1-azabicyclo[3.2.2]nonanes functionalized at carbon C2 and C6 with complete stereocontrol

[reaction: see text] In the presence of nucleophiles, Lewis acid mediated cleavage of alpha-amino ethers derived from quincorine and quincoridine affords a variety of C2-substituted and C6-vinylated 1-azabicyclo[3.2.2]nonanes. These are enantiopure and are formed in S(N)1-like reactions with complete stereocontrol. There is no leakage into 2-Nu en route to product 1-Nu or vice versa. Me(3)SiCN provides new Strecker-type alpha-amino nitriles. In the presence of TTMPP-BF(3).OEt(2), the ketene acetal Me(2)C=C(OMe)OSiMe(3) delivers enantiopure bicyclic beta-amino acid esters.

New developments in A1 and A2 adenosine receptor antagonists

The aim of this article is to briefly present progress in the development of the potent adenosine receptor (AR) antagonists with high selectivity for either A1, A2A, or A2B ARs. The structural requirements for each AR subtype were discussed as well as their potential therapeutic use. In the search for new AR antagonists, series of imidazo-, pyrimido-, and diazepino-purindione derivatives as well as oxazolo-, oxazino-, and oxazepino-purindiones were designed, synthesized, and preliminarily evaluated in pharmacological studies. Oxygen-containing tricyclic derivatives were shown to be moderately potent AR antagonists exhibiting selectivity either for A1 or A2A ARs. Tricyclic purindiones with nitrogen in the third ring were generally more A2A AR selective. The compounds tested in vivo according to the Antiepileptic Drug Development Program of the National Institutes of Health (USA) were generally active as anticonvulsants in chemically induced seizures.

New cyclohexadienone derivatives: preparation and chiral discrimination in high-pressure Diels-Alder cycloadditions

A wide range of cyclohexadienones has been synthesised in order to study their reactivity and their regio- and stereoselectivity with the enantiopure diene 1 under high-pressure conditions. Computational investigations were used to point out some parameters which affect the reactivity in this high chiral discrimination process. In addition, the resulting [4+2] cycloadducts allowed the preparation of new polyfunctional cyclohexenone derivatives.