The α-hydroxyphosphonate-phosphate rearrangement of a noncyclic substrate - some new observations.

Racemic ethyl hydrogen (1-hydroxy-2-methylsulfanyl-1-phenylethyl)phosphonate was resolved with (R)-1-phenylethylamine. The (R)-configuration of the (-)-enantiomer was determined by chemical correlation. Esterification of the (-)-enantiomer with a substituted diazomethane derived from 3-hydroxy-1,3,5(10)-estratrien-17-one delivered two epimeric phosphonates separated by HPLC. Methylation with methyl fluorosulfate at the sulfur atom and treatment with a strong base induced an α-hydroxyphosphonate-phosphate rearrangement with formation of dimethyl sulphide and two enantiomerically pure enol phosphates. Their oily nature interfered with a single crystal X-ray structure analysis to determine the stereochemistry at the phosphorus atom.

Functionalization of 3-Iridacyclopentenes.

Members of a series of iridacyclopentenes of composition [TpMe2 Ir(k2 -C,C-CH2 CR'=CRCH2 )(CO)] (TpMe2 =hydrotris(3,5-dimethylpyrazolyl)borate; R=R'=H, 1; R=Me, R'=H, 2; R=R'=Me, 3) have been subjected to common organic chemistry procedures for hydrogenation, cyclopropanation, epoxidation, water addition through hydroboration, cis-dihydroxylation, and ozonolysis. The stability of metallacycles 1-3, imparted by the presence of the co-ligands TpMe2 and CO, directs the reactivity towards the C=C double bonds, and furthermore the stereochemistry of the products formed is strongly dictated by the steric demands of the TpMe2 ligand. While the products obtained in some of the above-mentioned reactions are the expected ones from an organic chemistry point of view, in other cases the results differ from the outcomes of similar reactions carried out with the all-carbon counterparts.

Reaction of [TpRh(C2 H4 )2 ] with Dimethyl Acetylenedicarboxylate: Identification of Intermediates of the [2+2+2] Alkyne and Alkyne-Ethylene Cyclo(co)trimerizations.

The reaction between the bis(ethylene) complex [TpRh(C2 H4 )2 ], 1, (Tp=hydrotris(pyrazolyl)borate), and dimethyl acetylenedicarboxylate (DMAD) has been studied under different experimental conditions. A mixture of products was formed, in which TpRh(I) species were prevalent, whereas the presence of trapping agents, like water or acetonitrile, allowed for the stabilization and isolation of octahedral TpRh(III) compounds. An excess of DMAD gave rise to a small amount of the [2+2+2] cyclotrimerization product hexamethyl mellitate (6). Although no catalytic application of 1 was achieved, mechanistic insights shed light on the formation of stable rhodium species representing the resting state of the catalytic cycle of rhodium-mediated [2+2+2] cyclo(co)trimerization reactions. Metallacyclopentene intermediate species, generated from the activation of one alkyne and one ethylene molecule from 1, and metallacyclopentadiene species, formed by oxidative coupling of two alkynes to the rhodium centre, are crucial steps in the pathways leading to the final organometallic and organic products.

Synthesis and preclinical characterization of 1-(6'-deoxy-6'-[18F]fluoro-ß-d-allofuranosyl)-2-nitroimidazole (ß-6'-[18F]FAZAL) as a positron emission tomography radiotracer to assess tumor hypoxia.

Positron emission tomography (PET) using fluorine-18 (18F)-labeled 2-nitroimidazole radiotracers has proven useful for assessment of tumor oxygenation. However, the passive diffusion-driven cellular uptake of currently available radiotracers results in slow kinetics and low tumor-to-background ratios. With the aim to develop a compound that is actively transported into cells, 1-(6'-deoxy-6'-[18F]fluoro-ß-d-allofuranosyl)-2-nitroimidazole (ß-[18F]1), a putative nucleoside transporter substrate, was synthetized by nucleophilic [18F]fluoride substitution of an acetyl protected labeling precursor with a tosylate leaving group (ß-6) in a final radiochemical yield of 12±8% (n=10, based on [18F]fluoride starting activity) in a total synthesis time of 60min with a specific activity at end of synthesis of 218±58GBq/µmol (n=10). Both radiolabeling precursor ß-6 and unlabeled reference compound ß-1 were prepared in multistep syntheses starting from 1,2:5,6-di-O-isopropylidene-α-d-allofuranose. In vitro experiments demonstrated an interaction of ß-1 with SLC29A1 and SLC28A1/2/3 nucleoside transporter as well as hypoxia specific retention of ß-[18F]1 in tumor cell lines. In biodistribution studies in healthy mice ß-[18F]1 showed homogenous tissue distribution and excellent metabolic stability, which was unaffected by tissue oxygenation. PET studies in tumor bearing mice showed tumor-to-muscle ratios of 2.13±0.22 (n=4) at 2h after administration of ß-[18F]1. In ex vivo autoradiography experiments ß-[18F]1 distribution closely matched staining with the hypoxia marker pimonidazole. In conclusion, ß-[18F]1 shows potential as PET hypoxia radiotracer which merits further investigation.

Coordinating chiral ionic liquids.

A practical synthesis of novel coordinating chiral ionic liquids with an amino alcohol structural motif was developed starting from commercially available amino alcohols. These basic chiral ionic liquids could be successfully applied as catalysts in the asymmetric alkylation of aldehydes and gave high enantioselectivities of up to 91% ee.

Reactivity of iron complexes containing monodentate aminophosphine ligands - Formation of four-membered carboxamido-phospha-metallacycles.

Treatment of [FeCp(CO)2Cl] with 1 equiv of the amidophosphine ligands Li[R2PNR'] (R = Ph, iPr, R' = iPr, tBu, Cy) afforded complexes of the type [FeCp(CO)(κ2(C,P)-(C = O)-NiPr-PPh2)] (1a), [FeCp(CO)(κ2(C,P)-(C = O)-NtBu-PPh2)] (1b), and [FeCp(CO)(κ2(C,P)-(C = O)-NCy-PiPr2)] (1c) in 40-50% yields. Complex 1a was also formed when [FeCp(CO)2(PPh2NHiPr)]+ (2) was reacted with 1 equiv of KOtBu. These complexes feature a four-membered carboxamido-phospha-ferracycle as a result of an intramolecular nucleophilic attack of the amidophosphine ligand on coordinated CO. Upon treatment of 1a with the electrophile [Me3O]BF4 the aminocarbene complex [FeCp(CO)(κ2(C,P) = C(OMe)-NiPr-PPh2)]+ (3) was obtained bearing an aza-phospha-carbene moiety. Upon treatment of cis,trans,cis-[Fe(CO)2(Ph2PNHiPr)2(Br)2] (4a) and cis,trans,cis-[Fe(CO)2(Ph2PNHtBu)2(Br)2] (4b) with KOtBu the carboxamido-phospha-ferracycles trans-[Fe(CO)2(κ2(C,P)-(C = O)-NiPr-PPh2)(Ph2PNHiPr)Br] (5a) and trans-[Fe(CO)2(κ2(C,P)-(C = O)-NtBu-PPh2)(Ph2PNHtBu)Br] (5b) were formed in moderate yield. Finally, representative structures were determined by X-ray crystallography.

Spectroscopic, structural and magnetic investigations of iron(II) complexes based on 1-isopropyl- and 1-isobutyl-substituted tetrazole ligands.

Two partly new [Fe(intz)6](BF4)2 complexes with n = 3 and 4 (i3tz = 1-isopropyl-1H-tetrazole, i4tz = 1-isobutyl-1H-tetrazole) were synthesized and characterised by X-ray powder diffraction, magnetic susceptibility measurements, vibrational, electronic and 57Fe-Mößbauer spectroscopy as well as DSC. The [Fe(i3tz)6](BF4)2 complex was re-investigated and shows an incomplete spin transition at Tc âˆ¼ 109 K, while the [Fe(i4tz)6](BF4)2 features a complete but rather gradual spin transition with T½ = 223 K. In the lack of suitable crystals of [Fe(intz)6](BF4)2 with n = 3 and 4, we synthesized crystals of [Ni(intz)6](BF4)2 with n = 3 and 4, determined their X-ray crystal structures, and proved them to be homeotypic with the respective Fe-complexes by X-ray powder diffraction. DSC measurements showed an endothermic peak for the [Fe(i3tz)6](BF4)2 around T = 260 K not corresponding to a spin transition and suggesting a structural phase transition at this temperature. A well-developed peak at Tp = 225 K matches the spin-transition temperature T½ = 223 K for [Fe(i4tz)6](BF4)2.

Cs2.91Na1.34Fe(3+)0.25[Fe3O(SO4)6(H2O)3]·5H2O, a member of the Maus's salt family.

The title compound, tricaesium sodium iron(III) µ3-oxido-hexa-µ2-sulfato-tris[aquairon(III)] pentahydrate, Cs2.91Na1.34Fe(3+)0.25[Fe3O(SO4)6(H2O)3]·5H2O, belongs to the family of Maus's salts, K5[Fe3O(SO4)6(H2O)3]·6H2O, which is based on the triaqua-µ3-oxido-hexa-µ-sulfato-triferrate(III) anion, [Fe3O(SO4)6(H2O)3](5-), with Fe in a characteristically distorted octahedral coordination environment, sharing a common corner via an oxide O atom. Cs in four different cation sites, Na in three different cation sites and five water molecules link the anions in three dimensions and set up a crystal structure in which those parts parallel to (001) and within 0.05 < z < 0.95 have a distinct trigonal pseudosymmetry, whereas the cation arrangement and bonding near z ∼ 0 generate a clear-cut noncentrosymmetric polar edifice with the monoclinic space group C2. The structure shows some cation disorder in the region near z ∼ 1/2 where one Na atom in octahedral coordination is partly substituted by Fe(3+), and a Cs atom is substituted by small amounts of Na on a separate nearby site. One Na atom, located on a twofold axis at z = 0 and tetrahedrally coordinated by four sulfate O atoms of two [Fe3O(SO4)6(H2O)3](5-) units, plays a key role in generating the noncentrosymmetric structure. Three of the seven different cation sites are on twofold axes (one Na(+) site and two Cs(+) sites), and all other atoms of the structure are in general positions.

Redetermination of tamarugite, NaAl(SO4)2·6H2O.

The crystal structure of tamarugite [sodium aluminium bis-(sulfate) hexa-hydrate] was redetermined from a single crystal from Mina Alcaparossa, near Cerritos Bayos, southwest of Calama, Chile. In contrast to the previous work [Robinson & Fang (1969 ▶). Am. Mineral. 54, 19-30], all non-H atoms were refined with anisotropic displacement parameters and H-atoms were located by difference Fourier methods and refined from X-ray diffraction data. The structure is built up from nearly regular [Al(H2O)6](3+) octa-hedra and infinite double-stranded chains [Na(SO4)2](3-) that extend parallel to [001]. The Na(+) cation has a strongly distorted octa-hedral coordination by sulfate O atoms [Na-O = 2.2709 (11) - 2.5117 (12) Å], of which five are furnished by the chain-building sulfate group S2O4 and one by the non-bridging sulfate group S1O4. The [Na(SO4)2](3-) chain features an unusual centrosymmetric group formed by two NaO6 octa-hedra and two S2O4 tetra-hedra sharing five adjacent edges, one between two NaO6 octa-hedra and two each between the resulting double octa-hedron and two S2O4 tetra-hedra. These groups are then linked into a double-stranded chain via corner-sharing between NaO6 octa-hedra and S2O4 tetra-hedra. The S1O4 group, attached to Na in the terminal position, completes the chains. The [Al(H2O)6](3+) octa-hedron (〈Al-O〉 = 1.885 (11) Å) donates 12 comparatively strong hydrogen bonds (O⋯O = 2.6665 (14) - 2.7971 (15) Å) to the sulfate O atoms of three neighbouring [Na(SO4)2](3-) chains, helping to connect them in three dimensions, but with a prevalence parallel to (010), the cleavage plane of the mineral. Compared with the previous work on tamarugite, the bond precision of Al-O bond lengths as an example improved from 0.024 to 0.001 Å.

Trilithium thio-arsenate octa-hydrate.

The title compound, Li3AsS4·8H2O, is built up from infinite cationic [Li3(H2O)8](3+) chains which extend along [001] and are cross-linked by isolated tetra-hedral AsS4 (3-) anions via O-H⋯S hydrogen bonds. Two Li and two As atoms lie on special positions with site symmetries -1 (1 × Li) and 2 (1 × Li and 2 × As). The [Li3(H2O)8](3+) chain contains four independent Li atoms of which two are in octa-hedral and two in tetra-hedral coordination by water O atoms. An outstanding feature of this chain is a linear group of three edge-sharing LiO6 octa-hedra to both ends of which two LiO4 tetra-hedra are attached by face-sharing. Such groups of composition Li5O16 are linked into branched chains by means of a further LiO4 tetra-hedron sharing vertices with four adjacent LiO6 octa-hedra. The Li-O bonds range from 1.876 (5) to 2.054 (6) Šfor the LiO4 tetra-hedra and from 2.026 (5) to 2.319 (5) Šfor the LiO6 octa-hedra. The two independent AsS4 (3-) anions have As-S bond lengths ranging from 2.1482 (6) to 2.1677 (6) Š[ = 2.161 (10) Å]. The eight independent water mol-ecules of the structure donate 16 relatively straight O-H⋯S hydrogen bonds to all S atoms of the AsS4 tetra-hedra [ = 3.295 (92) Å]. Seven water mol-ecules are in distorted tetra-hedral coordination by two Li and two S; one water mol-ecule has a flat pyramidal coordination by one Li and two S. At variance with related compounds like Schlippe's salt, Na3SbS4·9H2O, there are neither alkali-sulfur bonds nor O-H⋯O hydrogen bonds in the structure.

Sodium selenite penta-hydrate, Na2SeO3·5H2O.

In the crystal structure of Na2SeO3·5H2O [disodium selen-ate(IV) penta-hydrate], two Se, two selenite O atoms and one water O atom are located on a mirror plane, and one water O atom is located on a twofold rotation axis. The coordination of one Na(+) cation is distorted trigonal bipyramidal, formed by three equatorial H2O ligands and two axial selenite O atoms. The other Na(+) cation has an octa-hedral coordination by six water mol-ecules. The two independent SeO3 groups form almost undistorted trigonal pyramids, with Se-O bond lengths in the range 1.6856 (7)-1.7202 (10) Šand O-Se-O angles in the range 101.98 (3)-103.11 (5)°, and both are µ2-O:O-bonded to a pair of Na(+) cations. Hydrogen bonds involving all water molecules and selenite O atoms consolidate the crystal packing. Although anhydrous Na2SeO3 and Na2TeO3 are isotypic, the title compound is surprisingly not isotypic with Na2TeO3·5H2O. In the tellurite hydrate, all Na(+) cations have an octa-hedral coordination and the TeO3 groups are bonded to Na(+) only via one of their three O atoms.

Chlorido[1-(2-oxidophen-yl)ethyl-idene][tris-(3,5-dimethyl-pyrazol-1-yl)hydro-borato]iridium(III) chloro-form monosolvate.

In the title compound, [Ir(C15H22BN6)(C8H7O)Cl]·CHCl3, the Ir atom is formally trivalent and is coordinated in a slightly distorted octa-hedral geometry by three facial N atoms, one C atom, one O atom and one Cl atom. The Ir=Ccarbene bond is strong and short and exerts a notable effect on the trans-Ir-N bond, which is about 0.10 Šlonger than the two other Ir-N bonds. The chloro-form solvent mol-ecule is anchored via a weak C-H⋯Cl hydrogen bond to the Cl atom of the Ir complex mol-ecule. In the crystal, the constituents adopt a layer-like arrangement parallel to (010) and are held together by weak inter-molecular C-H⋯Cl hydrogen bonds, as well as weak Cl⋯Cl [3.498 (2) Å] and Cl⋯π [3.360 (4) Å] inter-actions. A weak intra-molecular C-H⋯O hydrogen bond is also observed.

(Butane-1,4-di-yl)(trimethyl-phosphane-κP)[tris-(3,5-dimethyl-pyrazol-1-yl-κN (2))hydro-borato]iridium(III).

In the mononuclear title iridium(III) complex, [Ir(C4H8)(C15H22BN6)(C3H9P)], which is based on the [tris-(3,5-dimethyl-pyrazol-1-yl)hydro-borato]iridium moiety, Ir[Tp(Me2)], the Ir(III) atom is coordinated by a chelating butane-1,4-diyl fragment and a trimethyl-phosphane ligand in a modestly distorted octa-hedral coordination environment formed by three facial N, two C and one P atom. The iridium-butane-1,4-diyl ring has an envelope conformation. This ring is disordered because alternately the second or the third C atom of the butane-1,4-diyl fragment function as an envelope flap atom (the occupancy ratio is 1:1). In the crystal, mol-ecules are organized into densely packed columns extending along [101]. Coherence between the mol-ecules is essentially based on van der Waals inter-actions.

Nonradiative deactivation of europium(III) luminescence as a detection scheme for moisture.

The nonradiative deactivation of the excited state of europium(III)-based phosphors via OH-vibrations in the presence of water allows the detection of moisture in nitrogen at concentration levels down to at least 25 ppm (0.09% RH).

4-({(Z)-5-[(Z)-3-Eth-oxy-4-hy-droxy-benzyl-idene]-3-methyl-4-oxo-1,3-thia-zolidin-2-yl-idene}amino)-benzoic acid dimethyl-formamide monosolvate.

The mol-ecular structure of the title compound, C20H18N2O5S·C3H7NO, represents an essentially planar 5-benzyl-idene-thia-zolidine moiety (r.m.s. deviation from planarity without ring substituents = 0.095 Å) to which the 4-amino-benzoic acid fragment is inclined at 76.23 (1)°. In the crystal, the benzoic acid mol-ecules are arranged in layers parallel to [001] which are built up from inversion dimers held together by head-to-tail phenol-carb-oxy O-H⋯O hydrogen bonds and head-to-tail π-π stacking inter-actions between the 5-benzyl-idene-thia-zolidine moieties (ring centroid distance = 3.579 Å). These layers are separated by the dimethyl-formamide solvent mol-ecules which are firmly anchored via a short O-H⋯O hydrogen bond [O⋯O = 2.5529 (10) Å] donated by the -COOH group.

(3ß,18ß,20ß)-N-Eth-oxy-carbonyl-methyl-3-nitrato-11-oxoolean-12-ene-29-carboxamide methanol monosolvate.

The title compound, C(34)H(52)N(2)O(7)·CH(4)O, is the methanol solvate of a difunctionalized derivative of the therapeutic agent 18ß-glycyrrhetinic acid, a penta-cyclic triterpene. The five six-membered rings of the glycyrrhetinic acid moiety show normal geometries, with four rings in chair conformations and the unsaturated ring in a half-chair conformation. This moiety is substituted by a nitrate ester group and an O-ethyl-glycine group. In the crystal, the nonsolvent mol-ecules are packed parallel to (010) in a herringbone fashion with the nitrato, ethyl-glycine and methanol-O atom being proximate. The methanol solvent mol-ecule is anchored via a donated O-H⋯O(ac-yl) and an accepted N-H⋯O hydrogen bond, giving rise to infinite zigzag chains of hydrogen bonds parallel to [100]. Two weak intermolecular C-H⋯O interactions to the methanol and to an acyl oxygen establish links along [100] and [010], respectively.

2-[(Diisopropyl-thio-phosphor-yl)amino]-pyridinium tetra-fluoro-borate.

The title compound, C(11)H(20)N(2)PS(+)·BF(4) (-), is a salt of 2-(diisopropyl-thio-phospho-ryl-amino)-pyridine, a chelating bidentate ligand that furnishes an S atom as a soft donor and a pyridine N atom as a hard atom for transition-metal complexation. The title salt crystallizes with two formula units in the asymmetric unit. The two independent cations are protonated at the pyridine N atoms and have the S atoms syn-oriented to them so as to form bent intra-molecular N-H⋯S hydrogen bonds, one of which one is bifurcated by involving also an N-H⋯F inter-action. The phospho-ryl-amino NH groups form near linear hydrogen bonds to proximal tetra-fluoro-borate anions. Five weak C-H⋯F and three weak C-H⋯S inter-actions link the constituents into a three-dimensional framework. As a result of the crystal packing, the two cations differ notably in conformation, as can be seen from the S-P-N-C torsion angles of -18.7 (1)° in the first and -35.1 (1)° in the second cation.

1-(2,2-Diphenyl-eth-yl)-1H-tetra-zole.

The crystal structure of the title compound, C(15)H(14)N(4), contains chains of coplanar tetra-zole rings with the chain direction along b. These are formed through weak hydrogen bonds, donated by the tetra-zole H atoms and by one of the H atoms of the methyl-ene group, and accepted by two neighbouring N atoms of the adjacent tetra-zole ring. The chains are connected to each other in a staircase-like manner via weak hydrogen bonds, donated from the second H atom of the methyl-ene group and accepted by the N atom next to the C atom in the tetra-zole ring. The resulting layers are parallel to the bc plane.

Novel tocopherol derivatives. Part 32: On the bromination of pyrano[3,2-f]chromenes related to γ-tocopherol.

While bromination of γ-tocopherol (2) with elemental bromine affords 5-bromo-γ-tocopherol quantitatively (3), the analogous reaction of its truncated model compound, 2,2,7,8-tetramethylchromanol (2a) is known to be accompanied by side reactions and to produce hitherto unknown byproducts. These compounds originate from pyrano[3,2-f]chromene (6), a byproduct in the synthesis of model compound 2a, which affords bromochromene 7 as the major product. The reaction mechanism was shown to proceed via chromene 8 and its 1,2-dibromo addition compound 9, which eliminates HBr in an E1 process to finally afford 7. Analytical data including crystal structures of both 6 and 7 are reported.

The herbicide triflusulfuron-meth-yl.

The mol-ecule of the title compound [systematic name: methyl 2-({[4-dimethyl-amino-6-(2,2,2-trifluoro-eth-oxy)-1,3,5-triazin-2-yl]carbamo-yl}sulfamo-yl)-3-methyl-benzoate], C(17)H(19)F(3)N(6)O(6)S, features a nearly planar (r.m.s. deviation = 0.098 Å) dimethyl-amino-triazinyl-urea group with a short intra-molecular N-H⋯N hydrogen bond to a triazine N atom. An intra-molecular dipole-dipole inter-action between the sulfamide and carboxyl-ate groups, with O(s)⋯C(c) = 2.800 (1) Šand N(s)⋯O(c) = 2.835 (1) Å, controls the orientation of the methyl-benzoate group and the shape of the mol-ecule. The crystal structure is stabilized by inter-molecular N-H⋯N hydrogen bonding, C-H⋯X (X = N,O) inter-actions and arene π-π stacking.