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The title compounds have been synthesized by adding hydrogen peroxide to an aqueous solution of A2[Pt(CN)4] (A = K, Rb, Cs). They grow as yellow needles after concentrating and cooling to 4 °C. The structures were elucidated from single crystal analysis. The isostructural compounds crystallize monoclinically, in space group C2/c with Z = 4. K2Pt(CN)4·H2O2: a = 13.3751(7), b = 11.2713(6), c = 6.5461(3) Å, ß = 105.432(1)?, V = 951.3(3) Å3. Rb2Pt(CN)4·H2O2: a = 13.6103(2), b = 11.6759(1), c = 6.5683(7) Å, ß = 106.588(2)0, V = 1000.3(2) Å3. Cs2Pt(CN)4·H2O2: a = 13.9569(2), b = 12.2023(2), c = 6.5857(9) Å, ß = 107.590(3)0, V = 1069.1(2) Å3. As a remarkable feature, the hydrogen bonds O-H···N vary significantly with the cation size: in the Cs compound the O-H bonds are weakest, and the N· · ·H interactions are strongest. All three compounds were characterized by differential thermal analysis, thermogravimetry and infrared spectroscopy.

In this paper we report on the potential dependent electrocrystallization of [Ag(4,4′‐dimethyl‐2,2′‐bipyridine)2(NO3)2] (1) and Ag(4,4′‐dimethyl‐2,2′‐bipyridine)(NO3)2(2) from the same electrolytic bath. Thus it has been shown for the first time that the coordination number of silver ion to ligands can be tuned by the electrocrystallization potential. The single crystal structure analysis [1: C2/c, a = 18.6308(15), b = 14.5708(12), c = 11.5867(10) Å, β = 126.5910(10)°, Z = 4, R = 3.9 %] [2: P21/c, a = 8.5865(11) b = 11.0157(14) c = 16.4554(10) Å, β = 111.102(10), Z = 4 , R = 3.5 %] show divalent silver to be in an approximately square planar surrounding. Both complexes are paramagnetic following Curie's law with magnetic moments of 1.86 μBand 1.72 μBrespectively.

A new potassium molybdenum oxide, K6Mo10O33, was synthesized by solid state reaction from the appropriate quantities of pre-dried MoO3and K2MoO4, fired at around 650 °C for 2 d. The structure has been solved by using single crystal X-ray diffraction. The compound adopts the space group P1, with the lattice constants a = 7.7100(5), b = 11.9659(8), c = 17.1321(12) A° , α = 86.42 (10), β = 77.18(10), γ = 74.14(10)°. The structure is built up of infinite chains of edge-sharing MoO6octahedra and groups of four MoO6octahedra forming Mo4O17units. These sub-units are connected together by common vertices.

Chloral-derived ß-carbolines, which are structurally similar to the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 5), are discussed to contribute to neuronal cell death in idiopathic Parkinson’s disease. The cytotoxicity of 1-trichloromethyl- 1,2,3,4-tetrahydro-ß-carboline (TaClo, 4) to neuronal-like clonal pheochromocytoma PC12 cells was examined by the determination of lactate dehydrogenase (LDH) release. After incubation for 48 h, 4 showed a strong dose-dependent cytotoxic activity towards PC12 cells with an ED50value of 230 µ?. In PC12 cells reductive dehalogenation of 4 was observed giving rise to the formation of 1-dichloromethyl-1,2,3,4-tetrahydro-ß-carboline (6) as a main TaClo metabolite exhibiting a cytotoxic potential comparable to that of TaClo. An X-ray structure analysis, performed for the trifluoroacetyl derivative of 6, revealed the N-substituent of such a highly chlorinated agent to be dramatically pushed out of the ß-carboline ring ‘plane’ due to the high steric demand of the huge dichloromethyl group at C(1).

Ag2Te2O7, a Novel Silver Tellurate of Weberite Structure Type

New Silver(I) Oxotellurates(IV/VI)

Disilver Oxotellurate(VI), Ag2TeO4

The isotypical crystal structures of the mixed valent trihalides PtCl3and PtBr3were redetermined by single crystal methods (space group R3¯; trigonal setting; PtCl3: a= 21.213Å, c= 8.600Å, c/a= 0.4054; Z = 36; 1719 hkl; R = 0.035; PtBr3: a= 22.318Å, c= 9.034Å; c/a= 0.4048; Z = 36; 1606 hkl; R = 0.027). A cubic closest packing of X—anions forms the basis of an optimized arrangement of cuboctahedrally [Pt6X12] cluster molecules with PtIIand enantiomers of helical chains of edge‐condensed [PtX2X4/2] octahedra with PtIVin cis‐Δ‐ and cis‐Λ‐configuration, respectively. The bond lengths vary with the function of the X—ligands (d¯(PtII—X) = 2.315 and 2.445Å; d¯(PtII—PtII) = 3.336 and 3.492Å; d(PtIV—X) = 2.286 — 2.417Å and 2.437 — 2.563Å). The PtIIatoms are shifted outwards the X12cuboctahedra by 0.045Å and 0.024Å, respectively. The symmetry governed Periodic Nodal Surface, PNS, perfectly separates the regions of different valencies. Quantum chemical calculations exclude the possible additional interactions between PtIIand one of the exo‐ligands of PtIV.

Der Einkristallstrukturanalyse bei —173 °C zufolge kristallisiert α‐NaSO3CF3triklin in der Raumgruppe P1¯ mit den Gitterparametern a = 9, 6592(11), b = 11, 1752(12), c = 11, 2768(12) Å, α = 101, 878(2)°, β = 105, 292(2)°, γ = 110, 501(3)°, bei Raumtemperatur (22 °C) ergeben sich die Werte a = 9, 81304(18), b = 11, 3179(2), c = 11, 5910(2) Å, α = 102, 066(2)°, β = 105, 634(2)°, γ = 110, 205(2)° (Synchrotron‐Pulverdaten). In der Kristallstruktur liegen Doppelschichten aus Triflatanionen vor, in denen die unpolaren CF3‐Gruppen einander zugewandt sind. Die Natriumatome besetzen fünf verschiedene kristallographische Lagen. α‐NaSO3CF3ist ein fester Elektrolyt, dessen spezifische Leitfähigkeit im Bereich von 1, 75·10—8Ω—1cm—1bei 140 °C bis 8, 78·10—6Ω—1cm—1bei 237 °C liegt.

The West African plant Ancistrocladus barteri (Ancistrocladaceae) was investigated chemically for the first time. Besides the known naphthylisoquinoline alkaloids N-methyldioncophylline A and 7-epi-N-methyldioncophylline A (i.e. its atropo-diastereomer), a new naphthalene-free alkaloid, belonging to the ‘Dioncophyllaceae type’, was isolated. Its structure was elucidated by spectroscopic and degradative methods and confirmed by total synthesis. The new compound, named N-methylphylline, is exactly the isoquinoline “half” of both, N-methyldioncophylline A and its atropisomer. Furthermore, the related tetrahydroisoquinoline O,N-dimethylphylline, an intermediate in the chemical synthesis of N-methylphylline, was detected as a new natural product in crude extracts of A. barteri.

The crystal structure of Pt6Cl12(β‐PtCl2) was redetermined ($R \bar 3 m$ah= 13.126Å, ch= 8.666Å, Z = 3; arh= 8.110Å, α = 108.04°; 367 hkl, R = 0.032). As has been shown earlier, the structure is in principle a hierarchical variant of the cubic structure type of tungsten (bcc), which atoms are replaced by the hexameric Pt6Cl12molecules. Due to the 60° rotation of the cuboctahedral clusters about one of the trigonal axes, the symmetry is reduced from $Im \bar 3 m$to $R \bar 3 m$($I \bar 3 m$). The molecule Pt6Cl12shows the (trigonally elongated) structure of the classic M6X12cluster compounds with (distorted) square‐planar PtCl4fragments, however without metal‐metal bonds. The Pt atoms are shifted outside the Cl12cuboctahedron by Δ = +0.046Å ($\bar {\rm d}$(Pt—Cl) = 2.315Å; $\bar {\rm d}$(Pt—Pt) = 3.339Å). The scalar relativistic DFT calculations results in the full $m \bar 3 m$symmetry for the optimized structure of the isolated molecule with d(Pt—Cl) = 2.381Å, d(Pt—Pt) = 3.468Å and Δ = +0.072Å. The electron distribution of the Pt‐Pt antibonding HOMO exhibits an outwards‐directed asymmetry perpendicular to the PtCl4fragments, that plays the decisive role for the cluster packing in the crystal. A comparative study of the Electron Localization Function with the hypothetical trans‐(Nb2Zr4)Cl12molecule shows the distinct differences between Pt6Cl12and clusters with metal‐metal bonding. Due to the characteristic electronic structure, the crystal structure of Pt6Cl12in space group $R \bar 3 m$is an optimal one, which results from comparison with rhombohedral Zr6I12and a cubic bcc arrangement.

Rb2Co2O3wurde über die Azid/Nitrat‐Route dargestellt. Gemenge der Edukte Co3O4, RbN3und RbNO3im molaren Verhältnis von 6:17:1 wurden unter besonderer Temperaturführung in Silbertiegeln bis 450 °C aufgeheitzt und 50 h bei dieser Temperatur gehalten. Durch nachträgliches Tempern des erhaltenen Pulvers (450 °C, 500 h) in Silbertiegeln, die unter getrocknetem Ar in Glasampullen eingeschmolzen waren, wurden Einkristalle erhalten. Nach der Röntgenstrukturanalyse (Pnma, Z = 8, 11, 729(2), 6, 058 (1), 8, 004(1) Å) ist Cobalt trigonal planar von Sauerstoff atomen koordiniert. Die CoO3‐Einheiten sind über alle Ecken verknüpft und bilden ein neuartiges ∞2Co2O3‐Polyanion.

The atropo-enantioselective total synthesis of the axially chiral bicoumarin (+)-isokotanin A (1) is described. Key steps were the formation of a configurationally stable seven-membered biaryl lactone and its kinetic resolution by atroposelective ring cleavage. The previous assignment of the absolute configuration of (+)-isokotanin A (1) (and its synthetic precursors) was confirmed by quantum chemical CD calculations. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

3-Bromo-1-methyl-1,2,5,6-tetrahydropyridine(N−B)borane (7) was prepared from 3-bromopyridine by conversion to 3-bromo-1-methylpyridinium iodide, hydrogenation of the latter with sodium tetrahydroborate and treatment of the resulting 3-bromo-1-methyl-1,2,5,6-tetrahydropyridine (6) with borane−dimethyl sulfide. Whereas no trapping product of the possible intermediate 1-methyl-1-azacyclohexa-2,3-diene (4) could be observed on treatment of 6 with potassium tert-butoxide in the presence of furan, the subjection of 7 to the same conditions produced the hexahydroepoxyquinoline derivatives 8a−c. Treatment of 7, dissolved in styrene, with sodium bis(trimethylsilyl)amide furnished the hexahydrocyclobutapyridine derivatives 9a−c. The six-membered cycloallene 1-methyl-1-azacyclohexa-2,3-diene(N−B)borane (10) must be regarded as the key intermediate en route to 8 and 9.

The first total synthesis of the antimalarial alkaloid dioncophylline B (2) from Triphyophyllum peltatum(Dioncophyllaceae), and thus the first preparation of a 7,6′-coupled naphthylisoquinoline, is described. Key steps within this synthesis are the ortho-functionalization of the MOM-protected naphthalene and isoquinoline moieties 14and 7by directed ortho-metalation, with subsequent stannylation of the naphthalene part and bromination of the isoquinoline portion, and the regioselective intermolecular Stille coupling reaction of these building blocks. The presented synthesis opens the way for the preparation of further 7-coupled compounds of this class of alkaloids.

The absolute configuration of (+)-isoshinanolone, a wide-spread acetogenic metabolite from higher plants, has been determined by X-ray structure analysis of its new dibromide; accordingly, this natural tetralone is 3R,4R-configured, in agreement with previous degradative results. In addition, a first chiroptical on-line stereoanalysis for isoshinanolones is presented, i.a. by HPLC on a chiral phase coupled to CD spectroscopy, giving pure CD spectra of all of the four stereoisomers of isoshinanolone directly from stereoisomeric mixtures.

[Si(N(CH3)2)2(NLiC(CH3)3)2]2results from the reaction of silicon tetrachloride with excess terf-butylamine, followed by halogen substitution with LiN(CH3)2, and treatment with n-butyllithium in hexane. The title compound, found to be dimeric in the solid state, was characterised by single crystal X-ray diffraction (triclinic, Pi , a = 10.208(2), b = 12.140(2), c = 15.658(3) Å , a = 79.02(3), ß = 82.80(3), γ = 67.19(3)°, Z = 2, C24H60Li4N8Si2), and by solid state and solution NMR-spectroscopy and mass spectrometry.

Several N-alkanoyl derivatives (4-9 and 13-16) of the potent mitochondrial complex I inhibitor TaClo (1-trichlorom ethyl-1,2,3,4-tetrahydro-ß-carboline, 2) have been synthesized in order to elucidate the role of hydrophobic portion in the inhibitory action. Using rat brain homogenates or submitochondrial particles, the inhibitory effects of these compounds towards NADH-ubiquinone reductase (complex I) activity indeed appeared to correlate quite strongly with their lipophilic character. An X-ray structure analysis, exemplarily performed for N-acetyl-TaClo (4), revealed the N-substituent of such chlorinated agents to be dramatically pushed out of the ß-carboline ring ‘plane’ due to the high steric demand of the huge trichloromethyl group at C-1.

The liquid odorants (R)-6and (R)-7and their corresponding crystalline model substances (R)-8and (R)-13were synthesized. Based on the X-ray analyses of (R)-8and (R)-13, geometries for (R)-6and (R)-7were determined using semiempirical calculations.

The mammalian alkaloids tryptoline (1) and eleagnine (2) as well as the highly halogenated (X=F, Cl, Br) tetrahydro-β-carbolines (THβCs) 3–5, structurally similar to the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 6), were found to have a common feature of inducing a severe impairment of the nigrostriatal dopamine metabolism and inhibiting complex I of the mitochondrial respiratory chain highly selectively. Within the series of compounds tested, 1-tribromomethyl-1,2,3,4-tetrahydro-β-carboline (‘TaBro', 5), which was prepared in high yields from the biogenic amine tryptamine (‘Ta', 7) and the unnatural aldehyde bromal (‘Bro', 8) by a Pictet–Spengler cyclization reaction, turned out to be the most potent toxin in vitro and in vivo. As demonstrated by voltammetric measurements on rats, for all the THβCs 1–5investigated, intranigral application of a single dose of 10μg resulted in a significant reduction of the dopaminergic activity in the striatum, with the strongest effect being observed for TaBro (5). Using rat brain homogenates, again 5(IC50=200μM) as well as its dehydrohalogenation product 11(IC50=150μM) exhibited the most pronounced inhibitory potential on mitochondrial respiration. The halogen-free THβCs 1and 2as well as the MPTP metabolite 1-methyl-4-phenylpyridinium ion (MPP+), by contrast, showed only a moderate inhibition at concentrations in the millimolar range (e.g. for MPP+: IC50=3.5mM). For an elucidation of the role of hydrophobic portion in the inhibitory action against complex I activity, several N-acyl derivatives (15–21) of 5were synthesized and tested. An X-ray diffraction study on the 3-dimensional structure of trifluoroacetylated highly halogenated THβCs (12–14) revealed the tetrahydropyrido part to adopt a nearly planarized half-chair conformation. Because of the steric demand of the trihalogenmethyl moiety (CF3

2-Alkyl-1-methylquinazolinium hexafluorophosphates 9 are deprotonated by sodium or potassium hydride to afford solutions of 2-alkylidenedihydroquinazolines 10, which were investigated by NMR spectroscopy. Trapping with methanesulfonyl azide (5a) of 10 in situ or subsequent treatment with trifluoromethanesulfonyl azide (5b) gives mixtures of colourless (15) and intensely yellow N-sulfonylimino-1,4-benzodiazepines 16 along with products due to cleavage of the exocyclic double bond of 10, viz. 11 and 13. The ethylidene compound 10b yields the bicyclic products 18 and 19, apparently by complex sequences of reactions that are triggered by removal of the acidic proton at C-2 of 16b and 16f. The structures of the products are based on spectroscopic evidence and X-ray diffraction analyses performed on 15b, 16d, 16e, and 19.

2-Alkyl-1-methylquinolinium hexafluorophosphates 1 are deprotonated by sodium or potassium hydride to afford solutions of 2-alkylidenedihydroquinolines 2, which are investigated by NMR spectroscopy. 1,3-Dipolar cycloaddition of phenyl azide to 2 yields the spirocyclic products 10. While, at 80-110 °C, the [3 + 2] cycloaddition that afforded (u)-10f is reversible and accompanied by epimerisation to give (l)-10f, thermolysis of the dimethyl compounds 10b and d affords the ring-expanded products 14b and d, respectively, in good yields along with molecular nitrogen. Irradiation of 10d with light of λ > 320 nm results in the formation of similar amounts of 14d and [3 + 2] cycloreversion products, viz. 2-diazopropane (5b) and the N-phenylimine 15d. - Trapping of 2 by methanesulphonyl azide (18a) gives mixtures of the products of ring expansion (21b, d-f, 10-50 %) and [3 + 2] cycloreversion (22a, d, 10-80 %) of the apparently very labile intermediate spirocyclic cycloadducts 19. The ratio of 21 vs. 22 is significantly improved when 18a is replaced by trifluoromethanesulphonyl azide (18b), which affords the iminodihydrobenzazepines 21i-k in 50-75 % yield. The structures of the products are based on NMR evidence and X-ray diffraction analyses performed with 21b, d, and (ax,E)-21e.

Both title compounds were obtained in stereochemically pure form by refluxing 5,5-dim ethyl-1 ,3-thiazolidine-2,4-dicarboxylic acid (3) with methanolic HCl, followed by a separation of the two diastereomers 4a and 4b on silica gel. The X-ray structure analyses of these stereoisomers confirm the relative configuration to be cis for 4a and trans for 4b with respect to the two carboxymethyl substituents at C(2) and C(4). For both molecules, an envelopetype conformation of the thiazolidine ring was found with C(5)-S(1)-C(2)-N(3) being located in a plane showing a small ring torsion angle of -11.2° and -3.1° for the cis- and the rrafts-epimer, respectively. The trans-configured compound 4b adopts a nearly ideal envelope conformation with C(4) being the flap atom, while the cis-isomer 4a. apparently because of steric interactions of the C(2) and C(4) substituents, shows a twisted envelope conformation.

The molecular structure of the title compound 2-hexanoyl-1-tribromomethyl-1,2,3,4-tetra-hydro-β-carboline (3), a potent inhibitor of complex I of the mammalian mitochondrial respiratory chain, has been studied by single-crystal X-ray diffraction analysis. In the crystal, two heterochiral molecules of 3 (i.e., one R- and one S-configured molecule each) were found to be connected with one other in pairs via two intermolecular hydrogen bonds [O(215) ··· H(212)′ and O(215)′ ··· H(212)] to form an overall achiral ‘dimeric’ subunit

Axially chiral biaryls with diastereomeric ratiosof up to 95:5 are synthesized by highly atropo‐selective cleavage of configurationally unstable, lactone‐bridged biaryls with chiral metalated 1‐arylethlamines (see scheme). This methodology permits optional preparation of each of the two atropisomers from the same lactone precursor just by the use of the appropiate amine reagent or its enantiomer for the ring‐opening (atropo‐divergence), and offers the possibility of recycling the minor isomer back to the lactone. The chiral 1‐arylethyl(amine) group can subsequently split off without any loss of stereoinformation at the axis.

The deuterium-labelled 2,4,6,8-substituted barbaralanes [D5]-1a and b, and the two model barbaralanes 15 und 19 for the estimation of ¹³C chemical shifts in the slow-exchange limit are synthesised from bicyclo[3.3.1]nona-3,7-diene-2,6-dione (5). – The extension of Saunders' isotopic perturbation method bridges the gap between the limiting cases "perturbation of shift equivalence in delocalised systems" and "perturbation of degeneracy" by considering the simultaneous presence of delocalised species of higher symmetry and skewed equilibria between localised molecules that are degenerate in the absence of the isotopic perturbation. An equation (Equation 7) is derived for such multi-component systems which describes the temperature dependence of the relative isotopic splittings in ¹³C spectra with three parameters, viz. the isotopic perturbation parameters ΔH^P and ΔS^P of the skewed equilibria and the enthalpy difference ΔH⁰ between the delocalised and localised species. – Relative isotopic splittings Δδ^P/Δδ are calculated from estimated chemical shifts in the slow-exchange limit (Δδ) and isotopic splittings (Δδ^P) of signals in variable-temperature 151-MHz ¹³C NMR spectra recorded for solutions of [D5]-1a and b in [D8]toluene and N,N'-dimethylpropylene urea. The results obtained from [D5]-1a in both solvents and from [D5]-1b in the former are compatible with either a skewed equilibrium between localised valence tautomers alone or the simultaneous presence of localised and small amounts of delocalised valence tautomers. In striking contrast, the small isotopic splittings themselves and their small temperature dependence, observed for solutions of [D5]-1b in N,N'-dimethylpropylene urea, demonstrate that one half of the solvated compound exists in the delocalised state [D5]-1b*, which is more stable by 2 kJ mol^–1 than the equilibrating localised species [D5]-1b &rlhar2; [D5]-1b'.

Oxidation with barium manganate of the enol of tetraacetylethane (10) affords tetraacetylethylene (7a) in good yield. Treatment of the 1,3-diketones 15a and b with iodosobenzene in the presence of boron trifluoride does not result in oxidative coupling yielding 10 and diacetyldibenzoylethane 17, respectively, as has been reported by Moriarty et al. Instead the known difluoroborylenolates 16 are formed. Oxidative coupling of the sodium enolate of 15b with iodine affords the meso-tetraketone meso-17 and diacetyldibenzoylethylene (E)-7b besides small amounts of rac-17 and the bisenol 19. In the presence of 1,4-diazabicyclo[2.2.2]octane, meso-17 and 19 tautomerise yielding identical equilibrium mixtures of meso-17, rac-17, and 19 (26:29:45). Dehydrogenation with 5,6-dichloro-2,3-dicyanobenzoquinone of meso-17 yields (E)-7b and an isomer (77:23) which was assigned structure (Z)-7b on the basis of spectroscopic evidence. – Tetraacetylethylene (7a) reacts with 1,2-dimethylenecyclohexane to afford two different [4+2]cycloadducts, viz. the spirocyclic dihydropyran 25 (30 %) and the tetraacetyloctalin 27. Whereas the latter is stable, the former isomerises to the latter on heating. Formation of both [4+2]cycloadducts and the isomerisation 25 → 27 are interpreted by invoking the zwitterion 26 as common intermediate. Monoolefines that cannot generate stable carbenium ions don’t give [4+2]cycloadducts with 7a. In contrast, α-methylstyrene yields the oxa Diels–Alder product 30. The structures of (E)-7b, 19, 25, and 27 are established by X-ray diffraction analyses.

Configurationally unstable lactone-bridged biaryls 4 are cleaved atropo-diastereoselectively using chiral menthol-derived alkali metal alkoxides, to give axially chiral biaryl esters of type 5 in high yields and excellent diastereomeric ratios of up to > 99:1. The method permits the optional preparation of each of the two atropisomers from the same lactone precursor (“atropo-divergence”), simply according to the choice of the appropiate mentholate or its enantiomer as the O-nucleophile – or by the use of the mentholate in solution or in suspension. Undesired minor atropisomers of 5 possibly formed (if at all) can be recycled (“axially chiral economy”) by cyclization back to the lactone 4. For the preparation of larger amounts of enantiopure biaryl alcohols 9, an efficient reaction sequence was developed: alcoholysis of 4 → in situ reduction → crystallization. The synthetic value of these alcoholysis reactions for asymmetric biaryl synthesis is illustrated by the transformation of 5 into a broad series of enantiopure biaryls of type 6 with various functional groups ortho to the axis.

Diphenylbicyclo[3.3.1]nonane-2,6-dione rac-3 is resolved in 57 % overall yield by chromatographic separation of the diastereomeric (R)-N-(1-phenylethyl)carbamates 9 which are obtained from (R)-(1-phenylethyl) isocyanate (8) and the 6-hydroxydiphenylbicyclo[3.3.1]nonan-2-ones endo- and exo-4. The enantiomers (1R)- (e.r. = 98:2) and (1S)-3 (e.r. = 97:3) are regenerated from 9 by reduction with lithium aluminium hydride followed by Swern oxidation of the resulting diols 5. The title compound (1S)-1 is synthesised in three steps from (1S)-3 in improved yield on the route that had led to rac-1. The absolute configurations are established by X-ray diffraction analyses of the carbamates endo-(1R)-9 and exo-(1S)-9. X-ray diffraction analyses were also performed of the camphanoate (1R)-7, the intermediates rac-endo-4 and (1S)-3, and the title compound (1S)-1. Hydroxy ketone rac-endo-4 adopts similar conformations in the solid state and in solution as shown by a comparison of vicinal ¹H,¹H coupling constants from proton spectra with those calculated from torsional angles in the crystal. The molecular structures of (1S)-1 and (1S)-3 closely resemble those of the corresponding racemates investigated previously. These results show (i) that intermolecular interactions in the solid state are of minor importance and (ii) that the unusually long C2–C8 distance of (1S)-1 and rac-1 (168 pm) is a molecular but not an averaged property due to a non-degenerate Cope rearrangement in the crystal. CD spectra are reported for (1R)- and (1S)-3, the unsaturated dicarbonitrile (1S)-13, and (1S)-1. The CD spectrum of (1S)-1 exhibits a weak positive band at 459 nm where rac-1 shows a temperature-dependent absorption which has been assigned to the higher, vibronic state represented by rac-1*. The intensity of the weak CD band depends on the temperature and the solvents in the same way as the UV/Vis absorption of rac-1. This supports the conclusion that both bands originate from the same source, viz. the transition state 1* of the degenerate Cope rearrangement 1 &rlarr2; 1'.

Solutions of chloranil (CA) in toluene or benzene have been irradiated in the presence of the C7H8 valence isomers homobenzvalene (HB), norbornadiene (N), and quadricyclane (Q). In the case of HB, the adducts 3–6 were obtained, all of them having a rearranged structure. By a separate irradiation it was shown that 4 is a consecutive product of 3. The structure of 4 was established by X-ray diffraction analysis. These reactions are most probably initiated by an electron transfer (ET) from HB to ³CA, continue by bond formation between the radical ions to give the zwitterion 14, which undergoes Wagner–Meerwein rearrangements, and are completed by ring-closure between the charged centres of the resulting zwitterions. The oxidation potential of N is not larger than that of HB and the products 8–10 may well be formed through an ET to ³CA. However, the pathway leading to product 3 most probably involves diradical intermediates. This should also be the case for the adducts 11 and 12, which were produced upon irradiation of methyl phenylglyoxylate (PG) in the presence of N. In the case of Q, an ET to ³CA is again highly likely, followed by a combination of the radical ions to generate the zwitterion 29, which eventually collapses to produce the oxetane 8 as the sole identifiable product. The photoreactions of CA with N and Q proceeded much less efficiently in acetonitrile solution.

Orange crystals of Rb4[Ge9][en] are obtained after the exchange reaction of a solution of ‘NaGe2.25' (precursor) in ethylenediamine (en) with solid RbI at 363 K, followed by slow cooling. The compound is very sensitive to oxidation and hydrolysis. The thermal decomposition in dynamic vacuum starts at 350 K with the complete loss of enfollowed by the sublimation of Rb in four steps (Rb8Ge25, Rb8Ge44, RbxGe136with x ≤ 16, Ge). The Raman spectrum shows the characteristic bands of the [Ge9]4–anion (151, 163, 185 and 222 cm–1). Rb4[Ge9][en] crystallizes in a new structure type (space group P21/m; a = 15.353 Å, b = 16.434 Å, c = 15.539 Å, β = 113.75°; Z = 6; Pearson code mP198‐40), which can be described as a hierarchical derivative of the structures of Al4YbMo2and CrB4(initiators) formed by partial atom‐to‐aggregate replacement: B4[□][Cr] ≙ Al4[Yb][Mo]2≙ Rb4[Ge9][en]1–2. Three crystallographic independent [Ge9]4–clusters with different orientations are embedded in a 4‐connected 465net formed by the Rb atoms, a network of condensed tetraasteranes. The clusters are distorted monocapped tetragonal antiprisms with D1(Ge–Ge) = 2.57 Å (16 Ç ) and D2(Ge–Ge) = 2.84 Å (4 Ç ). The atoms of clusters with D1and D2lie at the surface of a rotational ellipsoid (a = b = 2.136 Å, c = 2.431 Å). The enmolecules are located in open channels along [1¯ 0 1]. The coordinations [Ge9] Rb12/4and Rb [Ge9]4/12en2/8show that the first step of solvation do not separate the cations from the cluster anions.

The crystal structures of pyridinium-di-trifluoroacethyl-methylide and the trichloro analog (2 a and2 b) have been determined by means of X-ray structure analyses. The synthesis of the monohalogenoacetyl derivatives4 a and4 b from the hydrobromides3 a and3 b is described.

4-Benzoyl-5-phenyl-furan-2,3-dione (1) reacts with various phenylhydrazones2 at 60–80°C to the pyrazole carboxylic acid3 a, which then can be decarboxylated to 4-benzoyl-1,5-diphenyl-pyrazole (5).1 and phenylhydrazine combine again yielding3 a as the main product and the isomeric pyridazinone6 as by-product. At higher temperatures (120–140°C) the reaction of1 with2 a leads to the formation of dibenzoyl acetic acid hydrazide derivatives8.

4-Benzoyl-5-phenylthiophene-2,3-dione (1) reacts witho-phenylendiamine to give the quinoxaline derivative2 which cyclizes either to the furo[2,3-b]quinoxaline4 or to the thieno[2,3-b]quinoxaline5 depending on the reaction conditions. On the other hand, the pyrrol-2,3-diones6 ando-phenylendiamine combine yielding the pyrrolidino[2,3-b][1,5]benzodiazepine derivatives7. The structures of all compounds were confirmed by IR and13C NMR spectroscopic measurements based on X-ray structure determinations of4/5 (mixed crystal) as well as7 b.4/5 crystallize triclinically in the space group P1 (Nr. 2) with two molecules per cell, while7 b crystallizes monoclinically in space group P21/a (Nr. 14) with four molecules7 b and four moleculesDMSO per cell. The reaction pathways leading to the compounds2,4,5, and7 are briefly discussed.

The title compound 2c, a potentially useful synthetic intermediate in stereoselective biaryl synthesis, has been prepared from the oxolactone 1c, by treatment with Lawesson′s reagent. An X-ray structure analysis reveals its strongly helically distorted structure, the overall molecular distortion even slightly exceeding that of the corresponding oxo compound 1c.

Treatment of the bridged oxepine (±)-1 with a large excess of powdered sodium methoxide in Et2O or with triphenylphosphonium methylide leads to the functionalized hydroazulenes (±)-2 (69%) and (±)-3 (81%). Regioselective and stereoselective cyclopropanation of (±)-2 leads to the dibromocyclopropane derivative (±)-4. Epoxidation gives the epoxides (±)-5 and (±)-6. The resolution of the hydro-azulenone (±)-2 is achieved by fractional crystallization of the quinine salt (–)-8 of the corresponding mono acid (±)-7. The absolute configuration of (+)-7 is established by X-ray analysis of the quinine salt (–)-8.