Structure and absolute configuration of the fungal ansabenzoquinone rhizopogone.

The main pigment of the basidiomycete Rhizopogon pumilionus is the [13]paracyclophane derivative rhizopogone (1). The structures of 1 and the accompanying 2-acetoxyrhizopogone (5) were determined by spectroscopic studies, including 1D and 2D NMR measurements. The absolute configuration of 1 was assigned by comparison of its CD spectrum with that of secotridentoquinone (4). The structures of 1 and tridentoquinone (3) suggest a common biosynthesis originating from 2-geranylgeranyl-6-hydroxy-1,4-benzoquinone (9). This supports the close taxonomic relationship of the genera Rhizopogon and Suillus (Boletales).

Anthracene carboxyimides and their dimers.

Soluble anthracenedicarboxyimides have been prepared and undergo a photodimerisation of the anthracene skeleton, which is important for their application as antitumour agents, such as azonafides. Reaction under strongly alkaline conditions causes C-C coupling to form soluble dimeric fluorescent dyes with bathochromic absorption and fluorescence in the NIR region. These dyes are of special interest because of their absorption at longer wavelengths.

Electrophilicity of 5-benzylidene-1,3-dimethylbarbituric and -thiobarbituric acids.

The kinetics of reactions of acceptor-stabilized carbanions 2a-m with benzylidenebarbituric and -thiobarbituric acids 1a-e has been determined in a dimethyl sulfoxide solution at 20 degrees C. Second-order rate constants were employed to determine the electrophilicity parameters E of the benzylidenebarbituric and -thiobarbituric acids 1a-e according to the correlation equation log k(20 degrees C) = s(N + E). With E parameters in the range of -10.4 to -13.9, the electrophilicities of 1a-e are comparable to those of analogously substituted benzylidenemalononitriles.

N-nitroso- and N-nitraminotetrazoles.

N-Nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) were synthesized from the corresponding aminotetrazoles (3a-c) either by the direct nitration with acetic anhydride/HNO3 or by dehydration of the corresponding nitrates (4a-c) with concentrated sulfuric acid. The conversion of the N-nitrosoaminotetrazoles (5a,c) with peroxytrifluoroacetic acid (CF3CO3H) yielded the corresponding nitramines in high yield (6a (82%), 6c (80%)). The N-nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) have been fully characterized by vibrational (IR, Raman) and multinuclear NMR spectroscopy (14N/15N, 1H, 13C), mass spectrometry, and elemental analysis. A detailed discussion of the 15N chemical shifts and 1H-15N coupling constants is given. The molecular structures in the solid state were determined by single-crystal X-ray diffraction (3a,c; 5a,c; 6a-c) and a detailed discussion of the molecular structures will be presented. Furthermore, the structure and bonding as well as N,N rotational barriers are discussed on the basis of theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). In the case of two N-nitraminotetrazoles (6a,c) the physicochemical properties (e.g., D, P, delta(f)H degrees) were evaluated. The heat of formation was calculated to be positive for 6a and 6c (+2.8 and +85.2 kcal mol(-1), respectively) and the calculated detonation velocity with 5988 (6a) and 7181 (6c) m s(-1) reaches values of TNT and nitroglycerin.

The dianion of 5-cyanoiminotetrazoline: C2N62-.

Several salts (alkali, Pd(NH(3))(3), and (i)PrNH(2)) of 5-cyanoiminotetrazoline (C(2)N(6)(2-), 5-cyanoiminotetrazolinediide, CIT) were investigated. A full characterization by means of X-ray, Raman, NMR techniques, mass spectrometry, and elemental analysis is presented for the (i)()PrNH(2) (4), Cs (5), and Pd(NH(3))(3) (6) salts. The CIT dianion represents a nitrogen-rich binary CN dianion, and 5 forms monoclinic crystals (a = 7.345(2) Angstroms, b = 9.505(2) Angstroms, c = 10.198(2) Angstroms, beta = 92.12(3) degrees, space group P2(1)/n, Z = 4). DSC and in situ temperature-dependent X-ray diffraction measurements of the cesium salt 5 revealed an astonishing thermal stability accompanied by a reversible phase transition from the low-temperature alpha modification to the metastable beta modification at 253 degrees C. Above the melting point (334 degrees C), the cesium salt decomposes yielding cesium azide and cesium dicyanamide, which decomposes under further heating under release of nitrogen. The reaction of Cs(2)CIT with SO(2) resulted in the surprising formation of a new cesium salt with the 5-cyaniminotetrazoline-1-sulfonate dianion (Cs(2)CITSO(3).SO(2) (7)). 7 crystallizes in the monoclinic space group P2(1) with one SO(2) solvent molecule (a = 8.0080(2) Angstroms, b = 8.0183(2) Angstroms, c = 9.8986(3) Angstroms, beta = 108.619(1) degrees, Z = 2). The structure and bonding of the 10pi dianion are discussed on the basis B3LYP/aug-cc-pvTZ computations (MO, NBO), and the three-dimensional array of the cesium salts with respect to the Cs(delta) (+)-N(delta)(-) in 5 compared to the Cs(delta)(+)-N(delta)(-) and Cs(delta)(+)-O(delta)(-) in 7 is discussed. Due to the expected rich bonding modes of the CIT anions, the coordination chemistry with palladium was also studied, yielding monoclinic crystals of [Pd(CIT)(NH(3))(3)].H(2)O (6, a = 7.988(2) Angstroms, b = 8.375(2) Angstroms, c = 13.541(3) Angstroms, beta = 104.56 degrees, space group P2(1)/n, Z = 4). In the solid state, the complex is composed of dimers, showing two agostic interactions and an unusual close interplanar pi-pi stacking of the tetrazole moiety of the CIT ligand.

Stereoselective functionalization of cyclopropane derivatives using bromine/magnesium and sulfoxide/magnesium exchange reactions.

The reaction of 2,2-dibromo-1-methyl-cyclopropanecarbonitrile (1) with i-PrMgCl in Et(2)O/CH(2)Cl(2) provides the cis-magnesium-carbenoid (2), which reacts with high retention of configuration with various electrophiles. If E = SPh, a stereoselective generation of a quaternary center via a sequential Br/Mg- and sulfoxide/Mg-exchange can be achieved. [reaction: see text]

Kinetic and donor stabilization of organotellurenyl iodides and azides.

The first tellurium compounds containing the extremely bulky tris(phenyldimethylsilyl)methyl (Tpsi) and 2,6-bis(2,4,6-triisopropylphenyl)phenyl (2,6-Trip(2)C(6)H(3)) moieties have been synthesized and isolated. Careful oxidation of the tellurolate TpsiTeLi (1) resulted in the formation of the crowded ditellane (TpsiTe)(2) (2), and iodination of 2 gave the alkanetellurenyl iodide TpsiTeI (3). In a similar fashion, the terphenyl-substituted ditellane (2,6-Trip(2)C(6)H(3)Te)(2) (9) and the arenetellurenyl iodide 2,6-Trip(2)C(6)H(3)TeI (10) were prepared. Reaction of the iodides TpsiTeI (3) and 2,6-Trip(2)C(6)H(3)TeI (10), as well as TripTeI, MesTeI (Trip = 2,4,6-triisopropylphenyl, Mes = 2,4,6-tri-tert-butylphenyl), and the donor-stabilized 2-Me(2)NCH(2)C(6)H(4)TeI, with AgN(3) resulted in the formation and isolation of the corresponding tellurenyl azides TpsiTeN(3) (4), TripTeN(3) (7), MesTeN(3) (8), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12). Furthermore, the corresponding tris(ethyldimethylsilyl)methyl-containing (Tesi) tellurium compounds (TesiTe)(2), TesiTeI (5), and TesiTeN(3) (6) have been prepared but could not be isolated in pure form. The crystal structures of TpsiTeLi (1), (TpsiTe)(2) (2), TpsiTeN(3) (4), 2,6-Trip(2)C(6)H(3)TeI (10), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12) have been determined by X-ray diffraction. Additionally, computational studies of the molecules for which experimental structural data were available were performed.

Derivatives of 1,5-diamino-1H-tetrazole: a new family of energetic heterocyclic-based salts.

1,5-Diamino-1H-tetrazole (2, DAT) can easily be protonated by reaction with strong mineral acids, yielding the poorly investigated 1,5-diaminotetrazolium nitrate (2a) and perchlorate (2b). A new synthesis for 2 is introduced that avoids lead azide as a hazardous byproduct. The reaction of 1,5-diamino-1H-tetrazole with iodomethane (7a) followed by the metathesis of the iodide (7a) with silver nitrate (7b), silver dinitramide (7c), or silver azide (7d) leads to a new family of heterocyclic-based salts. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, X-ray structure determination, and initial safety testing (impact and friction sensitivity). Most of the salts exhibit good thermal stabilities, and both the perchlorate (2b) and the dinitramide (7c) have melting points well below 100 degrees C, yet high decomposition onsets, defining them as new (7c), highly energetic ionic liquids. Preliminary sensitivity testing of the crystalline compounds indicates rather low impact sensitivities for all compounds, the highest being that of the perchlorate (2b) and the dinitramide (7c) with a value of 7 J. In contrast, the friction sensitivities of the perchlorate (2b, 60 N) and the dinitramide (7c, 24 N) are relatively high. The enthalpies of combustion (Delta(c)H degrees ) of 7b-d were determined experimentally using oxygen bomb calorimetry: Delta(c)H degrees (7b) = -2456 cal g(-)(1), Delta(c)H degrees (7c) = -2135 cal g(-)(1), and Delta(c)H degrees (7d) = -3594 cal g(-)(1). The standard enthalpies of formation (Delta(f)H degrees ) of 7b-d were obtained on the basis of quantum chemical computations using the G2 (G3) method: Delta(f)H degrees (7b) = 41.7 (41.2) kcal mol(-)(1), Delta(f)H degrees (7c) = 92.1 (91.1) kcal mol(-)(1), and Delta(f)H degrees (7d) = 161.6 (161.5) kcal mol(-)(1). The detonation velocities (D) and detonation pressures (P) of 2b and 7b-d were calculated using the empirical equations of Kamlet and Jacobs: D(2b) = 8383 m s(-)(1), P(2b) = 32.2 GPa; D(7b) = 7682 m s(-)(1), P(7b) = 23.4 GPa; D(7c) = 8827 m s(-)(1), P(7c) = 33.6 GPa; and D(7d) = 7405 m s(-)(1), P(7d) = 20.8 GPa. For all compounds, a structure determination by single-crystal X-ray diffraction was performed. 2a and 2b crystallize in the monoclinic space groups C2/c and P2(1)/n, respectively. The salts of 7 crystallize in the orthorhombic space groups Pna2(1) (7a, 7d) and Fdd2 (7b). The hydrogen-bonded ring motifs are discussed in the formalism of graph-set analysis of hydrogen-bond patterns and compared in the case of 2a, 2b, and 7b.

Blue alkali dinitrosomethanides: synthesis, structure, and bonding.

Explosive alkali dinitrosomethanides (M[HC(NO)2]; M = Li, Na, K, Cs) were prepared in a new, simple, high-yielding synthetic procedure, fully characterized, and shown to be stable at ambient temperature. Alkali dinitrosomethanides are of widespread interest to pharmaceutical and materials scientists alike.

Organotellurium(VI) azides and halides.

The reaction of azide with organotellurium(VI) halides Ph(5)TeBr and cis-(biphen)(2)TeF(2) (biphen = 2,2'-biphenyldiyl) resulted in the formation and isolation of Ph(5)TeN(3) (1) and cis-(biphen)(2)Te(N(3))(2) (2), which are the first tellurium(VI)-azide species. In addition to spectroscopic data, both crystal structures have been determined. Furthermore, the stability of possible Te(VI) species with higher azide contents Ph(x)()Te(N(3))(6)(-)(x)() and Me(x)()Te(N(3))(6)(-)(x)() as well as the syntheses and properties of their Ph/Me(x)()TeF(y)() precursors was investigated, including the crystal structure determination of trans-Ph(2)TeF(4) (3). Ab initio and density functional studies of all molecules regarding the structures and electronic populations were performed.

Diastereoselective remote C-H activation by hydroboration.

Hydroboration of tetrasubstituted or trisubstituted alkenes with BH(3) and subsequent thermolysis allows remote diastereoselective C-H activation of neighboring aryl rings. Tetrasubstituted and trisubstituted 1,1-diphenylethylene derivatives undergo a highly stereoselective 1,2-rearrangement followed by remote C-H activation to lead, after oxidative workup, to a diol in which the relative stereochemistry of two stereocenters has been controlled. The mechanism of this remote activation has been studied and extended to related molecules that undergo this stereoselective C-H activation, namely alkenylbiphenyl systems or alkenes with only one phenyl ring, such as alkenylbenzenes, or bicyclic systems. We have shown that this reaction allows diastereoselective synthesis of molecules with up to three contiguous chiral centers.

A novel dimerization mode of a cyclic ketene imine.

The strained seven-membered cyclic ketene imine 9, obtained by cycloaddition of thiocarbonyl ylide 6 with 2,3-bis(trifluoromethyl)fumaronitrile (7), underwent base-catalyzed dimerization at room temperature on treatment with KCN in acetonitrile or with proton sponge in acetonitrile or CDCl(3). Two diastereoisomeric dimers, (6SR,3'RS)-13 and (6SR,3'SR)-13, were formed in 1:1 ratio in high yield. X-ray analysis revealed a deep-seated structural change which is unrelated to known dimerization pathways of ketene imines. In 13, one of the seven-membered rings is opened, and attached to the second unit by a thioimidate group. An ionic chain reaction with a formal fluoride ion as transfer agent offers a rationalization.

Diastereoselective formation of metallamacrocyclic (arene)Ru(II) and CpRh(III) complexes.

The reaction of [(arene)RuCl(2)](2) (arene = cymene, 1,3,5-C(6)H(3)Me(3)) and [CpRhCl(2)](2) half-sandwich complexes with tridentate heterocyclic ligands in the presence of base has been investigated. In all cases, the chloro-ligands were substituted to give metallacyclic products with ring sizes between 4 and 18 atoms. The cyclization occurs in a highly diastereoselective fashion with chiral recognition between the different metal fragments. The complexes were comprehensively characterized by elemental analysis, NMR spectroscopy, and single crystal X-ray crystallography. For 2-hydroxy-nicotinic acid and 2-amino-nicotinic acid, dinuclear structures were obtained (15-17) whereas for 2,3-dihydroxyquinoline, 2,3-dihydroxyquinoxaline, and 6-methyl-2,3-phenazinediol, trimeric assemblies were found (19-22), and for 4-imidazolecarboxylic acid, a tetrameric assembly (18) was found.

Isolation of a stable covalent selenium azide RSeN3.

The first covalent selenium azide 2-Me2NCH2C6H4SeN3 has been synthesized and fully characterized including crystal structure determination. As shown by the experimental results, the relative stability of RSeN3 highly depends on the nature of the coordinating ability of the substituent R, resulting in a heterocyclic zwitterionic structure.

Synthesis of enantiomerically enriched propargylamines by copper-catalyzed addition of alkynes to enamines.

The first copper(I) bromide/Quinap-catalyzed synthesis of enantiomerically enriched propargylamines by addition of alkynes to enamines is reported. Various functionalized terminal alkynes add smoothly to Nprotected enamines to afford the corresponding amines in good to high yields and moderate to good enantiomeric excesses. The influence of the metal salt, the ligand, and the protecting group on the conversion, the reaction rate, and the stereoselectivity of the reaction are investigated. The scope of the reaction and further transformations of the resulting propargylamines (deprotection, Pauson-Khand reaction) are also described.

1,3-dithiolanes from cycloadditions of alicyclic and aliphatic thiocarbonyl ylides with thiones: regioselectivity.

The regiochemistry of 1,3-dithiolanes obtained from thiocarbonyl ylides 9 and thiones 10 shows a striking dependence on substituents. Previously and newly performed experiments indicate that sterically hindered cycloalkanethione S-methylides and dialkylthioketone S-methylides react with alicyclic and aliphatic thiones to give the 2,2,4,4-tetrasubstituted 1,3-dithiolanes 11 exclusively. Aryl groups in one or both reactants lead to a preference for, or even complete formation of, 4,4,5,5-tetrasubstituted 1,3-dithiolanes 12. Several mechanisms appear to be involved, but the paucity of experimental criteria is troubling. Quantum-chemical calculations (see preceding paper) on the cycloaddition between thioacetone S-methylide and thioacetone furnish lower activation energies for the concerted process than for the two-step pathways via C,S- or C,C-biradicals; the favoring of the 2,4-substituted 1,3-dithiolanes over the 4,5-substituted type would be expected to increase with growing bulk of substituents. Aryl groups stabilize intermediate biradicals. Experimental criteria for the differentiation of regioisomeric dithiolanes are discussed. Thiocarbonyl ylides 9 are prepared by 1,3-cycloadditions between diazomethane and thioketones and subsequent N(2) elimination from the usually isolable 2,5-dihydro-1,3,4-thiadiazoles 17; different ratios of the two rate constants lead to divergent product formation scenarios.