bluuebunny/crossref_metadata_2025 huggingface dataset:
Wasserstoffübertragungen, 15 Zum Ablauf der Dehydrierung von Dihydroarenen durch Chinone
Authors: Radtke Rainer , Hintze Horst , Rösler Klaus , Heesing Albert
Published: July 2007

Hydrogen Transfer Reactions, 15lI. ‐ On the Transition State in the Dehydrogenation of Dihydroarenes by Quinones

In the hydride abstraction from 1,2‐dihydronaphthalene by o‐chloroanile the regioselectivity correlates with the stability of the carbenium ions as shown by both kinetic tests and reactions of isotopomeric hydrogen donators. ‐ The temperature dependence of primary isotope effects does not correspond with any of the categories for the transition state as proposed by Kwart2). This was examined for 1,4‐cyclohexadiene and 9,10‐dihydroanthracene by a Bell correction and the parameters of activation (AH/AD und [ΔEA]D/H). A VAT mechanism3) is proposed to explain both these results and the large primary isotope effects.
Lineare Oligophosphaalkane, XXIV Synthese und strukturelle Charakterisierung von Cu8‐Mehrkernkomplexen mit Elektronenmangel‐Phosphidobrücken
Authors: Heßler Gisbert , Knüppel Peter C. , Stelzer Othmar , Sheldrick William S.
Published: July 2007

Linear Oligophosphaalkanes, XXIV. – Syntheses and Structural Characterisation of Cu8 Complexes with Electron‐Deficient Phosphido Bridges

Reaction of silylphosphanes (Me3Si)RP–CH2–PR(SiMe3) (R = iPr, tBu, 2,4,6,‐Me3C6H2) with four equivalents of copper(1) halides CuX (X = Cl, Br) or a mixture of two equivalents of CuCl and Cul in the presence of pyridine as an auxiliary ligand affords octanuclear copper(1) complexes of composition Cu8X4(RP–CH2–PR)2(Py)n(CH3CN)m (n = 5, m = 0; n = 4, m = 1; X = Cl, Br, I). Multinuclear compounds of this type may also be obtained by deprotonation of the disecondary phosphanes HRP–CH2–PRH (R = iPr, Ph, 2,4,6‐Me3C6H2) with strong organic bases (DBU) in the presence of CuCl and pyridine. The X‐ray structural analysis of Cu8Cl4(iPr–P–CH2–PiPr)2(Py)5 (3a) (space group P21/c) reveals a Cu4(P–C–P)2 skeleton to which four CuCl(Py)n units (n = 1, 2) are coordinated by Cu–Cl and Cu–P bridges. The phosphorus atoms of the electron‐deficient μ3–PRR′ bridges formed thereby show a distorted trigonal bipyramidal coordination with almost planar PCu3 units. Due to the multiple bridging of the Cu(I) ions in 3a the Cu ⃛Cu distances in the Cu8 complex are relatively short (247.1–276.5 pm).
Silylalkin‐ und Silylvinyliden‐verbrückte Heterometallcluster
Authors: Bantel Harald , Powell Anne K. , Vahrenkamp Heinrich
Published: July 2007

Silylalkyne‐ and Silylvinylidene‐Bridged Mixed Metal Clusters

Attempts to incorporate silylalkynes into FeCo2 or RuCo2 clusters by means of cluster buildup or capping reactions are reported. From RuCo2(CO)11 and Me3SiC≡CMe were obtained RuCo2(CO)9(μ3‐Me3SiC≡CMe) (5) and its more stable isomer RuCo2(CO)9(μ3‐C=C(Me)SiMe3) (6). Of the latter the isonitrile derivative 8 was characterized by structure determination. The silylalkyne‐bridged cluster 5 is very prone to desilylation forming RuCo2(CO)9(μ3‐HC≡CMe) (11). The silylvinylidenebridged cluster 6 undergoes cluster expansion with CpRh(CO)2 to form RuCo2RhCp(CO)8(μ4‐Me3siC≡CMe) (12), which again bears the silylalkyne ligand.
Alkinverbrückte Vierkerncluster durch Expansion von Dreikernclustern
Authors: Bantel Harald , Powell Anne K. , Vahrenkamp Heinrich
Published: July 2007

Alkyne‐Bridged Tetranuclear Clusters by Expansion of Trinuclear Clusters

Under photochemical activation Fe2(CO)9 is a suitable reagent for the expansion of alkyne‐bridged trinuclear clusters 1–7 (Fe3, FeCo2, FeNi2, RuCo2, FeCoNi, RuCoNi, RuCoMo) to the corresponding tetranuclear clusters 9–15 containing Fe(CO)3 building blocks. The analogous incorporation of RhCp building blocks was possible by heating RhCp(CO)2 together with the alkyne‐bridged Fe3, FeCo2, RuCo2, RuCoMo, and RuCoW clusters 1, 2a, 4, 7, and 8. The resulting clusters 16–20 with octahedral M4C2 frameworks showed framework isomerism in two cases [RuFeCo2 (11a, b) and RuCoMoRh (19a, b)]. Crystal structure determinations were performed for the Fe4 and Fe3Rh clusters 9, 16 as well as for both isomers 19a, b of the RuCoMoRh cluster.
Nitrogen Base – Dialkyl‐1,2,4,3,5‐triselenadiborolanes
Authors: Yalpani Mohamed , Köster Roland , Boese Roland
Published: July 2007

Stickstoffbase – Dialkyl‐1,2,4,3,5‐triselenadiborolane

3,5‐Dialkyl‐1,2,4,3,5‐triselenadiborolane RBSe3BR (1) [R = C2H5 (1a) und R = C3H7 (1b)] bilden bei Raumtemperatur mit überschüssigen N‐Basen [Pyridin (P), 3,5‐Dimethylpyridin (m2P), 3‐Chlorpyridin (cP) und Chinuclidin (Q)] stabile 2:1‐Additionsverbindungen [P2‐1a,b, (m2P)2‐1a, cP‐1a, Q2‐1a, b]. In Lösung existieren Gemische von (syn/anti)Q2‐1a (1H‐, 11B‐NMR). (syn)Q2‐1a steht bei –80°C mit Q‐1a und Q im Gleichgewicht. Festes Q2‐1a liegt als (anti) Q2‐1a vor (Kristallstrukturanalyse). In Lösung bilden 1 bei Raumtemperatur mit äquimolaren Mengen an N‐Basen die 1:1‐Addukte [(N‐Base)‐1], in denen nur ein Bor‐Atom vierfach koordiniert ist. 1: 1‐Addukte mit fluktuierender N‐Base zwischen den beiden Bor‐Atomen werden bei Temperatursteigerung beobachtet (120°C: 11B‐NMR). Hexamethylentetramin (Ur) bildet stabile, feste 1: 1‐ und 2: 1‐Addukte (Ur‐1a, Ur2‐1a).
Starke P – P‐Wechselwirkungen in Tetraphosphacubanen, PE‐spektroskopische Untersuchungen
Authors: Gleiter Rolf , Pfeifer Karl‐Heinz , Baudler Marianne , Scholz Guido , Wettling Thomas , Regitz Manfred
Published: July 2007

Strong P – P Interactions in Tetraphosphacubanes. A PE‐Spectroscopic Investigation

The comparison between the first peaks of the PE spectra of (tBuCP)4 (2a) yields about the same ionization energy for the first peak (4t2), but a large difference (ca, 0.8 eV) for the second peak (1t1). This difference is due to a strong interaction of the n orbitals at P with the P‐C σ bonds in 1. This n/σ interaction is much smaller in the case of 2. The energy difference between 24T2 and 23A1, corresponding to the lone‐pair combinations of the n orbitals at the P atoms, amounts to ≥ 3.4 eV for 1a and is estimated at ≥ 1.6 eV for 2a. The net charges for the P atoms in 1 are calculated to be positive, those for the C atoms negative. In the case of 2 negative values result for P and positive values for the net charges at Si.
Ringkontraktionsreaktionen von Octamethylcyclotetrasilazanen zu silylsubstituierten Cyclotrisilazanen
Authors: Dipel Kerstin , Klingebiel Uwe , Pauer Frank , Sheldrick George M. , Stalke Dietmar
Published: July 2007

Ring Contractions of Octamethylcyclotetrasilazanes to Silyl‐Substituted Cyclotrisilazanes

Reaction of the mono‐ and dilithium derivatives of bis(fluorsilyl)‐substituted cyclotetrasilazanes with fluorosilanes and fluoroboranes leads to ring contraction with formation of cyclotrisilazanes (1 – 8). The isomerisation is proved by the crystal structure determination of 1 and by NMR spectroscopy.
Synthese, Struktur und dynamisches Verhalten von 1,3,5‐Triaza‐2,4‐diphospha‐1,4‐pentadienen
Authors: Niecke Edgar , Detsch Ralph , Nieger Martin
Published: July 2007

Synthesis, Molecular Structure, and Dynamic Behaviour of 1,3,5‐Triaza‐2,4‐diphospha‐1,4‐pentadienes

Chloro(arylimino)phosphane (1) reacts with the 1,3‐diaza‐2‐phosphaallylic system 3 to form 1,3,5‐triaza‐2,4‐diphospha‐1,4‐pentadienes Ar‐N=P‐N(R)‐P=N‐Ar (Ar = 2,4,6‐tBu3‐C6H2; R = tBu, 2,4,6‐iPrc3C6H2) (4a‐c). the molecular structure of 4a (“Exo‐endo‐S conformation”) as well as the dynamic behaviour of the compounds in solution are discussed. the observed temperature dependance of the NMR spectra of 4c was interpreted as a sigmatropic 1,3‐rearrangement followed by a P‐N rotation.
Stereochemische Aspekte bei metallacyclischen Neunring‐Zirconoxycarbenkomplexen aus (Butadien)zirconocen, Hexacarbonylwolfram und Ketonen oder Aldehyden
Authors: Erker Gerhard , Sosua Friedrich , Noe Ralf
Published: July 2007

Stereochemical Aspects with Metallacyclic Nine‐Membered Zirconoxycarbene Complexes from Coupling (Butadiene)‐zirconocene, Hexacarbonyltungsten, and Ketones or Aldehydes

Reaction of (butadiene)zirconocene complexes with M(CO)6 (M =Cr, W) and subsequently with ketones or aldehydes O=CR1R2 (R1, R2 = H, alkyl, alkenyl, or aryl) produces the metallacyclic nine‐membered zirconoxycarbene complexes (7a‐r. The complexes trans‐7 contain chiral metallacyclic ring systems. Starting from many ketones two diastereomeric compounds trans‐7 and trans‐7′ are obtained. From the dynamic 1H‐NMR spectra an activation barrier of ΔG(317K)=16.5 ± 0.4 kcal/mol has been estimated fro the trans‐7k [(2R*)(4,5,6‐pS*)] → trans‐7k′ [(2R*)(4,5,6‐pR*)] rearrangement. For the tert‐alkyl‐substituted nine‐membered metalacycles trans‐7f‐h only the respective (2R*)(4,5,6‐pS*) isomers have been found Starting from aldehydes with less sterically demanding alkyl groups mixtures of the trans‐7 [(2R*)(4,5,6‐pS*)] compounds and their cis‐7 isomers are obtained. Using the more bulky bis(tert‐butylcyclopentadienyl)zirconium moiety for coupling butadiene and W(CO)6 with simple aldehydes leads to a large excess of the trans‐isomers (e. g. R1 = H, R2 = i‐C3H7: trans‐7q: Cis7q = 90: 10).
Chirale Homoenolat‐Äquivalente, III Asymmetrische synthese 3‐substituierter 3‐Phenylketone über metallierte SMP‐ Allylamine
Authors: Abbrecht Hobertas , Sommer Horst
Published: July 2007

Chiral Homoenolate Equivalents, 111. – Asymmetric Synthesis of 3‐Substituted 3‐Phenylketones via Metallated SMP‐ Allylamines

The diastereomeric excess obtained in alkylation reactions of the chiral homoenolate equivalents 7 with prolinol ether as chiral auxiliary leading to the formation of 3‐phenylketones 9 clearly depends on the temperature, the counter ion and the size of the alkyl iodide. But most important is the influence of the solvent used. By its variation even the course of induction may be controlled. Normally, the selectivity amounts to about 8 : 1 only. The best results (about 9 : 1) are obtained with lithium as counter ion and tert‐butyl methyl ether as solvent.
1,3,2‐Dithiazol‐2‐yl‐Radikale aus N‐substituierten 1,3,2‐Dithiazolen
Authors: Wolmershäuser Gotthelf , Kraft Gregor
Published: July 2007

1,3,2‐Dithiazol‐2‐yl Radicals from N‐Substituted 1,3,2‐Dithiazoles

Thermolysis of N‐substituted 1,3,2‐dithiazoles 1,2 as well as their reactions with bases affords the corresponding 1,3,2‐dithiazol‐2‐yl radical 3, 4. Radical 3 has been characterized by X‐ray structure analysis.
Beiträge zur Chemie des Bors, 203. Reaktionen einiger Nichtmetallelemente mit 9‐Fluorenyliden(2,2,6,6‐tetramethylpiperidino)boran
Authors: Mayer Erwin P. , Nöth Heinrich
Published: July 2007

Contributions to the Chemistry of Boron, 2031 Reactions of Some Non‐Metallic Elements with 9‐Fluorenylidene(2,2,6,6‐tetramethylpiperidino)borane

9‐Fluorenylidene(2,2,6,6‐tetramethylpiperidino)borane (1) is hydrogenated catalytically at its boron‐carbon double bond producing 9‐fluorenyl(2,2,6,6‐tetramethylpiperidino)borane (2). Similarly, chlorine, bromine, and iodine add to this double bond, but only the bromine adduct 6a has been fully characterized. 1 is oxygen‐sensitive. The oxidation product found is the 1,2‐oxaboretane derivative 7, which is prepared independently by a [2 + 2] cycloaddition reaction from 1 and 9‐fluorenone. Sulfur reacts with 1 to yield a trithiaborolane derivative, while P4 does not attach 1.
Diphosphinonitrenium and ‐phosphenium Cations, Jahn‐Teller Distorted Allyl Systems
Authors: Schoeller Wolfgang W. , Busch Thilo
Published: July 2007

Ab initio calculations at SCF, MCSCF, and ACPF level were performed on a series of the phosphenium‐ and nitreniumcation family. These show that they possess an allylic π‐system with 4 electrons, which is distorted from planarity when the terminal groups of the allylic system are PR2 (R  H) fragments. The distortion is such as to adopt C2 symmetry, and is the consequence of Jahn‐Teller distortion via mixing of the energy highest π2 orbital with an energetically low lying δ* orbital. The latter interaction is only operative if a symmetry breaking from C2v to C2 symmetry occurs. The importance of Jahn‐Teller distortion on the biradical character in these systems is investigated by correlation calculations.
Darstellung, Struktur und Stereoisomerie von 1,3‐Di‐tert‐butyl‐1,3,2,4‐diazadistibetidinen
Authors: Ross Bernd , Belz Johannes , Nieger Martin
Published: July 2007

Synthesis, Structure, and Stereoisomerism of 1,3‐Di‐tert‐butyl‐l,3,2,4‐diazadistibetidines

Starting from 1,3‐di‐tert‐butyl‐2,4‐dichloro‐1,3,2,4‐diazadistibetidine a series of 1,3,2,4‐diazadistibetidines [R–SbN–ttBu]2 with R = OMe (2), OPh (3), OtBu (4), N(Tms)2 (5), P(Tms)2 (6), Me (7), and tBu (8) has been synthesized. The NMR spectra prove most of the reaction products to be mixtures of geometrical isomers. The structure of trans‐tetra‐tert‐butyldiaza‐distibetidine 8a was confirmed by X‐ray structure determination.
Oxidative Addition von Halogenpentamethylcyclopentadienen an Metallcarbonyle: ein einfaches Verfahren zur Synthese von (η5‐Pentamethylcyclopentadienyl)metallhalogeniden
Authors: Jutzi Peter , Mix Andreas
Published: July 2007

Oxidative Addition of Halogenopentamethylcyclopentadienes to Metal Carbonyls: A Simple Method for the Synthesis of (η5‐Pentamethylcyclopentadienyl)metal Halides

The alkyl halides 5‐chloro‐1,2,3,4,5‐pentamethyl‐1,3‐cyclopentadiene (1), 5‐bromo‐1,2,3,4,5‐pentamethyl‐1,3‐cyclopentadiene (2) and 5‐iodo‐1,2,3,4,5‐pentamethyl‐1,3‐cyclopentadiene (3) add oxidatively to the metal centres of carbonyl complexes of group‐8 elements. Thus, 1 and 2 react with Fe(CO)5 to give compounds of the type (C5Me5)Fe(CO)2X (X = Cl, Br) (4, 5). Irradiation of Ru3(CO)12 together with 1 and 2 yields the compounds (C5Me5)Ru(CO)2X (X = Cl, Br) (6, 7). Reaction of 1, 2, and 3 with Co2(CO)8 and Ni(CO)4 leads to halide‐bridged dinuclear complexes of the type [(C5Me5)MX]2 (M = Co, Ni; X = Cl, Br, I) (8–12).
9,10‐Phenanthrenocyaninatoeisen(II) (PhcFe) und axial koordinierte Isocyanid‐Komplexe
Authors: Hanack Michael , Renz Günter
Published: July 2007

9,10‐Phenanthrenocyaninatoiron(II) (PhcFe) and Axially Coordinated Isocyanide Complexes

9,10‐Phenanthrenocyaninatoiron(II) (PhcFe) is synthesized from 9,10‐dicyanophenanthrene (3) and pentacarbonyliron. PhcFe exhibits similar spectroscopic properties (UV/VIS and Mößbauer spectra) and similar oxidation potentials as 1,2‐Naphthalocyaninatoiron(II) (1,2‐NcFe) and Phthalocyaninatoiron(II) (PcFe). Isocyanides RNC (R = tBu, cHx, Bzl, Me2Ph) react with PhcFe to form the corresponding bisaxially substituted 9,10‐phenanthrenocyaninatoiron(II) compounds 4–7. Reaction of PhcFe with 1,4‐diisocyanobenzene (dib) yields the bridged complex [PhcFe(dib)]n.
Synthese und Eigenschaften kalamitischer Flüssigkristalle aus desoxygenierten Kohlenhydrat‐Derivaten
Authors: Pudlo Peter , Thiem Joachim , Vill Volkmar
Published: July 2007

Synthesis and Properties of Calamitic Liquid Crystals from Deoxygenated Carbohydrate Derivatives

Treatment of the L‐arabino‐ and Llyxo‐configurated glycals 1 and 7 with trimethylsily cyanide leads to the formation of the anomeric nitriles 2, 3 and 15, 17, respectively. The configurational assignments are based on hydrogenated products such as 6 or 8 and 10. Depending on the configurations of the olefinic nitril sugars, various hydrogenation results are observed using palladium/charcoal or the Wilkinson catalyst. Methanolysis provides the corresponding methyl esters. The preparation of liquid‐crystalline derivatives follows the classical route. In comparing the properties of these saccharide‐based liquid crystals with the corresponding cyclohexane derivatives, the dominant influence of the anomeric effect on the tendency for phase formation can be observed. Some of the novel derivatives show highly twisted cholesteric and wide blue phases.
N‐[(2‐Naphthyloxy)methyl] benzazoles: Synthesis and Investigation by X‐ray Analysis and by Semiempirical MO Calculations
Authors: Katritzky Alan R. , Palenik Gus J. , Eynde Jean‐Jacques Vanden , Zhang Zeying , Anders Ernst , Tropsch Jiirgen G.
Published: July 2007

The crystal structures of 1‐[(2‐naphthyloxy)methyl]‐lH‐benzotriazole (4) and ‐1H‐benzimidazole (8) and the 3‐metho‐quaternary iodide 9 derived from 8 are reported. The experimentally determined geometries are compared with the corresponding results from MNDO, AM1, and PM3 calculations. Remarkably, the crystal structures differ significantly from those calculated by AM1 as most stable. – Thus, conformations of 9 (from the crystal structure) and 9a (the most stable AM1 structure) differ in energy by ca. 3.5 kcal/mol. This stabilization of 9a is due to the anomeric effect which cannot be expressed in conformation 9. Calculations of the alternative cleavage of the methyl or of the naphthyloxymethyl cation (Figure 6) clarify discrepancies between the experimental and the calculated bond lengths.
Vinamidin‐Chelate des Bors
Authors: Kuhn Norbert , Kuhn Annette , Speis Martin , Bläser Dieter , Boese Roland
Published: July 2007

Vinamidine Boron Chelate Compounds

The chelate compound 7 is obtained by the reaction of the vinamidine 6 with Et2O ‐ BF3. Protonation with HBF4 gives the cation 11. Comparison of the calculated and experimentally determined structures demonstrates 7 and 11 to be heterocyclic analogues of the cyclohexadienide 5 and 1,4‐cy‐cyclohexadiene (12).
Zur Kenntnis des „Phosphormonosulfids”︁ (PS)x
Authors: Frehn Angelika , Keck Helmut , Kuchen Wilhelm
Published: July 2007

New Results Concerning the “Phosphorus Monosulfide” (PS)x

The orange‐yellow solid of approximate composition (PS)x obtained by dehalogenation of P(S)Br3 with Mg proved to be a mixture of phosphorus sulfides e.g. P4S3, P4S4, P4S5, P4S7, and insoluble polymeric material. It is suggested that the latter contains a network of triply connected P atoms, many of which are substituted by groups. The conclusions are based on the results of analytical, mass‐spectrometric and 31P‐NMR‐spectroscopic findings.
Addukt eines fünfgliedrigen Trischwefeldistickstoffdioxid‐Rings an Titantetrachlorid
Authors: Roesky Herbert W. , Schimkowiak Jürgen , Schmidt Hans‐Georg , Noltemeyer Mathias , Sheldrick George M.
Published: July 2007

Adduct of a Five‐Membered Trisulfurdinitrogen Dioxide Ring with Titanium Tetrachloride

Reaction of S6N4O4 with TiCl4 lead to [(S3N2O2)TiCl4]2 (2). Single crystals of 2 were obtained by recrystallization from liquid SO2. 2 forms chains of five‐membered S3N2O2 rings connected by Ti2Cl8 units. The S2N2 part of the five‐membered ring may be described as a 6‐π electron system.
Transition‐Metal‐Catalyzed Oxidations, 2. Titanium‐ or Zirconium‐Catalyzed Selective Dehydrogenation of Benzyl Alcohols to Aldehydes and Ketones with tert‐Butyl Hydroperoxide
Authors: Krohn Karsten , Khambabaee Keramall , Rieger Hagen
Published: July 2007

Primary and secondary benzyl alcohols are selectivity converted in high yields into the corresponding aldehydes or ketones using tert‐butyl hydroperoxide and catalytic amounts of titanium or (better) zirconium alcoholates. Aliphatic hydroxy groups, double bonds (except those in allylic position to hydroxy groups), and phenolic hydroxy groups (except those in ortho position to the benzylic alcohol) are not attacked.
Substituenteneffekte auf die C–C‐Bindungsstärke, 8. Standardbildungsenthalpien und Spannungsenthalpien von 1,1,2,2‐Tetraethylethylenglykol‐dimethylether und D,L‐1,2‐Dimethyl‐1,2‐diphenylethylenglykol‐dimethylether
Authors: Dogan Barbara , Beckhaus Hans‐Dieter , Birkhofer Hermann , Rüchardt Christoph
Published: July 2007

Effects of Substituents on the Strength of C ‐ C Bonds, 81. ‐ Heats of Formation and Strain of 1,1,2,2‐Tetraethylethylene Glycol Dimethyl Ether and D,L.‐1,2‐Dimethyl‐l,2‐diphenylethylene Glycol Dimethyl Ether

The heats of combustion of the title compounds 1 and 2 were measured calorimetrically with the result (kcal mol ‐1, s. d. in parentheses) ΔH°c = − 1880.1 (± 0.6) and − 2373.3 (± 1.4). The heat of vaporisation of 1 ΔHv = 14.3 (± 0.3) and the heat of sublimation of 2 ΔHsub = 27.2 (± 0.5) were derived from their temperature dependance of the vapor pressure. The latter were determined between 30 and 80°C using a flow method. The resulting standard heats of formation ΔH°t(g) = −122.4 (± 0.7) and −43.8 (±1.5) for 1 and 2 correspond to a strain enthalpy (s) of 15.9 and 8.0 kcal mol‐1, respectively. The steric strain of the dimethoxyethanes 1 and 2 is about one fourth lower than the strain of the corresponding dimethylethanes 3 and 4 bearing the same substituents. Thus, a methoxy group causes less steric stress than a methyl group.
1,5‐Sigmatrope Umlagerung von Diels‐Alder‐Addukten bei der Reaktion von Alkatrienphosphonaten mit Acetylencarbonsäureestern – Ein neuer Weg zur Synthese von Benzyl‐ und Phenylphosphonaten
Authors: Mondeshka Diana , Tancheva Chonka , Angelov Christo
Published: July 2007

1,5‐Sigmatropic Rearrangements of Diels‐Alder Adducts in the Reaction of Alkatrienylphosphonates with Alkyl Acetylenecarboxylates ‐ A New Method for the Synthesis of Benzyl‐ and Phenylphosphonates

The reaction of dialkyl (3‐methyl‐1,2,4‐pentatrienyl)‐ and dialky] (3‐methyl‐1‐vinyl‐1,2‐butadienyl)phosphonic acids 1a–d an 5a, b, respectively, with alkyl esters of the acetylenecarboxylic acids 2a–d proceeds via 1,5‐sigmatropic rearrangement and aromatization of the initially formed Diels‐Alder adducts. The reaction with the unsymmetrical dienophiles 2a, b occurs with preferred formation of the cycloadducts A, leading to the benzylphosphonates 3a–h. The above reaction constitutes a new method for the preparation of difficulty accessible derivatives of the benzyl‐ and phenylphosphonic acids. The aromatic structures of the obtained compounds 3a–h, 4a–f, and 6a–d were proved by their IR, mass, and 1H‐NMR spectra.
Synthese mittlerer und großer Ringe, XXVII. Chromatographische Enantiomerentrennung von 3,6‐Heptanophthalid – ein Beitrag zur Frage der absoluten Konfiguration von [n]Paracyclophancarbonsäuren
Authors: Tochtermann Werner , Olsson Gese , Mannschreck Albrecht , Stühler Georgine , Snatzke Günther
Published: July 2007

Synthesis of Medium and Large Rings, XXVII1. ‐ Chromatographic Separation of the Enantiomeric 3.6‐Heptanophthalides. ‐ A Contribution to the Problem of the Absolute Configuration of [nJ Paracyclophanecarboxylic Acids

The partial chromatographic separation of the racemic title compound 1 (ee = 40%) was achieved on triacetylcellulose with ethanol using a recycling technique. Comparison of the CD spectra of (+)22365‐1 with (+)22365‐2 leads to the absolute configuration (P) for both compounds. This assignment is of interest in view of earlier configurational assignments for [n]paracyclophanecarboxylic acids.
α‐Methylene β‐S‐Thiolactones: Synthesis of a new Heterocycle by Sulfurization of an α‐Methylene β‐lactone and Its Structure
Authors: Adam Waldemar , Hasemann Ludiwig
Published: July 2007

An α‐methylene β‐S‐thiolactone, a new sulfur heterocycle, is prepared by sulfurization of the corresponding α‐methylene β‐lactone using Lawesson's reagent as sulfur source.
Contributions to the Chemistry of Boron, 205. Formation of Phosphinoborane Rings. A Reinvestigation of the Reaction of [(CH3)3Si]3P with Borane(3)
Authors: Lynn Wood G. , Dou Danan , Narula Chaitanya K. , Duesler Eileen N. , Paine Robert T. , Nöth Heinrich
Published: July 2007

Combination of (Me3Si)3P and H3B·THF results in the formation of the known adduct (Me3Si)3P·BH3 (1). The complex undergoes dehydrosilylation above 100°C, and two ring compounds, [(Me3Si)2PBH2]3 (2) and P[(μHB2H2)]{(BH2)2[P(SiMe3)2]2}2 (3), are isolated. The crystal structures of the compounds are compared with those of other phosphinoboranes.
Silber(I)‐ und Kupfer(I)‐Komplexe von 1,6‐Cyclodecadiin und 1,7‐Cyclododecadiin
Authors: Gleiter Rolf , Karcher Michael , Kratz Detlef , Ziegler Manfred L. , Nuber Bernhard
Published: July 2007

Silver(1) and Copper(1) Complexes of 1,6‐Cyclodecadiyne and 1,7‐Cyclododecadiyne

The reactions of 1,6‐cyclodecadiyne (1), 1,7‐cyclododecadiyne (2), and 1,8‐cyclotetradecadiyne (3) with silver(I) triflate and copper(I) triflate yield colourless crystals: [C10H12·AgCF3SO3]n (4), [C10H12·CuCF3SO3]n(5), [C12H16·AgCF3SO3]n (6), [C12H16·CuCF3SO3]n (7), and [C14H20·AgCF3SO3]n (8). The spectroscopic data of 4–8 indicate a weak interaction between the triple bonds and the metal ion. In the crystal structure of 4 double‐strands of 1,6‐cyclodecadiyne rings in the chair conformation are coupled by Ag(CF3SO3)2Ag units to form a two‐dimensional network. The X‐ray analysis of single crystals of 6 and 7 reveals twelve‐membered rings that are connected by silver or copper ions, respectively. Each triflate ligand in 6 and 7 uses two of its oxygen atoms to coordinate two different metal centers. The result is a complex three‐dimensional network. In the case of the silver complex 8, the X‐ray analysis also exhibits a similar polymeric structure. Only slight differences of the structural parameters are observed on comparison of the free cyclic dialkyne and that bound to a metal in 4, 6, and 7. The conformation of the 10‐ or 12 membered rings in 1 and 2 are more or less identical to those in 4 or 6 and 7.
Darstellung der ersten Sulfin‐imide (Thion‐S‐imide) mit Perfluormethylgruppen unter Verwendung von Natrium‐hexamethyldisilazanid als schonendes Dehydrohalogenierungsreagenz
Authors: May Andrew , Roesky Herbert W. , Stalke Dietmar , Pauer Frank , Sheldrick George M.
Published: July 2007

Preparation of the First Thione S‐Imides with Perfluoromethyl Groups by the Use of Sodium Hexamethyldisilazanide as a Mild Dehydrohalogenation Reagent

From the reaction of the sulfenyl chloride 1 with the monosilylated amines 2a, b the sulfenamides 3a, b are obtained in good yields. 1,3‐Dehydrohalogenation of 3a, b with sodium hexamethyldisilazanide yields the thione S‐imides 5a, b. Imide 5a reacts with norbornene (6) to produce the isothiazolidine derivative 7. The structures of 5b and 7 are confirmed by X‐ray analyses.
Notizen/Notes Synthesis of β‐Oxo Esters from Silyl Enol Ethers and Dichlorobis(phenoxy)methane
Authors: Mayr Herbert , Cambanis Anton , Bäuml Englbert
Published: July 2007

Dichlorobis(phenoxy)methane (1) reacts with trimethylsiloxyalkenes in the presence of 1.2 equiv. of TiCL4 to give β‐oxo esters in 44–82% yield. The title compound 1 is thus employed as a PhO2C⊕ equivalent.
Reaktionen an μ3‐verbrückenden Alkin‐Liganden auf Heterometallclustern
Authors: Bantel Harald , Powell Anne K. , Vahrenkamp Heinrich
Published: July 2007

Reactions of μ3‐Bridging Alkyne Ligands on Heterometallic Clusters

The metal‐exchange methods to obtain alkyne‐bridged heterometallic clusters from RuCo2(CO)9(μ3‐RCC') (2) were improved, and the new clusters RuCoMoCp(CO)8(PhCCPh) (3c), RuCoNiCp(CO)6(MeCCPh) (5b), RuMoNiCp2(CO)5‐(MeCCMe) (6a), and HFeRuMoCp(CO)8(MeCCMe) (7a) were obtained thereby. Some of the alkyne‐bridged clusters were found to react with additional alkyne. One alkyne unit was incorporated in the products RuCoNiCp(CO)6(RCC')2 (9), two alkyne units were incorporated in the products Ru‐Co2(CO)7(RCC')3 (8). In a side reaction, butyne was trimerized to hexamethylbenzene. Radical anions of the clusters FeCo2(CO)9(RCC') (1) were formed by reduction with cobaltocene. The reaction of these radical anions with alkylating reagents was accompanied by cluster fragmentation and CO insertion converting the former alkyne ligand by acylation into the new trisubstituted oxoalkenyl ligand in the products FeCo(CO)6(μ‐CRCR'‐CR″O) (11). The constitutions of the cluster types 7, 9 and 11 were confirmed by crystal‐structure determinations.
Functionalized cyclopentadienyl ligands, III. Preparation of cobalt half‐sandwich complexes with intramolecular CC bond coordination
Authors: Okuda Jun , Zimmermann Karl Heinz
Published: July 2007

Thermolysis of [1‐(3‐butenyl)‐2,3,4,5‐tetramethylcyclopentadienyl]carbonyldiiodocobalt, (η5‐C5Me4CH2CH2CHCH2)‐Co(CO)I2 (2), in boiling octane affords the dimeric diiodide [(η5‐C5Me4CH2CH2CHCH2)‐COI2]2 (3) without any interference of the 3‐butenyl chain with the cobalt center. 2 reacts with various two‐electron ligands L (LP(OMe)3, P(OPh)3, PPh3, PMe3, PMe2Ph, tBuNC] to give a series of cobalt(III) complexes of the general formulae (η5‐C5Me4CH2CH2CHCH2)‐Co(L)I2 (4–9). Sodium amalgam reduction of these “open‐chain” complexes 4–9 yields novel cobalt(1) complexes containing an intramolecularly coordinated CC bond (η5:η2‐C5Me4CH2CH2CHCH2)‐Co(L). For LCO (12), P(OMe)3 (13), and P(OPh)3 (14) low‐melting crystals are isolated and fully characterized by analytical and spectroscopic methods.
Kohlenwasserstoffverbrückte Komplexe, XVII. Darstellung und Kristallstruktur des Acyl‐verbrückten Komplexes (OC)3Fe{μ‐η1:η1‐C[CH2CH2Re(CO)5]O}2Fe(CO)3
Authors: Breimair Josef , Robl Christian , Beck Wolfgang
Published: July 2007

Hydrocarbon‐Bridged Complexes, XVII1) – Synthesis and Crystal Structure of the Acyl‐Bridged Complex

The addition of [Fe2(CO)8]2⊕ to [(OC)5Re(C2H4)]⊕ gives the diacyl‐bridged title complex 1 which was structurally determined by X‐ray diffraction.
Counterattack reagent bis(trimethylsilyl)acetamide in the disilylation of diols
Authors: Hwu Jih Ru , Anderson Denise A. , Wang Naelong , Buchner Meredith M. , Gani Paul , Tsay Shwu‐Chen
Published: July 2007

The counterattack method was applied to the disilylation of diols. Treatment of various diols with 0.3 or 1.1 equivalents of potassium hydride and 1.1 equivalents of bis(trimethylsilyl)‐acetamide in THF gave the corresponding disilyl ethers in good to excellent yields (60–95%). The diols may contain other functionalities, such as amide, amine, ether, and thioether. The diols used in the disilylation were 2a–14a. The newly developed disilylation proceeded in one flask by a sequential deprotonation‐silylation‐deprotonation‐silylation pathway. This disilylation also represents an example of a “tandem double‐counterattack process”. Bis(trimethylsilyl)‐acetamide acted as a counterattack reagent; it provided two Me3Si groups to diols and produced amides as bases.
Thermolyse von 5‐Alkyliden‐1,4‐dihydro‐5H‐tetrazolen
Authors: Quast Helmut , Bieber Lothar , Regnat Dieter
Published: July 2007

Thermolysis of 5‐Alkylidene‐1,4‐dihydro‐5H tetrazoles

In benzene solution at 100°C, the isopropylidenedihydrotetrazole 1 a decomposes mainly (80%) into molecular nitrogen and the aziridinimines (E)‐ and (Z)‐2a which are thermally unstable and afford methyl isocyanide and the imine 3a. In addition, the novel spirocyclic tetrahydropyrimidine 7a is formed (18% yield) in a [4 + 2] cycloaddition of 1a and the hypothetical intermediate 1,3‐diazabutadiene 19a generated from 1a through a [1,4] hydrogen shift and loss of molecular nitrogen. The thermolysis of the neopentylidenedihydrotetrazole 1b at 100°C is more complex. Only small amounts of the aziridinimines (E)‐ and (Z)‐2b and their decomposition products 3b and methyl isocyanide are observed. A major product is the spirocyclic tetrahydropyrimidine 7b which exhibits moderate thermal stability. Slow thermolysis of 7b affords the tetrahydropyrimidinimine 8b and methyl azide. The latter reacts with 1b in a [3 + 2] cycloaddition furnishing the spiro compound 5b which partially decomposes into the amino‐1,2,3‐triazole 16, thus regenerating methyl azide. This catalyzed isomerization 1b → 16 which is initiated through the thermal [3 + 2] cycloreversion of 7b involves a total of 19% of 1b. The structures of the products are elucidated by means of mass spectra and high‐field NMR spectra. The mechanism of formation of the 1,3‐diazabutadienes 19 from 1 is discussed.
A macrocyclic 2,19‐dioxo[3.3](3,3′) azobenzolophane by transition‐metal carbonyl complex‐mediated CO insertion and cyclization
Authors: Schmiegel Jürgen , Grützmacher Hans‐Friedrich
Published: July 2007

2,19‐Dioxo[3.3](3,3′)azobenzolophane (5) has been obtained in a total yield of 18% by way of CO insertion and cyclization of 1,2‐bis[3‐(bromomethyl)phenyl]‐4,4‐dimethyl‐3,5‐pyrazoli‐dinedione (1) using Co2(CO)8 in acetonitrile followed by the removal of the N‐protecting 4,4‐dimethylmalonyl groups. 5 is obtained predominantly as the trans / trans isomer 5a and can be isomerized by irradiation with λ=369 nm to a mixture of nearly equal amounts of the trans / trans, cis / trans, and cis / cis isomers 5a, 5b and 5c. The thermal isomerization back to 5a is slow but fast upon irradiation with λ=443 nm.
C5S2 (1,2,3,4‐Pentatetraen‐1,5‐dithion), ein neues Sulfid des Kohlenstoffs
Authors: Maier Günther , Schrot Jürgen , Reisenauer Hans Peter , Janoschek Rudolf
Published: July 2007

1,2,3,4‐Pentatetraene‐1,5‐dithione (4) can be prepared by 254‐nm photolysis or by flash pyrolysis of the precursors 3 and 5. The IR spectrum of matrix‐isolated 4 (argon, 12 K) as well as its 13C‐NMR and UV/VIS spectra are reported. The calculated electron excitation energies of C3S2 and C3S2 (4) are in accordance with the experiment.
Intramolekulare Donator‐Akzeptorwechselwirkungen in λ4P(V)‐Verbindungen Phosphor(V)‐Derivate des N,N,N′‐Trimethylethylendiamins
Authors: Becker Wilfried , Jones Peter G. , Schomburg Dietmar , Schmutzler Reinhard
Published: July 2007

Intramolecular Donor‐Acceptor Interactions in λ4P(V) Compounds. — Phosphorus(V) Derivatives of N,N,N′‐Trimethyl‐ethylenediamine

The chlorophosphino derivative of N,N,N′‐trimethylethyl‐enediamine Me2NCH2CH2(Me)NP(Cl)Me (1) and the 2‐(diethylamino)‐λ3‐phospholidinium salt [Me2magnified imageNEt2]+ Cl− (5) have been allowed to react with several oxidizing agents. Reaction of 1 with dimethyl sulfoxide furnishes the phosphonamidic chloride Me2NCH2CH2(Me)NP(O)(Cl)Me (3) while with elemental sulfur the phosphonamidothioic chloride Me2NCH2CH2(Me)NP(S)(Cl)Me (2) is obtained. The reaction of 2 with sodium tetraphenylborate furnished the 1,1,2,3‐tetramethyl‐1,3,2‐λ4‐diazaphospholidinium tetraphenylborate [Me2magnified image(S)Me]+ [BPh4]− (4). The reaction of 5 with phenyl azide, followed by sodium tetraphenylborate led to 2‐(diethylamino)‐2‐(phenylimino)‐1,3,2λ4‐diazaphospholidinium tetraphenylborate [Me2magnified image(NPh)NEt2]+ [BPh4]−1 (7). The methoxy‐λ3‐diazaphospholidinium salt [Me2magnified imageOMe]+ [BPh4]− (6) does not react with phenyl azide to produce the 2‐methoxy‐2‐(phenylimino)‐1,3,2λ4‐diaza‐phospholidinium salt analogous to 7; instead its rearrangement product, the dimeric 1,3,2λ4,4λ4‐diazadiphosphetidine tetraphenylborate [Me3NCH2CH2(Me)NP(O)NPh]2[BPh4]− (8), is isolated in low yield. Singlecrystal X‐ray structure determinations of 4 and 8 are described.
Übergangsmetall‐substituierte Diphosphene, XIX. Zur Reaktivität von Disilylphosphido‐Eisenkomplexen gegenüber 2,4,6‐(CF3)3C6H2PCl2und 2,6‐(CF3)2C6H3PCl2— Diphosphenylkomplexe mit Fluorarylsubstituenten
Authors: Weber Lothar , Schumann Hans , Boese Roland
Published: July 2007

Transition‐Metal‐Substituted Diphosphenes. XIX. ‐ On the Reactivity of Disilylphosphido Iron Complexes towards 2,4.6‐(CF3)3C6H2PCl2and 2.6‐(CF3)2C6H3PCl2. Diphosphenyl Complexes with Fluoroaryl Substituents

(η5‐C5Me5)(CO)2FeP(SiMe3)2(2a) and (η5‐C5H5)(CO)(PPh3)‐FeP(SiMe3)2(2c) react with ArylPCl2[3a: Aryl  2,4,6‐(CF)3‐C6H2;b: Aryl  2,6‐(CF)2C6H3] to yield the thermolabile diphosphenyl complexes (η5‐C5Me5)(CO)2FePP‐Aryl (4a,b) and (η5‐C5H5)(CO)(PPh3)FePP‐Aryl (4c,d), respectively. The isolation of the pure compounds4a‐dfailed. They are, however, intercepted as their (CO)5Cr adducts5a–dby treatment with [(Z)‐cyclooctene]Cr(CO)5‐ Complex (η5C5Me5)(CO)2FeP[Cr(CO)5] P‐C6H2(CF3)3‐(2,4,6) (5a) is characterized by single‐crystal X‐ray diffraction analysis.
[(Dimethylphenylsilyl)tetramethylcyclopentadienyl]thallium(I) und [(Benzyldimethylsilyl)tetramethylcyclopentadienyl]thallium(I) — polymere Metallorganyle mit Kettenstruktur
Authors: Schumann Herbert , Kucht Homa , Dietrich Andreas , Esser Lothar
Published: July 2007

[(Dimethylphenylsilyl)tetramethylcyclopentadienyl]thallium(I) and [(Benzyldimethylsilyl)tetramethylcyclopentadienyl]‐thallium(1) ‐ Polymeric Organometallic Compounds with Chain Structure

(Dimethylphenylsilyl)tetramethylcyclopentadiene (2) and (benzyldimethylsilyl)tetramethylcyclopentadiene (3) were prepared from (tetramethylcyclopentadienyl)lithium (1) and chlorodimethylphenylsilane or benzylchlorodimethylsilane, respectively. 2 and 3 react with TIOC2H5 (4) to form [C5Me4(SiMe2Ph))TI (5) and [C5Me4(SiMe2CH2Ph)]TI (6), respectively. The 1H‐ and 13C‐NMR spectra of the new compounds as well as the single‐crystal X‐ray structural analyses of the polymeric metallocenes 5 and 6 are described and discussed.
Trisilazan‐1‐yl‐cyclodisilazane — Expansionen, Kontraktionen und Ringkopplungen
Authors: Dippel Kerstin , Klingebiel Uwe
Published: July 2007

Trisilazan‐1‐yl‐cyclodisilazanes — Expansions, Contractions. and Ring Couplings

Lithiated trisilazan‐1‐yl‐cyclodisilazanes react in different ways. The lithium derivatives of 2 and 3 react with fluorosilanes with substitution to give 4 and 5. In the reaction of dilithiated 3 with chlorotrimethylsilane the cyclotrisilazane 6 is formed by ring expansion. In the same reaction the symmetrically substituted four‐membered ring 7 is obtained, which is formed by ring contraction of the anion of 6. The silyl‐bridged ring systems 8–11 are obtained on reaction of dilithiated 3 with fluorosilanes and F2BN(SiMe3)2. An analogous silylbridged four‐membered ring system 12 is formed in the reaction of the eight‐membered ring anion with F3SiN(SiMe3)2.
Chirale Homoenolat‐Äquivalente, IV. Kristallstruktur einer chiralen 1‐Aminoallyllithium‐Verbindung: dimeres, intramolekular chelatisiertes (3S)‐3‐Lithio‐1‐[(S)‐2‐(methoxymethyl)pyrrolidino]‐1,3‐diphenylpropen
Authors: Ahlbrecht Hubertus , Boche Gernot , Harms Klaus , Marsch Michael , Sommer Horst
Published: July 2007

Chiral Homoenolate Equivalents, IV. — Crystal Structure of a Chiral 1‐Aminoallyllithium Compound: Dimeric, Intra‐molecularly Chelated (3S)‐3‐Lithio‐1‐[(S)‐2‐(methoxymethyl)pyrrolidino]‐1,3‐diphenylpropene

The chiral title compound crystallizes from toluene as a dimer. Two molecules toluene cocrystallize outside the aggregate. The 1‐aminoallyl group is nearly planar. Both exo‐placed phenyl groups and the endo‐placed pyrrolidine group are twisted against the allylic plane. The nitrogen atom is pyramidal, the lone pair is directed to the allyl group (in‐conformer). The bond angle C1‐C2‐C3 is widened, and the bond distances C1‐C2 and C2‐C3 alternate slightly. This is indicative of a strongly delocalized 3‐metallated enamine structure. The lithium atom of one monomer unit is bound to the C3 atom and chelated intramolecularly by the nitrogen and oxygen atoms. Therefore it is placed on the Si side of the allylic plane. Its free coordination site is occupied by the benzyl group of the second monomer unit. The dimer can hence be regarded as being an allyl‐ as well as a benzyllithium compound at the same time. MNDO calculations reproduce the results of the X‐ray structure determination satisfactorily and allow some insight into possible structures in solution.
Zum Mechanismus der Cyclopropan‐„Walk”︁‐Umlagerung: Synthese und Eigenschaften von 2‐Diazopropan‐Aren‐Addukten; eine regiospezifische N2‐Eliminierung
Authors: Klärner Frank‐Gerrit , Glock Volker , Hemmes Jan‐Luiken
Published: July 2007

Mechanism of the Cyclopropane “Walk” Rearrangement: Syntheses and Properties of 2‐Diazopropane ‐ Arene Adducts; a Regiospecific N2 Elimination

The synthesis and the thermal and photochemical behavior of 2‐diazopropane adducts of toluene 1a, m‐xylene 1b,c, and Dewar benzene 2a,b are reported. At 60°C the thermal N2 elimination of the specifically deuterated compound 1c proceeds regiospecifically leading to 1,7,7‐trimethyl‐5‐(trideuteriomethyl)‐1,3,5‐cycloheptatriene (12c), whereas the photolysis of 1c sensitized by benzophenone yields both regioisomeric cycloheptatrienes 12c and 13c in a 51:49 ratio. This finding excludes the symmetrical diradical 3c as an intermediate in the thermal N2 elimination of 1c and suggests a novel pericyclic process for it. The formation of both regioisomeric cycloheptatrienes 25b and 25c in a 74:26 ratio in the thermolysis of the diazopropane‐tetradeuterio Dewar benzene adduct 2b indicates that in this case a multi‐step N2 elimination passing through the diradical intermediate 3e competes with the concerted process. According to force‐field calculations the course of the N2 elimination in 1a‐e might be controlled by the conformational equilibrium A⇆B
Synthese von 1,7‐Diazaperylen
Authors: Naumann Christoph , Langhals Heinz
Published: July 2007

Synthesis of 1.7‐Diazaperylene

The hitherto unknown 1,7‐Diazaperylene (2) has been prepared in a five‐step synthesis from 1,5‐diaminoanthraquinone (3) by a Meerwein arylation reaction. Applications as a fluorescent dye are discussed.
1H‐CIDNP bei einer Insertionsreaktion von Dimethylsilylenen
Authors: Lehnig Manfred , Reininghaus Frank
Published: July 2007

1H‐CIDNP During an Insertion Reaction of Dimethylsilylenes

During the reaction of photochemically generated silylenes Me2Si: with benzyl bromide, 1H‐CIDNP (chemically induced dynamic nuclear polarization) is observed in the radical abstraction‐recombination product PhCH2‐SiMe2Br formed from singlet states of Me2Si:.
Intramolekulare Cycloaddition von Nitronen
Authors: Aurich Hans Günter , Boutahar Mostafa , Köster Heiner , Möbus Klaus‐Dieter , Ruiz Luis
Published: July 2007

Intramolecular Cycloaddition of Nitrones

Nitrones 9 and 10, formed by treatment of the corresponding aldehydes with N‐substituted hydroxylamines, are converted into the cis fused bicyclic compounds 11 and 12, respectively. While this intramolecular cycloaddition as a rule occurs at room temperature, the formation of compounds 17/18 and/or 20/21 from the corresponding nitrones needs refluxing in toluene with exception of 17Ca. The N‐aryl‐substituted nitrones 14C/15C form dimers 22C/23C spontanously at room temperature. However, dimerization is reversible; thus 22/23C afford the bicyclic compounds 17/18 and/or 20/21 on heating in toluene via the corresponding nitrone intermediates. — Hydrogenation cleaves isoxazolidine ring of the bicyclic compounds. Thus, 17Ca and 18Ca yield the hexahydrothiepine 27C and oxepane derivatives 28C, respectively, 21Ca gives the tetrahydropyran 30C. Diastereomerically pure 29C arises by prolonged hydrogenation of 17Ca under reinforced conditions via 27C.
Neue Dienophile und Diene, III. Über die Addition von Cyanacetylen an [2.2]Paracyclophan
Authors: Witulski Bernhard , Ernst Ludger , Hopf Henning , Jones Peter G.
Published: July 2007

New Dienophiles and Dienes, III. — On the Addition of Cyanoacetylene to [2.2]Paracyclophane

Heating a benzene solution of [2.2]paracyclophane (2) in the presence of excess cyanoacetylene (1b) at 160°C in a sealed ampoule provides the novel 2:1‐addition product 10, as well as the previously obtained cycloadducts 7–9. It is suggested that these Nenitzescu hydrocarbon systems are formed via the cyclobutadiene intermediates 17 and 18. This hypothesis is supported by the isolation of the side‐products 1,2,4‐and 1,2,3‐tricyanobenzene (11 and 12). When a mixture of 7 and 8 is pyrolyzed at 220°C the novel dihydronaphthalene 24 is formed; the mechanism of this isomerization is discussed. The structures of 10 and 24 were confirmed by X‐ray structure determination.
Synthesen mit aliphatischen Dialdehyden, XLIV. Chirale Pentamethincyanin‐Farbstoffe und Heterocyclen aus Derivaten des (S)‐(+)‐2‐sec‐Butylmalonaldehyds
Authors: Reichardt Christian , Budnik Ulrich
Published: July 2007

Syntheses with Aliphatic Dialdehydes. XLIV. — Chiral Pentamethine Cyanine Dyes and Heterocycles from Derivatives of (S)‐(+)‐2‐sec‐Butylmalonaldehyde

Syntheses and UV/Vis‐spectroscopic properties of the chain‐substituted, homochiral pentamethine cyanine dyes 16 and 17 are described. 16 and 17 as well as the homochiral five‐, six‐, and seven‐membered heterocycles 11–15 are prepared from derivatives (5 and 6) of homochiral (S)‐(+)‐2‐sec‐Butylmalonaldehyde (8), the first known chiral malonaldehyde, which in turn is synthesized in a seven‐step procedure from homochiral (S)‐(‐)‐2‐methyl‐1‐butanol (1).
Organische Synthesen mit Übergangsmetallkomplexen, 48. Methyl(thiocarben)‐ und Alkenyl(thiocarben)‐Chrom‐Komplexe: Darstellung und Reaktionen
Authors: Aumann Rudolf , Schröder Jochen
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 48. — Methyl Thiocarbene and Alkenyl Thiocarbene Chromium Complexes: Synthesis and Reactions

Thiocarbene chromium complexes (CO)5CrC(SR1)R (4: R  Me, Ph; R1  c‐C6H11, CH2CHCH2, C2H5, C6H5) were readily obtained in up to 97% isolated yields from the corresponding ethoxycarbene chromium complexes 5a, b and thiols 6 in methanol in the presence of Na2CO3 as a catalyst. Reaction conditions, which lead to unfavorable side products, like thioacetals 8 and or thioenol ether 10, are discussed. Methyl thiocarbene complexes 4b–d undergo a facile aldol condensation with the aromatic aldehydes 14 or 16 to give alkenyl thiocarbene complexes 15b–d and 17, respectively. The CrC bonds of 15 prove to be reactive towards the insertion of isocyanides or oxygen. Thus, on addition of two equivalents of the isocyanide 18 to 15d, 1‐aza‐1,2,4‐pentatriene 20 is obtained. The oxidative decomposition of 15d on silica gel leads to the formation of thioester 25 and thioindene 26. Characteristic differences in the reactivity of thiocarbene complexes and ethoxycarbene complexes are discussed.
Übergangsmetall‐Silyl‐Komplexe, 35. Silber(I)‐Silyl‐Komplexe (R3P)nAgSiR'3 (n = 1‐3)
Authors: Wagner Herbert , Schubert Ulrich
Published: July 2007

Transition‐Metal Silyl Complexes, 35. — Silyl Complexes of Silver(I). (R3P)nAgSiR3' (n = 1‐3)

The complexes (R3P)nAgSiR'3 (n = 1‐3), dppm(AgSiR'3)2 and dppe(AgSiR'3)2 [SiR3 = Si(aryl)3 or, except for n = 3, Si(Si Me3)3) are prepared from the corresponding halide complexes or dppm/dppe(AgNO3)2 with LiSiR'3. The stability of the products increases with increasing n : the dppe‐ or dppm‐substituted complexes are distinctly more stable than the corresponding complexes with monodentate phosphane ligands. The silver‐silicon bond is highly polar as demonstrated by their properties.
Zum anomeren Effekt bei Dithiatriazinen
Authors: Jaudas‐Prezel Evelyn , Maggiulli Roberto , Mews Rüdiger , Oberhammer Heinz , Paust Thomas , Stohrer Wolf‐Dieter
Published: July 2007

The Anomeric Effect in Dithiatriazines

From (CF3CN3S2)n (1) and XeF2, Br2, or (CF3)2NO* the corresponding S,S‐substituted dithiatriazines CF3CN3S2F2 (2), CF3CN3S2Br2 (3), and CF3CN3S2[ON(CF3)2]2 (4) are prepared. An electron diffraction study of 2 in the gas phase results in a slightly aplanar 6‐membered ring with chair conformation and both S‐F bonds in axial position. MNDO calculations show that the position of the substituents at the sulfur atoms is strongly dependent on these substituents and on the ring geometry. The cis preference is the result of an anomeric effect.
Tin for organic synthesis, 3. Facile and effective synthesis of unusually substituted aromatic N‐phenylamides
Authors: Kobs Uwe , Neumann Wilhelm P.
Published: July 2007

A mild and effective new method for the preparation of a variety of arylamides 3a‐i as well as heterocyclic 5a,b and 6 and olefinic amides 7, 9 is described. The reaction of tri‐alkylstannyl‐substituted aromatic, heterocyclic or vinylic hy‐drocarbons with aryl isocyanates in the presence of aluminium trichloride provides the corresponding N‐aryl‐substituted am‐ides in good to excellent yields. The stannyl group serves as a powerful leaving group superior to hydrogen by several powers of ten which allows, via ips0 substitution, to obtain isomer patterns not accessible by normal electrophilic substi‐ tution reactions, e. g. substitution in meta position with respect to a methoxy group.