bluuebunny/crossref_metadata_2025 huggingface dataset:
Aminobenzole, 211), Elektronen‐Transfer bei den Reaktionen von Halogen‐σ‐Komplexen des 1,3,5‐Tris(1‐pyrrolidinyl)benzols mit Nucleophilen
Authors: Effenberger Franz , Bäuerle Peter , Seufert Walter , Stohrer Wolf‐Dieter
Published: July 2007

Aminobenzenes, 21. ‐ Electron Transfer in the Reactions of Halogeno G‐complexes of 1.3.5‐Tris(l‐pyrrolidinyl)benzene with Nucleophiles

Iodo, bromo, chloro, and thiocyanato σ‐complexes 4, accessible as crystalline compounds from 1,3,5‐tris(1‐pyrrolidinyl)benzene (1) with halogens and dirhodan, respectively, react with nucleophiles or bases under dehalogenation, deprotonation, dimerization, or H σ‐complex formation. The product formation depends on the redox potentials of the σ‐complexes (acceptors) and the nucleophiles (donors), on the leaving tendency of the substituents on C‐1 of the σ‐complexes, and on the reaction time. The unexpected reactions are interpreted by an electron transfer from the nucleophile Y| to the σ‐complex A+ to give the radical A*, a subsequent heterolytic dissociation to the 1,3,5‐tris(1‐pyrrolidinyl)benzene radical cation C.+, and its follow‐up reactions (addition of nucleophiles, dimerization, and H abstraction). The H σ‐complex 6 results the most stable final product after long reaction times because of its lowest acceptor properties and the poor nucleofugal leaving tendency of a hydride ion.
Reduktion von (Cyclobutadien)(cyclopentadienyl)‐ und (1,5‐Cyclooctadien)‐ (cyclopentadienyl)nickel‐Kationen
Authors: Kölle Ulrich , Ting‐Zhen Ding , Keller Hubert , Ramakrishna B. L. , Raabe Eleonore , Krüger Carl , Raabe Gerhad , Fleischhauer Jörg
Published: July 2007

Reduction of (Cyclobutadiene)(cyclopentadienyl)‐ and (1,5‐Cyclooctadiene)(cyclopentadienyl)nickel Cations

Cyclic voltammetry of the four cationic Ni sandwich complexes [Ni(C5R5)(C4R4')]+ (2: R = H, R' = Ph; 3: R = H, R' = Me; 4; R = Me, R' = Ph; 5: R = R' = Me) shows reversible one‐electron reductions for the phenyl derivatives 2 and 4 and a peak pattern characteristic of reductive dimerization/oxidative monomerization for the methyl derivatives 3 and 5. The product of the reduction of 3 was isolated and characterized analytically and by an X‐ray structure determination as the dimer 6 of 3, linked through cyclobutenyl rings, the first example for a dimerization of an electron‐rich sandwich complex at a substituted C atom. EPR spectra of the neutral complexes 2 and 4 are compared to those of (1,5‐cyclooctadiene)(cyclopentadienyl)nickel (7) and are interpreted in terms of a substantial static Jahn‐Teller distortion.
Alkali‐Salze des Octamethylcyclotetrasilazans – Synthese und Kristallstrukturen
Authors: Dippel Kerstin , Klingebiel Ume , Kottke Thomas , Pauer Frank , Sheldrick George M. , Stalke Dietmar
Published: July 2007

Alkali Salts of Octamethylcyclotetrasilazane ‐ Synthesis and Crystal Structures

Octamethylcyclotetrasilazane reacts with n‐butyllithium or the elements sodium and potassium to give the alkali salt 1, 2, and 3. 1–3 crystallize as dimeric THF adducts. In the dimers two eight‐membered rings are connected by a planar alkali metal‐nitrogen four‐membered ring. Lithium is tricoordinated in 1, sodium tetracoordinated in 2, and potassium penta‐ and hexacoordinated in 3. The crystal structures of the alkali salts are discussed and compared with one another. The coordinatively bonded TH in the lithium compound 1 can be exchanged with the Lewis base TMEDA. The crystal structure of 4 shows a higher symmetry than that of 1.
Tris(trimethylsilyl)arsan als Edukt für Tri‐ und Tetraferrioarsonium‐Salze; Kristallstruktur von [{Cp(CO)2Fe}3AsOH]B(C6H5)4
Authors: Lorenz Ingo‐Peter , Effinger Guido , Hiller Wolfgang
Published: July 2007

Tris(trimethylsily1)arsane as a Starting Compound for Tri‐ and Tetraferrioarsonium Salts; Crystal Structure of [{Cp(CO)2Fe}3AsOH]B(C6H5)4

Tris(trimethylsilyl)arsane (1) reacts with an excess of CpFe(O)2Cl (2) to give tetraferrioarsonium chloride [{Cp(CO)2Fe}4As]Clk (4a), which may be converted into the corresponding tetraphenylborate 4b by Na[B(6H5)4]. In the Presence of water one organometallic ligand is hydrolysed to yield the triferriohydroxyarsonium tetraphenylborate 5 which crystallizes in the triclinic space group P&1bar; and shows a trigonal pyramidal configuration at the arsenic atom.
Cr(CO)4(CNCF3)(CNCH3) und Cr(CO)4(CNCF3) (CNC6H5), Isocyanid‐Komplexe mit +I‐ und ‐I‐substituierten Isocyaniden
Authors: Lentz Dieter , Pötter Brigitte , Marschall Robert , Brügam Irene , Fuchs Joachim
Published: July 2007

Cr(CO)4(CNCF3)(CNCH3) and Cr(CO)4(CNCF3) (CNC6H5), Isocyanide Complexes with +I‐ and ‐ I‐substituted Isocyanides

Pentacarbonyl(trifluoromethyl isocyanide)chromium (1) undergoes photolytic substitution of exclusively one carbonyl ligand by THF. According to the IR spectrum, (CO)4Cr(CNCF3) (THF) (2) consists of a mixture of the trans and cis isomer. 2 reacts with methyl isocyanide (3) and phenyl isocyanide (4) forming 9CO)4Cr(CNCF3) (CNCH3) (5) and (CO)4Cr(CNCF3) (CNC6H5) (7), respectively. 5 is obtained as a mixture of the trans and cis isomer (10:1), which can be separated by chromatography. In addition, a small amount of the disubstituted compound (CO)3Cr(CNCF3) (CNCH3)2 (6) is obtained, which according to its spectroscopic data contains the CNCF3 ligand and one CNCH3 ligand in trans position. In the case of 7, the trans isomer is the only product observed. The structure of trans‐5 has been established by X‐ray crystal structure determination.
Beiträge zur Chemie des Bors, 200. Zur Kenntnis B‐funktionaler Diboryl‐silyl‐ und Boryl‐silyl‐stannyl‐amine
Authors: Gasparis‐Ebeling Theo , Nöth Heinrich
Published: July 2007

Contributions to the Chemistry of Boron, 200. ‐ B‐Functional Diboryl‐silyl‐ and Boryl‐silyl‐stannyl‐amines

Stannazane cleavage of Cl3‐nMenSiN(SnMe3)2 with an excess of BCl3 leads to bis(dichloroboryl)silylamines Cl3‐nMenSiN(BCl2, 2‐chlor‐1,3,2‐dithiaborolane, or 2‐chloro‐1,3,2‐benzodioxaborole produce boryl‐silyl‐stannyl‐amines of type X2BN(SiMe3)SnMe3 (2a–c). Cl2BN(SiCl3)SnMe3 (3) is obtained similarly from BCl3 and Cl3SiN(snMe3.)2. 3 decomposes on heating with SnN cleavage and formation of (Cl3SiN=BCl)4 (4). Asymmetrically substituted diborylamines Me3SiN(BX2)‐BY2 are prepared by substitution reactions using Me3SiN(BCl2)BY2 or by stannazane cleavage of Y2BN(SiMe3)SnMe3 (2) and an appropriate boron halide. Constitution and conformation of the new diboryl‐amines are deduced from multinuclear resonance spectra.
Säurekatalysierte Umlagerung von Tetracyclo[6.3.0.04,11.05,9]undec‐6‐en‐2‐on
Authors: Ipaktschi Junes , Herber Jürgen , Kalinowski Hans‐Otto , Amme Monika , Boese Roland
Published: July 2007

Acid‐Catalyzed Rearrangement of Tetracyclo[6.3.0.04,11.05,9]undec‐6‐en‐2‐one

The reaction of the enone1with formic acid selectively yields the formate2. The esters3band4are isolated as side products. The mechanism of this rearrangement is discussed.
Photo Diels‐Alder Additons, V1 1,4‐Photoadditions of α‐Morpholinoacrylonitrile to 1‐Acylnaphthalenes
Authors: Döpp Dietrich , Memarian Hamid Reza
Published: July 2007

Photoexcited 1‐naphthaldehyde (1a), 1‐acetonaphthone (1b), and 1‐naphthophenone (1c) add α‐morpholinoacrylonitrile (2a) in a [4 + 2] mode with exceptional regio‐ and stereoselective formation of only one diastereomer of the two possible regioisomeric 1,4‐dihydro‐1,4‐ethanonaphthalene adducts. An independently formed 1,2‐adduct 4 was detected and isolated in very low yield, 4 is thermally and photochemically (313‐nm, excitation) cleaved into the starting materials with no indication of direct interconversion into 3b. Compound 3b is stable towards 313‐nm radiation, but is efficiently isomerized to give the dihydrobenzosemibullvalene 7 upon 254‐nm excitation. – All observations point to the first excited triplet state as the starting point for the 1,4‐additions.
Electron‐Density Distribution in the Bonds of a Dewar Benzene Derivative
Authors: Irngartinger Hermann , Deuter Juurgen
Published: July 2007

We determined the difference electron densities [X–X] in the bonds of a Dewar benzene derivative from low temperature X‐ray data (94 K). The density maxima on all bonds are significant. The central bond with an internuclear distance of 1.594 Å has a strong bending character. From the difference densities a bending angle of 28° can be derived.
Zur Stereoselektivität der intramolekularen Diels‐Alder‐Reaktion von 1,7,9‐Decatrien‐3‐onen zu Octalonderivaten
Authors: Zschiesche Ruth , Frey Barbara , Reißig Hans‐Ulrich , Grimm Erich
Published: July 2007

Stereoselectivity of Intramolecular Diels‐Alder Reactions of 1,7,Q‐Decatrien‐3‐ones to Octalone Derivatives

2‐Alkenyl‐substituted 2‐siloxycyclopropanes 1 and 2 serve as protected enone equivalents and are converted into key building blocks 5–8 in excellent yields. After desilylation and ring cleavage these compounds provide 1,7,9‐decatrien‐3‐ones 9–12, which undergo smooth intramolecular Diels‐Alder reaction at room temperature or approximately 100°C. The resulting octalone derivatives 13–16 are formed with exclusive or preferred cis connection of the rings. The relative configurations of the cycloadducts are secured by equilibration experiments and NMR spectroscopy (selective proton decouplings). For 11 → 15 and 12 → 16 the cis selectivitiy can remarkably be enhanced by trifluoroacetic acid catalysis. This high noninduced diastereoselectivity is caused by the endo approach of the reactive molecular sites, whereas the configuration of the third stereogenic centre (C‐2) is determined by the folding of the linking carbon chain. Preference of a boat conformation with equatorial ester group endo‐Beq may be assumed and appears to be general for intramolecular cycloadditions of such trienones. This effect as well as the influence of further substituents at the diene or dienophile portion on stereoselectivity and the reactions of other model compounds are discussed.
Novel Access to Polyazamacrocycles: Non‐Template Cyclization of Terephthalaldehyde and Aliphatic Polyamines
Authors: Pietraszkiewicz Marek , Gasiorowski Rafal
Published: July 2007

Non‐template [2+2] condensation of terephthalaldehyde with bis(3‐aminopropyl)amine and N,N'‐bis(3‐aminopropyl)‐1,2‐diaminoethane leads to macrocyclic systems that can be reduced and derivatized further, whereas a similar reaction with bis(2‐aminoethyl)amine leads to polymeric material only.
Sextettumlagerungen als Solvens‐Polaritätssonde
Authors: Langhals Heinz , Hadizamani Katja
Published: July 2007

Sextett Rearrangements as Solvent Polarity Probes

The rate constant of the Chapman variant of the Beckmann rearrangement is used as a solvent polarity probe and is mainly influenced by the polarizability of the solvent. Analogies to SN reaction are discussed.
Deuterierte Bicyclo[3.2.0]heptan‐2‐one und ihre NMR‐Spektren
Authors: Kirmse Wolfgang , Schoen Sabine , Siegfried Rainer
Published: July 2007

Deuterated Bicyclo[3.2.0]heptan‐2‐ones and their NMR Spectra

[3,3‐2H2]‐, [6,7‐2H2]‐, [6,6‐2H2]‐, and [7,7‐2H2]bicyclo[3.2.0]heptan‐2‐ones were prepared, starting from 2‐cyclopenten‐1‐one (1). Using these derivatives, the 13C‐ and 1H‐NMR spectra of bicyclo[3.2.0]heptan‐2‐one (2) have been assigned.
Reaktionen von 2,2,4,4‐Tetrakis(trifluormethyl)‐1,3‐dithietan mit KNCS und KNCO – Struktur des Triphenylphosphan‐Gold(I)‐Komplexes eines Thiazolin‐4‐thiolats
Authors: Sundermeyer Jörg , Roesky Herbert W. , Lautner Jürgen , Jones Peter G.
Published: July 2007

Reactions of 2.2,4,4‐Tetrakis(trifluoromethyl)‐1.3‐dithietane phosphane Gold(1) Complex of a Thiazoline‐4‐thiolate with KNCS and KNCO ‐ Crystal Structure of a Triphenyl‐phosphane Gold(1) Complex of a Thiazoline‐4‐thiolate

2,2,4,4‐Tetrakis(trifluoromethyl)‐1,3‐dithietane (1) reacts with KNCS to yield the potassium salt of 4‐mercapto‐2,2,5,5‐tetrakis(trifluoromethyl)‐Δ3‐thiazoline (2). An oxidative workup procedure results in the formation of the disulfide 6. The salt 2 reacts with methyl bromoacetate, benzyl bromide, 3‐bromo‐1‐phenylpropene, and 1,3‐diiodopropane to form the thioethers 3–5 and 7, respectively. Protonation of 2 results in the formation of the thiolactam 9. Disulfide 6 reacts with Cl2 in the presence of FeCl3 to yield the sulfenyl chloride 8. C–S bond formation (→10) is observed by treating 8 with Me3SiCN. The gold(I) complex 11 is formed from 2 and Ph3PAuCl. 11 crystallizes in the monoclinic space group P21/n and contains a linear P–Au–S unit. The reaction of 1 with KNCO leads after protonation to the perfluorinated lactam 12 and the cyanuric acid derivative 13.
Lithium‐Verbindungen eines Chlorsilanols und von Fluor‐funktionellen Siloxanolen; Reaktionen und Kristallstrukturen
Authors: Schmidt‐Bäse Dieter , Klingebiel Uwe
Published: July 2007

Lithium Compounds of a Chlorosilanol and of Fluoro‐Functional Siloxanols; Synthesis and Crystal Structures

The lithiated disilanol (CMe3)2Si(OH)2 (1) serves as a starting material in the reaction with halosilanes for the stepwise construction of siloxanols (4, 5, 7). 4 and 7 react with n‐C4H9Li to give the lithium compounds 6 and 8, respectively. 6 crystallizes in hexane as a trimer with planar three‐coordinated lithium, bonded to two Si‐O atoms and one Si ‐ F atom. 8 reacts in THF with LiF elimination to give cyclotrisiloxane 9. The chlorosilanol 2 is prepared by hydroxy‐chlorine exchange in 1 with PCl5. The stable lithium derivative of 2 (3) forms a dimeric THF adduct with tetrahedral lithium.
Die Borierung von Lactamen und Harnstoffen mit einem Amino‐imino‐boran
Authors: Geisberger Gilbert , Neukirchinger Katharina , Nöth Heinrich
Published: July 2007

Contribution to the Chemistry of Boron, 201. ‐ Boration of Lactams and Ureas by an Amino‐Imino‐Borane

Pyrrolidon reacts with (tert‐butylimino)(2,2,6,6‐tetramethylpiperidino)borane (1) to give the N‐borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′‐triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.
Einfluß von (Ether‐Phosphan)‐Liganden bei der Alkylwanderung in Rhodium‐Komplexen
Authors: Lindner Ekkehard , Norz Hubert
Published: July 2007

Novel Basic Ligands for the Homogeneous Catalytic Carbonylation of Methanol, XXIII. ‐ The Influence of (Ether‐Phosphane) Ligands on Alkyl Migration in Rhodium Complexes

The cationic complexes [Rh(COD)(P∼O)2[SbF6] (4a, b) are obtained from [Rh(COD)THF)2SbF6] (2) and the ligands 3a, b [P∼O = Pr2PCH2CH2OCH3 (3a), Ph2PCH2CH2OCH3 (3b)] (P∼O = 2=P coordinated; PO = η2‐O,P coordinated). In 4a, b COD is displaced by CO to form [trans‐(P∼O)2Rh(CO)3][SbF6] (5a, b). 5a, b readily eliminate carbon monoxide to form the complexes [trans ‐(P∼O)(P∼O)Rh(CO)[[SbF6](7a, b_. The reaction is reversible. Oxidative addition of CH3I to 7a, b affords the cyl complexes [cis ‐(P∼O)(P∼O)Rh(I)(C)(O)CH3)][SbF6] (8b) and [cis‐(P∼O)2Rh(I)(C(O)CH3)](SbF6] (6a) containing one or two Rh–O bonds. In the case of 7a the 31P{1H}‐NMR spectrum shows the reactive intermediate [trans ‐(P∼O)‐(P∼O)Rh(I)(CH3)(CO)][SbF6] (9a). Similarly, with 13CH3I9′a and 6′a were formed. In the presence of CO and H2O 8b and 6a Yield CH3CO2H with cleavage of one or two Rh–O bonds and back reaction to 5a, b. The opening and closing mechanism” of the (ether‐phosphane) ligands 3a, b promotes the formation of the complexes within the reaction cycle. On using the phospanes PPrR2 (10a, b), oxidative addition of CH3I by way of [trans (R2PrP)2Rh(CO)3][Sbf6] (12a) and [trans ‐(R2PrP)2Rh(CO)(THF)][Sbf6] (15a) also occurs, but no acyl complexes are formed. At 20°C 15a forms [trans ‐[R2PrP)2Rh(I)(CO)] (14a), which in turn reacts with AgSbF6 and CO to re‐form 12a. Complex 13b does not react with CH3I. Even when THF is replaced by CO in 15a, migration of the methyl group does not occur, thus the product is [trans ‐(R2PrP)2Rh‐cis‐(CO)2(I)‐(CH3)](SbF6] (16a). 13CO and 13CH3I were used for the structural investigation of the complexes 12′a, 13′a, 15′a and 16′a by 31P{1H}‐ and 13C{1H}‐NMR spectroscopy. 13a reacts with EtI, PrI, and iPrI to form 14a, oxidative addition not being observed.
Hetero‐π‐Systeme, 181 Hochsubstituierte 2,4‐Di‐tert‐butyl‐1‐boracyclohexadiene
Authors: Maier Günther , Wolf Hans‐Josef , Boese Roland
Published: July 2007

Hetero π‐Systems, la. ‐ Highly Substituted 2,4‐Di‐tert‐butyl‐l‐boracyclohexadienes

Boracyclohexadiees 14 and 16 with three bulky groups should be ideal starting materials for the preparation of kinetically stabilized borabenzene derivatives. They are formed by substitution reactions of anion 11, which itself is derived from 2,4‐di‐tert‐1‐methoxy‐1‐bora‐2,5‐cyclohexadiene (10) by lithiation. Reaction of lithium compound 11 with ferrous chloride provides the sandwich‐type complex 12. As shown by X‐ray structure analysis, 12 has C2 symmetry with the boron atoms in a syn arrangement in staggered conformation, an unusal feature for borabenzene complexes. Exchange of the methoxy group in the trimethylsilylated substance 16 leads to compounds 18a, 18b, 18c, 18d. Pyrolyses of the various precursors are described.
[2.2](2,6)‐ and [2.2](2,5)Pyrazinophanes: Synthesis and Molecular Structure
Authors: Eiermann Uwe , Krieger Claus , Neugebauer Franz A. , Staab Heinz A.
Published: July 2007

The title compounds 1–3 and their methyl derivatives 4–7 were synthesized 2,11‐dithia[3.3]pyrazinophanes 24–26 or by Hofmann 1,6‐elimination of the appropriate [(5‐methyl‐2‐pyrazinyl)methyl]trimethylammonium hydroxides followed by dimerization of the generated 2,5‐dihydro‐2,5‐dimethylenepyrazines. α‐Chlorination of the methylpyrazines 8–10 with N‐chlorosuccinimide gave the required precursors 11, 12, 14, 17 and 18. The results of the X‐ray structure determinations for 1–4 and 7 which indicate an unequivocal isomer assignment are discussed with regard to steric strain in these molecules. The electronic spectra of the pyrazinophanes 7–7 are reported and compared with those of the parent methylpyrazines.
Über Katalysatoreffekte bei Umsetzungen α,β‐ungesättigter Ketone und Ester mit Haloformen unter Phasenstransfer‐Katalyse
Authors: Dehmlow Eckehard V. , Wilkenloh Jiirgen
Published: July 2007

Catalyst Effects on Reactions of α, β‐Unsaturated Ketones and Esters with Haloforms under Phase‐Transfer Catalysis

Reactions of acceptor‐substituted alkenes with haloform/sodium hydroxide and PT‐catalyst result in dihalocarbene additions competitive to Michael additions, with or without consecutive cyclization, and further reactions. Product compositions are strongly dependent on the nature of the phasetransfer catalyst: Sterically unhindered quaternary ammonium ions and benzo‐crown ethers favour processes via carbenes, large delocalized (soft) cations foster primary Michael additions. Thus, tert‐butyl cis‐crotonate is dichlorocyclopropanated stereospecifically with NMe4Cl. The respective stereospecific CBr2 conversion is successful only with PhHgCBr3.
Acylsilenes (3‐Oxo‐1‐sila‐1‐propenes) from Acyl(disilanyl)carbenes
Authors: Schneider Klaus , Daucher Birgit , Fronda Antonio , Maas Gerhard
Published: July 2007

UV photolysis of diazo(disilanyl)methyl ketones 2 in benzene generates acyl(disilanyl)carbenes 3, which rearrange to 3‐OxO‐1‐sila‐1‐propenes 4. The latter compounds are reactive intermediates which either cyclize to l‐oxa‐2‐sila‐3‐cyclobutenes 5 or form the eight‐membered cyclodimers 6, depending on the substituent of the acyl function. In a side reaction, isomerization of 4 to disilylketenes 7 takes place in some cases. On the other hand, photolysis of diazo ketone 13 yields both the l‐oxa‐2‐sila‐3‐cyclobutene 5a (via the acylsilene 14) and the adamantyl (trisilanyl)ketene 15 (by Wolff rearrangement).
Bis(trifluormethyl)sulfen, (CF3)2C = SO2: seine Darstellung und Isolierung als Amin‐Addukt
Authors: Hartwig Uwe , Rall Klaus , Sundermeyer Wolfgang
Published: July 2007

Bis(trifluoromethyl)sulfene, (CF3)2C = SO2: Its Synthesis and Isolation as Amine Adduct

Bis(trifluoromethyl)sulfene was obtained and stabilized as quinuclidine adduct 16 by three different methods: (1) by direct symmetrical splitting of the tetrakis(trifluoromethyl)‐1,3‐dithietane S‐oxides 11 and 18 as well as via the TAS salt 15. The structure of 16 exhibits a C–S double bond. The quinuclidinium sulfonate 17 is formed under hydrolysis of 16. In comparison, the corresponding pyridinium sulfonate 13 gives evidence also for the intermediate existence of the adduct 12. The sulfonic acid 7 was prepared, but instead of the sulfonyl chloride 5 the sulfonyl chloride 6 was obtained from 7 and PCl5.
2‐Azaallenyl‐Chromkomplexe; Insertion von 1‐Aminopropin in M = C‐ und C = 0‐Bindungen. Intramolekulare Cyclopropanierung sowie [3 + 2]‐Cycloaddition unter Bildung eines 1,3‐Diaminoindens
Authors: Aumann Rudolf , Heinen Heinrich , Krüger Carl , Betz Peter
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 43. ‐ 2‐Azaallenyl Chromium Complexes; Insertion of 1‐Amino‐propyne into M  C and C  0 Bonds: Intramolecular Cyclopropanation and [3 + 21 Cycloaddition with Formation of a 1,3‐Diaminoindene

Organic Synthese via Transition Metal Complexes, 431). ‐ 2‐Azaallenyl Chromium Complexes; Insertion of 1‐Aminopropyne into M = C and C = O Bonds; Intramolecular Cyclopropanation and [3+2]Cycloaddition with Formation of a 1,3‐Diaminoindene The 2‐azaallenyl complex LnM⊖ ‐C(Ph)=N⊕ = C(Ph)OCO‐Ph 3 [LnM = Cr(CO)5] adds to the 1‐aminopropyne Et2N‐C = C‐CH3 (4) to give the aminocarbene complexes LnM=C(NEt2)‐C(CH3)=C(Ph)‐N(COPh)2 [(E)‐5] and LnM=C(NEt2)‐C(CH3)=C(Ph)‐NH(COPh) [(E)‐9] (by insertion of 4 into the M = C bond of 3) as well as a 1,3‐diaminoindene 6 (by [3+2] cycloaddition). An iminocarbene complex LnM = C(Ph) ‐ N=C(Ph) ‐O‐C(Ph) = C(CH3)‐CONEt2 (7) is formed as a further product (by insertion of4 into the C=O bond of 3). The latter type of reaction can also be applied to metal‐free carbonyl compounds: thus phthalic anhydride reacts smoothly with 4 to give a γ‐lactone 12 and a 1,3‐indanedione 13 by insertion of 4 into a C=O and C‐O bond, respectively. The thermolysis of the iminocarbene complex 7 yields a cyclopropane derivative 14 by an intramolecular attack of the carbene carbon at the (O)C=C bond. The structure of 14 has been determined by a crystal structure analysis. On thermolysis of 3 a triphenyloxazole 15 is obtained. The mechanisms of these reactions are discussed.
Ein neuer Zugang zu enantiomerenreinen β‐Lactamen aus α‐Aminosäuren durch präparative Anwendung der Isonitril‐Nitril‐Umlagerung
Authors: Haaf Klaus , Rüchardt Christoph
Published: July 2007

A New Approach to Enantiomerically Pure β‐Lactams from a‐Amino Acids by Applying the Isonitrile‐Nitrile Rearrangement

(S)‐Phenylalanine (1) was converted into (S)‐3‐benzyl‐2‐azetidinone (8b) by a multistep reaction sequence. The key step of this approach is a stereospecific isonitrile‐nitrile rearrangement (3 → 4) by flash pyrolysis, which may be performed in 20‐g batches of 3. An improved procedure for the preparation of (S)‐Phenylalaninol (2a) is described.
Conformational Analysis of [3.3]Paracyclophane
Authors: Sako Katsuya , Meno Tatsuya , Shinmyozu Teruo , Inazu Takahiko , Takemura Hiroyuki
Published: July 2007

According to a VT‐NMR study, [2,2,11,11‐D4][3.3]paracyclophane (1‐D4) exists as a mixture of chair and boat conformers in the ratio of 1.0: 1.3 (ΔGo = 0.1 kcal/mol) at ‐70°C with an energy barrier for the chair‐boat inversion of 12.0 kcal/mol (270 MHz, ca. 1% CD2Cl2 solution, Tc = ‐ 15°C). The conformer ratio (chair/boat) is dependent on the concentration of 1‐D4; it is 1:1 in ca. 1% CD2Cl2 solution but 1:2 in ca. 5% CD2Cl2 solution, due to preferential crystallization of the chair conformer.
TiCl4/NaI ‐ A Novel, Efficient Reagent for Mild Reduction of the N ‐ O Bond in Amine N‐Oxides and Nitrones
Authors: Balicki Roman
Published: July 2007

Heteroaromatic N‐oxides and nitrones were readily and selectively deoxygenated to the corresponding bases or imines in excellent yields with the TiCl4/NaI reagent system.
Neue Synthesen Trifluormethyl‐substituierter Heterocyclen
Authors: Rabe Gerd , Sundermeyer Jörg , Roesky Herbert W. , Schmidt Hans‐Georg , Noltemeyer Mathias
Published: July 2007

New Syntheses of Trifluoromethyl‐Substituted Heterocycles

Dimeric hexafluorothioacetone (HFTA) (1) reacts with thiourea or phenylthiourea to give 1,2,4‐dithiazolines 2a and 2b. Similarly, 1,2,4‐thiaselenazoline 3 is obtained from the reaction of 1 with selenourea. Reaction of 1 with oxamic hydrazide or thiosemicarbazide leads to acyclic molecules 4 and 5. Besides 5, the cyclic isomer 6 is also observed in solution. The N‐trifluoroacetyl derivative 6a is obtained from the reaction of 5 with trifluoracetic anhydride. The structures of 2b, 3, 5, and 6a have been determined by single‐crystal X‐ray crystallography.
Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LXIX1) Unabhängige Mechanismen der Cyclocotrimerisierung von Thiophosphinitomangan‐Komplexen mit Alkinen. – Ein einfacher Zugang zu fünfgliedrigen Heterocyclen
Authors: Lindner Ekkehard , Käss Volker , Mayer Hermann A.
Published: July 2007

Metal‐Containing Heterocycles: Preparation, Properties, Reactions. LXIX It. – Independent Mechanisms of the Cyclocotrimerization of Thiophosphinito Manganese Complexes with Alkynes. – An Easy Access to Five‐Membered Heterocycles

In solution the dimeric thiophosphinitomanganese complexes (1), Et (2), nPr(3)] are in equilibrium with the monomeric species . For R1= iPr (7) and CY (8) the complexes are kinetically stabilized. In THF 4 – 8 react with different activated alkynes R2C≡CR2 to from the S‐isomeric five‐membered heterocycles (11a, b, e–i). With additional alkynes R2C≡CR2, 11a, b, e–i are trans membered heterocycles (10g to i are also obtained. In n‐hexane, the P‐isomeric seven membered thiaphosphamanganacycloheptadiens (14g‐K) are formed in a [2 + 2 + 2) cycloaddition of 7, 8 to two molecules of R2C≡CR2. at elevated temperatures 14g‐K eliminate CO with formation of the bicyclic compounds 12g‐k. the action of MeC≡CCO2Me on 8 affords the seven‐membered ring 15 in a regiospecific [2 + 2 +2] cycloaddition. 12a‐d, h, i and 15 are starting compounds for easy access to the different substituted thiophenes 17, 18a‐d, furans 19 h, i, and hte phosphole complexes 20a, b, h, i.
Azo‐Borane – eine neue Verbindungsklasse
Authors: Hünig Siegfried , Kraft Petra
Published: July 2007

Azo Bridges from Azines, XI. – Azo‐Boranes – A New Class of Compounds

Rigid systems with azo bridges of 2,3‐diazabicyclo[2.2.1]hept‐2‐ene (DBH)‐ and 2,3‐diazabicyclo[2.2.2]oct‐2‐ene (DBO)‐type form azo‐boranes as stable, colourless solids on addition of BH3‐SMe2 or BH3‐THF (1–3, 5, 6, 8). On reaction of stoichiometric amounts of the two components CC double bonds are not attacked (2, 8, exception 4). So far unexplained violet and blue colorations of the reaction mixtures are described.
Künstliche molekulare Anion‐Wirte. Die Synthese eines chiralen bicyclischen Guanidinium‐Salzes als funktionalisierte Ankergruppe für Oxo‐Anionen
Authors: Gleich Alexander , Schmidtcher Franz P. , Scheuplein Stefan W. , Kusche Andreas , Brückner Reinhard , Harms Klaus
Published: July 2007

Artificial Molecular Anion Hosts. Synthesis of a Chiral Bicyclic Guanidinium Salt Serving as a Functionalized Anchor Group for 0x0 Anions

Starting from 1‐asparagine, the synthesis of the S,S‐bis(hydroxymethyl)‐substituted bicyclic guanidinium salt 3 is described, which is obtained in 20% overall yield with a diastereomeric excess de > 98%. The guanidinium compound 3 may serve as a binding module in the enantioselective recognition of oxo anions in polytopic abiotic receptors.
Metal Ion Binding by Amino Acids. Potassium Hydrogen L‐Glutamate Monohydrate K(L‐GluH)·H2O
Authors: Schmidbaur Hubert , Mikulcik Patrizia , Müller Gerhard
Published: July 2007

The title compound is obtained by neutralization of aqueous solutions of L‐glutamic acid with potassium hydroxide, and crystallization from aqueous methanol. The compound shows a pH of 7 in water at ambient temperature and an optical rotation [α]20D of ‐4.30 (c = 3.0). In the crystal (orthorhombic, space group P212121) the potassium ion is in a distorted trigonal‐prismatic environment of six oxygen atoms of four different amino acids and of the water molecule. No nitrogen coordination is observed. Through the bridging function of some of the α‐carboxylate oxygen atoms (O1, O2) and through complexation of the metal through the γ‐carboxylate groups (O3), a layer‐coordination polymer, with strings of potassium ions running parallel, is formed. The layers are cross‐linked by hydrogen bonds involving the ammonium and γ‐carboxylate functions as well as the water molecule.
Organosubstituierte 1,6‐Dioxa‐2‐sila‐5‐bora‐3‐cycloalkene – Herstellung und Charakterisierung
Authors: Köster Roland , Seidel Günter , Boese Roland , Wrackmeyer Bernd
Published: July 2007

Organosubstituted 1,6‐Dioxa‐2‐sila‐5‐bora‐3‐cycloalkenes – Preparation and Characterisation1)

The cis‐alkenes ROSi(CH3)2C(R)  C(C2H5)B(C2H5)OR (R  CH3: 11; C2H5: 12; C6H5: 13) are prepared from CH3NSI[CH3)2C(R)C(C2H5)BC2H5 [R  CH3: A; R  C(CH3)  CH2: B] with the monohydroxy compounds ROH (R  CH3, C2H5, C6H5). A or B react with aliphatic dihydroxy compounds HOR′OH [R′  CH2CH2: 1; CH(CH3)CH2: 2; CH(CH3)CH(CH3): 3; C(CH3)2C(CH3)2: 4; (CH2)3: 5; (CH2)4: 6] to give 8‐, 9‐, and 10‐membered ring compounds OSi(CH3)2C(R)  C(C2H5)OR′ [15a,b, 16/16′, meso/rac‐17a, D‐17a,b, 18, 19, (20)n]. A is initially cleaved at the SiN bond with formation of 14 Compound 15a crystallises as the 16‐membered (15a)2 [X‐ray structure analysis). The aromatic dihydroxy compounds catechol (7), resorcinol (8), 2,3‐dihydroxynaphthalene (9), 1, 8‐dihydroxynaphthalene (10) react with A to form 21 to 24, but mainly by protolytic BCvinyl fission to give the 2,5‐dihydro‐1,2,3‐dioxaboroles (e.g. 7f1, 9f1, 10f1) and the acyclic boron‐free compounds 7f′3, 9f3, 10f3. The MS and NMR (1H, 11B, 13C, 29Si) data of the new compounds are discussed.
Hydrocarbonylierende Cyclisierung von Dienen, 8. Cyclisierung von 1,4‐Dienen mit funktionellen Gruppen in 3‐Stellung
Authors: Eilbracht Peter , Hüttmann Gerd‐Erich , Deußen Rainer
Published: July 2007

Hydrocarbonylating Cyclization of Dienes, 81. – Cyclization of 1,4‐Dienes with Functional Groups in 3‐Position

1,4‐Dienes 1a–i with functional groups at C‐3 were synthesized and treated under the conditions of metal‐catalyzed hydrocarbonylating cyclization. Under the usual conditions no cyclization products could be isolated. Modifications of the reaction conditions did not lead to the expected cyclopentanones of type 2 or 3 either. Instead, the original functional groups are split off. Depending on the reaction conditions, either the non‐functionalized 2‐cyclopentenones 5, the cyclopentanones 6, or the 2‐cyclopentenones 7 with a functional group introduced from the solvent into the 2‐methyl group are obtained. These unexpected products of type 7 at least formally correspond to allylic rearrangement products of the expected but not observed type‐3 exo‐methylenecyclopentanones. The mechanism of the formation of these products is discussed.
Carbonylierende Ringerweiterung, 3. Stereochemie der Komplexierung und carbonylierenden Ringerweiterung von 1,3,5‐Trimethyl‐1,3‐cyclohexadien
Authors: Eilbracht Peter , Hittinger Christel , Kufferath Klaus
Published: July 2007

Carbonylating Ring Enlargement, 31). – Stereochemistry of Complexation and Carbonylating Ring Enlargement of 1,3,5‐Trimethyl‐1,3‐cyclohexadiene

The stereochemical course of the complexation and the metal‐ and Lewis acid induced carbonylating ring enlargement of cyclohexadienes 1 to bicyclo[3.2.1]oct‐3‐ene‐2,8‐diones 4 via diene iron tricarbonyl complexes 2 and complexed sevenmembered ring ketones 3 is investigated by synthesis and conversion of the diastereomeric complexes exo‐ and endo‐12 of 1,3,5‐trimethyl‐1,3‐cyclohexadiene (7). It can be concluded, that the stereochemical information of the starting materials can be transferred to the product. In the first step exo and endo substituents retain their relative position towards the metal. The introduction of the second carbon monoxide unit and ketone bridge formation also occurs stereospecifically from the side of the complexing metal without loosing the preestablished position of the substituents. Mechanistic aspects of these results are discussed.
Präorganisierte Bis‐ethine: Molekulare π‐Pinzetten?
Authors: Vögtle Fritz , Papkalla Thomas , Koch Herbert , Nieger Martin
Published: July 2007

Preorganized Bis‐ethynes: Molecular π‐Tweezers?

1,8‐Bis[(arylethynylphenyl)]naphthalenes of type V (e.g. 10, 11) and 1,8‐bis[(arylethenylphenyl)]naphthalenes (6, 6a, 7, 7a) were synthesized for the first time. In contrast to the known 1,8‐bis(arylethynyl)naphthalenes VI their “stereologs” 10 and 11 are thermally stabile. Yet they react with pentacarbonyliron to yield dinuclear transition metal complexes of the type 12, 13, i.e. a strained cyclophane macrocycle is formed by C‐C bond formation. The X‐ray analysis of the di‐tert‐butyl compound 11 shows that the peri substituents diverge, but with increasing distance from the naphthalene skeleton one of the arylethynyl units is bent to the opposite direction (Figure 2). The question whether the new molecular skeleton V can be viewed as molecular tweezers is discussed: as the hydrocarbons react irreversibly with transition metal carbonyls, they may rather be taken as “tweezers for single use”.
Photochemical Dehydrogenation, Ring Contraction, and Ring Expansion of Hydrogenated Derivatives of Benzoxazino‐benzoxazine, Quinoxalino‐quinoxaline, and Bibenzothiazole
Authors: Tauer Erich , Grellmann Karl‐Heinz
Published: July 2007

The photochemical properties of the title compounds have been investigated and compared. The benzoxazino‐benzoxazine derivatives 1 are photochemically converted into hydrogenated oxazole derivatives. In some cases this ring contraction is accompanied by a dehydrogenation reaction whereby the heterocyclic ring system becomes aromatic. Hydrogenated quinoxalino‐quinoxalines also undergo a photodehydrogenation reaction and become aromatic. However, a ring contraction yielding the imidazolyl system does not take place. The only investigated sulfur‐containing analog has different properties. The stable form is the bibenzothiazole 23 which contains a five‐membered heterocyclic ring system. Photochemically 23 rearranges under ring expansion to give the benzothiazino‐benzothiazine 24.
Alkine und Cumulene, XXI. über einige neue Oligomere des Allens
Authors: Hopf Henning , Kretschmer Olaf , Ernstb Ludger
Published: July 2007

Alkynes and Cumulenes XXI1). – On Some New Oligomers of Allene

The thermaloligomerization of allene (1) in the gas phase has been reinvestigated. AT 260°C and low conversions, 1,6,7‐trimethylenespiro[3.5]nonan (14) and 1,2,5,6‐tetramethylene cyclooctane (15) have been detected besides the already known thermal oligomers 2‐8, increase of substrate concentration and reaction time lead to significant amounts of a hexamer fraction which contains the new allene oligomers 16‐23 according to sepctroscopic analysis, Possible routes of formation of the unusual hexamers 16and 20 are discussed.
Enolate, II. Einfache Synthese von 3,4‐Dihydro‐2,4‐dioxo‐2H‐pyranen und 2‐Pyronen Enolate als 1,3‐Dianion‐Äquivalente Kristall‐ und Molekülstruktur von 6‐Ethoxy‐3,4‐dihydro‐3,3‐dimethyl‐2,4‐ dioxo‐2H‐pyran‐5‐carbonsaure‐ethylester
Authors: Saalfrank Rolf W. , Gundel Jiirgen , Roomanna Gunther , Hanek Martin , Rost Walter , Petersb Karl , Schneringb Hans Georg Von
Published: July 2007

Enolate Ions, I11). – Convenient Synthesis of 3.4‐Dihydro‐2.4‐dioxo‐2H‐pyrans and 2‐Pyrones. – Enolate Ions as Synthetic Equivalents of 1.3‐Dianions. – Crystal and Molecular Structure of Ethyl 6‐Ethoxy‐3,4‐dihydro‐3,3‐dimethyl‐2,4‐dioxo‐2H‐pyran‐5‐carboxylate

Reaction of dimethylmalonyl chloride (Sa) or cyclic 1,l‐dicar‐ bony1 dichlorides 6b – d with two equivalents of lithium enol‐ ates 7, 22, and silyl enol ethers 8, respectively, yields 3,4‐ dihydro‐2,4‐dioxo‐2H‐pyrans 10, 24, or spiro compounds 11 – 13,25‐ 27. The spiro[2S]octenes 11 and 25 isomerize spontaneously to give 2‐pyrones 14, 28, whereas spiro[3S]nonenes 12, 26 rearrange only on heating in the presence of aluminium trichloride to form the corresponding 2‐pyrones 15 and 29.However, 10, 13 as well as 24, 27 do not isomerize under these conditions. Reaction of dicarbonyl dichlorides 6a, c with one equivalent of ketene acetal 16 leads to hydroxy‐dioxo‐2H‐pyr‐ ans 17a, c. On the contrary, treatment of tetraethoxyallene (18) with dicarbonyl dichlorides 6a, b leads to dihydro‐2,4‐dioxo‐2H‐pyran 19a (X‐ray structure analysis) and spiro[2.5]octene 19b, respectively. Isomerization of 19 b yields a mixture of 2‐pyrone 20 and 4‐pyrone 21.
Charge‐Transfer Cycloaddition of Homobenzvalene with Tetracyanoethylene
Authors: Kim Eunkyoung , Kochi Jay K. , Christl Manfred
Published: July 2007

The transient yellow color observed inthe cycloaddition of homobenzvalene (HB) with tetracyanoethylen (TCNE) is associated with the charge‐transfer complex [HB, TCNE]. The deliberate photoexcitation of [HB, TCNE] affords a mixture of charge‐transfer cycloadducts (1, 2, 3) that differs from that obtained in thermal cycloaddition. The relationship of [hb + TCNE.] radical‐io pai (as the critical reactive intermediate in charge‐transfer cycloaddition) to the activation process for thermal cycloaddition is discussed.
Pyrazole‐Organoboranes, VI. Monomeric and Dimeric 9‐Pyrazolyl‐9‐borabicyclo[3.3.1]nonanes
Authors: Yalpani Mohamed , Boese Roland , Köster Roland
Published: July 2007

Bis(9H‐9‐borabicyclo[3.3.1]nonane) (9H‐9‐BBN)2 reacts with pyrazole (Pz) and its 4‐bromo, 3‐methyl, 3‐phenyl, 3,5‐dimethyl, 3‐methyl‐5‐phenyl, 3,5‐diphenyl, 3,5‐di‐ert‐butyl, 3,5‐diadamantyl, 3,5‐di‐tert‐butyl‐4‐methyl, and 3,5‐di‐tert‐butyl‐4‐ethyl derivatives [brPz, mPz, pPz, m2Pz, mpPz, p2Pz, (tb)2Pz, (ad)2Pz, (tb)2mPz, and (tb)2mPz, and (tb)2ePz, respectively] to give the 9‐pyrazolyl‐9‐borabicyclo[3.3.1]nonanes with the dimeric structure (1)2–(3)2 (X‐ray, NMR, and MS analysis), and 4–11 with monomeric structures (X‐ray, NMR, MS).
Transformation of a Platinum Carbonyl into a Platinum Carbene Moiety by Reaction with (η4‐Butadiene)zirconocene
Authors: Erker Gerhard , Menjón Babil
Published: July 2007

While (η4‐butadiene)zirconocene and ‐hafnocene do not react with Pt(PPh3)2(CO)2 (2) in toluene solution at room temperature, cp2Zr(η4‐C4H6) (1a: cp = η5‐C5H5; 1b: cp = η5‐C5H4CH3) reacts with cis‐Pt(C6F5)2L(CO) (3: L = CO; 5: L = PiPr3) under similar conditions to give the metallacyclic Fischer‐type carbene complexes (4: L = CO; 6: L = PiPr3). When L = CO, isomerization takes place by UV irradiation (cis‐4⇌trans‐4) presumably as the result of a dissociative CO scrambling process. This is not observed when L = PiPr3.
β‐hydroxydithipozimtsäure als Ligand. Palladium(II)‐ und Platin(II)‐Komplexe von 2‐benzoyl‐1‐,1‐ethendithiolat. Kristallstrukturanalyse von cis‐{(Ph3P)2Pt[S2CCHC(O)C6H5]}
Authors: Weigand Wolfgang , Bosl Gabriele , Polborn Kurt
Published: July 2007

β‐Hydroxydithiocinnamic Acid as Ligand. Palladium(I1) and Platinum(I1) Complexes of 2‐Benzoyl‐1,l‐ethenedithiolate. Crystal Structure Analysis of cis‐{(Ph3P)2Pt[S2CCHC(O)C6H5]}

β‐Hydroxydithiocinnamic acid reacts with L2Mcl2 (L = Et3P, Ph3P, 1/2 dppe; M = Pd, Pt) to yield 2‐benzoyl‐1,1‐ethenedithiolate complexes L2M[S2CCHC(O)C6H5] (2a: L = Ph3P, M = Pd; 2b: L = Et3P, M = Pt; 2c: L = Ph3P, m = Pt; 2d: L = 1/2 dppe, M = Pt). The compounds 2a–2d were characterized by their spectroscopic data (IR; 1H, 13C, 31P NMR); the structure of 2c was determined by X‐ray diffraction. A fluid solution of 2c shows fluorescence.
Synthese und Charakterisierung von (Iodcyan)iodonium‐hexafluoroarsenat, [ICNI]⊕[AsF6]⊖
Authors: Tornieporth‐Oetting Inis , Klapötke Thomas
Published: July 2007

Synthesis and Characterization of (lodocyano)iodonium Hexafluoroarsenate. [ICNI]⊕[AsF6]⊖

(Iodocyano)iodonium hexafluoroarsenate, [ICNI]⊕[AsF6]⊖ (1), was synthesized quantitatively by the reaction of iodine cyanide with [I3]⊕[AsF6]⊖ and was characterized by chemical analysis, IR, Raman and 19F‐NMR data. The [ICNI]⊕ cation in 1 represents the first example of its kind which is stable at room temperature, formally containing an N⊕‐I bond.
Neuartige basische Liganden für die homogenkatalytische Methanolcarbonylierung, XXVI. Dynamisches und reaktives Verhalten von (Ether‐Phosphan)ruthenium(II)‐Komplexen in Abhängigkeit von der O‐Basizität
Authors: Lindner Ekkehard , Karle Berthold
Published: July 2007

Novel Basic Ligands for the Homogeneous Catalytic Carbonylation of Methanol, XXVIl). ‐ Dynamic and Reactive Behaviour of (Ether‐Phosphane)Ruthenium(II) Complexes in Dependence on the o‐Basicity

Reaction of the ether‐phosphane ligand Ph2PCH2C4H7O2 (3a) with Cl2Ru(PPh3)3 (2) results in the formation of the bis(chelate) complex trans‐Cl2Ru(PˆO)2 (4a). (P∼O = η1P‐coordinated; PˆO = η2O,P‐coordinated). With CO both Ru–O bonds are cleaved to give all‐trans‐Cl2Ru(CO)2(P∼O)2 (7a). At 35°C 7a is transformed into the monocarbonyl ruthenium complex trans‐Cl2(PˆO)(P∼O)RuCO (5a) with elimination of one CO molecule. On heating all‐trans‐7a to 110°C in toluene the thermodynamically more stable complex cis‐Cl2(OC)2Ru(trans‐P∼O)2 (6a) is obtained. All reaction steps are reversible. Upon irradiation cis,cis,trans‐6a is retransformed at 40°C into 4a via all‐trans‐7a and 5a. The latter and the corresponding complexes 5b, c, containing THF and CH2OCH3 as ether substituents, show fluxional behaviour. The coalescence temperatures (10, 80, and 55°C, resp.) and the estimated ΔG≢ values (52, 65, and 59 kJ/mol, resp.) of the exchange process indicate the weakest Ru‐O contact in 5a compared to 5b, c. The lower basicity of the dioxanyl function is also responsible for the different reaction behaviour of 4a, 5a, and 7a compared to the corresponding complexes with the ligands 3b, c.
The Reaction of Nitrilium Salts with Primary, Secondary, and Tertiary Carboxamides
Authors: Jochims Johannes C. , Glocker Michael O.
Published: July 2007

Nitrilium salts (5a,b) dehydrate primary carboxamides (6a,b) to give nitriles (8a,b) and O‐protonated carboxamides (7a,b). Secondary carboxamides (9a,b,e–g) add to nitrilium salts (5b–d) to furnish mixtures of tautomeric N‐acylamidinium salts (10a–d, 11a,c). However, with the stable acetylcyanamidium salt 5d the primarily formed amidinium salts 10 either cyclize with elimination of water to yield s‐triazinium salts (12f,g) or react with a further carboxamide to afford the N‐acylamidinium salts 14e,f. At low temperatures formamides (9g,h) are dehydrated by 5d to give isonitriles, which add to an excess of 5d to furnish the oxazolidines 15g,h. The triazinium salts 12 are characterized by 1,4‐addition of alcohols giving the new triazinium salts 16a–c. Tertiary carboxamides (17a–k) add to the nitrilium salts 5d–d to give N1‐acyl‐N1,N3,N3‐substituted amidinium salts 18a–k. This reaction was extended to a vinylogous tertiary carboxamide (19) affording the cyanine dyes 20a,b.
Arenhydride, 8. Konkurrenz zwischen SET und nucleophilem Angriff bei Reaktionen von α‐Bromisobutyrophenon mit Carbanionen. Fragmentierung des Anions von Tetrahydrobianthracen
Authors: Werry Jürgen , Stamm Helmut , Sommer Andreas
Published: July 2007

Arene Hydrides, 8. ‐ SET vs. Nucleophilic Attack in Reactions of α‐Bromoisobutyrophenone with Carbanions. Fragmentation of the Anion of Tetrahydrobianthracene

SET is the main reaction pathway between α‐bromoisobutyrophenone (1) and the carbanions 7a–j− of diarylmethanes or disubstituted acetonitriles: 7− → 7. + e and e + 1 →→ Br− PhCOCMe.2 (3). Main secondary reactions are dimerization of the radical 7. (to form 6) and further reduction of 3: 7− + 3 → 7. + 4 [enolate of isobutyrophenone (5)]. Occasionally substitution products (9) of 1 are obtained. They are probably formed by combination of 7. with 3 (0% 9e at room temperature, 38% 9e at −65°C). This combination seems to be favored by cation coordination. In the reaction with 7f− (“anthracene hydride”) the dimer 6f (and probably 9f, too) undergoes fragmentation to form anthracene. The epoxide 16, arising from 1 by carbonyl attack, has been found only once with 7a–j−; (1% 16b). In contrast, 16 was the (elusive) main product in the reaction of 1 with the carbanions 7k–n− of monosubstituted acetonitriles. Here, 6 and 9 have been found only once (61, 9n). The elusive 16k–n underwent eliminative ring fission.
Struktur von N,N′‐(Phenoxathiin‐4,6‐dicarbonyl)bis(prolin‐methylester) ‐ Konformation im Kristall und in Lösung sowie nach semiempirischen Methoden
Authors: Manero Javier , Feigel Martin , Knoch Falk
Published: July 2007

Structure of N,N′‐(Phenoxathiine‐4,6‐dicarbonyl)bis(proline methyl ester) ‐ Conformation in the Crystal, in Solution, and According to Semiempirical Methods

The title compound 1 is synthesized by coupling phenoxathiine‐4,6 ‐dicarboxylic acid (2) with proline methyl ester. An improved synthesis of 2 is presented. The conformation of 1 in the crystal structure and in solution is discussed. The geometry of the product is investigated by semiempirical methods.The conformative hypersurfaces (Ramachandran diagrams) of N‐acetylproline methyl ester and N‐acetylproline methylamide are calculated with PM3.
Metal Ions Control the Competition between β‐ and γ‐Hydrogen Transfer in the Generation of Propene from 1,7‐Octadiene in the Gas Phase
Authors: Dange Oliver , Steinrück Norbert , Stöckigt Detlef , Schwarz Helmut
Published: July 2007

The mechanistic details (i.e. β‐versus γ‐hydrogen transfer) of transition‐metal ion induced generation of propene from metastable ion complexes of 1,7‐octadiene with M+=Cr+, Fe+, Ni+ are strongly affected by the nature of M+. For Cr+ the major reaction involves the transfer of an allylically activated hydrogen atom to M+ (γ‐H transfer), followed by coupling of this hydrogen with the C3H5 unit (Scheme 3: 8 → 9→ 11 → C3H6). The hydrogen transfer 9→ 11 is preceded by substantial exchange reactions. A minor path for M+=Cr+ corresponds to the more traditional β‐hydrogen transfer 9→ 10. This process, however, represents the major route for propene loss induced by M+ = Fe+, Ni+.
Darstellung und Konformationsanalyse von 9,11‐Diphenyl[5](2,6)‐pyranophan‐10‐on
Authors: Massa Werner , Schween Michael , Steuber Friedrich W. , Wocadlo Sigrid
Published: July 2007

Preparation and Conformational Analysis of 9,ll‐Diphenyl[5](2,6)‐pyranophan‐lO‐one

Phanone 5 has been generated by pyrolysis of bis(sulfone) 4. This reaction is the first example of a combined allylic‐aliphatic pyrolysis of bis(sulfones); it follows a two‐step mechanism, as is concluded from the absence of cross products and the formation of mono(sulfone) 5a as a by‐product. The flipping of the pentamethylene chain of 5 is unhindered at room temperature as shown by 1H NMR. At 213 K this flipping process is slowed on the NMR time scale, and rotation about the C‐2C‐3 axis is no longer possible. The crystal structure of 5 shows the expected tub‐like conformation of the heterocycle.
Kurzmitteilung/Short Communication Mikrowellen‐induzierte Reaktionen organischer Substrate im Hohlraum von Zeolithen
Authors: Ipaktschi Junes , Brück Matthias
Published: July 2007

Microwave‐Induced Reactions of Organic Substrates in the Cage of Zeolites

Microwave irradiation of compounds 1, 7, 15, 19, 23, and 24adsorbed on Y zeolites has been studied. The reaction rate of the corresponding rearrangement, dehydrogenation and dehydration is dramatically enhanced as compared with reactions under thermal conditions.