bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beiträge zur Chemie des Bors, 199 Reaktionen eines Amino‐imino‐borans mit Anilin‐Derivaten und Carbonsäureamiden
Authors: Brandl Andreas , Geisberger Gilbert , Nöth Heinrich 
Published: July 2007

Contributions to the Chemistry of Boron, 199. ‐ Reactions of an Amino‐imino‐borane with Anilines and Carboxylic Acid AmidesThe addition of aniline derivatives to (tert‐butylimino)(2,2,6,6‐tetramethylpiperidino)borane (1) leading to the mixed triaminoboranes ArNH(Me3CNH)Btmp (2) (tmp = 2,2,6,6‐tetramethylpiperidino) is sterically controlled. Reactions of 1 with acetamide produces O,N‐diborylated acetimidic acid 4. On the other hand, N‐methylacetamide adds 1 to yield the N‐borylated N‐methylacetamide 5a exclusively. In contrast, N‐isopropyl‐ and N‐tert‐butylacetamide form also the O‐borated isomers (6b, c). Their proportion increases with the steric requirements of the N‐substituent of the acetamide derivative.
Trimethylsilylcyanid als Umpolungsreagens, XVIII Nucleophile Acylierung von α‐Chlorcarbonyl‐Verbindungen – ein neuer und diastereoselektiver Zugang zu substituierten α,β‐Epoxyketonen
Authors: Hünig Siegfried , Marschner Claus 
Published: July 2007

Trimethylsilyl Cyanide ‐ A Reagent for Umpolung, XVIII. ‐ Nucleophilic Acylation of α‐Chlorocarbonyl Compounds ‐ a Novel and Diastereoselective Approach to Substituted α,β‐fl‐Epoxy KetonesThe addition products of trimethylsilyl cyanide and benzaldehyde (1a), furfural (1b), and α,β‐unsaturated aldehydes 2a‐c, respectively, react after deprotonation with α‐chloroaldehydes and ‐ketones 3a‐d. By 1,4‐O,O‐silyl rearrangement and cyanide elimination O‐trimethylsilyl acyloins 4 and 9, respectively, are formed. With fluoride, 4 and 9 react to α,β‐epoxy ketones 5 and 10 in high yield and with E/Z selectivities from 80:20 to >95: 5. By this novel route even α,β‐unsaturated epoxy ketones (10) become available.
Thermolabile Kohlenwasserstoffe, 30 Thermische Stabilität und Bildungsenthalpie von 1,1,2,2‐ und 1,1,1,2‐Tetraphenylethan. – Die Stabilisierungsenergien von Benzhydryl‐ und Triphenylmethyl‐Radikalen
Authors: Beckhaus Hans‐Dieter , Dogan Barbara , Schaetzer Jürgen , Hellmann Siegrid , Rüchardt Christoph 
Published: July 2007

Thermolabile Hydrocarbons, 30. ‐ Thermal Stability and Heat of Formation of 1,1,2,2‐ and 1.1,1,2‐Tetraphenylethane. ‐Energy of Stabilisation of Benzhydryl and Triphenylmethyl RadicalsHeats of combustion of symmetrical (3) and unsymmetrical tetraphenylethane (4) were determined by combustion calorimetry: ΔH(c)(3) = ‐ 3249.5 ± 0.8;(4) = ‐ 3252.0 ± 0.6 kcal/mol. Enthalpies of sublimation of 3 (ΔH = 32.7 kcal/mol) and 4 (31.7 kcal/mol) were obtained from vapour‐pressure‐temperature relations, which were determined by a gassaturation method. The resulting heats of formation ΔH(g) (3) = 85.4 ± 1.3 and ΔH(g)(4) = 87.3 ± 0.8 kcal/mol correspond to low strain energies: H, (3) = 1.5 and Hs (4) = 4.6 kcal/mol. The thermolysis reactions above 200°C in solution with thiophenol as a scavenger are clean first order processes. The following activation parameters are obtained from kinetic measurements: ΔH# (3) = 47.3 ± 0.3, (4) = 45.0 ± 0.3 kcal/mol, ΔS# (3) = 12.8 ± 0.5 and (4) = 14.0 ± 0.6 e.u. From the presented thermodynamic and kinetic data the stabilisation energies of the benzhydryl (1) and the trityl radical (2) have been derived by comparison with the corresponding data for the alkanes 7 and 9. As a result 1 is stabilysed by 12.9 ± 0.9 and 2 by 20.0 ± 1.7 kcal/mol, compared with a secondary or tertiary alkyl radical, respectively. Thus the substituent effect of two (or three) phenyl rings in 1 (or 2) is smaller than twice (or thrice) the value for one phenyl group14): 7.8 ± 2.0 for a secondary and 8.4 ± 1.2 kcal/mol for a teriary benzyl radical. This can be explained by steric repulsion between the phenyl rings and steric inhibition of resonance.
Chirale dreilagige und kondensierte [2.2]Cyclophane Synthese, Struktur, Chiroptik
Authors: Vögtle Fritz , Ostrowicki Andreas , Begemann Birgit , Jansen Martin , Nieger Martin , Niecke Edgar 
Published: July 2007

Chiral Triple‐Layered and Condensed [2.2]Cyclophanes ‐ Synthesis, Structure, Chiroptical PropertiesThe helical title compounds 1‐5 are obtained using a simple one‐step cyclisation reaction with yields reaching or increasing those obtained by application of organometallic methods in [2.2]phane syntheses. The formation of the triple‐layered phanes 1 leads with high selectivity only to the “up‐down” isomers with fixed conformation, as shown by X‐ray crystallography and by the detection of strong NOEs of the inner hydrogen atoms. For studies on structure‐chiroptic relation‐ships a systematic sequence of helical [2.2]phanes with larger arene systems is synthesized. Enrichment of enantiomers is achieved by HPLC on (+)‐PTrMA; the kinetics of racemisation and the CD spectra are discussed.
Die Thermolyse oxidierter 1,3‐Dithiolane: Ein neuer Syntheseweg für Thiocarbonyl‐Verbindungen und Sulfine
Authors: Schuler Bernhard , Sundermeyer Wolfgang 
Published: July 2007

Thermolysis of Oxidized 1.3‐Dithiolanes: A New Route for the Synthesis of Thiocarbonyl Compounds and SulfinesCF3,‐substituted 1,3‐dithiolanes 3a–c could be synthesized and subsequently oxidized to the 1,3‐dithiolane 1‐oxides 4b,c, 1,1‐dioxides 5a‐c and 1,1,3,3‐tetroxide 6b. The thioketones CF3(R)C=S (R = C6H5, 9a; CH3, 9b) and the trifluorothioacetaldehyde (9c) could be obtained in good yields by flash vacuum pyrolysis of 5a–c. By further oxidation of 5a–c the 1,3‐dithiolane 1,1,3‐trioxides were formed, and by their pyrolysis the sulfines CF3(R)C = SO (R = C6H5, 10a; CH3, 10b) were prepared. A unique rearrangement of 7b led to the 1,4‐dithiane 1,1,4‐trioxide 8b. Various Diels‐Alder adducts were synthesized for chemical proof of the existence of 9a–c and 10a, b, and stereochemical considerations are presented.
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 NucleophilesIodo, 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 CationsCyclic 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 StructuresOctamethylcyclotetrasilazane 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)4Tris(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 IsocyanidesPentacarbonyl(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‐aminesStannazane 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‐oneThe reaction of the enone1with formic acid selectively yields the formate2. The esters3band4are isolated as side products. The mechanism of this rearrangement is discussed.
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 Derivatives2‐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.
Sextettumlagerungen als Solvens‐Polaritätssonde
Authors: Langhals Heinz , Hadizamani Katja 
Published: July 2007

Sextett Rearrangements as Solvent Polarity ProbesThe 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‐thiolate2,2,4,4‐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 StructuresThe 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‐BoranePyrrolidon 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 ComplexesThe 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‐boracyclohexadienesBoracyclohexadiees 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.
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 CatalysisReactions 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.
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 AdductBis(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.