bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental test of structural predictions of semiempirical methods: Bis (1,2‐dioxa‐4,6‐diazacycloheptano)[4′,5′,6′: 1,6,5][4″,5″,6″: 2,3,4]‐1,2,4,5‐tetraazacyclohexane, A 7:6:7‐Tricyclic system correctly calculated by AM1 as more stable than its 6:6:6‐Tricyclic isomer
Authors: Katritzky Alan R. , Luce Hudson H. , Anders Ernst , Sullivan John M.
Published: July 2007

The condensation product 3a of hydrazine sulfate, formaldehyde, and hydrogen peroxide, for which the tricyclic 7:6:7‐ring structure 3a was previously established for the solid state by X‐ray analysis, exists as a mixture of conformations 3a and 3b in solution. AM1 calculations show the two 7:6:7‐tricyclic conformers 3a and 3b to be of approximately equal energy, and substantially lower in energy than the three isomeric 6:6:6‐perhydroheteroanthracene conformers 2a, 2b and 2c. By contrast, analogous MNDO calculations predicted that the perhydroanthracene analog conformers 2, should be more stable than 3 [ΔHf(2) < ΔHf(3)]. AM1 calculations of model compounds, containing various subunits of the tricyclic systems, demonstrate that three significant factors are responsible for the relative energies: a) The 1,3‐lone pair repulsions in the 6:6:7 system. b) The ring strain of the central tetra‐aza unit in the 7:6:7 system. c) The advantageous energetic consequences of the anomeric effect in the stable conformation of the 7:6:7 system.
Reductive lithiation of sulfides and sulfones — A novel entry into [2,3] wittig rearrangements
Authors: Kruse Birgit , Brückner Reinhard
Published: July 2007

The reductive cleavages of allyl [(phenylthio)methyl] ethers (8, 11) and an allyl [(tolylsulfonyl)methyl] ether (14) with lithium naphthalenide in THF furnish homoallylic alcohols (9, 12). The steric course of these transformations (E/Z selectivity in the case of 9, syn/anti selectivity for 12) is very similar to that of analogous Wittig‐Still rearrangements.
A synthetic route to poly(silyl)methanes via poly(phenylsilyl)methanes and poly(bromosily)methanes
Authors: Hager Rudolf , Steigelmann Oliver , Müller Gerhard , Schmidbaur Hubert
Published: July 2007

A three‐step synthesis is presented for di‐ and tri(silyl)methane, two feedstock gases for the chemical vapour deposition of amorphous hydrogenated silicon/carbon alloys (a‐SiC:H). Chloro(phenyl)silane and di‐ or trihalomethanes react with magnesium in tetrahydrofuran to give high yields of bis‐ and tris(phenylsilyl)methane, respectively. The two products can be converted into bis‐ and tris(bromosilyl)methane by treatment with anhydrous hydrogen bromide. Bromide/hydride substitution in these precursors is accomplished with lithium aluminum hydride in a two‐phase system using a phase‐transfer catalyst. The compounds CH2(SiH2Ph)2, CH(SiH2Ph)3, CH2(SiH2Br)2, CH(SiH2Br)3, CH2(SiH3)2, and CH(SiH3)3 have been characterized by standard spectroscopic methods, and the crystal and molecular structure of CH(SiH2Ph)3 has been determined by single‐crystal X‐ray diffraction. The molecule adopts a conformation with crystallographic C3 symmetry. This result is discussed with regard to the structure of related molecules with three substituents of potential Cs symmetry at a tetrahedral center.
Naphthalenophane durch doppelte Photocyclodimerisierung von Distyrylnaphthalinen
Authors: Meier Herbert , Praß Ellen , Zertani Rudolf , Eckes Heinz‐Ludwig
Published: July 2007

Bei der Belichtung von Distyrylnaphthalinen entstehen in regiospezifischen Kopf‐Kopf‐Cycloadditionen Naphthalenophane. Je nach Stellung der Styryl‐Gruppen beobachtet man vollkommen stereospezifische Prozesse (1d → 2, 1g → 3, 1h → 4) und Dimerisierungen mit partiellen Stereoselektivitäten (1b → 5–8, 1i → 9, 10). Maßgeblich sind die Rotamerenpopulation im Ausgangsprodukt 1 und die elektronischen und sterischen Effekte in den Excimeren. Prinzipiell sind Excimere mit paralleler Anordnung möglichst vieler π‐Zentren bevorzugt — ein experimenteller Befund, der durch HMO‐Rechnungen untermauert wird.
Umsetzungen am Tricyclo[5.3.0.02,8]deca‐3,5‐dien‐System: Pyrolysen, photochemische Reaktionen und Synthese neuer (CH)10‐Isomerer
Authors: Gleiter Rolf , Steuerle Ulrich
Published: July 2007

Die Pyrolyse von Tricyclo[5.3.0.02,8]deca‐3,5‐dien (4) und von in der Ethano‐Brücke substituierten Derivaten führt zu Tricyclo‐[5.3.0.02,10]deca‐3,5‐dien (6) bzw. Derivaten von 6. π‐Substituenten erleichtern die [1,5]‐C‐Verschiebung und bedingen den selektiven Bruch der doppelt konjugierten Cyclobutan‐Bindung. Bei den Photolysen von 4 und seinen Derivaten findet man eine Konkurrenz zwischen dem elektrocyclischen Ringschluß der Butadien‐Einheit und einer [1,5]‐C‐Verschiebung; letztere erfolgt vermutlich aus dem Triplett‐Zustand. Bei Derivaten mit π‐Substituenten dominiert die [1,5]‐C‐Verschiebung. Die Synthese von Tetracyclo[5.3.0.02,8.03,6]deca‐4,9‐dien (5), einem neuen (CH)10‐Isomeren, wird beschrieben. Die Thermolyse und Photolyse von 5 führt zu einem Isomeren, 3,6‐exo‐Tetracyclo[5.3.0.02,10.03,6]deca‐4,8‐dien (54b).
The synthesis and molecular structure of tetra(isopropyl)silane
Authors: Anderson David C. , Rankin David W. H. , Robertson Heather E. , Frazão Carlos M. F. , Schmidbaur Hubert
Published: July 2007

Tetra(isopropyl)silane has been prepared using literature methods, with the individual steps improved by changes in some of the experimental conditions. The key reagent 2‐lithiopropene, which can now be obtained in good yields from 1‐methacrylic acid via 1,2‐dibromo‐1‐methylpropionic acid and 2‐bromopropene by treatment of the latter with ultrasound‐activated lithium metal, was shown to contain mono‐ and dilithiopropyne. The reaction with chlorotrimethylsilane led to the corresponding silylated derivatives, while with silicon tetrachloride tetra(isopropenyl)silane was obtained, which after purification is easily converted into the title compound by catalytic hydrogenation. — The gas phase molecular structure of [(CH3)2CH]4Si has been determined by electron diffraction. The parameters could be successfully refined for a model of S4 symmetry. Bond distances SiC, CC, and CH as well as bond angles SiCC and CCH show the steric compression of the four isopropyl substituents. Steric strain is minimized by twists of the methyl groups and the isopropyl groups away from the fully staggered conformations, but also by an increase of two of the CSiC angles as compared to the remaining four, which are decreased relative to the tetrahedral standard. The structure differs strongly (mainly in the twist angles) from that of the isoelectronic tetra(isopropyl)phosphonium cation in [(CH3)2CH]4P+[B(C6H5)4]−, but is very similar to those of tetra(cyclohexyl)silane and of tri(isopropyl)phosphonium isopropylide, where the pyramidal configuration of the ylidic carbon atoms leads to a pseudo homoleptic array of the substituents at phosphorus.
Niedermolekulare Phosphorsulfide in der Gasphase
Authors: Keck Helmut , Kuchen Wilhelm , Renneberg Heike , Terlouw Johan K. , Visser Herman C.
Published: July 2007

Low‐Molecular Phosphorus Sulfides in the Gas Phase

Ionized low‐molecular phosphorus sulfides, viz. PS+, PS, and P2S are generated by electron‐impact (EI) fragmentation of P4S10. The results of collisional‐activation (CA) mass spectra and semiempirical MO calculations suggest a linear structure for SPS+ (D∞;h) and a ring structure for P2S (D2h). As shown by neutralization‐reionization mass spectrometry (NRMS) all the ions mentioned above can be reduced to the corresponding neutral molecules. Thus, low‐coordinated phosphorus sulfides containing multiple‐bond systems prove to be stable molecules in the dilute gas phase.
Phenylvinylog erweiterte Triphenylmethylium‐Systeme
Authors: Hellwinkel Dieter , Fritsch Helmut
Published: July 2007

Als isokonjugierte Modelle für (Phenylazo)tritylium‐Ionen des Typs A wurden die einfach bis dreifach Styryl‐ und Phenylethinyl‐substituierten Trityliumsysteme 1–6 untersucht. Im Einklang mit einfachen theoretischen Modellbetrachtungen weisen diese Ionen wesentlich längerwellige VIS‐Absorptionen als das Tritylium‐Ion selbst auf und zeigen auch die erwarteten bathochromen Bandenverschiebungen von den einzweigigen (1, 4) zu den zwei‐ und dreizweigigen Systemen (2, 3 bzw. 5, 6) hin. Ebenso klar kommen auch die für die 4‐Methoxystyryl‐ (1b–3b) und 4‐(Dimethylammoniostyryl)tritylium‐Ionen 1c–3c sowie das 4‐(Nitrostyryl)tritylium‐Ion 1d vorhergesagten bathochromen und hypsochromen VIS‐Bandenverschiebungen zum Ausdruck. Von den meisten der neu hergestellten Trityliumsysteme konnten voll aufgelöste NMR‐Spektren erhalten werden, deren Signallagen sehr gut mit den aus dem elementaren Konjugationsmodell folgenden Ladungsdichteverteilungen vereinbar sind. Beim farblich dem 4‐Styryltritylium‐Ion 1a entsprechenden 4,4′‐(1,2‐Ethendiyl)bistritylium‐System 12 zeigen nur die Resonanzlinien der inneren Protonen 3,β‐H und Kohlenstoffe C‐4,β signifikante Abweichungen von den entsprechenden Signallagen der Referenzsysteme 1a und Tritylium (13).
Beiträge zur Chemie des Bors, 198 Über die Reaktion von Amino‐imino‐boranen mit Dioxaphospholanen, Dioxarsolanen und Dioxastibolanen
Authors: Brandl Andreas , Nöth Heinrich
Published: July 2007

Contributions to the Chemistry of Boron, 198. ‐ Reactions of Amino‐imino‐boranes with Dioxaphospholanes, Dioxarsolanes, and Dioxastibolanes

(tert‐Butylimino)(2,2,6,6‐tetramethylpiperidino)borane (1) inserts into the exocyclic PX bond of 2‐methoxy‐ and 2‐(dimethylamino)‐1,3,2‐dioxaphospholanes, while ring expansions to the seven‐membered dioxazaphosphaborepanes 4 and 5 are observed with fluoro‐, chloro‐, bromo‐, and methyl‐dioxaphospholanes and their benzo derivatives. These decompose at elevated temperatures producing the (tetramethylpiperidino)dioxaborolane 12 and benzodioxaborole 20, respectively, and diazadiphosphetidine derivatives. Insertion into the exocyclic bond occurs also between 1 and methoxy‐benzodioxarsole (16) and ‐benzodioxastibole (17). The chloro derivatives, however, react with 1 to give 20 and (tBuN = ECl)2 (E = As, Sb) products. (2,6‐Diisopropylphenylimino)(2,2,6,6‐tetramethylpiperidino)borane (6) behaves similarly with the exception that 2‐chloro‐1,3,2‐benzodioxaphosphole yields the exocyclic insertion product. It appears from these experiments that the insertion into the exocyclic bond of the heterocyclic compounds yields kinetically controlled products, while ring expansion followed by expulsion of a dioxaborolane is thermodynamically controlled.
Diphosphabicyclobutane
Authors: Niecke Edgar , Metternich Hans Jürgen , Streubel Rainer
Published: July 2007

Diphosphabicyclobutanes

Two isomeric diphosphabicyclobutanes (5,11) are obtained by treatment of the phosphaalkenes X‐P = C(Ph)Tms (1a) and X ‐ P = CTms2 (1b) (X = halogen Tms = trimethylsilyl) with 2, Mg, or Na. Both syntheses proceed by coupling of two phosphaalkene units affording, however, two different diphospha‐butadiene intermediates. 4 and 10 readily undergo isomerization reactions to form the diphosphabicyclobutanes. Irradiation of the phosphaalkenes Cp* ‐ P = C(Ph)Tms (12a) and Cp* ‐ P = CTms2 (12b) (Cp* = C5Me5) gives rise to a different reaction pathway. Dimerization of 12a, followed by homolytic cleavage of the Cp* ‐ phosphorus bond and intramolecular recombination produces the butterfly compound 5, whereas homolytic cleavage of the Cp* ‐ element bond in 12 b, followed by rearrangement and intermolecular recombination, affords the diphosphabicyclobutane 11.
Über Metallalkyl‐ und ‐aryl‐Verbindungen, 40 Strukturverfeinerung von Methyllithium durch Neutronenbeugung von (LiCD3)4 bei 1.5 und 290 K
Authors: Weiss Erwin , Lambertsen Thomas , Schubert Bernd , Cockeroft Jeremy Karl , Wiedenmann Albrecht
Published: July 2007

Metal Alkyl und Aryl Compounds, 40% ‐ Structure Refinement of Methyl Lithium by Neutron Diffraction of (LiCD3)4 at 1.5 and 290 K

The structure of deuterated methyl lithium has been refined by neutron powder diffraction at 1.5 and 290 K. At both temperatures a cubic body‐centered arrangement of (LiCD3)4 units (Td, symmetry) is found. In agreement with previous X‐ray powder investigations (290 K) each tetramer contains a distorted cubic Li4C4 core with pyramidal methyl groups in staggered positions with respect to the adjacent Li3 unit. Refined values, in particular precise D positions, have now been obtained.
Geminale Vinyldiazide, IX Oxazole aus 3,3‐Diazido‐2‐cyanacrylsäure‐methylester und Aminen
Authors: Saalfrank Rolf W. , Ackermann Erich , Fischer Michael , Wirth Uwe , Zimmermann Helmuth
Published: July 2007

Geminal Vinyl Diazides, IX. ‐ Oxazoles from Methyl 3,3‐Diazido‐2‐cyanoacrylate and Amines

Reaction of methyl 3,3‐diazido‐2‐cyanoacrylate (1) with amines 2 at ‐ 25°C yields methyl 3‐azido‐2‐cyanoacrylates 3, which on thermal or photochemical treatment give azirines 7 and/or oxazoles 10 (X‐ray structure analysis of 101), respectively. On the contrary, 1 reacts at 20°C with amines 13 to form methyl 2‐(cyanimino)glycinates 14. Reaction of methyl 3‐azido‐2‐cyanoacrylates 30,1 with triphenylphosphane leads to Staudinger adducts 15, which are transformed by elimination of nitrogen into phosphane imides 16.
Versuche zur Erzeugung von 1,5‐ und 2,3‐Didehydroquadricyclanen
Authors: Heywang Ulrich , Szeimies Günter
Published: July 2007

Experiments towards the Generation of 1.5‐ and 2.3‐Didehydroquadricyclanes

Metalation of the (hydroxymethyl)quadricyclanes 7a‐c with n‐butyllithium in ether is determined mostly by the chelating effect of the CH2O–Li group and only to a lesser extent by the magnitude of the 13C‐1H coupling constant of the position to be lithiated in the corresponding quadricyclane derivative. Similar results were obtained for 3‐quadricyclanol (20a). Treatment of the bromide 26a, prepared by lithiation of 7b, with strong bases apparently generates the 1,2‐didehydroquadricyclane 34 and not the 1,5‐didehydroquadricyclane 35. Attempts to convert the dihalide 9 into the 2,3‐didehydroquadricyclane 4 were unsuccessful.
Regiospecific Activation of C–H Bonds in Fe+ Complexes of ω‐Silyl‐substituted Alkanenitriles Caused by Metal‐Ion‐Mediated Cooperative Effects of Functional Groups
Authors: Hässelbarth Alexander , Prüsse Tilmann , Schwarz Helmut
Published: July 2007

In contrast to the monofunctinal compounds (i.e. 8,8‐dimethylnonanenitrile and n‐heptyltrimethylsilane) the Fe+ complex of 7‐trimethylsilyheptanenitrile (2‐Fe+) exhibits a unique reactivity in the gas phase which can only be explained by invoking a metal‐ion‐mediated cooperation of the SiMe3 and the CN group resulting in the regiospecific activation of C–H bonds. In contrast tot he Fe+ complexes of the monofunctional molecules, no C–C bond activation is observed for 2–Fe+.
Untersuchungen zur Chemie von Isoindolen und Isoindoleninen, XXXVI1. Reaktionen von 2‐Alkyl‐2H‐isoindolen mit Maleinimiden
Authors: Kreher Richard P. , Seubert Jürgen , Schmitt Dieter , Use Götz , Kohl Norbert , Muleta Tilahun
Published: July 2007

Studies on the Chemistry of Isoindoles and Isoindolenines, XXXVI ‐ Reactions of 2‐Alkyl‐2H‐isoindoles with Maleic Imides

2‐Alkyl‐2H‐isoindoles2react with maleic imides4exclusively in position 1 and 3 by cycloaddition to form Diels‐Alder adducts. The transformation of theendoisomers6into the thermodynamically more stableexoisomers7depends on the dienophile. The cycloaddition is useful for analytical detection of o‐quinoid hetarenes 2 and for the synthesis of 7‐azabicyclo[2.2.1]heptenes.
Synthese und Koordinationsverhalten von Selenoalkinylen R‐Se‐C≡C‐R′
Authors: Lang Heinrich , Keller Holger , Imhof Wolfgang , Martin Sabine
Published: July 2007

Synthesis and Coordination Ability of Selenoalkynes R ‐ Se ‐ C ≡ C ‐ R′

Several synthetic methods for the preparation of selenoalkynes R–Se–C≡C–R′ (1) are discussed. 1 reacts with octacarbonyl dicobalt to yield the η2‐π‐side‐on coordinated alkyne complexes R‐Se[(η2‐C≡C–R′)Co2(CO)6 (8) which contain a sterically hindered carbon–cobalt tetrahedrane cluster unit. The identity of compounds 1 and 8 is documented by analytical and spectroscopic [IR, MS, 1H‐, 77Se‐, and 13C‐NMR) data as well as by X‐ray analysis of C6H5)Co2‐(CO)6] (8a).
Synthese und chemische Eigenschaften von Pentafluorbenzolselenonsäure und Derivatisierung der Trifluormethanselenonsäure
Authors: Haas Alois , Schinkel Karen
Published: July 2007

Synthesis and Chemical Properties of Pentafluorobenzeneselenonic Acid and Derivatives of Trifluoromethaneselenonic Acid

Oxidation of C6F5SeO2H with KMnO4 in aqueous solution gives C6F5SeO3K(1a), which is converted into C6F5SeO3H·2H2O by 70% HClO4. Dehydration at 80°C in vacuo leads to C6F5SeO3H (1), which is converted into its anhydride 1h by further dehydration at 200°C in vacuo. The acid is neutralized with MOH (M = Li, Na, NH4, 1/2 Ba) to form the corresponding salts C6F5SeO3M (1b–e). By metatheses with MNO3 1a is converted to C6F5SeO3M′ [M′ = Cs, Ag (1f, g)]. With RI or (CH3)3SiCl, respectively, C6F5SeO3Ag (1f) forms C6F5SeO3R [R = CH3, C2H5, n‐C3H7, (CH3)3Si (2a–d)]. At – 40°C, reaction between C6F5SeO3C2H5 (2b) and (CH3)2NH leads to C6F5SeO2‐N(CH3)2 (2e), which decomposes above – 20°C. If (CH3)2NH is used in excess, 4‐(CH3)2NC6F4SeO2N(CH3)2 (2f) is formed. It hydrolyses to 4‐[(CH3)2NH2][4‐(CH3)2NC6F4SeO3] (2g). Chlorination of C6F5SeO2H with SO2Cl2 yields C6F5Se(O)Cl. Esterification of CF3SeO3H is accomplished by treating CF3SeO3Ag with C2H5I. The ester 3a reacts with (CH3)2NH at – 40°C to form CF3SeO2N(CH3)2 (3b), which like the pentafluorobenzene compound is also unstable above – 20°C.
B2N4Se‐Bicyclo[2.2.1]heptanes and B2N4Se2‐Bicyclo[2.2.2]octanes
Authors: Yalpani Mohamed , Köster Roland , Boese Roland
Published: July 2007

B2N4Se2‐Bicyclo[2.2.2]octanes

Aus 3,5‐Dialkyl‐1,2,4,3,5‐triselenadiborolanen [Alkyl = C2H5 (1a) und Alkyl = n‐C3H7 (1b)] werden mit Pyrazol (Pz), 3‐Methylpyrazol (mPz) und 3‐Phenylpyrazol (pPz) die Diselenabicyclo[2.2.2]octane 2–4 hergestellt. Demgegenüber reagieren 3,5‐Dimethyl‐ und 3,5‐Diphenylpyrazol (m2Pz, P2Pz) mit 1a zu den Monoselenabicyclo[2.2.1]heptanen 5 und 6. Von 2a und 5 liegen Kristallstrukturanalysen vor.
Zur Reaktion des Diphosphenyl‐Komplexes (η5‐C5Me5)(CO)2Fe – P=P – Aryl (Aryl = 2,4,6‐tBu3C6H2) mit elektronenarmen Alkenen. Röntgenstrukturanalyse des Diphosphetans
Authors: Weber Lothar , Frebel Matthias , Boese Roland
Published: July 2007

Transition‐Metal‐Substituted Diphosphenes, XVIII1). – On the Reactivity of the Diphosphenyl Complex (η5‐C5Me5)(CO)2Fe – P=P – Aryl (Aryl = 2,4,6‐tBu3C6H2) with Electron‐Deficient Alkenes. X‐ray Analysis of the Diphosphetane

The transition‐metal‐substituted diphosphene (η5‐C5Me5)(CO)2Fe – P=P – Aryl (1) reacts with fumarodinitrile (2a) to give the 1,2 diphosphetane all‐trans‐ as the result of a [2 + 2] cycloaddition. Similarly, compound 1 is converted by either dimethyl fumarate (2b) or dimethyl maleate (2c) into the same cycloadduct all‐trans‐ (3b). Diphosphetane 3a was completely characterized by a single‐crystal X‐ray analysis.
Übergangsmetall‐Silyl‐Komplexe, 34 Ein zweikerniger Gold‐Silyl‐Komplex mit Gold‐Gold‐Wechselwirkung zwischen einer (R3P)2Au‐ und einer (R′3Si)ClAu‐Einheit
Authors: Meyer Jürgen , Piana Hermann , Wagner Herbert , Schubert Ulrich
Published: July 2007

Transition‐Metal Silyl Complexes, 34. – A Dinuclear Gold Silyl Complex with Gold‐ Gold Interaction Between an (R3P)2Au and an (R′3,Si)ClAu Unit

Ph2MeP‐Au‐Cl reacts with Ph2MeP‐Au‐SiPh3 to form the dinuclear complex (Ph2MeP)2Au2(Cl)SiPh3, which is in equilibrium with its starting compounds. An X‐ray structure analysis reveals that it consists of a (Ph2MeP)2Au and a (Ph3Si)ClAu unit, which are held together by Au‐Au interaction [298.07(4) Pm]. The approximately linear AuL2 units are orthogonal to each other.
Clathratbildner mit Allenstruktur – Wirtverbindungen, Kristalleinschluß und Struktur eines Dioxan‐Clathrats
Authors: Weber Edwin , Seichter Wilhelm , Goldberg Israel
Published: July 2007

Clathrate Formers with Allene Structure – Host Compounds, Crystal Inclusion, and Structure of a Dioxane Clathrate

The tetraaryl‐substituted allenes 1–8 are synthesized, and their properties in crystal inclusion are determined. Dependent on the type and number of the substituents, host compounds result, which have different inclusion properties and clathrate selectivities. Host 1h forms inclusion compounds with a wide range of apolar and relatively polar cyclic guest solvents (26 inclusions altogether), while 2, 4, 5, and 7b form only one or two inclusions. In two‐component solvent systems, high inclusion selectivities are found for the host compounds. The crystal structure of the 4.dioxane (1:1) clathrate is reported. Relations between structure and inclusion selectivity are discussed.
Photochemistry of 2‐Methyl‐2‐trifluoromethyl‐ and 2,2‐Bis(trifluoromethyl)‐3(2H)‐furanone
Authors: Gebel Rolf‐Christoph , Margaretha Paul
Published: July 2007

The behaviour of 2‐methyl‐2‐trifluoromethyl‐3(2H)‐furanone (1b) and 2,2‐bis(trifluoromethyl)‐3(2H)‐furanone (1c) is compared to that of the parent dimethyl compound 1a for the following light‐induced reactions: (a) cyclodimerization, (b) [2 + 2] cycloaddition to 2,3‐dimethyl‐2‐butene, and (c) reductive (RH) addition to 2‐propanol. A pronounced acceleration due to the exchange of CH3 against CF3 is observed in this last reaction; the mechanistic aspects are discussed.
Ein Cyclobutadiencarboxylat als Hetero‐1,3‐dien bei Diels‐Alder‐Reaktionen mit 2H‐Azirinen
Authors: Regitz Manfred , Michels Gisbert
Published: July 2007

Antiaromatic Compounds, 26 – A Cyclobutadienecarboxylate as a Hetero‐1,3‐diene in Diels‐Alder Reactions with 2H‐Azirines

The cyclobutadienecarboxylic ester 1 adds 2H‐azirines (2a‐1) to yield the oxaazatricyclic compounds 4a‐f. Under thermolysis conditions cleavage of isobutylene and formation of tricyclic ketones occurs (4a, c–e → 7a–d). The Dear pyridone 11 arises from the photolysis of 7a. The structures of compounds 4b and 11 are confirmed by X‐ray crystal structure analyses.
Beiträge zur Chemie des Bors, 202. Borylierung von Aminosäuren mit einem Amino‐imino‐boran
Authors: Geisberger Gilbert , Nöth Heinrich
Published: July 2007

Contributions to the Chemistry of Boron, 2021). – Borylation of Amino Acids by an Amino‐imino‐borane

Reactions of (tert‐butylimino)(2,2,6,6‐tetramethylpiperidino)‐borane (3) with amino acid esters or N,N‐dimethyl amino acids lead to the N‐borylated products 5 and boryl esters 11, respectively. Amino acids and 3 yield the O,N‐bis‐boryl compounds 13 and/or 1,3,2‐oxazaborolidin‐5‐ones 14, depending on the size of the organyl substituent R at the α‐carbon atom of the amino acid. Increasing the bulk of this group favours the formation of 14 with elimination of tert‐butylamine. The five‐membered OBNCC ring of 14 is planar according to an X‐ray structure analysis of 14e. (2,6‐Diisopropylphenylimino)(2,2,6,6‐tetramethylpiperidino)borane reacts with amino acids similar to 3, but tetramethylpiperidine is eliminated on ring formation to produce 20. N‐Monoalkyl amino acids and 3 predominantly give oxazaborolidin‐5‐ones.
Additions‐ und Einschiebungsreaktionen von subvalenten Bor‐Verbindungen mit Aromaten
Authors: Meller Anton , Seebold Uwe , Maringgele Walter , Noltemeyer Mathias
Published: July 2007

Addition and Insertion Reactions of Subvalent Boron Species with Aromatic Compounds

Dichloro(diisopropylamino)borane reacts with pentamethyl‐cyclopentadienide providing the substitution product 1. A suspension of a sodium‐potassium alloy in 1,2‐dimethoxyethane and 1,2,4,5‐tetramethylbenzene reacts with difluoro(diisopropylamino)borane to give 1,4‐bis[fluoro(diisopropylamino)‐boryl]‐2,3,5,6‐tetramethyl‐2,5‐cyclohexadiene(3). If o‐xylene is used instead of 1,2,4,5‐tetramethylbenzene in this reaction, 1,4‐bis[fluoro(diisopropylamino)boryl]‐2,3‐dimethyl‐2,5‐cyclohexadiene (4) is the main product; however, the bicyclic compound 5 is also formed by formal insertion of two aminoborene units “BNR2” into the carbon skeleton and by addition of two (FBNR2) units. The compounds are characterized by elemental analyses and spectroscopically [MS, NMR (1H, 11B, 13C, 19F)]. An X‐ray structure analysis of 5 is presented.
Synthese und Reaktionen von 2‐Pyridylphosphan, 2‐C5NH4‐PH2
Authors: Spiegel Gerd U. , Stelzer Othrnar
Published: July 2007

Synthesis and Reactions of 2‐Pyridylphosphane, 2C5NH4‐PH2

By reduction of diethyl 2‐pyridylphosphonate (1) with LiAlH4 2‐pyridylphosphane (2) is accessible in ≈︁80% yield. H/D exchange experiments and acid/base exchange reactions between 2 and PhPHLi or Ph2PLi show (2) to be a stronger pH acid than PhPH2 and Ph2PH. Silylation of the lithium phosphides 2‐C5NH4‐PRLi (R  H, SiMe3) with Me3SiCl affords the corresponding silyl derivatives 2‐C5NH4‐PR2 with CH3I or CH2Cl2 yields the mono‐ or bidentate secondary phosphanes 2‐C5NH4‐PHMe (6) and 2‐C5NH4PHCH2PH‐2‐C5H4N (5), respectively. On treatment of 2 with CH3I or HCl the pyridinium salts [(2‐C5NH4R)PH2]+X− (R  H, Me; X= Cl, I) are formed. However, coordination of 2 to transition metals in low oxidation states occurs by the phosphorus atom. Addition of the PH bonds in 2 to the activated CC double bonds in acrylic acid esters, mesityl oxide, cinnamnic acid esters, and dimethyl vinylphosphonate leads to chiral P,N hybrid ligands with functional groups in the alkyl side chain.
Notizen/Notes. Natrium‐ und Kaliumfluorsilylamide – Synthese und Kristallstruktur
Authors: Pieper Ursula , Stalke Dietmar , Vollbrecht Susanne , Klingebiel Uwe
Published: July 2007

Sodium and Potassium Fluorosilylamides – Synthesis and Crystal Structures

tert‐Butyl(di‐tert‐butylfluorosilyl)amine (1) reacts with sodium or potassium to give the alkali salts 2 or 3, respectively. 2 and 3 crystallize as THF adducts and form head‐to‐tail dimers. Sodium is tetracoordinated in 2 and potassium hexacoordinated in 3. The crystal structures of the alkali salts are discussed.
Carbonylierende Ringerweiterung, 4. Diastereoselektive Synthesen von Bicyclo[3.2.1]oct‐3‐en‐2,8‐dionen durch doppelte Carbonylierung von (R)‐(‐)‐α‐Phellandren
Authors: Eilbracht Peter , Hittinger Christel , Kufferath Klaus , Henkel Gerald
Published: July 2007

Carbonylating Ring Enlargement, 41). – Diastereoselective Syntheses of Bicyclo[3.2.l]oct‐3‐ene‐2,8‐diones by Double Carbonylation of (It)‐(‐)‐α‐Phellandrene

In order to clarify the stereochemistry of the carbonylating ring enlargement of cyclohexadiene complexes 1 to complexed seven‐membered ring ketones 2 and the further carbonylation to bicyclo[3.2.1]oct‐3‐ene‐2,8‐diones 3 the exo and endo isomers of (R)‐(‐)‐α‐phellandrene complex 7 were synthesized in pure form and in various isomeric ratios and converted. The optically active ring‐enlargement products 11 and 12 obtained therefrom, as well as the enantiomerically pure bicyclooctenes 20–22, implicate a stereospecific reaction course under retention of the configuration predetermined by the starting material 6 and its complexes 7. This was confirmed by an X‐ray determination of the absolute configuration of exo‐12. Thus, the method is suitable for the diastereoselective synthesis of bicyclo[3.2.1]oct‐3‐ene‐2,8‐diones 3 from 1,3‐cyclohexadiene complexes 1.
4H‐3,1‐Benzoxathiine aus Benzothiet und Carbonylverbindungen
Authors: Schmidt Michael , Meier Herbert , Niedermann Hans‐Peter , Mengel Rudolf
Published: July 2007

4H‐3,1‐Benzoxathiines from Benzothiete and Carbonyl Compounds

The o‐quinoid 8‐π electron system 2, generated by thermal ring opening of benzothiete (1) undergoes [8π + 2π] cycloaddition reactions with electron‐deficient carbonyl compounds 3. In accordance with the frontier orbital theory, 4H‐3,1‐benzoxathiines (4) are obtained in a regioselective manner.
Gas‐Phase Thermolysis of 4‐Substituted 3,5‐Dihydro‐3,3,5,5‐tetramethyl‐4H‐ pyrazoles Studied by Photoelectron Spectroscopy and Flash Vacuum Pyrolysis
Authors: Kindermama Markus K. , Poppek Rainer , Rademachera Paul , Fuß Andreas , Quast Helmut
Published: July 2007

Gas‐phase thermolyses of the 3,5‐dihydro‐4 H‐pyrazoles 1 – 4 have been studied by photoelectron spectroscopy and flash vacuum pyrolysis. In the PE‐controlled thermolysis, 1–4 extrude molecular nitrogen, and the fragments cyclize immediately to different three‐membered rings. In the case of 2 and 3, the former 4‐substituent becomes part of the three‐membered ring, whereas 1 and 4 afford short living 0x0‐ and iminocyclopropanes. At higher temperatures and in flash vacuumpyrolysis, acyclic compounds and smaller molecules are formed in a second step. Based on MNDO, AM1, and PM3 calculations, the ionization potentials of 3,5‐dihydro‐3,3,5,5‐tetramethyl‐4‐methylene‐4H‐pyrazole (3) have been assigned to molecular orbitals. To aid the identification of the pyrolysis products, PE spectra of the methylenethiirane 9 and the methylenecyclopropanes 11 and 13 have been measured and interpreted with the aid of SCF calculations.
Sandwich‐ und Tripeldecker‐Komplexe des 1,4‐Diboracyclohexadiens ausgehend von 1,4‐Dibora‐2‐cyclohexen‐Derivaten1)
Authors: Wörner Karl‐Fred , Uhm Jae‐Kook , Pritzkow Hans , Siebert Walter
Published: July 2007

Sandwich und Triple‐Decker Complexes of 1,4‐Diboracyclohexadienes Starting with 1,4‐Dibora‐2‐cyclohexene Derivatives

Reactions of 1,4‐dibora‐2‐cyclohexene derivatives 1 with transition‐metal complex fragments yield the complexes of 1,4‐dibora‐2,5‐cyclohexadienes 2 by dehydrogenation. The tetra‐ and tricarbonyl complexes 4a, 5a, b are formed in the reaction of la, b with (CH3CN)3Cr(CO)3 and Fe2(CO)9, respectively: with bis(toluene)iron the sandwich 6b is obtained. The triple‐ decker complexes 7a and 8a, b are formed from 1 a, b and the dimeric carbonyl (cyclopentadienyl) complexes of nickel and iron, respectively. The bis(methallylnickel) triple‐decker 9a is obtained as a mixture of cis/trans isomers, la and [(C2H4)2‐RhCl]2 yield the tris(1,4‐diboracyclohexadiene)dirhodium triple‐decker sandwich 10a by elimination of the ethene ligands and the chlorine bridge.
Halogen(Silyl)phosphane – Synthese und Eigenschaften
Authors: Treubel Rainer , Niecke Edgar
Published: July 2007

Halogeno(si1yl)phosphanes ‐ Synthesis and Properties

Bis(trimethylsilyl)phosphanes 1a–d react with hexachloroethane to give chloro(trimethylsily)phosphanes 2a–d. The decomposition of these compounds to cyclophosphanes is found to be catalized by Lewis acids and bases. Nucleophilic substitution of the P‐chloro function of 2c leads to the bromo(9a), iodo‐ (9b) and azido derivative (10a). Methanolysis of 2a–d leads to tye secondary chlorophosphanes 11a–d.Reaction of 2a–e with chloromethylenephosphane 12a results in the formation of 1‐chlorodiphosphiranes 16a–e via a 1,2‐diphospha‐2‐propene intermediate 14. The 1‐bromo‐(19a) and 1‐iododiphosphirane 19b is accessible from 16c by exchange reaction with the corresponding halosilanes. The potential of halo(sily)phosphanes as phosphanediyl transfer reagents was unhindered in the reaction of 2c with different substituted phosphaalkenes 28a–d to the corresponding diphosphiranes 29a– d.
Synthesis and Reactivity of Chiral Rhenium Alcohol Complexes of the Formula [(η5‐C5H5)Re(NO)(PPh3)(ROH)]⊕BF4⊖
Authors: Agbossou Sénamé K. , Smith Whitney W. , Gladysz John A.
Published: July 2007

Reactions of dichloromethane complex [(η5‐C5H5)Re(NO)‐(PPh3)(ClCH2Cl)]⊕ BF4⊖ (2⊕ BF4⊖ and alcohols ROH give the title compounds [(η5‐C5H5)Re(NO)‐(PPh3)(ROH)]⊕ BF4⊖; (3⊕ BF4⊖; a: R = Me, b: Et, c: CH2Ph, d: t‐Bu) in 91–95% yields as air‐stable powders after workup. Reactions of 3a–c⊕ BF4⊖ and Et3N produce alkoxide complexes (η5‐C5H5)Re(NO)‐(PPh3)(OR) (4a–c, 80–90%), which in turn react with HBF4– OEt2 to give 3a–c⊕ BF4⊖. Reactions of 3a–c⊕ BF4⊖ and Ph3PX⊕ Br⊖ give the bromide complex (η5‐C5H5)Re(NO)‐(PPh3)(Br) (85‐98%) and alcohols ROH. 3b,c⊕ BF4⊖ and aldehydes react to give π complexes [(η5‐C5H5)Re(NO)(PPh3)(η2‐OCHR′)]⊕ BF4⊖ (>94%). Reaction of 3b⊕ BF4⊖ and HSi(OEt)3 generates the hydride complex (η5‐C5H5)Re(O)(PPh3)(H) (5, 77%). Reaction of 5 with Ph3C⊕ PF6⊖ and then ROH gives 3⊕ PF6⊖ (88–91%). NMR experiments establish the order OCHR > ROH > ROR for ligand binding energies to the rhenium fragment [(η5‐C5H5)Re(NO)(PPh3)]⊕.
Spektroskopische Studien an höheren Chromfluoriden. Zur Frage der Existenz von Chromhexafluorid, CrF6
Authors: Jacob Eberhard , Willner Helge
Published: July 2007

Spectroscopic Studies of Higher Chromium Fluorides. Controversy over the Existence of Chromium Hexafluoride, CrP6

Combustion of chromium with fluorine under various conditions led always to CrF5 as the highest chromium fluoride. The properties of pure CrF5 have been reinvestigated and IR, UV spectra of the gas‐phase molecule, and also the vapor pressure have been measured for the first time. Furthermore, it has been shown that the IR spectrum of matrix‐isolated CrF5 is identical to the IR spectrum of CrF6 quoted in the literature. It appears, that in principle the existence of CrF6 is doubtful.
Kopplung zwischen Polypyridinruthenium(II)‐ und Methylviologen‐Einheiten in π‐konjugierten Hybridsystemen
Authors: Kaim Wolfgang , Matheis Walter
Published: July 2007

Coupling between Polypyridineruthenium(II) and Methylviologen Moieties in n‐Conjugated Hybrid Systems

Complexes between the novel 3,3′‐diazamethylviologen chelate ligands and the [Ru(bpy)2]2+ fragment were synthesized and characterized by cyclic voltammetry, electronic absorption spectroscopy, and electron spin resonance. Incorporation into a common π system results in strong electronic coupling between the 4,4′‐bipyridinium and the tris(α‐diimine) metal chelate functions with significantly altered spectroscopic properties. The isomeric complexes with 4,4′‐diquaternized 2,2′‐bipyrazine ligands exhibit smaller electronic coupling and irreversible second reduction to a non‐Kekule system which helps to understand the superior photosensitizing properties of 2,2′‐bipyrazine complexes
Dreikernige Dithiadiaza[3.3.2]cyclophan‐ene
Authors: Schmiegel Jürgen , Funke Ulrike , Mix Andreas , Grützmacher Hans‐Friedrich
Published: July 2007

Trinuclear Dithiadiaza[3.3.2]cyclophan‐enes

The following five trinuclear dithiadiazacyclophanes have been prepared by means of the rigid‐group principle with a succinyl and dimethylmalonyl N,N′‐protecting group, respectively, and the high‐dilution technique: 2,11‐dithia‐19,20‐diaza[3.3.2]‐(1,4)(1,4)(1,4)cyclophan‐19‐ene (12), 2, 11‐dithia‐19,20‐diaza[3.3.2]‐(1,3)( 1,4)( 1,4)cyclophan‐19‐ene (13), 2,l l‐dithia‐19,20‐diaza[3.3.2]‐(1,4)(1,3)(1,3)cyclophan‐19‐ene (14), 2,11‐dithia‐19,20‐diaza[3.3.2]‐(1,3)(1,3)(1,3)cyclophan‐19‐ene (15), and 4,6‐dimethyl‐2,9‐dithia‐17,18‐diaza[2.2.2]( 1,3)(1,3)(1,3)cyclophan‐17‐ene (16). These cyclophanes contain an azobenzene moiety bridged in the case of 12 and 13 in the para‐positions by a benzene ring and two short links which forces 12 and 13 into a cis‐azo configuration. 14 – 16 are bridged in the meta‐positions of the azobenzene and can adopt a cis‐ and a trans‐azo configuration, respectively. 14 ‐ 16 are photoisomerized into the cis form by irradiation with γ = 369 nm. The isomerization back into the trans form occurs slowly thermally or rapidly by irradiation with λ = 443 nm.
Nucleophilic Attack at Heterocyclic Nitrogen: Unusual Reactivity of the Benzotriazole Heterocyclic Ring
Authors: Katritzky Alan R. , Rachwal Stanislaw , Offerman Rick J. , Najzarek Zbigniew , Yagoub Ahmed K. , Zhang Yougmin
Published: July 2007

Grignard reagents attack 1‐imidoylbenzotriazoles at the imidoyl carbon atom and also at the benzotriazolyl N‐2 and N‐3 atoms leading to complex reaction mixtures, the composition of which allowed identification of the main reaction paths. Mechanisms are discussed. Previous examples of nucleophilic attack on pyridine‐like nitrogen atoms are reviewed. The 1‐imidoylbenzotriazoles were prepared from amides with benzotriazole and phosphoryl chloride. Amides derived from secondary amines give α‐(benzotriazol‐1‐yl) enamines.
Dimroth‐Umlagerung von Iminen des 1,5‐Diaminotetrazols
Authors: Moderhack Dietrich , Goos Karl‐Heinz , Preu Lutz
Published: July 2007

Dimroth Rearrangement of Imines Derived from 1,5‐Diaminotetrazole

Heating the imines 1 in dimethyl sulfoxide (or partly in xylene) provides hydrazones such as 2. The reaction is greatly favoured by electron‐withdrawing groups attached to the imine carbon atom.
Fixierung von Harnstoffen und Thioharnstoffen auf dreikernigen Ruthenium‐Clustern: Synthese und Molekülstruktur von (μ2‐H)Ru3(CO)9(μ3‐NPhCSNHPh)
Authors: Bodensieck Ulf , Stoeckli‐Evans Helen , Süss‐Fink Georg
Published: July 2007

Fixation of Ureas and Thioureas on Trinuclear Ruthenium Clusters: Synthesis and Molecular Structure of (μ2‐H)Ru3(CO)9(μ3‐NPhCSNHPh)

Trinuclear clusters of the type (μ2‐H)Ru3(CO)9[μ3‐NRC(E)NHR] (EO, S; RH, Me, Ph) have been synthesized from Ru3(CO)12 and the corresponding ureas and thioureas, respectively. The X‐ray crystal structure analysis of the N,N'‐diphenylthiourea derivative 3 reveals the thiourea moiety to be coordinated to the trinuclear metal framework by the sulfur atom in a μ2‐like fashion and by one of the nitrogen atoms acting as a terminal ligand. While the SCN backbone has remained intact on the cluster site, one of the hydrogen substituents has been transferred from the coordinated nitrogen to the metal framework.
Die Reaktion von 3‐Borolenen mit terminalen Acetylenen: Ein neuer Zugang zu 2‐Borolenen
Authors: Herberich Gerhard E. , Wang Shaotian
Published: July 2007

The Reaction of 3‐Borolenes with Terminal Acetylenes: A New Route to 2‐Borolenes

3‐Borolenes (2,5‐dihydro‐1H‐boroles) (1a: R′H, RPh; 1b: R′H, RCy; 1c: R′Me, RPh) readily react with terminal acetylenes R″CCH (R″Bu, tBu, 1‐Cyclohexenyl, Ph, ClCH2, BrCH2) to give a variety of 3‐substituted 4‐vinyl‐2‐borolenes (2).
Synthese und Charakterisierung neuer Halogeno(methyl)arsen(V)‐Kationen: [(CH3)2AsI2]⊕ [AsF6]⊖, [CH3AsI3]⊕ [AsF6]⊖ und [(CH3)2AsF2]⊕ [AsF6]⊖
Authors: Tornieporth‐Oetting Inis , Klapötke Thomas
Published: July 2007

Synthesis and Characterization of Novel Halogeno(methyl)arsenic(V) Cations: [(CH3)2AsI2]⊕ [AsF6]⊖, [CH3AsI3]⊕ [AsF6]⊖ and [(CH3)2AsF2]⊕ [AsF6]⊖

The two new iodo(methyl)arsenic(V) hexafluoroarsenates [(CH3)2AsI2]⊕ [AsF6]⊖ (1) and [CH3AsI3]⊕ [AsF6]⊖ (2) have been prepared by direct oxidation of (CH3)2AsI or CH3AsI2 with IF in the presence of AsF5. (CH3)2AsF reacts quantitatively with F2 and AsF5 to yield [(CH3)2AsF2]⊕ [AsF6]⊖ (3). The reaction of 3 with CsF leads to the neutral compound (CH3)2AsF3 (4) and CsAsF6.
Chiral recognition of diastereomeric esters and acetals by EPR and NMR investigations
Authors: Mäurer Manfred , Stegmann Hartmut B.
Published: July 2007

The reaction of the racemic phenols I and II with chiral auxiliaries like the acid chloride III and particularly the lactols IV and V (Noe's reagent) leads to diastereomeric esters and acetals, respectively. The products may be synthesized either in the EPR sample tube or under preparative conditions with subsequent separation of the diastereomers by chromatographic methods. Oxidation of the phenols with lead dioxide in inert solvents provides the corresponding phenoxyls, which are investigated by EPR and ENDOR spectroscopy. The most striking features of these spectra are the differences in the β‐proton coupling constants of up to several Gauss, indicating a significant alteration of the hyperconjugation angle. These results are interpreted in terms of the population of specific conformations favored by stereoelectronic and steric interactions, which are confirmed by careful investigations of the shielding and deshielding effects in the 1H‐NMR spectra of the corresponding phenols.
Elektroreduktion organischer Verbindungen, 16. Elektroreduktion von ω‐Halogenalkandithiosäure‐methylestern
Authors: Böge Askan , Voß Jürgen
Published: July 2007

Intramolecular cyclization occurs on electroreduction of the methyl ‐haloalkanedithioates 1 in methanol. The expected semicyclic thioacetals 2 are formed according to an ECEH mechanism. The biheterocycles 12 result from dimerization of intermediate radicals whereas the semicyclic ketene dithio‐acetals 13 are formed by non‐electrochemical processes. The 2‐(methylthio)thiolanes 2 a and 16 are obtained with much higher yields and better selectivity by co‐electroreduction of the ‐dithio‐lactones 15 in the presence of dimethyl sulfate.
Siliciumverbindungen mit starken intramolekularen sterischen Wechselwirkungen, 41. Disilen‐Additionen an die CN‐Mehrfachbindungen von Isochinolin und Dicyclohexylcarbodiimid
Authors: Weidenbruch Manfred , Lesch Axel , Peters Karl , von Schnering Hans Georg
Published: July 2007

Silicon Compounds with Strong Intramolecular Steric Interactions, 41. ‐ Disilene Additions to the CN Multiple Bonds of Isoquinoline and Dicyclohexylcarbodiimide

Tetra‐tert‐butyldisilene (4), generated photolytically from hexa‐tert‐butylcyclotrisilane (3), reacts with isoquinoline in a [2 + 2] cycloaddition to give the 1,2,3‐azadisiletane derivative 7, whose structure was determined by X‐ray crystallography. Photolysis of 3 in the presence of dicyclohexycarbodiimide (8), however, yields the 1,2,4‐azadisiletanimine derivative 10, presumably formed by rearrangement of an intermediate [2 + 2] addition product of 4 to one of the CN bonds of 8. The X‐ray structure analysis of 10 reveals that the four ring atoms and the exocyclic nitrogen atom lie exactly in plane. The smallest bond angles inside the ring occur at the Si atoms.
Komplexchemischer Aufbau cyclischer 1,2‐Dithiolato‐Liganden mit dem nido‐Cluster [(CO)3FeS]2. — Molekülstruktur und partielle S‐Oxidation von Hexacarbonyl(μ2‐cis‐1,2‐cyclohexandithiolato‐S,S)dieisen
Authors: Kramer Anja , Lingnau Regine , Lorenz Ingo‐Peter , Mayer Hermann August
Published: July 2007

Complex‐Chemical Synthesis of Cyclic 1.2‐Dithiolato Ligands with the nido Cluster [(CO)3,FeS]2. — Molecular Structure and Partial S‐Oxidation of Hexacarbonyl(μ2,‐cis‐1,2‐cyclohexanedithiolato‐S,S)diiron

The cyclic alkenes, dienes, and trienes C6H10, C8C14, C5H6, C8C12 and C7H8 are inserted into the S‐S bond of the nido cluster [(CO)3FeS]2 (1) by photochemically induced [2+2] cycloaddition reactions to give the complexes 2–6; thus, saturated and unsaturated cyclic 1,2‐dithiolato ligands can be selectively built onto the complex in a μ2‐bridging fashion. According to an X‐ray structure analysis, the μ2‐1,2‐cyclohexanedithiolato‐S,S complex 2a with the pseudotetrahedral skeleton [(CO)3FeS]2 crystallizes in the monoclinic space group P21/c; the S2 moiety is bridged by cyclohexane with 1,2‐cis configuration. As an example, the partial S oxidation of 2a was carried out, leading to 2b by selective transformation of one thiolato into a sulfenato function.
[2.2](2,5)Pyrimidinophanes: Synthesis and molecular structure
Authors: Eiermann Uwe , Krieger Claus , Neugebauer Franz A.
Published: July 2007

The title compounds 1 and 2 are synthesized by photolytic sulfur extrusion from the 2,11‐dithia[3.3](2,5)pyrimidinophane 17. The molecular structures of 1 and 2 are determined by X‐ray structure analysis and are discussed with regard to the steric strain in these molecules. Thermolysis of [(5‐methyl‐2‐pyrimidinyl]methyl]‐ or [(2‐methyl‐5‐pyrimidinyl)methyl]‐trimethylammonium hydroxide (10 or 11) does not generate 1 and 2. α‐Chlorination of 2,5‐dimethylpyrimidine (3) with N‐chlorosuccinimide provides the required precursors 4–6.
Synthese von Reinst‐Rubicen und Rubicen‐Derivaten
Authors: Sachweh Volker , Langhals Heinz
Published: July 2007

Synthesis of Highly Pure Rubicene and Rubicene Derivatives

A simple one‐step synthesis of highly pure rubicene (2) from fluorenone (1) and magnesium with 24% yield is described and compared with other preparation procedures. Mono‐ and disubstituted rubicene derivatives are prepared by electrophilic aromatic substitution.
Folgereaktionen von Sulfenen aus Sulfonylchloriden und tertiären Aminen, 2. Bildung von Episulfonen, Sulfonylsulfen — Amin‐S,N‐Addukten und Chlorsulfinen aus primären Sulfonylchloriden und tertiären Aminen
Authors: Opitz Günter , Ehlis Thomas , Rieth Karlheinz
Published: July 2007

Secondary Reactions of Sulfenes from Sulfonyl Chlorides and Tertiary Amines, 2. — Formation of Episulfones, Sulfonylsulfene — Amine S.N‐Adducts. and Chlorosulfines from Primary Sulfonyl Chlorides and Tertiary Amines

The reaction of primary sulfonyl chlorides 1b–m with the tertiary amine bases quinuclidine, DABCO, Me3N, Et3N, Bu3N, EtiPr2N, and 1,2,2,6,6‐pentamethylpiperidine is studied in acetonitrile solution between − 40 and 80°C. The 2,3‐dialkylthiirane 1,1‐dioxides 4 (trans/cis > 1) and the alkenes 5 [(E)/(Z) > 1] are obtained in high yields with Et3N at − 40°C. The stereochemistry is influenced by the amine base B in the ring closure reaction and partially by epimerization of the episulfones 4. Hindered bases favor the cis, β‐branched sulfonyl chlorides the trans isomer. Competing formation of the sulfonylsulfene–amine S,N‐adducts 7 is only observed with quinuclidine, DABCO, and Me3N, which are also the most active amines in the epimerization of the cis‐2,3‐diarylthiirane 1,1‐dioxides 4. Methanesulfonyl chloride (1a) yields the mesylsulfene–amine S,N‐adducts 7a with Me3N and Et3N in MeCN, but thiirane 1,1‐dioxide (4a) with EtiPr2N in MeCN or with Et3N in Et2O. Formation of chlorosulfines 10 is favored by higher temperature (T > 20°C), hindered amine bases and β‐branched sulfonyl chlorides. Isolation of 10g and 10h in high yields shows that tert‐alkylchlorosulfines are rather stable sulfines.
Synthetic pathways to disilylmethane, H3SiCH2SiH3, and methyldisilane, CH3SiH2SiH3
Authors: Zech Joachim , Schmidbaur Hubert
Published: July 2007

Disilylmethane is available in a four‐step synthesis starting with phenylsilane. This is converted into chlorophenylsilane by HCl/AlCl3. The reaction of PhSiH2Cl and dibromomethane with magnesium in tetrahydrofuran affords bis(phenylsilyl)‐methane, which yields bis(bromosilyl)methane by treatment with anhydrous hydrogen bromide. (BrH2Si)2CH2 is converted into disilylmethane by reduction with LiAlH4 in a two‐phase system using a phase‐transfer catalyst. ‐ Methyldisilane is available by alkylation of a monohalodisilane, XSi2H5 (X  Cl, Br), with methyllithium in a high‐boiling ether or by silylation of bromomethylsilane with silylpotassium. Due to secondary silylation reactions the overall yields of methyldisilane are low in all cases.
Synthesis of acetyl‐substituted heterocyclic ketene aminals and their deacetylation reaction
Authors: Wang He‐Ting , Wang Xiao‐Jun , Huang Zhi‐Tang
Published: July 2007

The acetyl‐substituted heterocyclic ketene aminals 3 — 6 were synthesized by the reaction of ketene dithioacetals 2 with diamines. The deacetylation of heterocyclic diacetyl keteneaminals by alkali was studied, and the corresponding monoacetyl derivatives were obtained.
Geminale Substituenteneffekte, 4. Abhängigkeit des inversen anomeren Effektes geminaler Nitril‐Gruppen von der Struktur
Authors: Beckhaus Hans‐Dietr , Dogan Barbara , Pakusch Joachim , Verevkin Sergei , Rüchardt Christoph
Published: July 2007

Geminal Substituent Effects, 4. — The Dependence of the Inverse Anomeric Effect of Geminal Cyano Groups on the Structure

The heats of combustion and the heats of sublimation of malodinitrile (1a), ä‐alkyl‐ (1b,c) and å, å‐dialkylmalodinitriles (1 d ‐f) have been determined. From the obtained standard heats of formation group increments for CH2[CN]2], CH[(CN)2 Cl and C[CN)2C2] group are deduced. The comparison of their values with corresponding increments for monocyano alkanes reveals a synergetic destabilisation by two geminal cyano substituents of 11.5, 9.0 and 6.6 kcal/mol, respectively. Thus, this inverse anomeric effect decreases by increasing alkyl substitution.
SF5‐substituierte Ketene
Authors: Bittner Jürgen , Seppelt Konrad
Published: July 2007

SF5‐Substituted Ketenes

Ketenes F5S ‐ CR  C  O [R  H, CH3, C1. Br (2a ‐ d )] are pre‐pared by dehydration from the acids F5S ‐ CHR ‐CO2H (1a‐d), or in the case of R  CH3 (b) also by halogen elimi‐ nation with mercury. These ketenes exhibit remarkable sta‐bility, increasing in the sequence R  H, CH3, C1, Br. They undergo addition reactions across the C  C double bond in known fashion. The isomerization reaction of F5SCH  C  O (2a) to F,SCHCOF is not shown by any of the other ke‐tenes.