bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facile Synthesis of Ferrocene Biscrown Ethers and Ferrocene Cryptands: NMR Complexation Studies and the Redox‐Switched Bonding of H+ and Na+
Authors: Plenio Herbert , El‐Desoky Hanaa , Heinze Jürgen 
Published: July 2007

AbstractThe reaction of 1,1′‐ferrocenylene‐bis(methylenepyridinium) tosylate chloride (1) with aza‐x‐crown‐y (x/y = 12/4; 15/5; 18/6) gives the three novel ferrocene biscrown ethers 1,1′‐ferrocenylene‐bis(methylene‐aza‐x‐crown‐y) (x/y = 12/4, 2; 15/5, 3; 18/6, 4). The reaction of 1 with diaza‐18‐crown‐6 represents a new and simple route to the known ferrocene cryptands 1,1′‐zacyclooctadecane)] (5) and 1,1″:1′,1″‐bisferrocenylene‐bis‐[bis‐7,16‐methylene(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane)] (6). The solid‐state structure of 5 is described. The ferrocene bridge compresses the diaza crown ether leading to an internitrogen distance of 458 pm. The stoichiometry of Na+ and K+ complexes with 2 and 3 in CD3CN determined in NMR titration experiments suggests the formation of Na+ and K+ crown ether sandwich complexes in solution. Cyclic voltammograms of 2 and 5 in the presence of varying amounts of H+ and Na+ have been recorded. The redox potential of ferrocene is shifted by +180 mV in the case of 5 · Na+ and up to +600 mV in the case of 5 · H+H+ relative to 5, but only by + 70 mV with 2 · Na+ and 2. The protonation of 5 give rises to several isomers (exo and endo protonation) which differ significantly in their redox potential. The extremely large positive shift of the oxidation potential of the diprotonated ferrocene cryptand corresponds to an increase in the acidity of 5 · H+H+ upon oxidation by more than ten orders of magnitude and makes this system a candidate for the directed membrane transport of protons.
Zur Existenz des Hexahydroxoperiodonium‐Ions — Kristallzüchtung und Strukturanalyse von α‐ und β‐H6IO6HSO4
Authors: Kraft Thorsten , Jansen Martin 
Published: July 2007

On the Existence of the Hexahydroxoiodine(VII) Cation – Crystal Growth and Structure Analysis of α‐ and β‐H6IO6HSO4*Periodic acid H5IO6 dissolves at 50°C in 90–97% H2SO4 to give the hexahydroxoiodine(VII) cation H6IO6+. Depending on the concentration of the sulfuric acid, two modifications of H6IO6HSO4 can selectively and reproducibly be precipitated. The crystal structures determinations prove the existence of H6IO6+ in the solid state. The crystal structures and Raman spectra of α‐H6IO6HSO4 (1a) and β‐H6IO6HSO4 (1b) are discussed and compared. The temperature‐dependent behaviour of 1a and 1b is studied by means of DTA, temperature‐dependent X‐ray powder diffraction, and Raman spectroscopy.
Metallkomplexe mit biologisch wichtigen Liganden, LXVIII. Metallorganische Asparaginato‐Cobaltkomplexe als Liganden für Alkali‐Ionen
Authors: Bergs Ralph , Sünkel Karlheinz , Beck Wolfgang 
Published: July 2007

Metal Complexes of Biologically Important Ligands, LXVIII[1]. – Organometallic Asparaginato Cobalt Complexes as Ligands for Alkaline IonsThe trischelate complexes of the dianion of aspartic acid and β‐methylaspartic acid (η5‐C5Me5)magnified image] (R = H, Me) form adducts with alkali iodides MI (M = Li, Na, K). The polymeric structure of (η5‐C5Me5)Co(L‐asp.–2H+)KI (1c) was determined by X‐ray diffraction. In the crystal of 1c the potassium ions are surrounded by five oxygen atoms of the carboxylate groups whereby two oxygen atoms form bridges between two K+ ions. Similarly, trischelate complexes 4 and 5 have been obtained from (η5‐C5Me5)Co(CO)I2 and 2,3‐diaminopropionic, 2,4‐diaminobutyric acid, and asparagine, respectively.
Reaktionen von (Fluorsulfonylimino)‐λ6‐schwefeltetrafluorid FSO2N=SF4
Authors: Meier Thomas , Mews Rüdiger 
Published: July 2007

Reactions of (Fluorosulfonylimino)‐λ6‐sulfur Tetrafluoride FSO2N=SF4Herrn Professor Pedro J. Aymonino zum 60. Geburtstag gewidmet.
FSO2N=SF4 (1) reacts with CsF, HF and CIF to form Cs+N(SO2F)SF5– (2), HN(SO2F)SF5 (3) and ClN(SO2F)(SF5) (5); 5 adds to ethylene to give ClCH2CH2N(SO2F)SF5 (6).
Synthese optisch aktiver 2‐Siloxycyclopropancarbonsäureester durch asymmetrische Katalyse, I. Katalysatoreinfluß auf die Cyclopropanierung von (Z)‐1‐Phenyl‐1‐(trimethylsiloxy)prop‐1‐en
Authors: Dammast Franziska , Reißig Hans‐Ulrich 
Published: July 2007

Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, I. – Influence of the Catalyst on the Cyclopropanation of (Z)‐1‐Phenyl‐1‐(trimethylsiloxy)prop‐1‐eneThe cyclopropanation of silyl enol ether 1a with methyl diazoacetate (2a) and diazoesters 2b–d in the presence of optically active copper salicylimine complexes 4‐Cu was systematically studied. Up to 88% enantiomeric excess in products 3 were obtained by employing the appropriate reaction conditions and the optimal catalyst ligands. Thus, for the first time respectable optical yields were achieved in asymmetric cyclopropanations of silyl enol ethers with easily available copper‐Schiff base catalysts. The ring opening of the separated diastereomers of 3a employing nBu4NF provided methyl γ‐oxocarboxylate 6a in good optical purity. This demonstrates that this process occurs without racemization and also that 3a is formed with the same absolute configuration at C‐1.
Neue [m.n]Cyclophane durch sukzessive Ketonpyrolyse
Authors: Schmohel Erich , Ott Frank , Breitenbach Jörg , Vögtle Fritz , Nieger Martin 
Published: July 2007

New [m.n]Cyclophanes by Successive Ketone PyrolysisThe new cyclophane ketones 7, 10, 11, 13, 14, and 16 and the known hydrocarbons 8 and 15 are obtained by successive thermal elimination of carbon monoxide with C–C bond formation from the known [3n]cyclophane(ones)n and the new terphenylophanedione 4. X‐ray structure analyses of the ketones 3 and 4 and the anti‐isomer of the ketone 7a are performed.
Medium‐Sized Cyclophanes, 29. Synthesis and Desulfurization of 2,11‐Dithia[3]metacyclo‐ and 2,11‐Dithia[3]paracyclo[3](4,9)pyrenophanes
Authors: Yamato Takehiko , Miyazawa Akira , Tashiro Masashi 
Published: July 2007

Abstract2,11‐Dithia[3]metacyclo‐ (14b) and 2,11‐dithia[3]paracyclo[3]‐(4,9)pyrenophane (14c) were obtained by the coupling reactions of 4,9‐bis(chloromethyl)pyrene (12) with the corresponding bis(mercaptomethyl)benzenes (13b, c). Attempted pyrolysis of the disulfones 18b, 18c to afford [2]metacyclo‐ (19b) and [2]paracyclo[2](4,9)pyrenophane (19c) failed. Only the ring cleavage products 16 and 20 were obtained. The sulfur dioxide extrusion by vapor‐phase pyrolysis of the corresponding disulfone 18 to the highly strained 19 clearly demonstrates the limits of these preparative ring contraction method. The photolytic desulfurization of 14c afforded the [2](1,5)naphthal‐eno[2]paracyclophane analogue 21 instead of [2]paracyclo[1]‐(4,9)pyrenophane 21′. The mechanism of the pyrolysis and photolysis reactions is discussed.
Flow‐Vacuum Pyrolysis of Polycyclic Compounds, 6. Pyrolysis of Dibenzo [CH]8 Hydrocarbons
Authors: Banciu Mircea D. , Stanescu Michaela D. , Parvulescu Luminitza , Petride Aurica , Pop Mircea 
Published: July 2007

AbstractThe flow‐vacuum pyrolysis of dibenzo [CH]8 hydrocarbons 2,3,4, and 5 are studied at 1 Torr and in the temperature range between 400 and 650°C. The following new transformations have been observed: 2⇆4, 2→5, 3→5, 3⇆4, 3→2, 5→11, the last three presenting analogies in the [CH]8 and/or benzo [CH]8 series. A reaction mechanism is suggested.
On the Reaction of 1‐Aza‐2‐azoniaallene Salts with Carbodiimides
Authors: Wang Quanrui , Troll Carsten , Fischer Helmut , Jochims Johannes C. , Amer Atef 
Published: July 2007

Abstract1‐Aza‐2‐azoniaallene cations 3, prepared in situ from geminal (chloroalkyl)azo compounds 2, react with carbodiimides 4 to give 4,5‐dihydro‐5‐imino‐1H‐1,2,4‐triazolium salts 7. An X‐ray structural analysis was carried out for 71. According to AM1 calculations the cycloaddition of carbodiimides to 1‐aza‐2‐azoniaallene cations occurs in a nonconcerted manner via cyanamidium cations 5 as intermediates. Hetero‐Wagner‐Meerwein rearrangements of the primary cycloadducts 6 provide the final products 7.
Coordinated 1‐Aza‐1,3‐butadienes: Stable Intermediates in the Formation of Pyridines from [(β‐Aminoethenyl)carbene]chromium Complexes
Authors: Duetsch Michael , Stein Frank , Funke Frank , Meijere Armin De , Pohl Ehmke , Herbst‐Irmer Regine 
Published: July 2007

Abstract[(β‐Aminoethenyl)carbene]chromium complexes 3a–c rearrange to coordinated 1‐aza‐1,3‐butadienes 6a–c, which undergo cycloadditions with alkynes 7a, c to pyridines 9a, 10a–c.
Ligand Effects on the Gas‐Phase Reactions of (π‐L)FeI Complexes with n‐Pentanenitrile
Authors: Stöckigt Detlef , Sen Semiha , Schwarz Helmut 
Published: July 2007

AbstractThe gas‐phase ion chemistry of the previously studied system Fe(n‐pentanenitrile)+ is dramatically changed, when the metal ion bears substituents L (L = C2H4, C3H6, C4H6, i‐C4H8, 1‐C4H8, 2‐C4H8, and C6H6), and the major ion‐molecule reactions of Fe(L)+ with RCN (R = n‐C4H9) are as follows: (i) Ligand substitution Fe(L)+ + RCN → Fe(RCN)+ + L is observed for all L studied except L = C4H6, C6H6; (ii) the formation of association complexes Fe(L)(RCN)+ takes place for all ligands L, except L = C2H4; (iii) dehydrogenation of the L is confined to L = 1‐C4H8 and 2‐C4H8; (iv) carbon–carbon and carbon–nitrogen bond activation of the nitrile, typical for the behaviour of bare Fe+, are absent in the reactions of all Fe(L)+ with RCN, Dehydrogenation of the nitrile is observed only for L = 1‐C4H8 and 2‐C4H8, and the molecular hydrogen originates exclusively from the γ/δ‐position of the alkyl chain following the well‐established “remote functionalization” concept. In contrast to the reaction of bare Fe+ with n‐pentanenitrile, dehydrogenation in the Fe(L)(RCN)+ system is not preceded by a degenerate isomerization of RCN, bringing about equilibrations of the C(α)/C(γ) positions. Rate constants were derived and compared with those calculated by the ADO and CAP theories. All reactions of the ligated Fe(L)+ ions were found to occur with collision rate, again in contrast to the bare Fe+. Based on the ADO formalism, the dipole locking constant “c” of n‐pentanenitrile was redetermined to c = 0.47.
Zur Energiedelle von Diradikalen, IV[1]. 2‐Methylen‐1,4‐cyclohexadiyl
Authors: Roth Wolfgang R. , Wollweber Detlef , Offerhaus Rolf , Rekowski Volker , Lennartz Hans‐Werner , Sustmann Rainer , Müller Wolfgang 
Published: July 2007

The Energy‐Well of Diradicals, IV[1]. – 2‐Methylene‐1,4‐cyclohexadiylThe energy surface of the title compound 2 is derived from the kinetics of its precursors 5, 6, 7, and 8, the oxygen dependance of its trapping rate, and heat of hydrogenation measurements of 5, 6, 7, and 15. These data lead to a heat of formation for the diradical 2 of 69.8 kcal/mol and an energy well of 8.2 kcal mol–1. From the Curie plot of the ESR spectrum and oxygen trapping experiments a singlet‐triplet splitting of 1.4 kcal mol–1 is indicated, with the triplet being the ground state.
Reaction of 6‐(CF3)‐ and 6‐(CH3)‐2‐(tert‐Butyl)‐1,3‐dioxan‐4‐one Li Enolate with Two Equivalents of an Aldehyde – Unusual Reorganizations of Aldolates
Authors: Lapierre Jean‐Marc , Gautschi Markus , Greiveldinger Guy , Seebach Dieter 
Published: July 2007

AbstractThe Li enolate of (2S,6R)‐2‐(tert‐butyl)‐6‐trifluoromethyl‐1,3‐dioxan‐4‐one (1) reacts with isobutyraldehyde, pivalaldehyde and cyclohexanecarboxaldehyde to give unexpected aldols [3a–5a, (1′R,2R,5R,6R)‐2,6‐dialkyl‐5‐(2′,2′,2′‐trifluoro‐1′‐hydroxyethyl)‐1,3‐dioxan‐4‐ones]. The Li enolate of (2R,6R)‐2‐(tert‐butyl)‐6‐methyl‐1,3‐dioxan‐4‐one (2) reacts with pivalaldehyde to give (1′R,2S,5S,6R)‐2,6‐di‐(tert‐butyl)‐5‐(1′‐hydroxyethyl)‐1,3‐dioxan‐4‐one (7), another “strange” aldol‐type product resulting from one enolate and two aldehyde molecules. There is an unusual reorganization involving a transacetalization process under basic conditions. The structures of two products (4a and 7) were determined by X‐ray crystallography, and a mechanism of formation is proposed.
Titan‐, Zirconium‐ und Hafniumkomplexe mit 1,2,4‐Tri‐tert‐butylcyclopentadienyl‐Liganden
Authors: Sitzmann Helmut , Zhou Pu , Wolmershäuser Gotthelf 
Published: July 2007

Titanium‐, Zirconium‐ and Hafnium Complexes with 1,2,4‐Tri‐tert‐butylcyclopentadienyl LigandsLithium salts of easily available 1,3,5‐tri‐tert‐butylcyclopentadiene and 1,2,3,4,5‐pentaethylcyclopentadiene are used to synthesize the trichlorides [Cp‴MCl3] [Cp‴ = C5H2tBu3‐1,2,4; M = Zr (1), Hf (2), Ti (3)] and [(Et5C5)ZrCl3] (4). Complex 1 is converted into the mixed zirconocene dichlorides [Cp‴CpZrCl2] (5), [Cp‴Cp‐ZrCl2] (6), [Cp‴Cp″ZrCl2] (7), [Cp‴Cp4ZrCl2] (9) (Cp = C5H5, Cp* = C5Me5, Cp″ = C5H3tBu2‐1,3, Cp4 = C5iPr4H) and into the benzyl complexes [Cp‴Zr(PhCH2)2Cl] (10) and [Cp‴Zr(PhCH2)3] (11). Variable‐temperature 1H‐NMR spectra of 6–9 (8 is the Ti analogue of 7) indicated hindered oscillation of the Cp‴ ligand with ΔG≠ values between ≤8 kcal/mol (7, 9) and 13.2 kcal/mol (6). X‐ray structural analyses of complexes 7 and 9 reveal strong distortions owing to extreme steric congestion.
Synthese, Struktur und elektronische Eigenschaften von Cu0.69NbTe2
Authors: Tremel Wolfgang , Wortmann Ulrich , Vomhof Thomas , Jeitschko Wolfgang 
Published: July 2007

Synthesis, Structure and Electronic Properties of Cu0.69NbTe2Cu0.69NbTe2 is obtained from the elements in a sealed quartz ampoule at 850°C. The structure of Cu0.69NbTe2 is related to the CdI2 type. The Cu atoms are disordered and situated in tetrahedral sites between the NbTe2 layers. The Nb atoms form zig‐zag chains extending in one direction within the layers. This deformation of the Nb sublattice from trigonal symmetry is typical for CdI2 derivatives with formal electron counts close to d2 on the early transition metal. The magnetic susceptibility is temperature‐independent between 4 K and 300 K (Pauli paramagnetism). Resistivity measurements confirm the metallic behavior of the compound. The crystal structure and the physical properties are in agreement with the results of tight‐binding band‐structure calculations.
1,2‐Azaborolyl‐Komplexe, XXIX. Synthese und Eigenschaften von 1,2‐Azaborolylboranen
Authors: Schmid Günter , Haske Stefan , Zaika Dagmar , Boese Roland , Bläser Dieter 
Published: July 2007

1,2‐Azaborolyl Complexes, XXIX[1]. — Synthesis and Properties of 1,2‐AzaborolylboranesThe Li salts of variously substituted 1,2‐azaboroles 1a–1c react with numerous halogenoboranes to give the corresponding mono(1,2‐azaborol‐3‐yl)boranes 2‐12. In the case of 11, which is substituted by SiMe3 at C‐3, 2,5‐dihydro isomers can be observed as intermediates by NMR spectroscopy with a B(Cl)NMe2 group at C‐5 and the SiMe3 substituent either at C‐4 (11a) or at C‐3 (11b). The thermodynamically stable final product 11 is probably formed from 11b via an allylic transition state. The X‐ray structure analysis of 11 at ca. 0°C proves the suggested structure. The first and only example of a bis(1,2‐azaborol‐3‐yl)borane 13 was realized by the reaction of (1‐tert‐butyl‐2,3‐dihydro‐2‐methyl‐1H‐1,2‐azaborol‐3‐yl)‐chloro(dimethylamino)borane (3) with 1‐tert‐butyl‐2‐methyl‐1,2‐azaborolyllithium (1a). The X‐ray structure analysis of bis(1‐tert‐butyl‐2,3‐dihydro‐2‐methyl‐1H‐1,2‐azaborol‐3‐yl)‐(dimethylamino)borane (13) shows one of the two NMR‐spectroscopically observed diastereoisomers with perpendicularly oriented azaborolyl rings. Two iron sandwich complexes were synthesized; 15 is formed via 1‐tert‐butyl‐3‐[bis(dimethylamino)boryl]‐2‐methyl‐1,2‐azaborolyllithium (14) and FeCl2, whereas the ClB‐substituted sandwich complex 16 results from the reaction of 15 with BCl3.
Beiträge zur Chemie des Bors, 221. Kinetische und thermodynamische Produktkontrolle bei der Addition von HX‐Verbindungen an ein Amino‐phosphanylimino‐boran R2NBNPR2′
Authors: Nöth Heinrich , Stolpmann Holger , Thomann Martina 
Published: July 2007

Contributions to the Chemistry of Boron, 221[1]. — Kinetic and Thermodynamic Product Control in the Addition of HX Compounds to an Amino Phosphanylimino Borane R2NBNPR2′The reaction of equimolar amounts of HI with tmp=BNPtBu2 (3) (tmp = 2,2,6,6‐tetramethylpiperidino group) in an unpolar solvent yields the phosphonium salt [tmp‐BNPHtBu2]I (4). No such well‐defined reaction was observed with triflic or tetrafluoroboric acid. In contrast, HCl reacts with 3 to produce a mixture of tmp‐B(Cl)‐NH‐PtBu2 (5) and tmp—B(Cl)—NPHtBu2 (6). On heating or on standing at ambient temperature the unique proton of 5 migrates from the N to the P atom with formation of 6, which, therefore, is thermodynamically more stable than 5.
Synthesis of Platinum(II) Alkane‐ and Arenethiosulfinato Complexes — Crystal Structure Analysis of N‐[(Benzylsulfinyl)thio]phthalimide
Authors: Weigand Wolfgang , Wünsch Ralf , Robl Chrtian , Amreinb Walter 
Published: July 2007

AbstractThe oxidative addition of N‐[(alkyl‐ and arylsulfinyl)thio]‐phthalimides 3a–d to Pt(PPh3)2(C2H4) gives the platinum(II) thiosulfinato complexes cis‐Pt[(S‐S(O)‐R)(Nphth)(PPh3)2] 4a–d; the structure of N‐[(benzylsulfinyl)thio]phthalimide (3c) has been characterized by X‐ray crystallography.
Synthesis of 5‐Methoxy‐ and 5‐(Dialkylamino)bicyclo[3.2.0]hept‐2‐en‐6‐one Derivatives by cine Substitution with Methoxide Anions and Dialkylamines
Authors: Butenschön Holger 
Published: July 2007

Abstractexo‐7‐Chloro‐endo‐7‐phenylbicyclo[3.2.0]hept‐2‐en‐6‐one (5) undergoes cine substitution reactions with methoxide anions and with dialkylamines to give 5‐methoxy or 5‐dialkylamino derivatives 13, 14, 16–19 in high yield. While attempts directed to an acetalization have failed, the addition of Grignard reagents to the methoxy derivatives proceeds stereoselectively in high yield. Hydrochlorides 20/21 lose amine at 110°C to form 2‐phenyltropone (22). Thermolysis of diethylamino derivative 24 at 170°C (temperature determined by DSC) results in the formation of the dienaminone 25.
Benzoanellated Centropolyquinanes, 14. Synthesis of Tribenzotriquinacene by Stereocontrolled Cyclization of Phenyl‐Substituted Cs‐Diindans (4bα,9,9aα,10‐Tetrahydroindeno[1,2‐α]indenes)
Authors: Kuck Dietmar , Neumann Ekkehard , Schuster Andreas 
Published: July 2007

AbstractThe synthesis of tribenzotriquinacene 4 by a stepwise cyclization strategy involving phenyl‐substituted diindan intermediates is discussed in detail. Based on the determination of the anti (α) stereochemistry of the previously known phenyldiindanone 8 by standard electron impact mass spectrometry as well as on synthetical evidence (8 → 12 → 14), the conversion of 8 to the syn (β) phenyl‐substituted isomer 20 by means of dehydrogenation‐rehydrogenation sequences has been achieved. In particular, the preparation of the isomeric diindenones 15 and 16 as key synthetic intermediates by thermal syn elimination of the corresponding phenylsulfinyl and phenylseleninyl ketones 22 and 25 is described and contrasted to a bromination/dehydrobromination approach adopted from a previous report. The synthesis is completed by reduction of 20 to diindanol 27 followed by cyclodehydration, giving 4 in 14–19% overall yield from 8. Non‐cyclizing dehydration of 27 and the isomeric diindanol 9 gives the Δ4b,9‐diindene 30 as the most stable non‐cyclized isomer of 4. The steric effect of the syn‐ or anti‐oriented phenyl substituents on the preferred conformation of the diindan skeleton is deduced from the contrasting vicinal 1H‐1H spin coupling observed for the stereoisomers, e.g. the 9‐phenyldiindans 28 and 29.
Kleine Ringe, 79. Synthese und Eigenschaften neuer Silyl‐substituierter Cyclobutadiene und Tetrahedrane
Authors: Maier Günther , Wolf Reinhard , Kalinowski Hans‐Otto , Boese Roland 
Published: July 2007

Small Rings, 79[1]. — Synthesis and Properties of Novel Silyl‐Substituted Cyclobutadienes and TetrahedranesThe cyclobutadienes 2b, d as well as the corresponding tetrahedranes 3b, d have been prepared according to the “Masamune route” by starting from the diazo compounds 1b, d. Low‐temperature 13CNMR measurements of the cyclobutadienes 2a, b, d lead to the first exact values of the barrier heights in the interconversion of the two rectangular forms of the cyclobutadienes. Fluorodesilylation of 3d probably proceeds via tri‐tert‐butyltetrahedrane (3h) and cyclobutadiene 2h and finally yields diketone 18. Reaction of tetrahedrane 3d with LiAlH4 in boiling THF leads to tetrahedrane 3e, which is much less stable than all previously known tetrahedrane derivatives.
Tri‐tert‐butyl(trimethylgermyl)cyclobutadien und Tri‐tert‐butyl(trimethylgermyl)tetrahedran
Authors: Maier Günther , Wolf Reinhard , Kalinowski Hans‐Otto 
Published: July 2007

Small Rings, 80[1]. — Tri‐tert‐butyl(trimethylgermyl)cyclobutadiene and Tri‐tert‐butyl(trimethylgermyl)tetrahedraneIn the course of our research on silyl‐substituted diazo compounds as precursors of cyclobutadienes and tetrahedranes the synthesis of the title compounds 16 and 17 has also been accomplished. Their properties are comparable to those of the silyl‐substituted homologous compounds. Tri‐tert‐butyl(trimethylgermyl)tetrahedrane (17) melts without decomposition at 143°C and thus proves to be as stable as tri‐tert‐butyl(trimethylsilyl)tetrahedrane. The interconversion of the rectangular forms of tri‐tert‐butyl(trimethylgermyl)cyclobutadiene (16) proceeds with an activation energy below 4 kcal/mol, which is nearly the same as of tri‐tert‐butyl(trimethylsilyl)cyclobutadiene.
Die Dipol‐Route zu Furo‐/Thieno‐Pyrrolen und α‐Pyridonen, sowie deren Benzo‐Derivaten
Authors: Bussenius Jörg , Laber Norbert , Müller Thomas , Eberbach Wolfgang 
Published: July 2007

A Novel Route to Isoannulated Heteroaroamtic Compounds, 2[1]. — The Dipole Route to Furo/Thieno Pyrroles and α‐Pyridones, and Their Benzo DerivativesA new methodology involving 1,7‐dipolar cyclizations of conjugated dipoles followed by a multistep rearrangement affording ring‐contracted products has been employed for the synthesis of various examples of the title compounds. Under different thermolysis conditions the annulated alkynyl nitrones 15–19, 45, and 46 are converted into isoannulated pyrroles and α‐pyridones, respectively, with yields up to 90% (general reaction A → B + C). The product distribution is strongly influenced by the nature of the terminal substituent R, hence supporting a mechanism with oxo carbenes as central intermediates which undergo either 6‐π cyclization to the pyrrole systems or Wolff rearrangement leading to conjugated ketenes, the precursors of the observed α‐pyridones (see Scheme 1). Diels‐Alder reactions were performed with benzofuropyridone 40a, napthopyridone 62 as well as with the corresponding dihydronaphtho compounds 64a, b. Whereas the tert‐butyl derivatives 22b, 23b and 41b are rather unreactive against dienophiles, they are easily transformed into the cyclic imides 31, 32 and 52, respectively, under the influence of oxygen and light suggesting the formation and subsequent [4 + 2] cycloaddition of 1O2 as important steps.
A New Synthetic Approach to Pyridinium N‐Phenoxide Betaine Dyes
Authors: Sander Wolfram , Hintze Frank 
Published: July 2007

AbstractThe reaction of 3,5‐di‐tert‐butyl‐4‐oxo‐2,5‐cyclohexadienylidene (3d) with pyridine affords 2,6‐di‐tert‐butyl‐4‐(2,4,6‐tri‐tert‐butylpyridinio)phenolate (1d) — which is not accessible by the classical route via pyrylium salts — in reasonable yield. Carbene 3d is generated by thermal decomposition of the corresponding quinone diazide 2d in cyclohexane. Betaine 1d shows the expected large solvatochromism.
Ein neuartiger chiraler Synthesebaustein mit Neopentangerüst: Chemo‐enzymatische Darstellung von (R)‐CH3C(CH2OSO2CF3)(CH2Cl)(CH2Br)
Authors: Heidel Horst , Huttner Gottfried , Vogel Rainer , Helmchen Günter 
Published: July 2007

A Novel Chiral Building Block with Neopentane Framework for Synthesis: Chemo‐Enzymatic Preparation of (R)‐CH3C(CH2OSO2CF3)(CH2Cl)(CH2Br)The pig liver esterase (PLE) catalysed hydrolysis of the prochiral malonic ester (BzlOCH2)(Me)C(COOMe)2 (1) leads to its chiral monoester 2 in selectivities up to 81% ee. Compound 2 is an ideal entry point for the enantioselective synthesis of 1,1′,1″‐substituted neopentanes CH3C(CH2X)‐(CH2Y)(CH2Z) with three different leaving groups, X, Y, and Z. CH3C(CH2OSO2CF3)(CH2Br)(CH2Cl) (8) is a versatile reactive building block for the asymmetric synthesis of compounds containing the neopentane‐C5 skeleton.