bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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.
Mass‐Spectrometric and GAUSSIAN2 Studies of the Diazene (HNNH) and Isodiazene (H2NN) Molecules and Their Radical Cations
Authors: Goldberg Norman , Holthausen Max C. , Hrušák Jan , Koch Wolfram , Schwarz Helmut
Published: July 2007

Collision experiments demonstrate that isodiazene (H2NN) and its radical cation are viable molecules in the gas phase. The mass‐spectrometric experiments are complemented by extensive ab‐initio MO calculations using the GAUSSIAN‐2 procedure in order to map out relevant parts of the potential energy surface of H2N2 (singlet) and H2N2+· (doublet).
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 Ligands

Lithium 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 Cu0.69NbTe2

Cu0.69NbTe2 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‐Azaborolylboranes

The 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

The 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

exo‐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

The 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 Tetrahedranes

The 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)tetrahedrane

In 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 Derivatives

A 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

The 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.
Untersuchungen am System Phosphirenimin/Iminophosphan — Insertionsreaktionen und Isomerisierung
Authors: Link Manfred , Niecke Edgar , Nieger Martin
Published: July 2007

Investigations of the System Phosphirene Imine/Iminophosphane ‐ Insertion and Isomerization Reactions

Treatment of the iminophosphanes R1PNR2 1 [R2 = tBu, R1 = Et3C (a); R2 = Aryl, R1 = Et (b), Me (c)] with 1,4‐diphenyl‐butadiyne (2) leads to the phosphirene imines R1‐(R2N=)P̌(Ph)CCCPh 3a‐c and [R1(R2N=)P̌(Ph)CC]2 4a‐c. Further reaction with 1a, c gives the 1,2‐diphosphetes R1(R2N)PP(R1)(NR2)C(Ph)CCCPh 5a, b, which isomerize in the case of R1 = Me into the triphosphabicyclo[3.2.0]‐hepta‐1,6‐diene 7. In the reaction of the phosphirene imines R1(ArylN)P̌(R2)C(R2) 3 [R1 = Me, R2 = Ph (d); R1 = Et, R2 = COOMe (e)] with the iminophosphanes 1b, d the initially formed diphosphetes 9a, b isomerize to the 1,2‐diazaphosphole Cl(Mes*N)PN(Mes*)P(Me)C(Ph)C(Ph) 10 or the dioxadiphosphabicyclooctadiene CC(OMe)OP(N‐Mes*)(Et)CC(OMe)OP(NMes*)(Et) 12 depending on the substituents. A reaction of the phosphirene imine 3d with dimethylamino‐borane furnishes the vinylphosphane. Ph(H)CC(Ph)P(Et)N(H)Mes* (14) by ring opening. The compounds 7, 10, 12 have been characterized by X‐ray structure analyses.
Metallkomplexe funktioneller Isocyanide, XXI. N‐Isocyandialkylamin‐Derivate von Carbonyl‐ und Aren‐Metallverbindungen
Authors: Fehlhammer Wolf Peter , Metzner Robert , Kunz Rainer
Published: July 2007

Metal Complexes of Functional Isocyanides, XXI[1]. — N‐Isocyanodialkylamine Derivatives of Metal Carbonyl and Arene Compounds

The N‐isocyanodialkylamine complexes [M(CO)6‐n‐(CNNR2)n] (M = Cr, Mo, W; n = 1–3) (2a–7c), [Mn(CO)2(η‐C5H5)CNNR2] (8b,c), and [RuCl2(η‐TMB)CNNR2] (9a‐c) (TMB = 1,2,4,5‐tetramethylbenzene) have been prepared from appropriate metal carbonyl and arene precursors and the “free” N‐isocyanides CNNEt2 (1a), CNNiPr2 (1b), and CNNCH(Me)(CH2)3CHMe (1c), respectively. The structural assignments are made on the basis of IR, NMR (1H, 13C), and mass spectrometry as well as of an X‐ray structure analysis of [RuCl2(η‐TMB)CNNiPr2] (9b).
Strukturen und Moleküleigenschaften sterisch überfüllter Moleküle, 43. Triisopropylammonium‐chlorid: Einkristallstruktur und Berechnungen zur Protonierung des p‐Typ‐Stickstoff‐Elektronenpaares
Authors: Bock Hans , Göbel Ilka , Bensch Wolfgang , Solouki Bahman
Published: July 2007

Structures and Molecular Properties of Sterically Overcrowded Molecules 43[1]. — Triisopropylammonium Chloride: Single‐Crystal Structure and Calculations Concerning the Protonation of the p‐Type Nitrogen Electron Pair[2]

The protonation of triisopropylamine, which contains an almost planar NC3 skeleton of C3 symmetry and, therefore, a p‐type N electron pair, with HCl in methanol causes severe structural perturbation due to extreme steric overcrowdedness: the single‐crystal structure determination (orthorhombic Pbca, Z = 8) proves that the molecular symmetry is reduced to C5 by the rotation of one isopropyl group around its CN axis by almost 90° and the decrease of the angles CNC from 119° each to 115, 115 and 111°, respectively. The Cl⊖ ⃛(H)N hydrogen bond distance of 315 pm is presumably slightly increased by steric overlap of the van der Waals radii of Cl⊖ and one of the three adjacent methyl groups. The protonation of the p‐type lone pair of triisopropylamine including the pyramidalization of the nitrogen centre and the twist of one isopropyl group can be simulated by a one‐dimensional energy hypersurface calculation, if H⊕ attack outside the C3 axis is assumed.
Elektrophile Additionen an das Bicyclo[1.1.0]butan‐System von 1‐Phenyl‐ und 1‐(4‐Anisyl)tricyclo[4.1.0.02,7]heptan: Säure‐katalysierte Reaktionen mit Wasser und Methanol, Anlagerung von Essigsäure und Oxymercurierung
Authors: Christl Manfred , Gerstner Erwin , Kemmer Ralf , Llewellyn Gareth , Bentley T. William
Published: July 2007

Electrophilic Additions to the Bicyclo[1.1.0]butane System of 1‐Phenyl‐ and 1‐(4‐Anisyl)tricyclo[4.1.0.02,7]heptane: Acid‐Catalyzed Reactions with Water and Methanol, Addition of Acetic Acid, and Oxymerucuration

1‐(4‐Anisyl)tricyclo[4.1.0.02,7]heptane (37) was prepared from 1‐(4‐anisyl)cyclohexene, tetrabromomethane, and methyllithium in a one‐pot reaction. Starting from 37 and the analogous phenyl compound 19, the oxymercuration/demercuration sequence provided the exo‐6‐aryl‐endo‐6‐norpinanols 30a and 20a, respectively. By reaction with triphenyl‐stannane, the bromo compound 27a was converted into endo‐6‐phenyl‐exo‐6‐norpinanol 28a. Treatment of 19 with aqueous sulfuric acid led to a mixture of the alcohols 20a–25a. Mixtures of a very similar composition were obtained on hydrolysis of the 3,5‐dinitrobenzoates 20b and 28b of 20a and 28a in 80% aqueous acetone. Kinetic measurements revealed the same rate for the hydrolysis of 20b and 28b. The proof of the presence of 20a among the products of the reactions of 19, 20b, and 28b showed the intermediacy of an unrearranged cation, to which the classical structure 16 is ascribed. That acetic acid is too weak a nucleophile to intercept 16 follows from the structure of the adducts to 19. All of them (21b, 22b, 25b, 26b) have rearranged skeletons. In contrast, the stronger nucleophile methanol trapped 16 more efficiently than water to give the diastereomeric 6‐norpinyl methyl ethers 20d and 28d. The reaction of 37 with acetic acid and 10−4 M hydrochloric acid as well as the hydrolysis the 3,5‐dinitrobenzoate 30c of 30a produced mainly the diastereomeric 6‐norpinyl acetates 30b and 31b and 6‐norpinanols 30a and 31a, respectively. Whereas the protonation of 19 and 37 gives the classical cations 16 and 17, respectively, the oxymercuration of these substrates results in the generation of the nonclassical cations 44 and 46. This was concluded from the configuration of the demercuration products 20a and 30a and the absence of the diastereomers 28a and 31a.
Diastereoselective Functionalization of a Spherand‐Type Calixarene
Authors: O'Sullivan Patrick , Böhmer Volker , Vogt Walter , Paulus Erich F. , Jakobi Ralf A.
Published: July 2007

Condensation of 5,5′‐di‐tert‐butyl‐2,2′‐dihydroxybiphenyl (1) with formaldehyde yields a cyclic trimer 2 (and tetramer 3) having three (four) methylene groups less than a calix[6]‐arene (calix[8]arene). Alkylation of the (flexible) trimer with ethyl bromoacetate gives exclusively the stereoisomer 4 with C2 symmetry, while the isomer with D3 symmetry is not observed. Two isomers 6a and 6b (C2 and C1 symmetry) are obtained by treatment with tert‐butyl bromoacetate which both are converted by transesterification with methanol into the same hexamethyl ester 5 having C2 symmetry. These results are rationalized by restricted rotation around ArAr bonds for larger O‐alkyl groups also around ArCH2Ar bonds. The structure of the hexaethyl ester 4 is also confirmed by single crystal X‐ray analysis.
Darstellung und Eigenschaften von S‐(Trifluormethyl)polysulfanmonosulfonaten CF3SxSO2M [x = 1, M = OH, NH40O, 1/2 HgO2, (CH3)3SiO, (CH3)2N, NH2; x = 2, M = NH4O]
Authors: Brosius Axel , Haas Alois , Pryka Michael
Published: July 2007

Synthesis and Properties of S‐(Trifluoromethyl)polysulfanemonosulfonates CF3SxSO2M [x=1, M = OH, NH4O, 1/2 HgO2, (CH3)2N, NH2; x=2, M = NH4O]*

Hydrolysis of CF3SNSO with 2 equiv. of H2O provides [NH4][CF3SSO3] (1), which on treatment with chlorine gives CF3SCl and [NH4][ClSO3]. Trifluoromethyl thiosulfates are synthesized from Hg(SCF3)2 and ClSO2M [M = NH4O, (CH3)3SiO (2), (CH3)2N (3), NH2 (4)]. Insertion of SO3 into Hg(SCF3)2 provides Hg[CF3SSO2O]2 (6). Similarly, S‐(trifluoromethyl)thiosulfuric acid (5) is obtained from CF3SH and SO3. New preparations for CF3SXNSO (x=1, 2) are described. These compounds are formed either from Hg(NSO)2 or (CH3)3SiNSO and CF3SxCl in good yields. CF3SSNSO (8) reacts with water to give [NH4][CF3SSSO3] (9). A 1:1 adduct (10) is obtained from CF3SNSO and AsF5. A preliminary X‐ray structure investigation proved that AsF5 is coordinated to the oxygen atom. Some reactions of [NH4][CF3SSO3] and CF3SSO2OSi(CH3)3 are mentioned.
Funktionalisierte Tripod‐Liganden: Synthese und Koordination von Tris[(diphenylphosphanyl)methyl]methan
Authors: Janssen Bernd C. , Asam Alexander , Huttner Gottfried , Sernau Volker , Zsolnai Laszlo
Published: July 2007

Functionalized Tripod Ligands: Synthesis and Coordination of 1,1,1‐Tris[(diphenylphosphanyl)methyl]methane

The tripod ligand HC(CH2PPh2)3 (4) is easily available from the reaction of 1,3‐dichloro‐2‐(chloromethyl)propane (3) with lithium diphenylphosphide. The ligand 4 itself and two of its coordination compounds, [(HC(CH2PPh2)3)Co(OOCMe)]+‐[BPh4]− (5 · BPh4) and [(HC(CH2PPH2)3)Co(OOCMe)]2+ · 2[BF4]− [7 · (BF4)2] have been characterized by X‐ray analyses. Coordination of 4 leads to an opening of the CH2CHCH2 bond angles (114° in 7 · (BF4)2 and 5 · BPh4 versus 111° in 4). This change in structure is reflected by the unusual low field shift of the methine hydrogen of 7 · (BF4)2 (δ = 3.90) in comparison with the corresponding signal of the free ligand 4 (δ = 1.53).
Study of Calixarenes, V. Friedel‐Crafts Reaction of Calixarenes
Authors: Huang Zhi‐Tang , Wang Guo‐Qiang
Published: July 2007

The para‐acylation of calix[4]arene (2), calix[6]arene (3), and calix[8]arene (4) by Friedel‐Crafts reaction with a wide variety of acyl chlorides leads to 5–7 in moderate to good yields. Friedel‐Crafts reaction of 26,28‐dimethoxycalix[4]arene (8) gave products 9 selectively disubstituted in the para‐positions of phenol rings.
Comparison of the Nucleophilicities of Alkynes and Alkenes. Quantitative Determination of the Nucleophilicities of Alkynes toward Carbenium Ions
Authors: Mayr Herbert , Gonzalez Jose L. , Lüdtke Kerstin
Published: July 2007

Relative reactivities of alkenes and alkynes toward diarylmethyl cations have been determined by direct rate measurements and by competition experiments in dichloromethane. At −70°C alkynes are found to be one to two orders of magnitude less reactive than analogously substituted alkenes (e.g. phenylacetylene/styrene), but the reactivity difference reduces strongly as the temperature is raised. The stereochemistry of the vinyl chlorides produced by addition of benzhydryl chlorides to alkynes is characterized.
Metal Complexes with Tetrapyrrole Ligands, LXVI. Synthesis, Characterization, and Variable‐Temperature 1H‐ and 19F‐NMR Investigations of Cerium(IV) Double‐Deckers Derived from Monofunctionalized Tetraarylporphyrins
Authors: Buchler Johann W. , Eiermann Volker , Hanssum Helmut , Heinz Georg , Rüterjans Heinz , Schwarzkopf Markus
Published: July 2007

The synthesis of a cerium(IV) bisporphyrinate 1b starting from (p‐hydroxyphenyl)tris(p‐tolyl)porphyrin 2b is described. Derived from 2b by substitution of the phenolic OH group, the monofunctionalized tetraarylporphyrins 2c‐f and their cerium(IV) sandwich complexes 1c‐f were synthesized. The complexes are characterized by UV/Vis, IR, and 1H‐NMR spectroscopy. 19F‐NMR spectra of 1f show the presence of a vicinal and a transversal isomer due to the rigid squareantiprismatic coordination geometry of cerium(IV) bisporphyrinates. Variable‐temperature 1H‐ and 19F‐NMR spectra were recorded to investigate the rotational rigidity of the double‐decker system. The spectra show that the vicinal and transversal isomers are stable up to 140°C, i.e. rotation of the two porphyrin macrocycles with respect to each other does not occur.
Metallkomplexe mit biologisch wichtigen Liganden, LXX. Synthese, Stereochemie und Reaktionen von Ruthenium(II) und Osmium(II)‐Komplexen mit α‐Aminocarboxylat‐Liganden
Authors: Severin Kay , Sünkel Karlheinz , Beck Wolfgang
Published: July 2007

Metal Complexes of Biologically Important Ligands, LXX[1].‐ Synthesis, Stereochemistry and Reactions of Ruthenium(II) and Osmium(II) Complexes with α‐Amino Carboxylates

Herrn Professor Helmut Werner zum 60. Geburtstag gewidmet.

The reactions of MHCl(CO)(PPh3)3 with salts of α‐amino acids give the hydrido‐N,O‐chelate complexes MH(CO)(NH2CHR‐COO)(PPh3)2 (1a–g;) M = Ru, Os). Complexes 1a–c can alternatively be prepared by oxidative addition of the appropriate α‐amino acid to Ru(CO)3(PPh3)2. The crystal structure of 1b has been determined by an X‐ray structural analysis. The leucinato compound 1c is an effective catalyst for the decomposition of formic acid. In contrast, reactions of RuHCl‐(CO)(PPh3)3 with α‐amino acids afford the chloro‐N,O‐che‐late complexes RuCl(CO)(NH2CHRCOO)(PPh3)2 2a–h. The decomposition reactions of 2c, 2g and2h have been investigated.
Koordinationschemie mit den komplexen Chelatliganden [{Fe2Cp2(CO)3}2{CN[CH2]nNC}] (n = 2, 3). Heteropentanukleare „Superkomplexe”︁ mit μ5Diisocyanid‐Brücken
Authors: Schrölkamp Stephan , Sperber Wilfried , Lentz Dieter , Fehlhammer Wolf Peter
Published: July 2007

Coordination Chemistry with the Complex Chelating Ligands [{Fe2Cp2(CO)3)2{CN[CH2]n NC}] (n = 2, 3). Heteropentanuclear “Supercomplexes” with μ5‐Diisocyanide Bridges

Herrn Professor Dr. O. J. Scherer zum 60. Geburtstag gewidmet.

The tetranuclear complexes [(Fe2Cp2(CO)2(μ‐CO)}2(μ4‐CN[CH2]nNC}] [n = 2 (2), 3 (3)] act as bidentate chelating ligands towards the Lewis‐acidic metal halides MnCl2, MnBr2, FeCl2, CoCl2, NiCl2, NiBr2, CuCl2, CuBr2, ZnCl2, ZnI2, CdCl2, CdI2, HgCl2, the chloro complexes [MCl2‐(NCPh)2] (M = Pd, Pt), Zn(OAc)2 · H2O, and [Mo(CO)4(η‐NBD)] (NBD = 2,5‐norbornadiene) to give a total of 22 pentanuclear “supercomplexes” ,6–21, which have been characterized by elemental analyses and IR and NMR (1H, 13C) spectra. Reaction of 2 with [Ni(COD)2] in CH2Cl2 gave only rise to the dichloronickel(II) species 9a. Very remarkably, the pentairon complex [(Fe2Cp2(CO)2(μ‐CO)2(μ5‐CN(CH2)2‐NC)}]FeCl2 (7) also formed spontaneously (!) when 2 was refluxed in chloroform for several hours. The X‐ray structure analysis of [{Fe2Cp2(CO)2(μ‐CO))2{μ5‐CN(CH2)2NC}]CdI2 (14b) confirms the twofold μ3‐(C,C,N) bridging mode of a diisocyanide ligand in a cis/cis‐anti‐configurated [Fe2]2Cd pentanuclear system of crystallographic C2 symmetry.
Metallkomplexe funktioneller Isocyanide, XXIII. N‐Isocyandialkylamin‐Komplexe des Bors, Rhodiums, Palladiums, Platins und Kupfers
Authors: Fehlhammer Wolf Peter , Metzner Robert , Sperber Wilfried
Published: July 2007

Metal Complexes of Functional Isocyanides, XXIII[1]. ‐ N‐Isocyanodialkylamine Complexes of Boron, Rhodium, Palladium, Platinum, and Copper

The N‐isocyanodialkylamines CNNEt2, CNNiPr2, and CNNCH(Me)(CH2)3CHMe (1a–c) react with triphenylboron, various transition metal halides, and mono‐ and dinuclear chloro complexes by addition, substitution, bridge cleavage and reduction to give the complexes Ph3BCNNR2 (2b, c), [MX2(CNNR2)2] (M = Pd, Pt; X = Cl, Br, I) (3–7), [M(Cl)‐(CNNR2)(PPh3)2]BF4 (8, 9), cis‐ and trans‐[PtCl2(CNNR2)‐(PR′3)] (R′ = Et, Ph) (10–12), [Rh(CNNR2)4]Cll (15b, c) and [Cu(CNNR2)4]ClO4 (16b, c). The complexes [PdX2(CNNR2)(PPh3)] (X = Cl, Br) (13c, 14c) have been obtained by substitution of an N‐isocyanide ligand in 3c and 4c, respectively, with PPh3. The structural assignments are made on the basis of IR, NMR (1H, 13C, 31P, 15N) and mass spectrometry as well as of an X‐ray structure analysis of [PdI2(CNNiPr2)2] (5b).
Synthese von (—)‐(Acetoxymethyl)(hydroxymethyl)methyl(phenyl)german [(—)‐MePhGe(CH2OAc)(CH2OH)] durch eine Esterase‐katalysierte Umesterung: Die erste enzymatische Synthese eines optisch aktiven Germans
Authors: Tacke Reinhold , Wagner Stephan A. , Sperlich Jörg
Published: July 2007

Synthesis of (—)‐(Acetoxymethyl)(hydroxymethyl)methyl(phenyl)germane [(—)‐MePhGe(CH2OAc)(CH2OH)] by an Esterase‐Catalyzed Transesterification: the First Enzymatic Synthesis of an Optically Active Germane

The prochiral germane MePhGe(CH2OH)2 (1) was synthesized by a six‐step synthesis starting from GeCl4 (3) [3 → Cl2Ge(CH2Cl)2 (4) → Ph2Ge(CH2Cl)2 (5) → (CF3S(O)2O)PhGe(CH2Cl)2 (6) → MePhGe(CH2Cl)2 (7) → MePhGe(CH2OAc)2 (8) → 1]. Reaction of 1 with Ac2O/NEt3 (molar ratio 1: Ac2O = 1:1) gave the racemic germane rac‐MePhGe(CH2OAc)(CH2OH) (rac‐2). Stereoselective transesterification of 1 with vinyl acetate (acetate source and solvent), catalyzed by immobilized porcine liver esterase (PLE; E.C.‐3.1.1.1), yielded the optically active germane (—)‐MePhGe(CH2OAc)(CH2OH) [(—)‐2] (yield 57%, enantiomeric purity 50% ee).
Reaktive EC(p‐p)π‐Systeme, XXXVII. Pentafluorethanselenol: Synthese, Spektren und Gasphasen‐Struktur
Authors: Blau Hanne , Grobe Joseph , Van Duc Le , Mack Hans‐Georg , Oberhammer Heinz
Published: July 2007

Reactive EC(p‐p)π Systems, XXXVII[1]. ‐ Pentafluoroethaneselenol: Synthesis, Spectra, and Gas‐Phase Structure

Herrn Professor Wolfgang Sawodny zum 60. Geburtstag gewidmet.

Pentafluoroethaneselenol HSeC2F5 (1) and its deuterated analogue DSeC2F5 (2) are obtained in moderate yields by cleavage of the diselane (SeC2F5)2 with Me3SnH and Me3SnD, respectively. Complete characterization of the labile compounds was accomplished by spectroscopic investigations (IR, Raman, MS; 1H, 13C, 19F, 77Se NMR). The molecular structure was determined by electron diffraction in the gas phase together with ab initio calculations.
Synthese und Struktur von (R3P)Ni(1,6‐Heptadiin)‐Komplexen
Authors: Proft Bernd , Pörschke Klaus‐Richard , Lutz Frank , Krüger Carl
Published: July 2007

Synthesis and Structure of (R3P)Ni(1,6‐Heptadiin) Complexes

Displacement of the alkene ligand in Ligand‐Ni(0)(1,6‐diene) complexes by 1,6‐heptadiyne, the parent 1,6‐diyne, affords the complexes (Me3P)Ni(η2,η2‐C7H8) (1) and (Ph3P)Ni(η2,η2‐C7H8) (2). According to an X‐ray structure analysis of the PMe3 derivative 1 the nickel atom is ideally trigonal‐planar coordinated by the phosphane and both CC bonds. The increased stability of the complexes as compared to Ligand‐Ni(HCCH)2 complexes is referred to the strong chelating effect which is special to the 1,6‐functionalization. The compounds can be considered to be model complexes for the key intermediates of numerous transition metal‐mediated coupling reactions of (substituted and unsubstituted) 1,6‐diynes.
Reaction of (α,β‐Epoxyalkyl)silanes with α‐Sulfonyl Anions and α‐Sulfonyl Anions in the Presence of a Lewis Acid. A Method for the Synthesis of (Z)‐sec‐Allylic Alcohols and β,γ‐Unsaturated Alkyl Phenyl Sulfones
Authors: Masnyk Marek , Wicha Jerzy
Published: July 2007

The reaction of 2‐alkyl‐3‐(trimethylsilyl)oxiranes (la or 1b) with anions generated from alkyl phenyl sulfones (2a‐f) followed by hydrolysis affords sec‐allyl alcohols 3–7. An analogous reaction in the presence of BF3 · Et2O affords adducts 8–11. Treatment of 8–11 with NaOH under phase‐transfer conditions affords stereospecifically the corresponding allylic alcohols 4a–5c. Reaction of oxirane 1a with anions derived from sterically hindered sulfones 2e or 2f in the presence of BF3 · Et2O was investigated. Reaction of compounds 8, 9 with phosphorus tribromide in pyridine affords β,γ‐unsaturated sulfones 19.
Synthese, Kristallstruktur und Reaktionen neuartiger metallacyclischer Dioxo‐ und Aminooxocarben‐Komplexe des Eisens
Authors: Förtsch Walter , Hampel Frank , Schobert Rainer
Published: July 2007

Synthesis, Crystal Structure, and Reactions of Novel Metallacyclic Dioxo‐ and Aminooxocarbene Complexes of Iron

The novel cationic iron carbene complexes 9 and 11 are readily prepared from the corresponding ferra lactones 7 and lactams 10, respectively. With nucleophiles the complexes 9 react chemoselectively either at the methyl group of the methoxy residue or at the terminal allylic C atom. In contrast to similar tungsten complexes 6, compounds 9 show “carbene activity” only when olefin and carbene ligands are separated by two atoms. Novel tricarboryl(2H‐pyran)iron complexes 18 are obtained by a regioselective intramolecular carbene transfer in 9 once switched to the active form 17 by deprotonation using silyl enol ether 16 as a base.
Organische Synthesen mit Übergangsmetallkomplexen, 69. [2‐(Acylamino)ethenyl]ketenimine aus [2‐(Acylamino)ethenyl]carben‐Komplexen sowie deren Ringschluß‐Metathese zu Pyrrolen oder deren Elektrocyclisierung zu 1,4‐Diaminonaphthalinen
Authors: Aumann Rudolf , Jasper Beate , Goddard Richard , Krüger Carl
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 69[1]. — 2‐(Acylamino)ethenyl Ketene Imines from [2‐(Acylamino)ethenyl]carbene Complexes and their Ring‐Closing Metathesis to Pyrroles or Electrocyclization to 1,4‐Diaminonaphthalenes

Herrn Prof. Helmut Werner zum 60. Geburtstag gewidmet.

[2‐(Acylamino)ethenyl]carbene complexes LnM = C(OEt) CHCPh[N(COR)Ph] 5 [LnM = (CO)5Cr, (CO)5W; R = C6H5, pMeOC6H4, pNO2C6H4, OtBu] are obtained by N‐acylation of [2‐(amino)ethenyl]carbene complexes LnMC (OEt)‐CHCPh(NHPh) (Z)‐3 in 72–90% chemical yields with high stereoselectivity. The reaction of (Z) ‐ or (E)‐5 with two equivalents of isocyanides RNC 6 (R = cC6H11, tBu) at 20°C gives the isocyanide complexes LnM(RNC) 9 and the [2‐(acylamino)ethenyl]ketene imines RNCC(OEt)CH = CPh[N(COR)Ph] 8 (>95% yields) with configurational retention at the CC(N) bond. Thermolysis of (Z)‐8 (20–80°C) provides an efficient route to pyrroles 11 (90–95%) by a ring‐closing metathesis with elimination of isocyanates 10, while the thermolysis of (E)‐8, e.g. (E)‐8g, at 20°C leads to the formation of 1,4‐diaminonaphthalenes, e.g. 12g (>95% yield), by an electrocyclic ring closure.
Molekulare Pinzetten aus Cyclophan‐Bausteinen
Authors: Güther Ralf , Nieger Martin , Rissanen Kari , Vögtle Fritz
Published: July 2007

Molecular Tweezers from Cyclophane Building Blocks

Molecular tweezer compounds 1–6 with convergent carboxyl groups are prepared from suitable functionalized [2.2]‐and dithia[3.3]metacyclophane building blocks by using several multistep strategies. The CC coupling of two cyclophanes according to the Hagihara method leads to alkynespacered double cyclophanes. These new preorganized, acyclic host compounds of the cyclophane‐type react as molecular tweezers and can selectively “grasp” guest molecules and bind them strongly. X‐ray analyses underline the syn conformations of the dithia[3.3]‐ and the anti conformation of the [2.2]metacyclophanes.
A Convenient One‐Pot Preparation of Bis(nitroaryl) Tellurides Using a Tellurium‐Copper Couple as the Telluration Reagent
Authors: Suzuki Hitomi , Nakamura Tohru
Published: July 2007

The Te‐Cu couple generated in situ by the reaction of disodium telluride with copper(I) iodide in dry N‐methyl‐2‐pyrrolidone has been found to be a convenient telluration reagent for some activated iodoarenes 1. Using this reagent system, we have prepared by a one‐pot synthesis in satisfactory yields several bis(nitroaryl) tellurides 4, which are otherwise laborious to obtain.
Seven‐Membered Heterodimetallic Ring Systems from (Conjugated Diene) Group 4 Metallocene Complexes and Organoaluminium Reagents
Authors: Erker Gerhard , Noe Ralf , Wingbermühle Doris
Published: July 2007

The (s‐trans/s‐cis‐η4‐butadiene)zirconocene reagent adds dimethylaluminium chloride to yield the heterodimetallacyclic main group/transition‐metal system 2b, containing a seven‐membered metallacyclic framework that exhibits a “π‐agostic” s̀‐allyl zirconium interaction. Similar compounds (2c–f, 5a, 6) are obtained upon reaction of (butadiene)zirconocene with Et2All and (butadiene)hafnocene with Me2AlCl or Et2AlI. Addition of Me2AlCl or Et2AlI to (isoprene)zirconocene proceeds regioselectively to yield the corresponding heterodimetallacycles bearing the methyl substituent at C‐3 (i.e. near to the attached aluminium center). The iodide‐bridged heterodimetallacycles exhibit dynamic NMR spectra that indicate a rapid enantiomerization process on the NMR time scale (ΔG±ent ≈ 11–12 kcal mol−1). It is assumed that this automerization reaction proceeds by rate‐limiting aluminium‐halogen bond cleavage leading to an acyclic mixed metal heterodimetallic intermediate. This process is markedly inhibited by the presence of excess diethylaluminium iodide.
1,3,5‐Triphenyl‐2,4,6‐trimesityl‐1,3,5,2,4,6‐triphosphatriborinane: A 6π‐Electron Heteroaromatic Ligand
Authors: Kaufmann Bernhard , Metzler Nils , Nöth Heinrich , Paine Robert T.
Published: July 2007

The preparation of tricarbonyl(η6‐1,3,5‐triphenyl‐2,4,6‐trimesityl‐1,3,5,2,4,6‐triphosphatriane)chromium (4) is reported. Its X‐ray structure reveals an orientation of the Cr(CO)3 moiety with respect to the almost planar B3P3 ring typical of an arene metal tricarbonyl complex.
Metallkomplexe funktioneller Isocyanide, XXIV. Reaktionen von N‐Isocyandialkylamin‐Metallkomplexen mit sekundären Aminen
Authors: Fehlhammer Wolf Peter , Metzner Robert , Sperber Wilfried
Published: July 2007

Metal Complexes of Functional Isocyanides, XXIV. — Reactions of N‐Isocyanodialkylamine Complexes with Secondary Amines

Reactions of pentacarbonyl(N‐isocyanodialkylamine) group 6‐metal complexes [M(CO)5CNNR2] [M = Cr, W; R = Et, iPr; 2R = ‐{MeCH(CH2)3CHMe}‐] with secondary amines proceed with cleavage of the NN bond and C→N migration of the metal to give the corresponding N‐cyanamide complexes [M(CO)5NCNR′2] (1a–2g) [R′ = Me, Et, nPr, nBu; 2R′ = (CH2)4, (CH2)5, (CH2)2O(CH2)2]. However, when diiodobis(N‐isocyanodialkylamine)platinum(II) was allowed to react with an excess of the amine amine(guanidine)platinum(II) complexes [PtI2(HNR′2){HNC(NR′2)2}] (3a–c) [R′ = Et; 2R′ = (CH2)5, (CH2)2O(CH2)2] were obtained. Structural assignments are made on the basis of IR, NMR (1H, 13C), and mass spectroscopy as well as of an X‐ray structure analysis of trans‐[PtI2(HNEt2){HNC(NEt2)2}] (3a).
Synthesis of Silver(I) Complexes with the Bis(diphenylphosphanyl)‐o‐carborane Ligand. Crystal Structure of [Ag(phen){(PPh2)2C2B10H10}]ClO4 and [Ag{(SPPh2)2CH2}{(PPh2)2C2B10H10}]ClO4 · CH2Cl2
Authors: Bembenek Eberhard , Crespo Olga , Concepción Gimeno M. , Jones Peter G. , Laguna Antonio
Published: July 2007

Silver(I) perchlorate or nitrate react readily with bis(di‐phenylphosphanyl)‐o‐carborane to give the complexes [AgX{(PPh2)2C2B10H10}] [X = ClO4 (1), NO3, (2)]. The perchlorate ligand is weakly bound to the silver atom and thus can be displaced by other ligands affording the three‐coordinated complexes [AgL{(PPh2)2C2B10H10}]ClO4 [L = PPh3 (3), PPh2Me (4), AsPh3 (5), C5H4NCOOH (6), C9H6NCOOH (7), SPPh3 (8)]. Compounds 3 and 4 can also be obtained by reaction of [Ag(OClO3)PR3] with the diphosphane. Treatment of complex 1 with bidentate ligands leads to the cationic four‐coordinated [Ag(LL){(PPh2)2C2B10H10}]ClO4 [LL = (PPh2)2C2B10H10 (9), bipy (10), phen (11), (SPPh2)2CH2 (12)] or to the neutral [Ag(S2CNR2){(PPh2)2C2B10H10}] [NR2 = NEt2 (13), NC4H8 (14)]. The crystal structures of 11 and 12 have been established by X‐ray crystallography. In both complexes the silver(I) atoms exhibit tetrahedral coordination by two phosphorus and two nitrogen or two sulfur atoms, respectively.
Electroorganic Synthesis, 58. Synthesis of Substituted Benzoquinones and their Use for Mediated Electrochemical Conversions
Authors: Riering Helmut , Schäfer Hans J.
Published: July 2007

Hydroxy‐ (1a‐3a) and hydroxyalkyl‐substituted benzoquinones (6a‐8a, 27a), suited to be immobilized by esterification with polyacrylic acid, are prepared. Their cathodic reduction potential Ep,c (1) correlates linearly with their substituent constant. The cathodic reduction of dioxygen and the palladium(II)‐catalyzed anodic oxidation of alkenes are mediated by the benzoquinones 7b, 8b and 27b, respectively.
Carbon‐Carbon Bond Cleavage of the [2.2]Paracyclophane Radical Cation Generated by Electron Transfer Oxidation with Cerium(IV) Ammonium Nitrate
Authors: Adam Waldemar , Miranda Miguel A. , Mojarrad Fatemeh , Sheikh Hamid
Published: July 2007

Single electron transfer (SET) oxidation of [2.2]paracyclophane (1) with cerium ammonium nitrate (CAN) produces the corresponding radical cation (1+.), which undergoes cleavage of the carbon‐carbon bond of the ethano bridge to generate the double‐benzylic radical cation 2+. Trapping of this intermediate by oxygen and nucleophiles gives rise to aldehydes 3, while a second oxidation and subsequent nucleophilic trapping affords nitrates 4. This facile cleavage of the carbon‐carbon bond is explained by alignment of the latter with the π systems in the rigid structure of [2.2]paracyclophane, which enables charge delocalization across both benzene rings. When the reaction is carried out in methanol, aromatic substitution takes also place as a minor reaction pathway, which is responsible for the formation of the polyfunctionalized cyclophane 5d.
Dendrimere und Dendrimer‐Bausteine mit trisubstituiertem Benzol und “Hexacyclen” als Kern
Authors: Kadei Klaus , Moors Rolf , Vögtle Fritz
Published: July 2007

Dendrimers and Dendrimer Building Blocks with Trisubstituted Benzene and “Hexacyclene” as Core Units

The preparation of new dendritic compounds containing 1,3,5‐substituted aromatic units or “hexacyclene” is described. Bulky dendrimers are obtained in few generations starting with polyfunctional core units like 1, 4, 5, 12, and hexacyclene (21). The dendrimers were synthesized by using both the divergent method (for 7) and the convergent method (for 13 and 22). 22 is the first dendrimer containing a crown unit as core.
Chelat‐kontrollierte diastereoselektive Addition an α,ß‐Epoxy‐Aldehyde
Authors: Ipaktschi Junes , Heydari Akbar , Kalinowski Hans‐Otto
Published: July 2007

Chelate‐Controlled Diastereoselective Addition to α,β‐Epoxy Aldehydes

LiClO4‐mediated reaction of trans‐substituted α,β‐epoxy aldehydes 1 with allyltributyltin (2) or trimethylsilyl cyanide provides a general method for the synthesis of the corresponding syn‐alcohols 3 with high selectivity. In the case of cis‐substituted α,β‐epoxy aldehydes the selectivity depends on the size of the substituents.
Michael Addition of Imines to Alkynylcarbene Complexes with Subsequent Intramolecular Cyclization ‐ An Efficient Three‐Step Synthesis of 2H‐Pyrroles
Authors: Funke Frank , Duetsch Michael , Stein Frank , Noltemeyer Matthias , Meijere Armin De
Published: July 2007

Imines 7, 11–13 were added to (1‐alkynylcarbene)chromium complexes 6a–d to form {[2‐(methyleneamino)ethenyl]‐carbene}chromium complexes 8a–d, 14a–d, 15a–d, 16a–d in good to very good yields (63–98%) except for two cases (41–59%). The carbene ligands of the latter compounds cyclize to 2H‐pyrroles 9a–d, 17a–d, 18a–d, 19a–d upon heating in tetrahydrofuran solution to 50–55°C.
Erzeugung von 2‐substituierten 1‐Ethenyl‐Kationen aus Ethylendiazonium‐Salzen
Authors: Bott Kaspar
Published: July 2007

Thermal decomposition of 2‐substituted ethylenediazonium salts 1a–d produces the corresponding 1‐ethenyl cations 2a–d as short‐lived intermediates. The primary vinyl cation 2d or the rearranged and energetically favored analogues 3a–c of 2a–c are intercepted by chloride to give the decomposition products 4d and 5a–c, respectively. The generation of 4d and 5a–c as well as a kinetic study of the thermolysis reaction provide no indication that the elimination of nitrogen from 1a–d is occurring with the intermediate formation of cyclic cations 6 or 7.
Ring Cleavage of Benzofurans and Tetrahydrobenzofurans by m‐Chloroperbenzoic Acid Epoxidation
Authors: Adam Waldemar , Ahrweiler Michael , Sauter Markus
Published: July 2007

The oxidation of the benzofurans 1a–f (tetrahydrobenzofurans 1g, h) with excess m‐CPBA is reported. The in situ generated, highly reactive benzofuran epoxides 2a–f and their quinone methides 3a–f (cis‐ene diones 3g, h) afford the labile tautomeric peroxy esters 5 and 5′ by nucleophilic addition of the peroxy acid. On elimination of m‐chlorobenzoic acid, the peroxy esters 5/5′ of the benzofuran derivatives 1a–f rearrange thermally to the keto esters 6 by CC cleavage or to the spiro epoxides 7 by CO cleavage. The latter undergo thermal isomerization to the 1,3‐benzodioxoles 8 and Diels‐Alder cycloaddition to the corresponding dimers 9. Independently, the keto esters 6 and the 1,3‐dioxoles 8 were synthesized by thermolysis of the dioxetanes 11. The tautomeric m‐CPBA adducts 5/5′ of the persistent ene diones 3g, h, derived from the tetrahydrobenzofuran derivatives 1g, h, rearrange as well to the spiro epoxides 7g, h. In contrast to the benzofuran derivatives 6a–f, the keto enol ester 6h suffers Baeyer‐Villiger rearrangement with another molecule of m‐CPBA to form the ene diester 10h.
Effect of Fluorine and Chlorine Substituents on Stabilities of Diphosphaallene, Diphosphirene, and Phosphanylphosphaalkyne Isomers (XX′ CP2 Species with X, X′ = H, F, and Cl)
Authors: Fitzpatrick Noel J. , Brougham Dermot F. , Groarke Peter J. , Nguyen Minh Tho
Published: July 2007

Ab initio MO calculations at the QCISD(T)/6–31G* */MP2/6–31G* * + ZPE level on the XX′CP2 isomers (X = H1 F and Cl) show that the energies of the isomeric species are often reordered following halogen substitution. The phosphorushalogen moiety behaves as the main stabilizing factor on the rest of the molecular structure. This is particularly true when X = F is involved. In the dihalogenated series phosphanyl‐phosphaalkyne (4) becomes the most stable species followed by diphosphaallene (3) and 1 H‐diphosphirene (6). The effect on the geometry following halogenation is larger if substitution takes place at carbon than at phosphorus. The behaviour of the P species is found to be quite different from, if not opposite to, that of their nitrogen analogues. Finally, the infrared spectra of the most stable isomers are also predicted.
Bis(trifluormethylsulfonyloxy)organosilicium‐Verbindungen als Synthesebausteine für neuartige Siliciumpolymere
Authors: Uhlig Wolfram
Published: July 2007

Bis(trifluoromethylsulfonyloxy)organosilicon Compounds as Synthetic Materials for New Silicon Polymers

The new polycarbosilanes, polysiloxanes, and polysilylenealkynes 1c–6c were obtained by condensation of electrophilic α,ω‐bis(trifluoromethylsulfonyloxy)organosilicon compounds 1b–6b with nucleophiles such as organolithium and organomagnesium compounds. The required silyl triflate derivatives 1b–6b have been prepared by reaction of the corresponding amino‐, allyl‐, or phenylsilanes 1a–6a with trifluoromethanesulfonic acid.