bluuebunny/crossref_metadata_2025 huggingface dataset:
Reductive transformations, 20. Synthesis of n‐alkyl‐substituted perylenes and terrylenes via alkali‐metal induced cyclization of oligonaphthylenes
Authors: Anton Ute , Göltner Christine , Müllen Klaus
Published: July 2007

The synthesis of two novel n‐alkyl‐ or aryl‐substituted perylenes and of an n‐alkylated terrylene is possible by an alkalimetal induced cyclization of the corresponding bi‐ or trinaphthyls. Differences in reactivity of the naphthylenes in the ringclosure reaction are caused by the different substitution pattern. UV and fluorescence spectra as well as the stability of the resulting rylenes[2] are discussed as a function of substitution.
Metallkomplexe in Biologie und Medizin, IV. Darstellung und Kristallstruktur von Bis(2–aminoethanthiolato)bismut(III)‐nitrat–Monohydrat
Authors: Herrmann Wolfgang A. , Kiprof Paul , Scherer Wolfgang , Pajdla Liba
Published: July 2007

Metal Complexes in Biology and Medicine, IV[1]. – Synthesis and Structure of Bis(2–aminoethanethiolato)bismuth(III) Nitrate Monohydrate

Reaction of bismuth(III) nitrate with 2–aminoethanethiol results in the formation of bis(2–aminoethanethiolato)bismuth(III) nitrate monohydrate (1), the solid–state structure of which has been established by single–crystal X–ray diffraction. The bidentate chelating ligand leads to the formation of five–membered rings. Due to interaction of neighbouring units via Bi–S bonds, a polymeric three–dimensional structure results in the crystal lattice. The bismuth atom has an eightfold coordination with two coordination sites being provided by sulphur atoms of adjacent molecules.
Highly Functionalized Vinylcyclopropane Derivatives by Regioselective and Stereoselective Reactions of Fischer Carbene Complexes with 1,4–Disubstituted Electron–Deficient 1,3–Dienes
Authors: Buchert Matthias , Reißig Hans–Ulrich
Published: July 2007

The thermal reaction of Fischer carbene complex 1 with electron–deficient 1,3–dienes such as methyl (E,E)‐2,4–hexadienoate (2) provided functionalized vinylcyclopropanes like 3 in good yields. Similar results were obtained by employing related unsaturated esters 4, 17, and 21 or nitrile 6. The periselectivity as well as regioselectivity of these carbene–transfer reactions are generally very high, and the diastereomer with the methoxy group cis‐positioned with respect to the olefinic moiety is largely favoured (>85:15). A mechanistic rationale of these observations is given. Double adducts were only formed as minor sideproducts in these reactions, but by employing amide 13 as electron–deficient diene they were very easily formed with 1. The [2 + 1] cycloaddition could also be extended to methylcarbene complex 24 and diene 2, but the corresponding vinylcyclopropane 25a was so far only obtained in low yield.
Chiral Organometallic Reagents, IX. On the Origins of the Diastereoselectivity in the Bromine/Lithium Exchange of 3–Alkoxy–1,1–dibromoalkanes
Authors: Hoffmann Reinhard W. , Brumm Karen , Bewersdorf Martin , Mikolaiski Wolfgang , Kusche Andreas
Published: July 2007

The 3–alkoxy–1,1–dibromopentanes 5 are compounds, which according to MM2 calculations populate one conformation to >80% at −110°C. On reaction with n‐butyllithium the bromine atom which resides in the extended position is exchanged with selectivities around 80:20, irrespective of the nature of the oxy residue at C–3. The role of this substituent is solely to bias the conformational equilibria in favor of the conformer 17. Coordination of the butyllithium to the oxygen functionality plays an important role only in the carbamoyl derivative 5f, for which the sense of the asymmetric induction is reversed.
Kristallstruktur und Gasphasenuntersuchungen von lithiiertem Acetessigsäure‐tert‐butylester
Authors: Waldmüller Delia , Mayer Bernhard , Braun Manfred , Hanuschik Andreas , Krüger Carl , Guenot Pierre
Published: July 2007

Crystal Structure and Gas–Phase Investigations of Lithiated tert‐Butyl Acetoacetate

The lithium enolate 2, generated either by deprotonation of tert‐butyl acetoacetate (1) or by pyrolysis of lithiated tert‐butyl acetate (3) is crystallized from toluene. The X–ray diffraction analysis of unsolvatized 2 reveals a hexameric structure. Thereby, the central skeleton is formed by two Li–O six–membered rings, and the carbonyl group of the ester moiety serves to complete the fourfold coordination of the lithium atom. The thermal stability of 2 enables the very first mass spectrometric and photoelectron spectroscopic investigation of a lithium enolate. The lithium compound 2 forms aggregates even in the gas phase. The first vertical ionization energy of 2 is found to be significantly lower than those observed in the photoelectron spectra of both the enol ether 5 and the ester 1.
Preparative, X‐ray, and NMR Studies of the Interaction of Beryllium with Salicylic and o‐Cresotic Acid: Crystal Structures of (NH4)2[Be(C6H4OCO2)2] · 2.25 H2O and Na3[Be(C7H6OCO2)(OH)(CO3)Be(C7H6OCO2)] · 8 H2O
Authors: Schmidbaur Hubert , Kumberger Otto
Published: July 2007

The existence of well‐defined crystalline beryllium salicylate(2 – ) and bis[salicylato(2 – )]beryllate complexes as well as of their o‐cresotate analogs is established. The structure of (NH4)2[Be(C6H4OCO2)2] · 2.25 H2O has been determined by an X‐ray structure analysis. It contains a beryllate anion of the composition [Be(C6H4OCO2)2]2– with two salicylate(2 – ) ligands acting as chelate ligands. The considerable 9Be NMR chemical shifts observed for aqueous solutions of the pure compounds indicate in all cases the persistence of the complexation of the metal ion by the catecholate ligands. 9Be NMR studies of aqueous solutions containing BeSO4 · 4 H2O and sodium salicylate(1 – ) or sodium o‐cresotate(1 – ) in the molar ratios 1:1 and 1:2 show that a variety of beryllium/salicylate(2 – ) and beryllium/o‐cresotate(2 – ) species are present in solution, the most prominent being Be(C6H4OCO2)‐(H2O)2 and [Be(C6H4OCO2)2]2– (and their o‐cresotate analogs). From such solutions in contact with air, a novel dinuclear beryllium hydroxido/o‐cresotato(2 – )/carbonato complex of the stoichiometry Na3[Be2(OH)(CO3)(C7H6OCO2)2] · 8 H2O is isolated. According to an X‐ray analysis the compound contains a cyclic beryllate anion with two Be(C7H6OCO2) chelate units linked by bridging hydroxide and carbonate anions. In the light of the ubiquitous availability of phenolic and carboxylic groups in many biomolecules, the finding of strong bonding of Be2+ to these functions in aqueous solution is very important.
Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LXXX. Insertions‐ und Additions‐Reaktionen an Diphosphamanganacyclopropanen mit aktivierten Alkinen
Authors: Lindner Ekkehard , Darmuth Monika , Mayer Hermann August , Fawzi Riad , Maichle Cäcilia , Steimann Manfred
Published: July 2007

Metal‐;Containing Heterocycles: Preparation, Properties, Reactions, LXXX. — Insertion and Addition Reactions on Diphosphamanganacyclopropanes with Activated Alkynes

The thermally and kinetically stable diphosphamanganabicyclooctadienones 3a — e [R2 = tBu: R1 = iPr (a), nPr (b), Ph (c); R2 = Cy: R1 = nPr (d), Ph (e)] are obtained by the reaction of the alkyne (CCO2Me)2 with the diphosphamanganacyclopropanes (OC)4Mn‐PR=PR2 (2a — e). Depending on steric factors the formation of 3a — e occurs in two different ways. In a first step the alkyne is inserted into the P — P bond of 2a — e to give the kinetically labile five‐membered rings 1a — e. Subsequently another alkyne is added to the PR2 and a CO group of 1a — e to give 3a — e. In an alternative way the alkyne is added first to the PR2 and a CO group of 2a with formation of the diphosphamanganabicyclohexenone 4a. Insertion of a second alkyne into the P — P bond of 4a affords the bicyclooctadienone 3a. Compound 2a, 3c, and 4a have been characterized by X‐ray structural analyses.
Metallkomplexe in Biologie und Medizin, V. Neue Hydroxycarboxylat‐Komplexe von Bismut. Synthese und Struktur von Bismut(III)‐malat‐monohydrat und Bismut(III)‐tartrat‐trihydrat
Authors: Herrmann Wolfgang A. , Herdtweck Eberhardt , Scherer Wolfgang , Kiprof Paul , Pajdla Liba
Published: July 2007

Metal Complexes in Biology and Medicine, V. — New Bismuth Hydroxycarboxylate Complexes. Synthesis and Structure of Bismuth(III) Malate Monohydrate and Bismuth(III) Tartrate Trihydrate

Reaction of Bi(NO3)3 · 5 H2O with L‐(–)‐malic acid results in the formation of bismuth(III) malate monohydrate Bi[O2CCH2CH(O)CO2] · H2O (1) containing the tridentate ligand [L‐(–)‐malate]3– with all donating functions deprotonated. By way of contrast, reaction of Bi(NO3)3 · 5 H2O with L‐(+)‐tartraic acid gives bismuth(III) tartrate trihydrate (2), in which two different tartrate ligands, [L‐(+)‐tartrate]1– and [L‐(+)‐tartrate]2– are present. The solid‐state structures have been determined by single‐crystal X‐ray methods and confirmed by powder diffraction measurements. The structure analyses exhibit a three‐dimensional network in the crystalline state resulting from bridging and chelating properties of the polydentate hydroxycarboxylate ligands. Bismuth shows high coordination numbers.
Selektive Ketonpyrolyse: Neue Beispiele
Authors: Ott Frank , Breitenbach JüRg , Nieger Martin , Vügtle Fritz
Published: July 2007

Selective Ketone Pyrolysis: New Examples

The known ketone4, the new paracyclophane ketones6, 7, and9–12and the known hydrocarbons5, 8, and13are obtained by successive thermal extrusion of carbon monoxide from the [3n]paracyclophane(ones)n1, 2, and3(n= 2,3,4). The X‐ray structure analyses of the 20‐membered6and the 26‐membered ring10are reported.
Preparation of 3,4,5‐Trisubstituted 1,2,4‐Oxadiazolium Salts from Nitrilium Salts
Authors: Abu‐;El‐Halawa Rajab , Shrestha‐;Dawadi Prativa Bade , Jochims Johannes C.
Published: July 2007

1,3‐Cycloadditions of stable nitrile oxides 2 to nitrilium salts 1 afford high yields of 3,4,5‐trisubstituted 1,2,4‐oxadiazolium salts 3. N‐Hydroxycarboximidoyl chlorides 4 add to nitrilium salts 1 to give isolable [(chloroalkylidene)aminooxyalkylidene]ammonium salts 5. A thermal stereomutation around the C = N+ bond is observed. On heating neat or in solution most compounds 5 cyclize to oxadiazolium salts 3. In cases where decomposition of 5 is faster than cyclization O‐silylated N‐hydroxycarboximidoyl chlorides 7 are treated with nitrilium salts 1 to furnish oxadiazolium salts 3.
Reversibility of the [2 + 2] Cycloaddition of Isocyanates to Glycals
Authors: Kaluża Zbigniew , Chmielewski Marek , Salański Piotr , Jurczak Janusz
Published: July 2007

[2 + 2] Cycloadducts obtained by the addition of tosyl isocyanate to glycals (10 – 13) undergo retro‐addition upon heating or even at room temperature. The rate of retro‐addition increases with rising temperature and polarity of the solvent.
Organosubstituiertecis‐1,2‐Diborylalkene als elektrophile Chelatbildner
Authors: Köster Roland , Seidel Günter , Wagner Klaus , Wrackmeyer Bernd
Published: July 2007

Organosubstitutedcis‐1,2‐Diborylalkenes as Electrophilic Chelates

Triethylborane (1), 9‐ethyl‐9‐borabicyclo[3.3.1]nonane (9‐ethyl‐9‐BBN) (2), and thecis‐1,2‐diborylalkenes (Z)1‐R2BC(R′)C(Et)BEt2[3: REt, R′Me;4: R,R′Et;5: REt, R′Ph;6: R2C8H14, R′Et;7: RPh, R′Et] react with alkali metal salts MX [MNa, K; XH, OMe, OtBu, OSiMe3, OSiEt3] in toluene to give the borates MX‐1, MX‐2, and the cycliccis‐1,2‐diborates M, resp., [e.g. KH‐3to KH‐7; NaOMe‐4to NaOMe‐6; KOtBu‐4, KOSiMe3‐4, KOSiEt3‐4] with BHB‐and B(OR)B‐bridges (IR, Multi NMR). Reaction of1, 2, and3–6with KCN leads to the monoborates KCN‐1, KCN‐2, and to the acycliccis‐1,2‐diborates KCN‐3to KCN‐7. — Thecis‐2‐Boryl‐1‐silylalkenes (E)1‐Me3SiC(R′)C(Et)BEt2[8: R′Me;9: R′Et] and KX [XH, CN, OMe] form the acyclic borates K[Me3SiC(R′)C(Et)1‐BEt2X]. The cyclic salts KOtBu‐4and KOSiEt3‐4undergo aB1‐substituent exchange to the acycliccis‐1,2‐diborates K[Et3BC(Et)C(Et)B(Et)OR] (K‐10: RtBu; K‐11: ROSiEt3).
Übergangsmetallaktivierte organische Verbindungen, XXXVIII. Chemoselektive nucleophile Methylierungen durch In‐Situ‐Blockierung von Aldehydgruppen unter α1‐Phosphonioalkoxid‐Bildung
Authors: Kauffmann Thomas , Abel Thomas , Li Weichang , Neiteler Gabriele , Schreer Martin , Schwarze Dieter
Published: July 2007

Transition Metal‐Activated Organic Compounds, XXXVIII[1]. — Chemoselective Nucleophilic Methylation Reactions by In‐Situ‐Blocking of Aldehyde Groups by α1‐Phosphonioalkoxide Formation

Herrn Professor Ulrich Schöllkopf zum 65. Geburtstag gewidmet.

For the selective methylation of a keto group in the presence of an aldehyde group the complex MeTiCl3·PPh3 and especially the reagent system [TiC]4·PPh3 + 0.5 Me2Zn] proved to be favourable. For instance, 6‐oxoheptanal (8) was methylated by [TiCl4·PPh3 + 0.5 Me2Zn] at the keto group with 89% yield and 99:1 selectivity, whereas it was methylated by [TiCl4 + 0.5 Me2Zn] at the aldehyde group with 81% yield and 96:4 selectivity. A selective methylation of benzaldehyde in the presence of heptanal was achieved with MeNbCl4·PPh3 or [NbCl5·PPh3 + 0.75 Me2Zn] to give (1‐chloroethyl)benzene (14; yield 92 or 53%; selectivity in each case 93:7) or with [TaCl5·PPh3 + 1.5 Me2Zn] to give mainly 1‐phenylethanol (15) besides 16. A 96:4‐selective benzylation (yield 74%) of a ketone in the presence of an aliphatic aldehyde was possible with [TiCl4·PPh3 + 1 PhCH2MgBr]. — The high chemoselectivity is caused by irreversible blocking of aliphatic aldehyde groups by α1‐phosphonioalkoxide formation[1], whilst the corresponding reaction of keto groups[1] and of benzaldehyde is reversible.
Synthese, Struktur und Reaktivität von Diphosphiranen
Authors: Streubel Rainer , Nieger Martin , Niecke Edgar
Published: July 2007

Synthesis, Structure, and Reactivity of Diphosphiranes

The 1,1‐diamino‐1,2‐diphospha‐2‐propen (2,6‐Me2C5H8N)2P – PC(SiMe3)2 (3) is obtained by treatment of bis(2,6‐dimethyl‐piperidino)(trimethylsilyl)phosphane (1) with [bis(trimethylsilyl)methylene]chlorophosphane (2). Compound 3 readily undergoes thermally isomerization to the diphosphirane 2,6‐ Nucleophilic substitution of the P1‐chloro function of 1‐chloro‐2‐(diisopropylamino)1‐3,3‐bis(trimethylsilyl)diphosphirane (6) leads to alkyl, amino, phosphanyl, and arsanyl derivatives 7a – d. The corresponding hydrogen derivative 7e is formed by reduction of 6 with tri‐n1‐butylstannane. The molecular structure of 7c as well as the NMR data of the diphosphiranes are discussed.
Neue Beiträge zur Chemie des Mangans: Synthese und Strukturen zweier monomerer MnII1‐Verbindungen und eines hexanuklearen MnII/III1‐Komplexes
Authors: Köhler Katrin , Roesky Herbert W. , Noltemeyer Mathias , Schmidt Hans‐Georg , Freire‐Erdbrügger Cristina , Sheldrick George M.
Published: July 2007

New Contributions to the Chemistry of Manganese: Syntheses and Structures of two Monomeric MnII Compounds and a Hexanuclear MnII/III Complex

Two novel mononuclear manganese(II) complexes, Mn[OSi(OtBu)3]2·(Py)3 (2) and Mn[PhC6H4C(NSiMe3)2]2·THF (3), and a hexanuclear mixed‐valence manganese(II/III) complex Mn6O2(O2CtBu)10·(Py)4 (5) have been prepared, and their structures have been determined by X‐ray crystal structure analyses.
Highly Strained Cage Compounds from a Fourfold Bridged Tricyclo[4.2.0.02,5]octa‐3,7‐diene
Authors: Gleiter Rolf , Pflästerer Georg , Irngartinger Hermann
Published: July 2007

The fourfold bridged tricyclo[4.2.0.02,5]octa‐3,7‐diene derivative 3 reacts with diazomethane and m1‐chloroperbenzoic acid (mCPBA) to yield the monoadduct 5 in good and the bisadduct 4 in poor yield as well as the mono‐and bisepoxides 7 and 8 in good yields, respectively. Also the “mixed” product 6 is obtained. All five compounds are strained propellanes. The X‐ray crystallographic structure analysis of 8 reveals a distance of 2.812 Å between the epoxide rings.
Mono‐, Di‐, Tri‐, Tetra‐, Penta‐und Hexaphenylbullvalene
Authors: Rebsamen Karl , Röttele Herbert , Schröder Gerhard
Published: July 2007

Mono‐, Di‐, Tri‐, Tetra‐, Penta‐and Hexaphenylbullvalenes

Lithium diphenylcuprate reacts with the corresponding bromobullvalenes to yield the phenylbullvalenes 1–6, whose substitution patterns are deduced from their 1H‐NMR spectra. Starting with triphenylbullvalenes 3 some isomers show a relatively high kinetic stability which culminates in the case of the hexaphenylbullvalenes 6a and 6b in the loss of the phenomenon of fluctuating structure for the bullvalene skeleton.
Alkyleisen‐und Alkylcobalt‐Reagenzien, VIII. Eisen(II)1‐alkyle als Reagenzien und Katalysatoren für die Überführung von Acylchloriden in Ketone
Authors: Kauffmann Thomas , Voß Karl‐Uwe , Neiteler Gabriele
Published: July 2007

Alkyliron and Alkylcobalt Reagents, VIII[1]. – Alkyl‐Iron(II) Compounds as Reagents and Catalysts for the Transformation of Acyl Chlorides into Ketones

Me2Fe, Bu2Fe, Me3FeLi, or Bu3FeLi – prepared in situ by reduction of FeCl3 to FeCl2 and subsequent alkylation with MeLi, MeMgBr, BuLi, or BuMgBr – are useful reagents for the conversion of acyl chlorides into ketones. The system (RMgX + catalytic amount of FeCl3) react like the alkyl FeII reagents with acyl chlorides to give ketones even at –65°C. Competition experiments with benzoyl chloride/2‐methoxy‐benzoyl chloride show that the selectivity increases (competition constants Kk9.9, 10.7, 10.9, 15.0, ca. 110) in the sequence MeFeCl, Me2Fe, Me3Fe(MgBr), Me4Fe(MgBr)2, and catalytic system [MeMgBr + 2.5 mol % FeCl3] (= 2, 3, 4, 5, and 40 MeMgBr per 1 FeCl3, respectively). A new hypothesis on the nature of the active catalyst is discussed.
Ein weiterer Beitrag zur Stabilisierung der Iminoborane RB≡NR′
Authors: Kiesgen Jutta , Münster Jochen , Paetzold Peter
Published: July 2007

A Further Contribution to the Stabilization of Iminoboranes RB≡NR'

The iminoboranes (tBuB≡NR (1a, b, R=iPr, Ph) and RB≡NR (1c, d; R=Me3CCH2, Me3SiCH2) were prepared by gas‐phase thermolysis of Cl(tBu)BN(R)SiMe3 (6a, b) and R2BN3 (7c, d), respectively. At room temperature, the molecules 1a–c cyclodimerize to the diazadiboretidines 2a–c, whereas the borane 1d cyclotrimerizes to the borazine 3d; these stabilization reactions are discussed in terms of the steric demand of the organic ligands. The ethyloboration of 1a, c with BEt3 BCl to 1a yields the diborylamine 9d. Benzyl azide and 1c, d undergo a [3 + 2] cycloaddition with formation of the tetrazaborolidines 10c, d.
Electroorganie Synthesis, 55[1]. Influences on the Selectivity of the Kolbe versus the Non‐Kolbe Electrolysis in the Anodic Decarboxylation of Carboxylic Acids
Authors: Klocke Elisabeth , Matzeit Agnes , Gockeln Marianne , Schäfer Hans J.
Published: July 2007

The anodic decarboxylation of 3‐oxanonanoic acid (2a) and 3‐oxapentadecanoic acid (2b) in methanol leads exclusively to products of the non‐Kolbe electrolysis. The influence of co‐electrolysis, solvent, current density, degree of neutralization and chain length of the alkoxy group on the anodic decarboxylation of 2a, b have been investigated. An extended alkyl chain in the alkoxy group, coelectrolysis with long‐chain fatty acids, ethanol or dimethylformamide as solvent, and a high current density favor the Kolbe coupling against the non‐Kolbe electrolysis.
Cycloaddition Reactions Initiated by Photochemically Excited Pyrylium Salts
Authors: Martiny Martin , Steckhan Eberhard , Esch Thomas
Published: July 2007

Several pyrylium, thiapyrylium, and pyridinium salts have been synthesized and used as sensitizers for photochemically induced electron‐transfer (PET) reactions. The salts have been tested in the mixed cycloaddition reactions of styrenes 9 with 1,3‐cyclohexadiene (8) or 1,1'‐dicyclohexenyl (23). In the case of the PET [4 + 2] cycloaddition of styrene (9a) to 1,3‐cyclohexadiene (8), the reaction takes place via the cation radical of the diene. When chloroform instead of dichloromethane is used as the solvent, only [2 + 2] cycloaddition products are obtained. In contrast, if 1,3‐cyclohexadiene (8) is replaced by 1,1'‐dicyclohexenyl (23), the key step of the reaction seems to be the oxidation of styrene (9). The product ratios depend on the sensitizers used. If solvent‐separated ion pairs are formed, styrene reacts as diene to give 1‐cyclohexenyloctahydro‐phenanthrene derivatives 28; cycloaddition via contact ion pairs leads to the Diels‐Alder product with styrene acting as the dienophile.
Flüssigkristalline Verbindungen, 79[1a]. Amphiphile und mesogene Kohlenhydrate, V[1b]. Amphiphile Fluorglucose‐ und Fluorscyllitol‐Derivate
Authors: Miethchen Ralf , Prade Heiko , Holz Jens , Praefcke Klaus , Blunk Dirk
Published: July 2007

Liquid Crystalline Compounds, 79[1a].–Amphiphilic and Mesogenic Carbohydrates, V[1b].–Amphiphilic Fluoroglucose and Fluoroscyllitol Derivatives

In order to look at the influence of the OH‐F substitution in the cyclic, hydrophilic section (head group) of amphiphilic sugars and of scyllitol derivatives on their liquid crystalline properties for the first time, we synthesized various differently structured fluoro‐D‐glucose derivatives [2‐O‐decyl‐α‐D‐glucopyranosyl fluoride (4), 4‐O‐tetradecyl‐α‐D‐glucopyranosyl fluoride (5), 6‐O‐hexadecyl‐α‐D‐glucopyranosyl fluoride (6), 6‐deoxy‐6‐fluoro‐2,3‐di‐O‐hexadecyl‐D‐glucopyranose (9), 2‐deoxy‐2‐fluoro‐4,6‐O‐alkyliden‐D‐glucopyranosen (11a–d), 3‐deoxy‐3‐fluoro‐5,6‐di‐O‐tetradecyl‐D‐glucofuranose (15)] as well as the 2‐deoxy‐2‐fluoro‐2,3,4,5,6‐tetra‐O‐hexyl‐scyllo‐in‐osit (19). Substitution of an OH group for a fluorine atom in amphiphilic derivatives destabilizes the thermotropic mesophase as it was to be expected so that either no or only narrowrange mesophases result. Both thermotropic and lyotropic liquid crystal phases occur in the series of 2‐deoxy‐2‐fluoro‐D‐glucopyranose acetals 11 which are discussed in detail and which are compared with the analogous 2‐hydroxy derivatives 12. Only 11c–d are thermotropic fluoro mesogens.
Auf dem Weg zu makrocyclischen para‐Phenylenen
Authors: Friederich Rolf , Nieger Martin , Vögtle Fritz
Published: July 2007

On the Way to Macrocyclic para‐Phenylenes

Strategies are presented to synthesize the hitherto unknown [On]Paracyclophanes 1. Open chain belt‐type molecules based on 1,4‐connected carbocyclic six‐membered rings were prepared. Functionalization of the outer rings in 4‐position is the prerequisite for cyclization or lengthening of the molecular belts. In order to obtain the macrocyclic target molecules 1, well preorganized cis‐isomers of 1,4‐disubstituted cyclohexanes were prepared. X‐ray structural analyses reveal the static stereochemistry of the intermediates 8, 9, 17, 18, and 24. The macrocyclic hydrocarbon 29 containing five cyclohexylidene units was detected.
Solvolysis of Tricyclo[3.1.0.02,6]hex‐3‐yl and Bicyclo[2.1.1]hex‐2‐yl Sulfonates
Authors: Bentley T. William , Norman Simon J. , Gerstner Erwin , Kemmer Ralf , Christl Manfred
Published: July 2007

Solvolyses of cis‐tricyclo[3.1.0.02,6]hex‐3,4‐diyl ditosylate (12) and cis‐bicyclo[2.1.1]hex‐2,3‐diyl ditosylate (27) have been carried out in 80% aqueous ethanol in the presence of ethyl‐diisopropylamine. In the former case, endo,endo‐tricyclo[2.2.0.02,6]hexane‐3,5‐diol (13a), its monoether 13b and diether 13c were products whereas in the latter the monoethers 28b, d, e, g and the diethers 28a, c, f of bicyclo[3.1.0]hexane were formed. In pure ethanol, 12 was converted into pure 13c in good yield. In the presence of the weaker base 2,6‐lutidine, the solvolysis of 12 in aqueous ethanol gave different products, i.e. exo,exo‐4,6‐diethoxybicyclo[3.1.0]hex‐2‐ene (14a) and several aldehydes, inter alia cyclopentadiene‐1‐carboxaldehyde (15). In control experiments, the tricyclic compounds 13b, c were converted into 14a, 15 and further aldehydes as well as into the bicyclo[2.1.1]hexene derivatives 19a, b. Sulfonates of tricyclo[3.1.0.02,6]hexan‐3‐ol (21a) could not be isolated but its mesylate 21c was characterized by NMR spectroscopy and hydrolysed in aqueous acetone to give tricyclo[2.2.0.02,6]hexan‐endo‐3‐ol (22a). It is concluded from these results that the dissociations of the above sulfonates do not lead to unrearranged carbocations. Rather, they proceed with participation of the β‐carbon in trans position relative to the leaving group resulting in the immediate generation of rearranged cations.–Kinetic studies show that the tricyclic mesylate 21c solvolyses in 80% ethanol/water 1.4 · 105 times as fast as bicyclo[2.1.1]hex‐2‐yl tosylate (25), and the tricyclic ditosylate 12 solvolyses 6 · 105 as fast as the corresponding bicyclic ditosylate 27. These rate enhancements are similar to those previously observed for less strained cyclopropylcarbinyl substrates.
Cyclopropanierung von Fullerenen
Authors: Bingel Carsten
Published: July 2007

Cyclopropylation of Fullerenes

Cyclopropylation of fullerenes C60 and C70 is achieved by a tandem process. Michael addition of a stabilized α‐halocarbanion to fullerenes followed by intramolecular substitution of the halogen yields fullerene derivatives with functional groups.
Derivate des Imidazols, VI. Stabile Carben‐Borane
Authors: Kuhn Norbert , Henkel Gerald , Kratz Thomas , Kreutzberg Jörg , Boese Roland , Maulitz Andreas H.
Published: July 2007

Imidazole Derivatives, VI[1]. — Stable Carbene Boranes

Stable imidazol‐2‐ylidene—borane adducts 8 and 9 are obtained from 1,3,4,5‐tetraalkylimidazol‐2‐ylidenes 7 and Me2S BH3 or Et2O BF3. An X‐ray structure analysis of 8b has been performed. An ab initio calculation [MP2(fu)/6–31G**] reveals a low energy difference between two rotamers. The bond orders of the cyclic bonds imply only a minor interaction between the N—C—N and the C—C fragment.
Direct Observation and Trapping of a Heterocyclic α‐Oxo Ketene: 3‐Carbonyl‐1,3‐dihydro‐1‐methyl‐2H‐indol‐2‐one
Authors: Kappe Thomas , Oliver Kappe C. , Wentrup Curt , Färber Gerald
Published: July 2007

The title compound 8a was generated by both flash vacuum pyrolysis and matrix photolysis of diazoquinolone 7 and identified by Ar‐matrix IR spectroscopy and mass spectrometry. Trapping of the highly reactive α‐oxo ketene 8a with methanol leads to β‐keto ester 9, whereas dimerization of 8a furnishes spiro compound 10.
Oxidation von Bis[2,4,6‐tris(trifluormethyl)phenyl]stannandiyl mit Triplett‐ und komplex gebundenem Disauerstoff
Authors: Grützmacher HansjÖRg , Pritzkow Hans
Published: July 2007

Oxidation of Bis[2,4,6‐tris(trifluoromethyl)phenyl]stannanediyl by Triplet and Complex‐Bound Dioxygen

Homogeneous oxygenation of the stannanediyl [2,4,6‐(CF3)3C6H2]2Sn (15) by molecular triplet oxygen in toluene solution or heterogeneously in the solid state leads to the formation of the cyclotristannoxane 17. In a pure oxygen matrix 15 does not react either thermally (10–45 K) or photochemically. Upon treatment of 15 with the dioxygen complex (Ph3P)2Pt(O2) (16) a stable five‐membered Pt–Sn–O ring 18 is obtained which is a rare example of a covalently linked main group metal‐transition metal heterocycle. The oxygenation products 17 and 18 were characterized by X‐ray structure analyses which revealed the non‐planarity of both heterocycles.
Metallkomplexe mit biologisch wichtigen Liganden, LXVII[1]. Synthese von α‐Aminosäuren aus Palladium(II)‐ und Rhodium(III)‐koordinierten Iminen und Oximen von α‐Oxocarboxylaten
Authors: Krämer Roland , Wanjek Herbert , Polborn Kurt , Beck Wolfgang
Published: July 2007

Metal Complexes of Biologically Important Ligands, LXVII[1]. – Synthesis of α‐Amino Acids from Palladium(II)‐ and Rhodium(III)‐Coordinated Imines and Oximes of α‐Oxocarboxylates

The bis‐chelate complexes Pd[O2CC(R1)=NOR2]2 (1) and Pd[O2CC(R1)=NR2]2 (2, R2 optically active substituent) are synthesized by template condensation of an α‐oxocarboxylic acid with a hydroxylamine or amine component, respectively. Similarly, the Rh(III) complexes Cp*Rh(Cl)[O2CC(R)=N(CHMePh)] (3a: R = H, 3b: R = Me) were obtained from α‐oxocarboxylic acids and optically active 1‐phenylethylamine. Catalytic hydrogenation of 1 and 2 gives directly the free α‐amino acids with, in case of 2, ee's between 0 and 36%. Nucleophilic attack by the carbanions of RC(O)CH2CO2Et and H2NCH(CO2Et)2 at the imino carbon atom of 3a leads to the α‐amino carboxylato complexes 4 and 5. – Compounds 4a and 5 have been characterized by X‐ray diffraction. Reaction of 3a with NaBH4 or NaBD4 followed by decomposition of the complex with HCl yields N‐substituted glycine and N‐substituted α‐deuterio‐glycine, respectively. The diastereoselectivity (70:30) of the α‐deuteration could be determined by NMR spectroscopy.
Organophosphorverbindungen, 73. Der Tri‐tert‐butyl‐2‐cyclopropen‐1‐yl‐Rest als kinetisch stabilisierende Gruppe für 1‐Aza‐3‐phosphaallene
Authors: Wegmann Thomas , Hafner Michael , Regitz Manfred
Published: July 2007

Organophosphorus Compounds, 73[1]. – The Tri‐tert‐butyl‐2‐cyclopropen‐1‐yl Substituent as Kinetically Stabilizing Group for 1‐Aza‐3‐phosphaallenes[2]

The cyclopropenylphosphane 5 reacts with the isocyanates 6a–g to form the phosphaalkenes 7a–g. An analogous transformation occurs with the same phosphane and the bifunctional isocyanates 8a, b (→ 9a, b). In contrast, the reaction 5 + 6h ends at the stage of the tautomers 11h ⇆ 12h. Methanolysis of 7b and of 11h ⇆ 12h leads to the carbamoyl‐cyclopropenylphosphanes 14a and b, respectively. Sodium hydroxide‐catalyzed elimination of hexamethyldisiloxane from 7b, g and the tautomer mixture 11h ⇆ 12h yields the target 1‐aza‐3‐phosphaallenes 16a–c.
Chlorthiatriazine
Authors: Chen Shan‐Jia , Mews Rüdiger , Behrens Ulrich , Fischer Eberhard , Pauer Frank , Sheldrick George M. , Stalke Dietmar , Stohrer Wolf‐Dieter
Published: July 2007

Chlorothiatriazines

From (ClSN)3 (1) and ClCN (2) 1,3,5‐trichloro‐1,3,2,4,6‐dithiatriazine (ClCN)(ClSN)2 (3) was prepared in 26% yield. 3 reacts slowly further with excess 2 to give thiatriazine (ClCN)2(ClSN) (14) and triazine (ClCN)3 (16). A mechanism for the (ClSN)/(ClCN) exchange is proposed. The structures of 3, 14, and 16 have been determined by X‐ray diffraction. The bonding situation in the system (ClSN)n(ClCN)3–n (n = 0 – 3) is discussed.
Gas‐Phase Thermolysis of Pyrazolines, 2[1]. Electronic Structure and Gas‐Phase Thermolysis of 4,5‐Dihydro‐3H‐pyrazoles Studied by Photoelectron Spectroscopy, Semiempirical Quantum‐Chemical Calculations, and Flash Vacuum Pyrolysis
Authors: Kindermann Markus Karl , Kowski Klaus , Muchall Heidi M. , Rademacher Paul
Published: July 2007

The PE spectra of the 4,5‐dihydro‐3H‐pyrazoles 1, 2, of 2,5‐dihydro‐1,3,4‐oxadiazole 3, and 2,5‐dihydro‐1,3,4‐thiadiazole 4 have been recorded. Based on HAM/3, MNDO, AM1, and PM3 calculations, the ionization potentials have been assigned to molecular orbitals. The gas‐phase thermolyses of 1–4 have been studied by PE‐controlled gas analysis. Extrusion of molecular nitrogen leads to reactive species which cyclize to three‐membered rings of different stability. At higher temperatures and in flash vacuum pyrolysis, consecutive reactions may lead to smaller acyclic molecules. The cyclo‐propanol 7, obtained by denitrogenation of 2, is thermally rather stable. Its PE spectrum has been recorded and analyzed.
Synthese optisch aktiver 2‐Siloxycyclopropancarbonsäureester durch asymmetrische Katalyse, II[1]. Einfluß der Silylenolether‐Struktur auf die enantioselektive Cyclopropanierung mit Diazoessigsäure‐methylester
Authors: Dammast Franziska , Reißig Hans‐Ulrich
Published: July 2007

Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, II[1]. – Influence of the Silyl Enol Ether Structure on the Enantioselective Cyclopropanation with Methyl Diazoacetate

On the basis of reactions of (Z)‐1‐phenyl‐1‐(trimethylsiloxy)‐1‐propene (1a) with methyl diazoacetate (2) in the presence of different chiral (Schiff base) copper catalysts 4‐Cu we extended our study to the silyl enol ethers 1b–1j. The highest enantiomeric excesses were obtained in most cases with catalyst 4b‐Cu. Whereas cyclopropanations of 1‐aryl‐ and 1‐alkenyl‐substituted silyl enol ethers 1b–1h gave moderate to good enantioselectivities (up to 80%ee), alkyl‐substituted olefins 1i and 1j provided less satisfactory results. By deprotonation and alkylation of 3c, 3h, and 3i it could be established that for these cyclopropanes the predominating absolute configuration of cis‐ and trans‐cyclopropanes is equal at C‐1, but consequently opposite at C‐2. The influence of the silyl enol ether structure on the enantioselectivities achieved is briefly discussed.
Functionalized, 1,1‐Ethenedithiolates as Ligands, III. Palladium(II) and Platinum(II) Complexes with Ferrocenyl‐Substituted 1,1‐Ethenedithiolate Ligands. Crystal Structure Analyses of cis‐(Ph3P)2M[S2CCHC(O)‐(η5‐C5H4)Fe(η5‐C5H5)] (M = Pd, Pt)
Authors: Buchweitz Jörg , Gompper Rudolf , Polborn Kurt , Sailer Maria‐Theresia , Robl Christian , Weigand Wolfgang
Published: July 2007

The ferrocenyl‐substituted mono‐ (3) and 1,1′‐bis‐dithiocarboxylic acids (4) have been prepared. These acids react with L2MCl2 (M = Pd, Pt; L = PEt3, PPh3, and 1/2 dppe) in the presence of sodium acetate to give the cis heterodi‐ and heterotrimetallic complexes cis‐L2M[S2CCHC(O)–(η5‐C5H4)Fe(η5‐C5H5)] (5a: M = Pd, L = PPh3; 5b: M = Pt, L = PPh3; 5c: M = Pt, L = 1/2 dppe) and [cis‐L2MS2C = CHC(O)‐(η5C5H4)]2Fe (6a: M = Pd, L = PPh3; 6b: M = Pt, L = PEt3; 6c: M = Pt, L = PPh3; 6d: M = Pt, L = 1/2 dppe). The structures of 5a and 5b have been determined by single‐crystal X‐ray diffraction.
Zur Chemie der Galliumverbindungen, II. Darstellung und Struktur von Bis(2,2,6,6‐tetramethylpiperidino)‐[tris(trimethylsilyl)silyl]gallium — ein erstes Beispiel für ein monomeres Bis(amino)gallan mit Gallium‐Silicium‐Bindung
Authors: Frey Ronald , Linti Gerald , Polborn Kurt
Published: July 2007

On the Chemistry of Gallium Compounds, II[1]. — Preparation and Structure of Bis(2,2,6,6‐tetramethylpiperidino)‐[tris(trimethylsilyl)silyl]gallium — ein First Example for a Monomeric Bis(amino)gallane with Gallium‐Silicon Bond

The title compound tmp2GaSi(SiMe3)3 (4) (tmp = 2,2,6,6‐tetramethylpiperidino) was prepared by the reaction of (Me3Si)3SiLi · 3 THF (2) with tmp2GaCl (3). The NMR data (1H, 13C, 29Si) and the crystal structure of 4 are discussed. It contains a trigonal planar‐coordinated gallium atom with long Ga‐N and GaSi bonds of 191 and 247 pm, respectively. This compound is the first fully characterized monomeric gallium bis(amide) and the second structurally investigated compound with a gallium‐silicon bond.
Synthese dienophiler und enophiler Phthalocyanine
Authors: Feucht Carola , Linßen Torsten , Hanack Michael
Published: July 2007

Synthesis of Dienophilic and Enophilic Phthalocyanines

From 1,2,3,4‐tetrahydro‐2,3‐dimethylen‐1,4‐epoxynaphthalene‐6,7‐dicarbonitrile (2) or the corresponding 1,3‐diimino‐1,3‐dihydroisoindole 3 the hexadecahydro‐octamethylenetetraepoxynaphthalocyanine 4 as well as the nickel and the iron complexes 5 and 6 containing enophilic side groups have been synthesized. From 1,4‐dihydro‐1,4‐epoxynaphthalene‐6,7‐dicarbonitrile (8) and its corresponding 1,3‐diimino‐1,3‐dihydroisonindole 9 the octahydro‐tetraepoxynaphthalocyanines 10, 11, and 12, respectively, which contain dienophilic substituents, are obtained. 11 reacts with 2,3‐dimethylbutadiene to form the adduct 13.
Benzoanellated Centropolyquinanes, 15. Benzoanellated Fenestranes with [5.5.5], [5.5.5.6], and [5.5.5.5] Frameworks: The Route from 1,3‐Indandione to Fenestrindan
Authors: Kuck Dietmar
Published: July 2007

The synthesis and spectroscopic characterization of several benzoanellated [5.5.5]‐, [5.5.5.6]‐, and [5.5.5.5]fenestranes, including the parent difuso‐centrotriindan 7, the parent tetrafuso‐centrotetraindan 8 (“fenestrindan”) as well as the tribenzo[5.5.5.6]‐ and tribenzo[5.5.5.5]fenestranes 27 and 35, are described and discussed in full experimental detail. The highly efficient twofold cyclodehydration of 2,2‐dibenzyl‐1,3‐indandiol 15 and the related spiro‐condensed 1,3‐indandiols 23 and 29 is the keystep of the synthetic strategy. The new synthetic variant involving the one‐pot cyclodehydration/deketalization of the dispiro‐ketal diol 29 is particularly convenient. In the case of 7, an alternative Lewis acid‐catalyzed double cyclization has been developed. Stereochemical aspects of the 1,3‐indandiols and the key tribenzo[5.5.5.6]fenestranes 24 and 25 are discussed in detail.
Tris(perfluororganochalkogenyl)methyl‐Verbindungen: Synthesen, Strukturen und Eigenschaften
Authors: Boese Roland , Haas Alois , Lieb Max , Roeske Ulrich
Published: July 2007

Tris(perfluoroorganochalkogenyl)methyl Compounds: Synthesis, Structures, and Properties

Reaction of (CF3S)2CHC(OC2H5)3 with CF3SCl or CF3SeCl in the presence of NaH in ether provides X(CF3S)2CC(O)OC2H5 (1a, b: X = CF3S, CF3Se). These compounds react with NH3 to form (CF3S)2CHC(O)NH2 (2b) which is also obtained from (CF3S)2CHC(O)OC2H5 and NH3. Dehydration of the amide 2b yields (CF3S)2CHCN (3b), which reacts with NaH and then with CF3SX (X = Cl, SCF3) or with RfCl (Rf = CF3Se, C6F5S) to give Rf (CF3S)2CCN [Rf = CF3S (3c), CF3Se (3d), C6F5S (3e)]. 3c is also obtained from (CF3S)3CBr and AgCN. Hydrolysis of 3c with conc. H2SO4 leads almost quantitatively to (CF3S)3CC(O)NH2 (2c), which on treatment with COCl2 gives only 3c and not the corresponding isocyanate. If phosgene is replaced by oxalyl chloride and treated with 2c in a 1:1 molar ratio, (CF3S)3CC(O)NCO (4a) is formed. The urea derivative (CF3S)3CC(O)NHC(O)NHC(O)C(SCF3)3 (4b) is obtained either by using a 2:1 molar ratio of 2c and [C(O)Cl]2 or from 2c and 4a. Attempts to substitute (CF3S)2CHCO2H ‐ after treatment with NaH in ether ‐ with CF3SCl provides low yields of 2,4‐bis[bis(trifluoromethylsulfanyl)methylene]‐1,3‐dithietane (5). X‐ray structure analyses are performed for (CF3S)3CCN (3c) and the 1,3‐dithietane 5.
Trimethylsilylierte 1,4‐Diborinane und 1,3‐Diborolane ‐ Bildung, Isomeren‐Trennung und Charakterisierung
Authors: Köster Roland , Seidel Günter , Lutz Frank , Krüger Carl , Kehr Gerald , Wrackmeyer Bernd
Published: July 2007

Trimethylsilylated 1,4‐Diborinanes and 1,3‐Diborolanes – Formation, Isomer Separation, and Characterisation

Me3SiCCH (A) reacts with excess (Et2BH)2 via the compounds 1, 1′ and 2, 2′ to yield a mixture of four regio‐ and stereoisomeric 1,4‐diethyl‐2,5(6)‐bis(trimethylsilyl)‐1,4‐diborinanes (3a–d) and minor amounts of 1,3‐diethyl‐2‐methyltrans‐2,5‐bis(trimethylsilyl)‐1,3‐diborolane (4a). The 2,5‐ee‐(Me3Si)2 compound 3d is isolated as the adduct 3d(Pic)2 (X‐ray structure analysis), from which pure 3d is obtained with Et2O‐BF3. 3d and Me3P form equilibria of the 1:1 and 1:2 addition compounds 3d(Me3P)n (n = 1,2) at room temperature. Me3SiCCMe (B) reacts with (Et2BH)2 via 5 to give 6–10, and Me3SiCCSiMe3 (C) reacts with (Et2BH)2 to form the ring compounds 12 and 13 via the presumably threo/erythro mixture of 11a and b.
Synthesis and Structure of N‐Silylated Anilines
Authors: Mitzel Norbert W. , Angermaier Klaus , Schmidbaur Hubert
Published: July 2007

The new N‐(arylsilyl)anilines 1–5 have been obtained by the reaction of aryl(halo)silanes with the corresponding anilines in the presence of the auxiliary base triethylamine. The benzene parts of the anilines have been chosen such that their fluoro, methyl, and methoxy substituents exert different electronic effects. The molecular structures of the monosilylated anilines 3 and 4 have been determined by single‐crystal X‐ray diffraction analysis. The coordination geometry of the nitrogen atoms have been found to be planar. Heteronuclear NMR spectra (1H, 13C, 15N, 29Si) have been recorded and the structural results correlated with the one‐bond coupling constant 1J(29Si15N).
Derivate des Imidazols, IX. Stabilisierung von Selendiiodid durch Komplexbildung
Authors: Kuhn Norbert , Kratz Thomas , Henkel Gerald
Published: July 2007

Imidazole Derivatives, IX. — Stabilisation of Selenium Diiodide by Complexation

Herrn Professor Helmut Werner zum 60. Geburtstag gewidmet.

Stable selenium diiodide complexes 2 are obtained by the reaction of the 2‐selenoxoimidazolines 1 with iodine. An X‐ray structure analysis of 2c reveals its monomeric nature. In the trigonal bipyramid, the iodo substituents are situated in axial positions forming elongated iodine bonds [Se–I(1) 2.854(1), SeI(2) 2.768(1) Å; I(1)SeI(2) 175.4(0)°].
Zur Thermolyse von Amin—arachno‐Nonaboran
Authors: Meyer Franc , Englert Ulli , Paetzold Peter
Published: July 2007

On the Thermolysis of Amine‐arachno‐Nonaborane

Two molecules of diethylamine‐arachno‐nonaborane, B9H13‐(NHEt2), undergo a condensation at 140°C to give diethylamine‐conjuncto‐bis[6′,5′:5,6]decaborane, B18H20(NHEt2) (4). The deprotonation of 4 yields the anion [B18H19(NHEt2)]‐which can be crystallized with the cation [NEt3(CH2Ph)]+ (space group P1).
Cycloadditionen von 2H‐Benzo[b]thiet und Verbindungen mit kumulierten Doppelbindungen
Authors: Gröschl Dieter , Niedermann Hans‐Peter , Meier Herbert
Published: July 2007

Cycloaddition Reactions of 2H‐Benzo[b]thiete and Compounds with Cumulated Double Bonds

o‐Thiobenzoquinone methide (2), generated by thermal ring opening of 2H‐benzo[b]thiete (1), reacts with allene 3, ketene imine 7, the carbodiimides 9a‐c, and the N‐sulfinylamines 11a‐c in highly specific [8π + 2π] cycloaddition processes to form novel types of heterocyclic systems 4, 8, 10a‐c, and 12a‐c with exocyclic double bonds. The 1:1 adduct 4 can add a further molecule of allene to yield the spiro compounds 5 and 6.
Zur oxidativen Dimerisierung von CH‐Säuren
Authors: Peek Reinhold , Streukens Marlies , Thomas Hans Günter , Vanderfuhr AndrÉ , Wellen Ulrich
Published: July 2007

Oxidative Dimerization of CH Acids

Anodic oxidation of alkyl‐ (1) and acylmalonic acid esters (7) yields the dehydromiers 4 and 8, respectively. Preparative electrolyses are performed in acetonitrile in the presence of a base to generate the carbanion corresponding to the CH acid. The carbanions are oxidized to the radicals which dimerise on the electrode surface. The yields of the preparative electrolyses and the formation of the dehydrodimers 4 and 8 are discussed in terms of the CH acidity and enolization of starting materials.
Regio‐ and Diastereoselective Synthesis of Stannyl Epoxy Alcohols by Direct Hydroxy Epoxidation of Vinylstannanes
Authors: Adam Waldemar , Klug Peter
Published: July 2007

The direct synthesis of stannyl epoxy alcohols 3 from vinylstannanes 1 is described. The procedure involves the photooxygenation of Vinylstannanes 1, which proceeds in a highly regioselective manner with predominant hydrogen abstraction geminal to the stannyl group. Subsequent reaction of the resulting hydroperoxides 2 with Ti(OiPr)4 afforded in a one‐pot procedure the epoxy alcohols 3 in high diastereomeric excess, which ranged from 81:19 to greater than 95:5. This convenient and effective method was applied to acyclic and cyclic vinylstannanes as well as to γ‐trydroxyvinylstannane 1e, which was converted into the stannyl epoxy diol 3e. In this novel hydroxy epoxidation of vinylstannanes the regioselectivity of the singlet oxygen ene reaction (Schenck reaction) is controlled by the stannyl group.
Übergangsmetall‐katalysierte Reaktionen von ungesättigten α‐Diazo‐α‐(trimethylsilyl)essigestern mit Carbonylverbindungen
Authors: Alt Mechthild , Maas Gerhard
Published: July 2007

Transition Metal Catalyzed Reactions of Unsaturated α‐Diazo‐α‐(trimethylsilyl)acetates with Carbonyl Compounds

Some reactions of unsaturated α‐diazo‐α‐(trimethylsilyl)acetates with aldehydes or acetone under the catalytic action of rhodium(II) perfluorobutyrate or copper(I) triflate have been investigated. Thus, the allylic ester 6a affords 1,3‐dioxolan‐4‐ones 8 under Rh(II) catalysis; the Cu‐catalyzed reaction yields 8, oxirane 9, and the 3‐oxabicyclo[3.1.0]hexane 10. The propargylic ester 6b does not react in a clear fashion with benzaldehyde, 1,3‐Dioxolanes result from the homoallylic ester 6c and aldehydes, but enol ether 14 from 6c and acetone.
Triphenanthro‐anellierte [18]Annulene mit Alkoxy‐Seitenketten — Eine neue Klasse discotischer Flüssigkristalle
Authors: Kretzschmann Holger , Müller Klaus , Kolshorn Heinz , Schollmeyer Dieter , Meier Herbert
Published: July 2007

Triphenanthro‐Anellated [18]Annulenes with Alkoxy Side Chains ‐ A Novel Class of Discotic Liquid Crystals

Two different types 6 and 16 of [18]annulenes condensed with phenanthrene systems were prepared by cyclocondensation reactions (Schemes 2 and 3). The central 18‐membered rings do not show a macrocyclic diamagnetic ring current. Conformational analyses and X‐ray analyses in the solid state reveal non‐planar structures in which aromatic “islands” are connected by (E)‐configurated olefinic bridges. The introduction of long alkoxy side chains yields a new class of discotic liquid crystals; either ND or hexagonal columnar phases are generated, which were characterized by DSC, microscopy with polarized light, and small‐angle scanning X‐ray.
How Electrophilic are Ferrocenylmethyl Cations? Kinetics of their Reactions with π Nucleophiles and Hydride Donors
Authors: Mayr Herbert , Rau Doris
Published: July 2007

Second‐order rate constants for the reactions of the ferrocenylmethylium ions 2a—e with silyl enol ethers, allylsilanes, allylstannanes, and hydride donors have been determined photometrically and conductometrically in dichloromethane. The ferrocenylmethylium ions 2a—d (fc‐CHR+, R = H, Me, Ph, An) are slightly stronger electrophiles than the tropylium ion, and their electrophilic reactivities depend only slightly on the nature of R. The bis(ferrocenyl)methylium ion 2e is a considerably weaker electrophile, comparable to the tricarbonyl(cyclohexadienyl)iron cation.
Palladium‐Catalysed Multiple Coupling Reactions of β‐Bromostyrene with Norbornene and Dicyclopentadiene
Authors: Albrecht Karsten , Meijere Armin De
Published: July 2007

(E)‐β‐Bromostyrene [(E)‐2] reacts with norbornene (1a) or dicyclopentadiene (1b) in the presence of Pd(OAc)2, K2CO3, and nBu4NBr in DMF to yield a mixture of the 2:1 coupling products 4 and 5, while (Z)‐β‐bromostyrene [(Z)‐2] gives exclusively 5. Under analogous conditions, (Z)‐3‐iodoacrylic acid (6) reacts with norbornene (1a) to give the diene 11 with an exo, exo‐2,3‐disubstituted norbornane skeleton.
Synthese und Struktur von Cobalt(III)‐Komplexen mit doppelt deprotoniertem Anhydroerythrit, Methyα‐D‐mannopyranosid und Methyl‐β‐D‐galactopyranosid
Authors: Burger Joachim , Klüfers Peter
Published: July 2007

Polyol Metal Complexes, XII[1]. — Synthesis and Structure of Cobalt(III) Complexes with Doubly Deprotonated Anhydroerythritol, Methyl α‐DMannopyranoside, and Methyl α‐DGalactopyranoside

The polyols anhydroerythritol (AnEryt), methyl α‐D‐mannopyranoside (Me‐α‐D‐Manp), and methyl α‐D‐galactopyrano‐side (Me‐α‐DGalp) are deprotonated twice to form the cobalt(III) complexes [(en)2Co(AnErytH‐2)]I (1), δ‐[(en)2‐ Co(Me‐α‐DManp3,4H‐2)]ClO4 · NaClO4 · 2H2O (2), and δ‐[(en)2Co(Me‐α‐DGalp2,3H‐2)]ClO4·H2O (3), resp., in aqueous, alkaline solutions of trans‐[(en)2CoCl2]Cl. The crystal structures of 1–3 have been determined by X‐ray diffraction.
Synthesis, X‐Ray Crystal Structure and Magnetic Characterization of the First “Ni3S4N3” Nickel Thiolate Cluster
Authors: Berkessel Albrecht , Bats Jan W. , Hüber Martina , Haase Wolfgang , Neumann Thomas , Seidel Lutz
Published: July 2007

The tridentate N,O,S‐ligand (RS)‐2‐[(2‐mercapto‐1‐methylamino)ethyl]phenol (rac‐1) was prepared from ortho‐hydroxy‐chloroacetophenone in three steps. When this ligand was treated with nickel(II) acetate, the novel “Ni3S4N3” cluster rac‐3 was obtained. The X‐ray crystal structure of rac‐3 unambiguously revealed the pseudo‐C3 symmetric structure of this novel nickel cluster, which is made up by three nickel ions, one sulfide sulfur atom, and three homochiral ligand molecules, each contributing one thiolate sulfur atom and one amine nitrogen atom to the ligation of the metal ions. According to NMR‐spectroscopic results, this highly symmetric structure is maintained in solution. The magnetic studies revealed diamagnetic behavior in the solid state, although antiferromagnetic interaction of the metal centers cannot absolutely be excluded.