bluuebunny/crossref_metadata_2025 huggingface dataset:
Homo‐ und Hetero‐Metall‐Amide des Tris(tert‐butylamino)methylsilans – Polycyclen und Cluster mit Li, Na, Mg, Al und Tl
Authors: Veith Michael , Spaniol Armin , Pöhlmann Jürgen , Gross Frank , Huch Volker
Published: July 2007

Homo and Hetero Metal Amides of Tris(tert‐butylamino)methylsilane – Polycycles and Clusters with Li, Na, Mg, Al and Tl

The hydrogen atoms attached to nitrogen in tris(tert‐butyl‐amino)methylsilane (1) can be substituted by metallic main‐group elements in a quite general way. If 1 is treated with trimethylaluminium apart from the monosubstituted product MeSi(tBuNH)2(tBuNAlMe2) (2) the trisamide MeSi(tBuNAlMe2)3 (3) is obtained. In similar ways complete substitution of the amino hydrogen atoms in 1 yields the compounds MeSi[tBuNMgN(SiMe3)2]3 (6), [MeSi(tBuNLi)3]2 (10), and [MeSi(tBuNTl)3]2 (11), the later two being dimeric. If methyl‐magnesium iodide is allowed to react with 1 the intermediate MeSi(tBuNMgI)3 (4) in some instances can be isolated as the THF adduct or may react with a further equivalent of the Grignard compound to generate the complex [MgI‐(THF)5]+ [MeSi(tBuNMgI)3CH3 · THF]– (5). The aluminium compound 2 has been used to access to heterometallic amides combining aluminium and sodium as in MeSi(tBuNAlMe2)(tBuNNa)(tBuNH) (7) or magnesium and aluminium as in the dimeric compounds [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgI)]2 (8) and [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgMe)]2 (9). X‐ray structure analyses reveal 3 (tricyclic SiN3Al3 skeleton with Al – N distances from 2.014 to 2.025 Å), 6 (tricyclic Si‐N3Mg3 skeleton), and 7 [bicyclic SiN3AlNa skeleton with Na – N distances of 2.47(1) and 2.52(1) Å] to be monomeric even in the solid state. The compounds 8 and 9 (both pentacyclic with spiro magnesium atoms) form centrosymmetric dimers by Mg – I – Mg and Mg – (CH3) – Mg bridges, respectively. The dimers 10 and 11 are completely different in terms of chemical bonding: while in the lithium compound 10 a centrosymmetric polycycle is formed by principly ionic interactions of the lithium atoms with corresponding nitrogen atoms, the centrosymmetric dimer in 11 is held together by Tl – Tl bonds. The X‐ray structure analysis of 5 reveals the anion containing a Mg‐coordinated CH3–.
1‐Sila‐3‐alumina‐4‐aluminatacyclopentan mit Al–Al‐Bindung und C2Al2Si‐Heterocyclus
Authors: Uhl Werner , Schütz Uwe , Vester Annegret , Karsch Hans H.
Published: July 2007

1‐Sila‐3‐alumina‐4‐aluminatacyclopentane with an Al–Al Bond and a C2Al2Si Heterocycle

Tetrakis[bis(trimethylsilyl)methyl]dialuminium(4) (1) with an aluminium–aluminium bond reacts in the presence of tetramethylethylenediamine (TMEDA) with the sterically highly shielded bases bis(trimethylsilyl)methyllithium or bis(dimethylphosphanyl)methyllithium to yield under deprotonation of a methyl group a carbanionic species, which is stabilized by an interaction with one of the coordinatively unsaturated Al atoms. The five‐membered heterocycle 5 is formed containing two Al, one Si and two C atoms. The Al–Al bond remains uncleaved. Interestingly, 5 crystallizes in different crystals with and without crystal ether, which were both characterized by crystal‐structure determinations. The Al–Al bond length in 5 [264.1(2) and 266.5(3) pm, respectively] is only slightly changed in comparison to the neutral starting compound 1 (266.0 pm). Under similar conditions the sterically less demanding ethyllithium leads to a β‐elimination and addition of the thereby formed LiH to one of the two Al atoms to give the recently published hydridodialuminate(5) Li(TMEDA)2+ [R2Al–AlHR2]– (2).
Metallorganische Verbindungen der Lanthanoide, 82[1]. (2,5‐Di‐tert‐butylpyrrolyl)‐Komplexe von Neodym(III), Samarium(II) und Ytterbium(II): Synthese und Röntgenstrukturanalyse von dimerem Natrium‐dichlorobis(2,5‐di‐tert‐butylpyrrolyl)(tetrahydrofuran)neodymat(III)
Authors: Schumann Herbert , Winterfeld Jörn , Hemling Holger , Kuhn Norbert
Published: July 2007

Organometallic Compounds of the Lanthanoids, 82[1]. – [2,5‐Di‐tert‐butylpyrrolyl) Complexes of Neodymium(III), Samarium(II), and Ytterbium(II): Synthesis and X‐Ray Structural Analysis of Dimeric Sodium Dichlorobis(2,5‐di‐tert‐butylpyrrolyl)(tetrahydrofuran)neodymiate(III)

NdCl3(THF)1,8 reacts with Na[pyr*
η3‐Allyl‐ und η3‐Benzyl‐Rhodiumkomplexe: Synthese, Strukturdynamik und Reaktionen mit Carbonsäuren
Authors: Werner Helmut , Schäfer Martin , Nürnberg Oliver , Wolf Justin
Published: July 2007

η3‐Allyl and η3‐Benzyl Rhodium Complexes: Synthesis, Structure Dynamic, and Reactions with Carboxylic Acids

The (η3‐allyl)rhodium complexes [Rh(η3‐2‐RC3H4)(PiPr3)2] (3–5) have been prepared in 70–90% yield from the in situ generated chlororhodium precursor [RhCl(PiPr3)2] (2) and 2‐RC3H4MgX. On a similar route, the corresponding ethene(phosphane) derivative [Rh(η3‐2‐MeC3H4)(PiPr3)] (9) has been obtained. Compound 9 smoothly reacts with PiPr3 and PMe3 to give 4 (R = Me) and [Rh(η3‐2‐MeC3H4)(PMe3)‐(PiPr3)] (10), respectively. In contrast to the η3‐allyl complexes which are configurationally stable, the η3‐benzyl analogues [Rh(η3‐CH2C6H4R) (PiPr3)2] (11, 12), prepared from 2 and 4‐RC6H4CH2MgCl, are highly fluctional in solution. At room temperature, an antarafacial (π‐δ‐π) as well as a suprafacial rearrangement occurs, the first one of which is frozen out at 263 K. On cooling to 193 K, the faster process (equally designated as a metallotropic shift) is also slowed down, and the rigid structure of 11 and 12 is observed. The ΔG* values for the antara and suprafacial rearrangements of 11 and 12 which have been determined from the 1H‐ and 31P‐NMR spectra at variable temperature are 60.0 ± 1.5 and 39.5 ± 1.0 kJ/mol, respectively. The η3‐benzyl compound 11 reacts even at –78°C with CO to give the monocarbonylrhodium(I) complex trans‐[Rh(η1‐CH2C6H5)(CO)(PiPr3)2] (13). Treatment of 3,4, or 11 with RCO2H (R = CF3, CH3, C6H5, C6H4‐4‐OMe, C6H4‐4‐NO2) affords the monomeric η2‐carboxylatorhodium(I) compounds [Rh(η2‐O2CR) (PiPr3)2] (14–18) almost quantitatively. If the reaction of 3 or 4 with CF3CO2H is performed at −20°C in pentane, the octahedral (η3‐allyl)hydrido complexes [Rh(η3‐2‐RC3H4)(H)(η1‐O2CCF3)(PiPr3)2] (19, 20) are isolated. The crystal structures of 12 (at 223 K) and of 15 (at 298 K) have been determined by X‐ray diffraction studies. They confirm that the η3‐benzyl ligand is highly unsymmetrically and the acetato ligand completely symmetrically bound to the [Rh(PiPr3)2] unit.
Fe(I)‐Mediated Regio‐ and Stereoselective CC/CH Bond Activation of Internal Methylene Groups of α,ω‐Diphenylalkanes
Authors: Raabe Norbert , Karraß Sigurd , Schwarz Helmut
Published: July 2007

For three α,ω‐diphenylalkanes the mechanistic details of the Fe+‐mediated activation of CH and CC bonds in the gas phase have been elucidated by isotopic labelling experiments. The unimolecular reactions, i.e. dehydrogenation of the alkane chain, formation of ethylene from internal methylene groups, and generation of toluene, proceed largely with high selectivity. Particularly interesting are the results for the dehydrogenation of the Fe+ complex 3‐Fe+ of 1,8‐diphenyloctane which involves to 93% the internal methylene groups C‐4/C‐5. In addition, the study of the stereoisotopomers 3c–d provides evidence for the operation of isotopically sensitive branching (“metabolic switching”) in the reaction, and the analysis of the data suggests that the selectivity of the reaction is, most likely, due to a sandwich‐type structure.
Dinuclear Paramagnetic Metallocenes Bridged by Silyl Groups — Synthesis and Intramolecular Interactions
Authors: Atzkern Hermann , Bergerat Pierre , Fritz Monika , Hiermeier Johann , Hudeczek Peter , Kahn Olivier , Kanellakopulos Basil , Köhler Frank H. , Ruhs Michael
Published: July 2007

The dilithium salt of the 3a,4,7a,8‐tetrahydro‐4,4,8,8‐tetra‐methyl‐4,8‐disila‐s‐indacenediyl dianion (L2−, 2) was allowed to react with the solvated metal halides MX2 (M = Ni, Co, Cr) in the presence of the cyclopentadienyl (Cp) anion to give trans‐CpMLMCp (3NiNi, 3CoCo, and 3CrCr) in yields up to 80%. The only cis isomers which could be detected were 4NiNi and 4CoCo. Similarly, the reaction of 2 with [CpVCl(PEt3)]2 gave the trans‐vanadium analogue 3VV while the successive reaction of 2 with CrCl3 (THF)3 and PEt3 yielded the bridged half‐sandwich (Et3P)Cl2CrLCrCl2(PEt3) (5CrCr). The mixed‐metal dinuclear metallocene CpFelNiCp (3FeNi) was synthesized from CpFel−, Cp− and solvated NiBr2. The molecules were characterized by mass spectrometry, elemental analyses, cyclic voltammetry, 1H, 13C, and 29SiNMR spectroscopy and solid‐state magnetic measurements. Cyclic voltammetry showed up to six electron transfers per molecule. A metal‐dependent splitting of the half‐wave potentials of up to 355 mV indicated rather strong electrostatic interaction between the metallocene units. The NMR results established unpaired spin on the ligands. Its distribution within the bridging ligand was correlated with the molecular orbital splitting and the magnetic interaction. Antiferromagnetic interaction was found for 3NiNi, 3CrCr, and 3VV with J = −11.6, −2.56, and −1.34 cm−1, respectively (H = ‐J · SA · SB). A temperature‐dependent folding of the bridging ligand was deduced from the temperature behavior of the 1HNMR signal shifts.
Ambiphile Tripod‐Komplexe: Synthese und Komplexchemie langkettiger funktionalisierter Tripod‐Liganden RC(CH2PPh2)3 mit R = Pentyl oder 8‐Nonenyl
Authors: Muth Andreas , Asam Alexander , Huttner Gottfried , Barth Annette , Zsolnai Laszlo
Published: July 2007

Ambiphilic Tripod Complexes: Synthesis and Coordination Chemistry of Long‐Chained Functionalized Tripod Ligands RC(CH2PPh2)3 with R ‐ Pentyl or 8‐Nonenyl

Tripod ligands RC(CH2PPh2)3 with R = pentyl (3a) and R = 8‐nonenyl (3b) are accessible from the corresponding triols. By using appropriately selected activation procedures the triols 1a, b are transformed into the tripodal ligands 3a, b. In addition to their direct characterisation the tripod ligands 3a, b have been further structurally analysed by the syntheses and X‐ray analyses of specific cobalt (4a) and iron (4b) coordination compounds. An interesting side result from the X‐ray analysis of [(3b)Fe(NCCH3)3](BF4)2 (4b) is the organisation of its solid‐state structure by the hydrophobic 8‐nonenyl substituents in the ligand backbone.
Synthesen, Struktur und Eigenschaften von 1,2,5‐Phosphadiborolanen
Authors: Frankhauser Pascal , Drieß Matthias , Pritzkow Hans , Siebert Walter
Published: July 2007

Syntheses, Structure and Properties of 1,2,5‐Phosphadiborolanes

Reactions of (Z)‐1,2‐bis[chloro(diisopropylamino)boryl]ethane with Li2PC6H5 and of 1,2‐bis[chloro(diisopropylamino)boryl]‐1,2‐diisopropylideneethane with [LiPh2·dme] yield the 1,2,5‐phosphadiborolanes 1 and 2, respectively. The compounds are characterized by 1H‐, 11B‐, 13C‐, and 31P‐NMR spectroscopy as well as an X‐ray structure analysis of 2. Low‐temperature 1H‐NMR studies show that the inversion barrier at P is distinctly lower than that of related unsaturated compounds. This might be the result of a favorable BP‐π interaction in the transition state of the inversion at the phosphorus atom. Reaction of 1 with S8 or CS2 leads to the 1,2,5‐thiadiborolane 3.
Stabilization of Triorganotin Cations — Competition between Intramolecular Coordinative O, S or NSn Bonds and Side‐on π Coordination to CC Bonds
Authors: Wrackmeyer Bernd , Kundler Sabine , Milius Wolfgang , Boese Roland
Published: July 2007

Di‐1‐alkynyltin compounds 1 of the type Me2Sn(CCUL)2 [LU = 2‐pyridyl (a), Me2NCH2 (b), MeOCH2 (c), MeOCHCH (d), EtSCH2 (e)] were prepared and the 1,1‐organoboration of 1 with triethyl‐ (2a) and triisopropylborane (2b) has been studied. The first detectable intermediates were in all cases zwitterionic compounds 3 (from Et3B) and 4 (from iPr3B) with a cationic triorganotin fragment, stabilized by coordinative s̀ LSn bonds and by side‐on coordination to the CC bond of an alkynylborate moiety. The nature of this stabilization has been established by three X‐ray analyses (3b, 4b, and 4d) in the solid state and by multinuclear NMR (1H‐, 11B‐, 13C‐, 15N‐, 119Sn NMR) in solution. The comparison of the molecular structure of 3b, 4b, and 4d with that of intermediates without functional groups shows that the distance of the tin atom to the CC bond is elongated. However, the planar arrangement of all relevant atoms proves that the side‐on coordination of the tin atom to the CC bond is still present. These intermediates 3 and 4 rearrange to stannoles 5, 6 and/or to 1‐stanna‐4‐bora‐2,5‐cyclohexadienes 9, 10. In the case of 3b and 3e, 119Sn NMR indicates that dialkenyltin compounds 7b and 7e are also formed as minor products. In the case of 3e, the 3‐stannolene 8e is one of the final products. In the stannoles 5 and 6 a coordinative LB bond is evident, and there is NMR spectroscopic evidence of a weak coordinative L—Sn bond.
Elektrophile Additionen an das Bicyclo[1.1.0]butan‐System von Tricyclo[4.1.0.02,7]heptan‐Derivaten: Halogen‐Elektrophile
Authors: Gerstner Erwin , Kemmer Ralf , Christl Manfred
Published: July 2007

Electrophilic Additions to the Bicyclo[1.1.0]butane System of Tricyclo[4.1.0.02,7]heptane Derivatives: Halogen Electrophiles

The known reactions of 8,8‐dibromotetracyclo[5.1.0.02,4.03,5]octane (3a) and homobenzvalene (7) with pyridinium bromide perbromide and iodine, respectively, were carried out in the presence of tetra‐n‐butylammonium chloride. The formation of the chloro‐substituted norpinane derivatives 6a and 9 is evidence for cationic intermediates. The same mechanism is operative in the reaction of pyridinium bromide perbromide with the dichlorotetracyclooctane 3b, which was prepared from 7 and dichlorocarbene. On exposure of tricyclo[4.1.0.02,7]heptane (1) to N‐bromosuccinimide in acetone/water/triethylamine, the bromonorpinanol 22, the bromonorcaranols 23, and cyclohex‐1‐ene‐1‐carboxaldehyde (24) were obtained. On the basis of the steric course and thermodynamic considerations, the cationic intermediates generated in the above reactions by attack of the electrophiles at the bicyclobutane systems are assigned the halonium ion structure 38 and the nonclassical structures 34 and 35, respectively. Elemental bromine and iodine converted the phenyltricycloheptane 10 into the respective diastereomeric norpinanes 11 and 12, which were transformed smoothly into the diastereomeric methyl ethers 13 and 14 by treatment with sodium methoxide in methanol. The reactions of 10 with pyridinium bromide perbromide in pyridine, cyanogen bromide in the presence of aluminium trichloride, and N‐bromosuccinimide in acetone/water gave rise to norpinane derivatives, i.e. the pyridinium salt 15, the nitrile 16, and the alcohol 18, respectively. In the case of cyanogen iodide in acetonitrile, the solvent participated in the process to yield the 2‐(norpinylimino)propionitriles 17. Corresponding to the configurations of the products, the attack of a halogen electrophile at 10 leads to classical 6‐phenyl‐6‐norpinyl cations 41, which may be approached by nucleophiles from the two possible faces. As origin for the low tendency of the cations 33–35 and 41 to rearrange to norcaryl cations, the electronegativity of the halogen atoms is suggested. The reduced migratory aptitude of a CHHal relative to a CH2 group results from its electron deficiency and from the decreased stability of 7‐halo‐2‐norcaryl relative to the parent 2‐norcaryl cations. The chlorophenyltricycloheptane 25 was prepared from 10 and treated with aqueous sulfuric acid to give the norpinanol 27. Formed by protonation of the bicyclobutane system of 25, the cationic precursor of 27 shows a behaviour similar to that of cations 41.
Messung der Donorstärke substituierter 1‐Naphthole
Authors: Laatsch Hartmut , Sigel Christoph , Kral Andreas
Published: July 2007

Measurement of the Donor Strength of Substituted 1‐Naphthols

The oxidation potential of various substituted naphthols is available by cyclovoltammetry. The donor strength of substituents on the oxidation potential may be explained on the base of substituent increments. When correlating the oxidation potential with the transition energy of charge transfer complexes with TCNE, 1‐naphthols with 8‐alkoxy substituents and naphthols without oxygen in position 8 are giving different correlation curves. The experimental values correlate well with semiempirically calculated HOMO energies. Our measurements allow to predict the oxidation potentials of hitherto unknown substituted 1‐naphthols with high probality. Thus, it may be possible to synthesize 1‐naphthols with a defined oxidation potential.
Bis(benzo[4,5]thieno)[3,2‐c:2′,3′‐e][1,2]dithiin, ein Valenzisomer von „Dithioxo‐thioindigo”︁
Authors: Schroth Werner , Hintzsche Ekkehard , Viola Horst , Winkler Ralf , Klose Heike , Boese Roland , Kempe Rhett , Sieler Joachim
Published: July 2007

Bis(benzo[4,5]thieno)[3,2‐c:2′,3′‐e][1,2]dithiin, ein Valenzisomer von „Dithioxo‐thioindigo”︁

3‐Mercaptobenzo[b]thiophene (1) is transformed with assistance of bases, especially of amines, into the benzo[b]‐thieno‐annellated 1,2‐dithiine 6 and not into the originally claimed “Dithioxo‐thioindigo” trans‐3. Primarily, the formation of 6 from 1 involves oxidation to the disulfide 4 which may also be used separately. Conceivable rationalizations are discussed. The same compound is accessible (in lower yield)by thionation of thioindigo with the aid of the Lawesson reagent. X‐ray elucidation of 6 reveals a non‐planar structure of the cyclic disulfide with a dihedral CSSC‐angle of 53°. Despite of the absence of any established chromonphoric moiety, 6 is deeply red in the crystal and in solution, as it is representative for the “undisturbed” 1,2‐dithiine system. Contrary to the usual behaviour of the non‐annellated 1,2‐dithiines, 6 displays no spontaneous sulfur extrusion under mild conditions, but only at high temperatures and in the presence of sulfur‐binding agents, leading to the benzo[b]thieno‐annellated thiophene 22. Moreover, 6 may be reduced to the dithiol 14 (or 13, respectively) and regenerated exclusively from this by oxidation. Further characteristic reactions of 6 are described (e.g. to the sulfoxide 18, to the pyridazine 19, and to the thiphosphoric ester 21).
Komplexe mit makrocyclischen Liganden, I. Zweikernige Kupfer(II)‐Komplexe mit vollständig π‐konjugiertem Makrocyclus vom Schiff‐Basen‐Typ: Synthesen, Strukturen, elektro‐ und magnetochemische Eigenschaften
Authors: Brychcy Klaus , Dräger Klaus , Jens Klaus‐J. , Tilset Mats , Behrens Ullrich
Published: July 2007

Complexes with Macrocyclic Ligands, I. ‐ Dinuclear Copper(II) Complexes with a Totally π‐Conjugated Macrocycle of Schiff Base Type: Syntheses, Structures, Electro‐, and Magnetochemical Properties

The dinuclear copper(II) complexes 6, 7, and 8 of three novel macrocyclic ligands were synthesized by the Schiff base condensation of 2 equiv. of 1,2‐phenylenediamine and 2,6‐diformylphenol in the presence of 2 equiv. of copper(II) perchlorate and were characterized by X‐ray structure analyses, electrochemical investigations (DCV), and variable‐temperature magnetic susceptibility measurements. Complex 6 exists in two different solvated crystalline forms. The Copper(II) ions in all three complexes are octahedrally coordinated with long axial distances to solvent molecules or perchlorate ions. The copper ions in 6 (in solvate a) are only five‐coordinate and square‐pyramidal. The CuIICuII complexes were reduced in successive, quasi‐reversible, one‐electron steps. The antiferromagnetic exchange interactions were determined. Upon dissolution in acetonitrile complex 8 decomposed to form [Cu(MeCN)4]+ClO−4 and the benzimidazolium percholorate 9 (X‐ray structure determination).
(2,4,6‐iPr3C6H2)(tBu)Si(AsH2)2: Das erste Diarsanylsilan und seine Umwandlung in ein 1,3‐Diarsa‐2‐sila‐4‐germacyclobutan und ein 1,3‐Diarsa‐2‐sila‐4‐germabicyclo[1.1.O]butan‐Derivat
Authors: Drieß Matthias , Pritzkow Hans
Published: July 2007

(2,4,6‐iPr3C6H2)(tBu)Si(AsH2)2: The First Diarsanylsilane and Its Transformation into a 1,3‐Diarsa‐2‐sila‐4‐germabicyclobutane and a 1,3‐Diarsa‐2‐sila‐4‐germabicyclo[1.1.0]butane Derivative*

The crowded diarsanylsilane (2,4,6‐iPr3C6H2)(tBu)Si(AsH2)2 (1) is synthesized by the reaction of (2,4,6‐iPr3C6H2)(tBu)‐SiCl2 with two equivalents of [LiAsH2(dme)] in 80% yield. Treatment of 1 with two equivalents of nBuLi yields the dilithio compound 7, which reacts with Mes(tBu)GeF2 to give the corresponding 1,3‐diarsa‐2‐sila‐4‐germacyclobutane 8. The X‐ray crystal structures of 1 and 8 were determined. The bond angles at silicon of 1 lie between 113.0(4) and 96.1(4)° indicating a distorted tetrahedral geometry. The four‐membered SiGeAs2 ring in 8 is puckered (As1‐Si1‐As2/As1‐Ge1‐As2 23.5°) with the two tBu groups being transoriented. Dilithiation of the AsH positions in 8 with nBuLi and subsequent reaction with tBuHgCl leads to the 1,3‐bis‐(tert‐butylmercurio) compound 9. The light‐induced elimination of the tBu groups in 9 gives the tBu/tBu‐exo,endo‐SiGeAs2‐bicyclo[1.1.0]butane 10 in 91% yield. 10 does not rearrange to the exo,exo isomer 11.
Halogen‐Kohlenstoff‐Schwefel‐Verbindungen: Zur Chemie von 1,1,1,4,4,4‐Hexafluor‐2‐buten‐2,3‐bissulfenylchlorid
Authors: Reimann‐Andersen Stefan , Pritzkow Hans , Sundermeyer Wolfgang
Published: July 2007

Halogen‐Carbon‐Sulfur Compounds: Syntheses with 1,1,1,4,4,4‐Hexafluoro‐2‐butene‐2,3‐bissulfenyl Chloride

The bifunctional bissulfenyl chloride 3 is obtained by chlorination of the dithiete 1 or tetrathiocine 2. By excessive chlorination the saturated bissulfenyl chloride 4 is formed. 3 reacts with primary amines to yield the 1,3,2‐dithiazoles 5a–e, whereas by reactions with active methylene compounds like ketones or β‐dicarbonyls the compounds 7–14 are obtained with HCl elimination. 13 as well as 14 are converted into the carboxylic acid 15 from which the 1,3‐dithiole 17 is obtained by decarboxylation. 3 reacts with disulfene to form tetrakis‐(trifluoromethyl)tetrathiafulvalene as well as 4,4′,5,5′‐tetrakis(trifluoromethyl)‐2,2′‐spirobi[1,3‐dithiole] (18), whose crystal structure has been determined.
In 2‐ und 3‐Stellung verzweigte, enantiomerenreine 4,4,4‐Trifluor‐3‐hydroxy‐buttersäure‐Derivate aus 6‐Trifluormethyl‐1,3‐dioxan‐und ‐dioxin‐4‐onen
Authors: Gautschi Markus , Schweizer W. Bernd , Seebach Dieter
Published: July 2007

Preparation of Enantiomerically Pure 4,4,4‐Trifluoro‐3‐hydroxy‐butanoic Acid Derivatives, Branched in the 2‐ or 3‐Position, from 6‐Trifluoromethyl‐1,3‐dioxan‐ and ‐dioxin‐4‐ones

Enantiomerically pure 3‐hydroxy‐3‐trifluoromethyl‐propionic acid and esters, substituted in the 2‐ or 3‐position, are prepared (13 examples) from (R)‐ or (S)‐4,4,4‐trifluoro‐3‐hydroxy‐butanoic acid. Key intermediates are the 2‐t‐butyl‐6‐trifluoromethyl‐1,3‐dioxan‐ and ‐dioxin‐4‐ones. The Li enolate of the cis‐dioxanone is generated with t‐BuLi and reacts with electrophiles (alkyl halides, aldehydes, imines, nitroolefins, Br2, I2) with predominant formation of trans,trans‐2,5,6‐trisubstituted dioxanones (9 examples). Elimination of HBr from the 5‐Br‐substituted dioxanone gives the (R)‐ or (S)‐dioxinone, a chiral derivative of 4,4,4‐trifluoro‐3‐oxo‐butanoic acid (trifluoro‐acetoacetate). Michael additions of cuprates or of CuCl‐doped Grignard reagents to the dioxinone produce 6,6‐disubstituted dioxanones (10 examples) bearing a CF3 group in the 6‐position. In most cases this addition is highly diastereoselective, with the new substituent winding up in the trans position. There are, however, surprising exceptions, such as the product formed with benzylmagnesium chloride which is an abnormal adduct with a p‐quinoid structure (26) and with the newly introduced group in the cis position with respect to the t‐Bu group. The structures of four trisubstituted dioxanones bearing CF3 groups are determined by X‐ray crystal structure analysis (Figure 1, Table 1), one of them including the absolute configuration (by anomalous diffraction). Besides the well‐known sofa, a twist‐boat conformation of dioxanones appears to be favorable. The solution conformations of the different types of CF3‐substituted dioxanones are derived from Nuclear Overhauser NMR measurements and compared with the crystal structures (Figure 3).
Funktionalisierung von C60 mit Nitriloxiden zu 4,5‐Dihydroisoxazolen und deren Strukturbestimmung
Authors: Irngartinger Hermann , Köhler Claus‐Markus , Huber‐Patz Ursula , Krätschmer Wolfgang
Published: July 2007

Functionalization of C60 with Nitrile Oxides to 4,5‐Dihydroisoxazoles and Their Structure Determination

Cycloadducts 3 of nitrile oxides 2 with C60 (1) are synthesized and isolated. The cycloadducts are characterized by 13C‐NMR spectroscopy and high‐resolution FAB mass spectrometry. X‐ray structure determination of the 3‐(9‐anthryl)‐4,5‐dihydroisoxazole derivative 3a of C60 with CS2 included in the crystals is achieved at 173 K without disorder problems.
Bis[2,3‐naphthalenediolato(2 — )](pyrrolidiniomethyl)germanate—Tetartoacetonitrile, the First Zwitterionic λ5‐Germanate: Synthesis and Crystal Structure Analysis
Authors: Tacke Reinhold , Sperlich Jörg , Becker Beate
Published: July 2007

The zwitterionic spirocyclic λ5‐germanate bis[2,3‐naphthalenediolato(2—)](pyrrolidiniomethyl)germanate (8) was synthesized and the crystal structure of its tetartoacetonitrile solvate 8 · 1/4 CH3CN studied by single‐crystal X‐ray diffraction. Compound 8 was prepared by reaction of (MeO)3‐GeCH2NC4H8 (11; NC4H8 = pyrrolidino) with two equivalents of 2,3‐naphthalenediol (isolated as 8 · 1/4 CH3CN; yield 92%). The coordination polyhedron around the pentacoordinate germanium atom of 8 · 1/4 CH3CN can be described as a strongly distorted trigonal bipyramid (the structure is displaced by 38.9% from the ideal trigonal bipyramid towards the ideal square pyramid), the carbon atom occupying an equatorial position. In the crystal lattice of 8 · 1/4 CH3CN, the zwitterions form intermolecular NH ⃛O hydrogen bonds leading to the formation of dimers. 1H‐ and 13CNMR studies revealed that 8 also exists in solution ([D6]DMSO).
Enantioselective Oxidation of Chiral Titanium Enolates Derived from Propiophenone by Dimethyldioxirane or 3‐Phenyl‐2‐phenylsulfonyloxazirdine
Authors: Adam Waldemar , Prechtl Frank
Published: July 2007

The stereoselective oxidation of the optically active titanium enolate complexes 2 of propiophenone by dimethyldioxirane (3) (as acetone solution) and 3‐Phenyl‐2‐phenylsulfonyloxaziridine (4) has been investigated. The chiral titanium enolates 2 were synthesized by the reaction of the lithium enolate of propiophenone and the respective optically active chlorotitanate complexes 1. For 3 as oxidant, the stereoselectivity of the α hydroxylation strongly depends on the substitution pattern at the central titanium atom and reached for the best case, namely 2e, an enantiomeric excess (ee) of 63%. Solvent and temperature exhibited only small effects on the stereoselectivity. Compound 4 as oxidant gave lower enantiomeric excesses than 3.
Thermally Initiated Free‐Radical Chain Addition of Alkanes to Alkynes, II. Kinetics of the Addition of Cyclohexane to Phenylethyne under Supercritical Fluid Conditions
Authors: Metzger Jürgen O. , Bangert Fritz
Published: July 2007

The kinetics of the addition of cyclohexane (2) to phenylethyne (1) proceeding via 2‐cyclohexyl‐1‐phenylethenyl radical (3) to give 1‐cyclohexyl‐2‐phenylethene (4) was investigated in the temperature range from 260 to 340°C. The radical chain is initiated by a bimolecular reaction of cyclohexane with phenylethyne to give a cyclohexyl radical and a 1‐phenylethenyl radical. The physical state of the reaction mixture was varied from liquid to supercritical and to gasphase conditions. No effect on the reaction rate constant near the critical point was observed.
Bimolekulare Radikalbildung durch H‐Transfer, 7. Katalyse der Transferhydrierung von α‐Methylstyrol durch 9,10‐Dihydroanthracen mit 7H‐Benz[de]anthracen
Authors: Gerst Matthias , Morgenthaler Jens , Rüchardt Christoph
Published: July 2007

Bimolecular Formation of Radicals by H‐Transfer, 7[1]. — Bimolecular Formation of Radicals via H‐Transfer with Catalysis by 7H‐Benz[de]anthracene

The transfer hydrogenation of α‐methylstyrene (2) by 9,10‐dihydroanthracene (1) (DHA) with 7H‐benz[de]anthracene (8) as a catalyst proceeds already at 210–260°C. Isotopic labeling, ESR spectroscopy, radical clock experiments, solvents effects, and thermochemical calculations support the postulated stepwise radical mechanism induced by bimolecular formation of radicals.
Transition Metal‐Catalyzed Annulation Reactions, VII. Palladium‐Catalyzed CH Activation at Methoxy Groups: Regiochemistry of the Domino Coupling Process
Authors: Dyker Gerald
Published: July 2007

By palladium catalysis substitutedortho‐iodoanisoles (5, 8, 10, 13) are transformed either to annulated pyran (6) or furan derivatives (7, 9, 11, 14, 15), depending on the reactivity of additional substituents. The regiochemistry of the domino coupling processes is analyzed and a mechanistic rationale developed. Key step is the CH activation at methoxy groups.
Gürtelförmige Moleküle mittels repetitiver Synthesestrategie
Authors: Josten Wolfgang , Karbach Detlef , Nieger Martin , Vögtle Fritz , Hägele Klaus , Svoboda Michael , Przybylski Michael
Published: July 2007

Belt‐Shaped Molecules by a Repetitive Synthetic Strategy

Belt‐shaped molecules of the general type 2 containing up to five benzene ring units (cf. 37) have been synthesized by macrocyclisation reactions of ribbon‐shaped precursors. An intermolecular cyclization step generates the macroheterocycles 38 and 40. The fourfold‐bridged cyclophane 36 are prepared by intra‐and intermolecular cyclization reactions. The X‐ray structure analyses of 14, 16, 22, 23, 28, and 36 show S‐shaped conformations of the molecules.
Distinction of Fe+NCH and Fe+CNH Complexes by Gas‐Phase Ion‐Molecule Reactions
Authors: Stöckigt Detlef , Schwarz Helmut
Published: July 2007

The bond dissociation energies and the heats of formation of the complexes Fe+NCH (6) and Fe+CNH (10) have been determined. The HCN ligand in 6 is by 3 kcal/mol less strongly bound to Fe+ than HNC in 10, and complex 6 is 13 kcal/mol more stable than 10. Isomerization of 10 to 6 is difficult if not impossible to bring about as, upon collisional activation, mutual isomerization cannot compete with ligand detachment. In addition, the ion‐molecule reactions of 6 and 10 with O2 give rise to distinct product distributions.
Pentamethylcyclopentadienyl‐substituiertes Selenadiphosphiran und Selenatriphosphetan: Synthese, Struktur, Dynamik und einige Reaktionen
Authors: Jutzi Peter , Brusdeilins Norbert , Stammler Hans‐Georg , Neumann Beate
Published: July 2007

Pentamethylcyclopentadienyl‐Substituted Selenadiphosphirane and Selenatriphosphetane: Synthesis, Structure, Dynamic, and Some Reactions

Herrn Prof. R. Schmutzler zum 60. Geburtstag gewidmet.

1,2,3‐Tris(pentamethylcyclopentadienyl)cyclotriphosphane (1) reacts with selenium to form the insertion product 2,3,4‐tris(pentamethylcyclopentadienyl)selenatriphosphetane (2), which is trapped as the selenium‐coordinated pentacarbonylchromium complex 4. Compound 4 is the first isolated selenatriphosphetane complex. Reaction of 2 with selenium yields 2,3‐bis(pentamethylcyclopentadienyl)selenadiphosphirane (3). 3 replaces thf of Cr(CO)5thf to give the chromium complex 5. The reaction of 3 with K[Fe(CO)2Cp*] leads to the substitution product 6 and the bicyclic phosphane 7. The X‐ray structures of 3 and 4 are presented. The dynamic behavior of 3–6 is discussed.
Evidenz für eine Struktur‐Reaktivität‐Beziehung bei sperrig substituierten Lithium(fluorsilyl)phosphaniden
Authors: Drieß Matthias , Winkler Uwe , Imhof Wolfgang , Zsolnai Laszlo , Huttner Gottfried
Published: July 2007

Evidence for a Structure‐Reactivity Relationship of Crowded Substituted Lithium (Fluorosilyl)phosphanides

The molecular structures and the reactivity of the new solvated lithium (fluorosilyl)phosphanides 1a, 2a, and 2b has been investigated. The unusual solid state structures of 1a and 2b are established by X‐ray crystallography. Whereas the lithium centre in 1a is bound to phosphorus and solvated by three molecules of THF, the electronical saturation of the lithium centre in 2b is achieved by a LiP bond, tridentate chelatization (fluorine, phosphorus, nitrogen), and the additional coordination of one molecule of THF. The trigonal‐planar geometry at phosphorus in 1a is unprecedented for derivatives of this type and reflects the steric demand around the phosphorus and the possibility of πp/σ*sic hyperconjugation. The SiP bond lengths [PSiC(Phenyl) 2.186(2) and PSiF 2.164(2) Å] are significantly shorter than in related pyramidally configurated derivatives (1b, c: PSiC 2.21, PSiF 2.18 Å). Both phosphorus atoms in 2b are pyramidally coordinated, but the intramolecular chelate coordination of the lithium centre causes much smaller bonding angles at the SiP phosphorus atom [sum of bonding angles 238.4(2) (PSi), 312.5(1)° (PN)]. 1a as well as 2a, b show quite different reactivity as compared to 1b–d due to their unusual structures. Heating of solutions of 1a and 2a, b in toluene or hexane does not give the expected stable silylidenephosphanes (SiP) by elimination of LiF. Instead, rearrangement reactions of the SiP intermediates 6, 8 lead to the new heterocycles 5, 9. A single‐crystal X‐ray diffraction analysis of 5 has been performed. The Si2P2 cyclobutane ring is planar, and the NMe2 groups at the ring silicon atoms are cis‐orientated. — Interestingly, 2b eliminates LiNiPr2 at 20°C in a kinetically controlled process to form the tetraphosphacyclobutane 7 as the major product. Presumably, the diphosphene 8 is an intermediate in this reaction.
Thianthrene 5‐Oxide (SSO) as a Mechanistic Probe of the Electrophilic Character in the Oxygen Transfer by Dioxiranes
Authors: Adam Waldemar , Golsch Dieter
Published: July 2007

Thianthrene 5‐oxide (SSO) is established as a useful and convenient chemical probe to assess the electronic character (Xso) of oxygen transfer agents. Thus, H2O2 under basic conditions (HOOH/nBu4NOH) gives an Xso value of 1.00, while H2O2 under acidic conditions (HOOH/HClO4) affords an Xso value near zero. On this Xso scale, dimethyldioxirane (Xso = 0.13 at 0°C) and methyl(trifluoromethyl)dioxirane (Xso = 0.10 at 0°C) are, as expected, definitely strong electrophilic oxidants.
Preparation of 2H‐Benzoxetes by Photoinduced [2 + 2] Cycloaddition of Quinone Methides, Accessible by Dimethyldioxirane (DMD) Oxidation of 2,3‐Dimethylbenzofurans
Authors: Adam Waldemar , Sauter Markus , Zünkler Corinna
Published: July 2007

Irradiation (λ > 366 nm) of the quinone methides 3, which were formed by valence isomerization of the methyl‐, chloro‐, and tert‐butyl‐substituted 2,3‐dimethylbenzofuran epoxides 2, afforded the novel 2H‐benzoxetes 4 by photochemical [2 + 2] cycloaddition. These strained and highly labile benzoxetes 4 were spectrally (1H and 13C NMR) characterized at subambient temperatures. On prolonged storage (2–3 d) at –20 to –10°C, the benzoxetes 4 reverted to the quinone methides 3 and/or benzofuran epoxides 2.
Tin for Organic Synthesis, 11. A Mild and Effective Synthesis of α,β‐unsaturated Carboxamides and Sulfonamides by Electrophilic Substitution of Alkenylstannanes with Isocyanates
Authors: Niestroj Michael , Neumann Wilhelm P. , Thies Olaf
Published: July 2007

A new and effective method for the preparation of a variety of olefinic carboxamides 6a–k and N‐(4‐methylphenyl‐sulfonyl) carboxamides 7a–d is described. The reaction of aryl and alkyl isocyanates 4a–c or 4‐methylphenylsulfonyl isocyanate 5 with 1‐alkenyltrialkylstannanes 1a–e and di‐1‐alkenyldibutylstannanes 2a–c in the presence of aluminium trichloride provides the corresponding N‐aryl‐substituted olefinic carboxamides 6a–k or the N‐(4‐methylphenyl‐sulfonyl)‐substituted olefinic carboxamides 7a–d in good yields. The stannyl moiety is superior to hydrogen as a leaving group and enables electrophilic ipso substitution at the vinylic system. In the case of di‐1‐alkenyldibutylstannanes the substitutions are also stereospecific, whereas the reactions of 1‐alkenyltrialkylstannanes with isocyanates proceed with partial isomerisation.
Cycloallene, 9. 1‐Phenyl‐1‐aza‐3,4‐cyclohexadien, das erste Isodihydropyridin: Erzeugung und Abfangreaktionen
Authors: Christl Manfred , Braun Martin , Wolz Erich , Wagner Willi
Published: July 2007

Cycloallenes, 9. — 1‐Phenyl‐1‐aza‐3,4‐cyclohexadiene, the First Isodihydropyridine: Generation and Interception

The generation of the title cycloallene 4 from 6,6‐dibromo‐3‐phenyl‐3‐azabicyclo[3.1.0]hexane (10) with methyllithium according to the Doering‐Moore‐Skattebøl method is reported. In the presence of styrene, 1,3‐butadiene, furan, 1,3‐cyclohexadiene, and 1,3‐cyclopentadiene, 4 is intercepted in [2 + 2] and [4 + 2] cycloadditions with formation of the hexahydrocyclobuta[c]pyridines 6 and 11 and the hexahydroisoquinolines 12–15, respectively. The starting compound 10 is prepared via the cis‐disubstituted 1,1‐dibromocyclopropanes 8 and 9 from the known dioxepine derivative 7, the synthesis of which has been considerably improved. On treatment with n‐butyllithium, the dichlorophenylazabicyclohexane 3 is converted into 4 as well. However, in the competition for 4, styrene is not successful against n‐butyllithium, which transforms 4 into the pentadienylamine 5.
A Convenient Synthesis of New Macrocyclic Naphthalenophanes
Authors: Grützmacher Hans‐Friedrich , Nolte Gerald
Published: July 2007

The (1,4)naphthalenophanes 6a, 6b, 7a, and 7b were synthesized regiospecifically in two steps from the appropriate α,β‐di‐1‐naphthylalkanes by a Friedel‐Crafts acetylation of the two naphthalene groups followed by cyclization/dimerization of the resulting diketones by a McMurray reaction. The macrocyclic naphthalenophanes 6a and 6b exist in solution as a mixture of conformers while 7a and 7b were identified as the anti isomers.
A Convenient Synthesis of Macrocyclic[2.1.2.1]Paracyclophanes
Authors: Grützmacher Hans‐Friedrich , Mehdizadeh Ahmed , Mülverstedt Astrid
Published: July 2007

The [2.1.2.1]paracyclophanedienes 9–11 were prepared in good yields by a McMurry cyclization of the bis(4‐acylphenyl)methanes 5 and 6 and of bis(4‐acetylphenyl) ether (7), respectively.
Zur Chemie des Galliums, IV. Darstellung und Strukturen monomerer (2,2,6,6‐Tetramethylpiperidino)gallane
Authors: Linti Gerald , Frey Ronald , Polborn Kurt
Published: July 2007

On the Chemistry of Gallium Compounds, IV. ‐ Synthesis and Structure of Monomeric (2,2,6,6‐Tetramethylpiperidino)‐gallanes

Monomeric dimethyl‐ and diethyl(2,2,6,6‐tetramethylpiperidino) gallanes have been synthesized and spectroscopically characterized. Starting from bis(2,2,6,6‐tetramethylpiperidino)gallium halides (tmp)2GaX (16, 17, X=Cl, Br) various (aryloxy)‐ and organylbis (amido) gallium compounds (tmp)2GaY (18–21, Y = OAr, Ph, Me) have been obtained. The crystal structures of (tmp)2GaOPh (18) and (tmp)2GaPh (20) show trigonal planar‐coordinated gallium atoms. Planarcoordinated nitrogen atoms with a GaN bond length of 188 pm are present in 20. In contrast, 18 shows one planar‐ and one slightly pyramidal‐coordinated nitrogen atom, and this results in two different bond lengths of 184.9 and 181.8 pm, respectively.
Derivate des Imidazols, XI. (C8H14N2)M(CO)5 (M = Mo, W) ‐ Terminale Koordination eines Olefins in Pentacarbonylmetall‐Komplexen
Authors: Kuhn Norbert , Bohnen Hans , Bläser Dieter , Boese Roland
Published: July 2007

Imidazole Derivatives, XI. ‐ (C8H14N2)M(CO)5 (M = Mo, W) ‐ Terminal Coordination of an Olefin in Pentacarbonyl Metal Complexes

Herrn Professor Reinhard Schmutzler zum 60. Geburtstag gewidmet.

The 2‐methylenimidazoline complexes (C8H14N2)M(CO)5 (M = Mo, W; 6) are obtained from M(CO)6 and 1,3,4,5‐tetramethyl‐2‐methyleneimidazoline (5). Spectroscopic data reveal the strong donor character of the ylidic ligand in 6. The end‐on coordination mode of the olefin is demonstrated by an X‐ray structure analysis of 6a.
Umsetzung von Isothiocyanaten und Isonitrilen mit R2Al–AlR2 [R = CH(SiMe3)2]; ein‐ und zweifache Insertion von Isonitril in die Aluminium‐Aluminium‐Bindung
Authors: Uhl Werner , Schütz Uwe , Hiller Wolfgang , Heckel Maximilian
Published: July 2007

Reaction of Isothiocyanates and Isonitriles with R2Al–AlR2 [R = CH(SiMe3)2]; Single and Double Insertion of Isonitrile into the Al–Al Bond

Tetrakis[bis(trimethylsilyl)methyl]dialuminium(4) 1 reacts with phenyl or tert‐butyl isothiocyanate with cleavage of the C = S double bond. Two compounds are formed: R2Al‐S‐AlR2 [R = CH(SiMe3)2] 3 and R2Al‐C(NR')‐AlR2 (4 R' = C6H5; 5 R'= CMe3) with a sulfur atom or an isonitrile group inserted between the aluminium atoms. Compounds 4 and 5 were isolated in high yield by the reaction of 1 with the appropriate isonitriles. By using an excess of phenyl isonitrile a dark red compound 6 is obtained with two isonitrile units inserted into the Al–Al bond and formation of a C–C single bond. According to crystal structure determinations of 4 and 6 a three‐membered heterocycle is formed by the interaction of the nitrogen lone‐pair to one of the Al atoms in 4, while in 6 both Al atoms are four‐coordinated by bonding to a nitrogen and a carbon atom with formation of two across the C–C bond anellated four‐membered heterocycles. As shown by NMR spectroscopy the molecular structure of 4 with one stereochemically saturated and one unsaturated Al atom is unchanged in solution even upon heating to 100°C.
Twofold Deprotonated Citric Acid as a Bidentate Ligand of Pentacoordinate Silicon: Synthesis and Structural Characterization of the Zwitterionic λ5Si‐Spirosilicate Bis[citrato(2–)‐O3,O4][(dimethylammonio)methyl]silicate Hydrate
Authors: Mühleisen Mathias , Tacke Reinhold
Published: July 2007

The zwitterionic λ5Si‐spirosilicate bis[citrato(2–)‐O3,O4][(dimethylammonio)methyl]silicate (4) was synthesized by reaction of (MeO)3SiCH2NMe2 (3) with citric acid (molar ratio 1:2) in acetonitrile at room temperature and isolated, after crystallization from water, as the hydrate 4 . H2O (yield 81%). The crystal structure of 4 . H2O was studied by single‐crystal X‐ray diffraction. The alcoxide oxygen atoms and central carboxylate oxygen atoms of two citrato(2–) ligands and one carbon atom coordinate to the silicon atom of 4 . H2O. The coordination polyhedron around the pentacoordinate silicon atom (SiO4C framework) can be described as a distorted trigonal bipyramid, the two carboxylate oxygen atoms occupying the axial sites. The λ5Si‐silicon(IV) complex 4 also exists in solution (DMSO, H2O).
Synthesis, Absorption Spectra, and Photostability of Triarylmethane Dye Ethynylogues Containing Trifluoromethyl Group(s)
Authors: Muramatsu Hiroshige , Okumura Akinori , Shibata Katsuyoshi , Matsui Masaki
Published: July 2007

Triarylmethane dye ethynylogues 7′– 11′ containing trifluoromethyl group(s) are synthesized in moderate to good yields by treating 1,1,3‐triaryl‐2‐propyn‐1‐ols, prepared from diaryl ketones and lithium arylacetylides bearing trifluoromethyl group(s), with perchloric acid. The first absorption bands of a series of triarylmethane dye ethynylogues containing trifluoromethyl group(s) 11′ are observed around 700 nm. The photostability of the triarylmethane dyes is also examined.
Synthesis and Characterization of Nitrido(tetra‐tert‐butylphthalocyaninato)‐ rhenium(V) and Nitrido(phthalocyaninato)rhenium(V)
Authors: Ziener Ulrich , Hanack Michael
Published: July 2007

4‐tert‐Butylphthalodinitrile (1) reacts with ammonium perrhenate, NH4ReO4, to yield nitrido(tetra‐tert‐butylphthalocyaninato)rhenium(V), (tBu)4PcReN (2), which is characterized by IR, UV/Vis, CV, MS, 1H and 13C NMR, and elemental analysis. It shows good solubility in common organic solvents. In solution 2 is assumed to be monomeric whereas in the solid state also dimers or higher aggregates are present. From the NMR spectra it is concluded that different constitutional isomers of 2 are formed but not in the expected ratio of a statistical distribution. By analogy with 2, the already known nitrido(phthalocyaninato)rhenium(V), PcReN (3), is prepared for comparison.
Synthesis and Thermolysis of a Chiral, Non‐Racemic Iminoaziridine11
Authors: Quast Helmut , Aldenkortt Sven , Heller Eberhard , Schäfer Peter , Schmitt Edeltraud
Published: July 2007

The 2‐halo imidoyl chlorides 7 are obtained from the amide 5 and the 2‐halo amides 6 by the action of phosphorus pentachloride and thionyl chloride, respectively. Non‐racemic (S)‐6a is converted into 7a which is racemic, however. The reaction of Lawesson's reagent with 6a furnishes the diaste‐reomeric 1,3,2‐thiazaphospholidine derivatives 15. Treatment of (S)‐6a (98% ee) with methyl triflate affords 2‐chloro imidate 8 (95% ee) which reacts with methanamine in the presence of methanammonium chloride to yield the 2‐chloro amidine (S)‐9a (90% ee). The 2‐halo imidoyl halides 7a and b react with methanamine to produce the 2‐halo amidines 9a and b. — Strong bases, e.g. potassium tert‐butoxide or sodium hydride in the presence of catalytic amounts of tert‐butyl alcohol, eliminate hydrogen chloride or bromide from the 2‐halo amidines 9a and b and (S)‐9ato yield mixtures of the 2‐iminoaziridines (E)‐ and (Z)‐4, and (E,R)‐ and (Z,R)‐4 (83% ee), respectively. The 1,3‐elimination of hydrogen bromide from 9b is diastereoselective at ‐30 to ‐40° [(E)‐4:(Z)‐4 = <10:>90]. The diastereomers equilibrate at 36° with (kEZ + kZE) = (5.92 ± 0.08) . 10−5 s−1 (K = kEZ/kZE = 0.428 ± 0.013). ‐ The thermolysis of (E)‐ and (Z)‐4 in [D6]benzene solution yields the imine 16 and methyl isocyanide (17). The decomposition follows the first‐order rate law. The following Arrhenius and Eyring parameters are calculated from five rate constants obtained in the temperature range of 70–110°: Ea = (115.2 ± 0.4) kJmol−1, IgA = (12.06 ± 0.28), δH‡ = (112.1 ± 0.4) kJmol−1, δS‡ = (‐23.9 ± 0.7) JK−1 mol−1, δG‡373K = 121 kJmol−1. The enantiomeric excess of the surviving fraction of (E,R)‐ and (Z,R)‐4 is unchanged after two half‐lives at 80°.
Enantioselective Synthesis of Polyfunctional Small Building Blocks with a Quaternary Stereogenic Center
Authors: Enders Dieter , Zamponi Andreas , Schäfer Thomas , Nübling Christoph , Eichenauer Herbert , Demir Ayhan Sitki , Raabe Gerhard
Published: July 2007

Application of the SAMP‐/RAMP‐hydrazone method offers an efficient and flexible access to compounds with a quaternary stereogenic center. Examples bearing silyl, thio, phenyl, aldo, keto, ester, and alkyl functionalities are described. The 2‐phenylaldehydes and ‐ketones and the β‐keto esters 4 were obtained in good overall yields and with variable enantiomeric excesses. The synthesis of the thiolated 2‐formyl and 3‐formyl carboxylic esters 12 was achieved in high overall yields and with high enantiomeric excesses. The silylated carboxylic ester and acids 16 were produced in moderate to high overall yields and with moderate to excellent enantiomeric excesses, depending on the electrophile used for the quaternization. The absolute configurations of the compounds 12 and 16 were determined by X‐ray structure analyses, and the mechanism of the quaternization is postulated.
LiClO4‐induzierte Dreikomponenten‐Aminoalkylierung von Aldehyden
Authors: Reza Saidi M. , Heydari Akbar , Ipaktschi Junes
Published: July 2007

LiClO4 Induced One Pot Three‐Component Aminoalkylation of Aldehydes

LiClO4‐mediated one‐pot reaction of isobutyraldehyde (1) or benzaldehyde (5) with (trimethylsilyl)dialkylamines 2 and C nucleophiles such as O‐silylated ketene acetals 3, 6, allyl Grignard, lithium (trimethylsilyl)acetylide, triinethylsilyl cyanide, and diethylzinc afforded in high yields the corresponding aminoalkylation products 4 and 7–13. The lithium enolate of cyclohexanone adds in 5 M LiClO4 solution in an Ik manner to the corresponding mannich base (19, 20) with good yield.