bluuebunny/crossref_metadata_2025 huggingface dataset:
Verbindungen mit dem 1,3‐dimethyl‐1,3,2‐diazaphosphetidin‐4‐on‐Grundgerüst: Synthese von 1,3‐Dimethyl‐1,3,2‐diazaphosphetidin‐4‐on‐2‐oxid‐Derivaten
Authors: Breker Johannes , Schmutzler Reinhard
Published: July 2007

Compounds Involving the 1,3‐Dimethyl‐1.3,2‐diazaphosphetidin‐4‐one Framework Synthesis of 1,3‐Dimethyl‐1.3,2‐diazaphosphetidin‐4‐one 2‐Oxide Derivatives

The oxidation of 1,3,2‐diazaphosphetidinones 3, 4, 7–9 to the respective P‐oxides using NO2 (3→5 and 4→6) or (Me3SiO)2 (7→10, 8→11, and 9→12) is described. Other diazaphosphetidinone P‐oxides 13–15 are obtained by the reaction of N,N′‐dimethylurea with phosphonic dichlorides in the presence of triethylamine as an HCl acceptor. The compounds 5, 6, 10 – 15 contain the novel structural element, involving λ4P. The reaction of 10 and 15 with methanol leads to the formation of the acyclic methyl esters MeOP‐(O)(Y)N(Me)C(O)N(Me)H (20) [Y = N(CH2)4] and (21) [Y = Ph].
Funktionalisierte meso‐Arylporphyrine als Edukte für die Synthese von Oligoporphyrinylen
Authors: Hammel Dirk , Kautz Christian , Müllen Klaus
Published: July 2007

Functionalized meso‐Arylporphyrins, Precursors for the Synthesis of Oligoporphyrinyls

Lithiation and subsequent formylation of bromo‐substituted tetraarylporphyrins 3a–d, prepared under Adler‐Rothemund conditions, afford a mixture of the porphyrinylbenzaldehydes 4a–d and the corresponding dialdehydes (cis and trans isomer) 7a/7d and 8a/8d, which may beisolated by column chromatogrphy. The readily available porphyrins are suitable precursors for the synthesis of oligoporphyrinyl systems which is demonstrated for the case of the novel stilhene‐linked diporphyrinyl 12. Alkyl substitution of the nonfunctionalized aryl groups brings about sufficient solubility of the porphyrins in organic solvents.
Organische Synthesen mit Übergangsmetallkomplexen, 41. Thioenolether durch Insertion von Alkinen in MC‐Bindungen von Thiocarben‐Komplexen und Liganden‐Abspaltung an Kieselgel
Authors: Aumann Rudolf , Schröder Jochen , Heinen Heinrich
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 41 1. ‐ Thioenol Ethers by Insertion of Alkynes into M = C Bonds of Thiocarbene Complexes and Disengagement of Ligands on Silica Gel

A first example of reactions between alkynes and thiocarbene complexes is described. Et2NCCCCH3 (2) adds to (alkylthio)phenylcarbene complexes LnMC(SR)C6H5 (1) [LnM = Cr(CO)5. W(WO)5; RCH2CHCH2, CH2C6H5, c‐C6H11, t‐C4H9, C6H5] with insertion of the CC into the MC bond to form stereoselectively [(E)‐β‐(alkylthio)alkenyl]aminocarbene complexes LnMC(NEt2) ‐ C(CH3)C(SR)C6H5 [(E)‐3a–g]. With tungsten, but not with chromium, small amounts of indanone derivatives 4–6 were also obtained. We describe a straightforward and efficient method for the disengagement of ligands from carbene chromium complexes 3 on silica gel. Metal residues remain attached to the solid phase, and products are isolated by elution. Depending on the reaction conditions, different thioenol ethers 7–9 were obtained. Thus (E)‐3a–d on silica gel at ambient temperature under the influence of air give β‐(alkylthio)propenamides OC(NEt2)‐C(CH3)C(SR)C6H5 [(E)‐] and β‐(alkylthio)propenals OCH–C(CH3) = C(SR)C6H5 [(E)‐8]. Thermolysis of 3 on silica gel in the absence of oxygen leads to the formation of aldehydes 8 and 3‐(alkylthio)‐1‐indanones 5. Thermolysis of 3 on silca gel in the presence of sulfur yields β‐(alkylthio)propenethioamides 9 as the only products.
Intramolecular Ene and Related Reactions, 53g). Stereoselective Formation of trans‐1,2‐Disubstituted Cyclopentanes by Intramolecular Cyclisation of Allylsilane Alkylidene 1,3‐Dioxo Compounds
Authors: Tietze Lutz F. , Ruther Michael
Published: July 2007

The alkylidene 1,3‐dioxo compounds 4a–d with an allylsilane moiety undergo a fluoride‐, Lewis acid‐ and TMSOTf‐induced intramolecular cyclisation to give almost exclusively the trans‐1,2‐disubstituted cyclopentanes 5a–d in good to excellent yields. The diastereoselectivity of the reaction was determined as a function of the 1,3‐dioxo moiety and the inductor. The best results were obtained with FeCl3/Al2O3 followed by TMSOTf and Me2AlCl1 the highest selectivity was found in the cyclisation of 4b with TMSOTf leading to 5b and 6b in a ratio of 99.8:0.2. FeCl3/Al2O3 and TMSOTf have not previously been used for this type of reaction. The alkylidene 1,3‐dioxo compounds 4a–d were synthesised by Knoevenagel condensation of the aldehyde 11 with the malonic acid derivatives 11a–d.
(E)‐ und (Z)‐Enole von β‐Ketocarbonsäureamiden
Authors: Wengenroth Horst , Meier Herbert
Published: July 2007

(E)‐ and (Z)‐Enols of β‐Ketocarboxylic Acid Amides

Reaction of dimesitoyldiazomethane (1) with ammonia (3a), primary and secondary amines (3b – o and 3p – v, respectively) leads to the completely enolized amides 4a – v. Besides the chelated Z configuration the unusual E isomer exists in the most cases, too. The Z/E distribution in the equilibrium depends on the steric and electronic effects present in the amide group CONR2R3 and on the solvent.
A Novel Methylenation Method of aldehydes Mediated by Dibutyl Telluride
Authors: Li Sao‐Wei , Huang Yao‐Zeng , Shi Li‐Lan
Published: July 2007

In the presence of dibutyl telluride, (iodomethyl)triphenylphosphonium iodide (1) reacted with aldehydes 2 in THF at 80°C yielding he methylenation products 3 under neutral conditions in good yields.
Facile Diastereoselective Synthesis of 2,6‐Dialkyl‐5‐methylene‐1,3‐dioxan‐4‐ones via α‐Activated Vinyl Esters
Authors: Drewes Siegfried E. , Emslie Neville D. , Karodia Nazira , Khan Abdullah A.
Published: July 2007

Vinyl esters such as 2, in the presence of DABCO, undergo intial reaction with aldehydes, followed by nucleophilic attack on a second aldehyde molecule. Subsequent intramolecular transesterification affords the dioxanones 5 in high yields and high diastereomeric excesses.
Notizen/Notes A Novel vic‐Dioxime with Crown Ether Moieties
Authors: Gök YaŞar , Kantekin Halit
Published: July 2007

The novel vic‐dioxime 2 has been synthesized by reaction of the thiourea 1 with cyanogen N,N′‐dioxide. The IR and NMR data indicate that 2 is the (E,Z) isomer. However, in the Co(III) complex of 2, the metal ion is coordinated to the nitrogen atoms of the vic‐dioxime moiety as in the case of the (E, E) isomers.
Nonacarbonylbis(μ3‐methylidin)trieisen
Authors: Lentz Dieter , Michael Heike
Published: July 2007

Nonacarbonylbis(μ3‐methylidyne)triiron

Halogen exchange reaction in Fe3(CO)9(μ3CF)2 (1) with BBr3 (3) yields Fe3(CO)9(μ3CBr)2 (4), which can be converted by (C4H9)3SnH (5) into Fe3(CO)9(μ3CH)2 (6). 6 is the parent compound of the bis(alkylidyne)triiron clusters. Selective reduction of the CBr moiety in Fe3(CO)9(μ3CBr) (μ3CCO2CH3) (7) results in the formation of Fe3(CO)9(μ3CH) (μ3CCO2CH3) (8). The structure of 8 has been elucidated by an X‐ray crystalstructure determination.
Nickel(0)‐katalysierte Kupplung von (Tricyclo[4.1.0.02,7]hept‐1‐yl)‐magnesiumbromid und verwandten Grignard‐Verbindungen mit Aryl‐, Vinyl‐ und Alkinylhalogeniden
Authors: Kottirsch Georg , Szeimies Günter
Published: July 2007

Nickel(0)‐Catalyzed Cross Coupling Reactions of (Tricyclo[4.1.0.02,7]hept‐1‐yl)magnesium Bromide and Related Grignard Reagents with Aryl, Vinyl, and Alkynyl Halides

(Tricyclo[4.1.0.02,7]hept‐1‐yl)magnesium bromide (1c) and similar Grignard reagents like 2c, 3a–d, and 4 were cross‐coupled with a series of aryl, vinyl, and alkynyl chlorides or bromides in the presence of approximately 1% of [1,2‐bis(diphenyl‐phosphino)ethane]nickel dichloride (NidppeCl2) leading to bridgehead‐substituted aryl‐, vinyl‐, and alkynylbicyclo[1.1.0]‐butanes in varying yields.
Use of Magnesium Anthracene·3THF in Synthesis: Generation of Grignard Compounds and Other Reactions with Organic Halides
Authors: Bogdanovic̀ Borislav , Janke Nikolaus , Kinzelmann Hans‐Georg
Published: July 2007

The course (a), (b), (c) (Scheme 1) of the reaction of magnesium anthracene·3THF (1) with organic halides (RX) is dependent on the nature of RX. With alkyl halides in THF 1 reacts as a nucleophile, whereby primary as well as secondary alkyl halides produce dialkyldihydroanthracenes (4–4′′) and tertiary alkyl halides yield primarily monoalkyl‐substituted dihydroanthracenes (2, 2′). With bromo‐ and iodobenzene in THF 1 reacts predominantly as a radical with H atom abstraction from the solvent affording benzene and 9. The formation of Grignard compounds (5) and anthracene (6), originating from primary and secondary alkyl and aryl halides and 1 in toluene or ether at elevated temperatures, is not caused by the reaction of 1 but by the “active magnesium” (Mg*) formed by decomposition of 1 in these solvents. In contrast, allyl, propargyl, and benzyl halides react with 1 independently of the solvent under mild conditions to produce 5 and 6. Allyl‐ and the difficultly accessible allenylmagnesium chloride can be prepared in THF at –78 and 0°C, respectively, from the corresponding halides and ordinary Mg powder via catalytic amounts of 1.
Magnesium Adducts of Substituted Anthracenes – Preparation and Properties
Authors: Bogdanovic̀ Borislav , Janke Nikolaus , Kinzelmann Hans‐Georg , Seevogel Klaus , Treber Joachim
Published: July 2007

2‐Methyl‐, 1,4‐dimethyl‐, 9‐methyl‐, 9‐ethyl‐, 9,10‐dimethyl‐, and 9‐phenylanthracene (1a–f) react with magnesium in THF at room temperature to afford the corresponding substituted magnesium anthracenes 2a‐i. 9,10‐Diphenylanthracene (1g), however, reacts with magnesium under the same conditions to produce the deep‐blue magnesium bis(9,10‐diphenylanthracenide) · 6 THF (4g). Upon heating to 60°C in THF, 4g reversibly dissociated to give magnesium 9,10‐diphenylanthracene · 3 THF (2g) and 1g, while prolonged heating at 60°C causes decomposition of 2g to active magnesium (Mg*) and 1g. In THF 2a–c, e, and f exhibit temperature‐dependent equilibria with 1a–c, e, and f and magnesium. Compared with magnesium anthracene · 3 THF (2), these equilibria are strongly shifted toward substituted anthracenes and magnesium, and only at 0°C high conversions are achieved. The magnesium exchange between 2 and the substituted anthracenes 1a,b, and f in THF has been experimentally verified. 2a,e, and f react with organic halides in the same way as 2, however, in the case of allyl, propargyl, and benzyl chloride the yields of Grignard compounds are lower than for 2; with bromobenzene, the tendency for the radical transfer reaction is stronger than for 2. Magnesium 9,10‐dimethylanthracene (2e) reacts with ethyl acetate to give the bicyclic tertiary alcohol 9 by an intramolecular C–C coupling reaction.
Metal ion binding by amino acids: Strontium and barium l‐aspartate trihydrate Sr/Ba(l‐Asp) · 3 H2O
Authors: Schmidbaur Hubert , Mikulik Patrizia , Müller Gerhard
Published: July 2007

Strontium and barium l‐aspartate are obtained by neutralization of aqueous solutions of l‐aspartic acid with strontium or barium hydroxide, respectively. Slow crystallization from hot water affords the crystalline trihydrates, saturated solutions of which show pH values of 11.0 and 10.8 at ambient temperature. – The crystal structure of the two compounds has been determined by single crystal X‐ray diffraction. The compounds are isomorphous (orthorhombic, space group P212121), and the structural parameters are very similar as expected from the small differences in the ionic radii of the two metals. – The cations are arranged in double strings parallel to the b axis. The l‐aspartate dianions are bridging these double strings by chelating contacts of the two carboxylate groups with the metal atoms of different strings to give layers. While the α‐carboxylate groups are only bidentate and associated with one metal atom each, the β‐carboxylate oxygen atoms are also each bridging two adjacent metals of the neighbouring string. The three water molecules are all coordinated to the metal atoms, which attain coordination number 9. The amino groups are not engaged in metal coordination, but are part of a system of hydrogen bonds cross‐linking the layers.
Über Metallalkyl‐ und ‐aryl‐Verbindungen, 44 Darstellung und Struktur von Methylnatrium. Strukturbestimmung an NaCD3‐Pulvern bei 1.5 und 300 K durch Neutronen‐ und Synchrotronstrahlenbeugung
Authors: Weiss Erwin , Corbelin Siegfried , Cockcroft Jeremy Karl , Fitch Andrew Nicholas
Published: July 2007

Metal Alkyl and Aryl Compounds, 441) – Preparation and Structure of Methylsodium. Structure Determination using NaCD, Powders at 1.5 and 300 K by Neutron and Synchrotron Radiation Diffraction

[D3]Methylsodium (NaCD3) has been obtained by the reaction of [D3]methyllithium with sodium tert‐butoxide. Its crystal structure has been determined from NaCD3 powder samples using the combination of neutron and synchrotron radiation diffraction techniques. Studies at 1.5 and 300 K show a new structure type (orthorhombic, space group I222, Z16). Na and C atomic positions have been obtained from synchrotron radiation data and subsequently D positions by neutron diffraction. The complete structure has been refined using Rietveld methods. – Half of the ions are arranged in tetramers, (NaCD3)4, similar to those in methyllithium. The orientation of the methanide ions with respect to the three next Na ions is staggered. The remaining 8 Na and 8 methanide ions interconnect the tetramers by Na‐C contacts; their Na ions are arranged in zigzag chains. Thus, the structure of methylsodium shows elements of the methyllithium and methylpotassium structure. All methanide ions are trigonal‐pyramidal with C‐D 109 pm and D‐C‐D angles of 106° (1.5 K). Na‐C distances vary from 253 to 291 pm, depending upon the methyl‐Na orientation. IR data of NaCD3 are given.
N‐Aryl‐O‐(α‐aminoacyl)hydroxylamine: Modellreaktionen zur Aktivierung von monocyclischen aromatischen Aminen zu ultimaten Carcinogenen durch α‐Aminosäuren
Authors: Meier Chris , Boche Gernot
Published: July 2007

N‐Aryl‐O‐(α‐aminoacyl)hydroxylamines: Model Reactions for the Activation of Monocyclic Aromatic Amines into Ultimate Carcinogens with α‐Amino Acids

The rearrangement of the new α‐aminohydroxamic acids 15 and 18 to the likewise new N‐(α‐aminoacyloxy)arylamines [“N‐(acyloxy)arylamines”] 19 and 20, respectively, is observed in amine‐catalyzed model reactions. N‐(acyloxy)arylamines such as 19 and 20 are indicated to be ultimate carcinogens of aromatic amines which are able to react with bionucleophiles such as the DNA bases. The formation of 19 and 20 was proven by trapping these reactive intermediates with the model nucleophile N‐methylaniline (21) to give the hydrazines 22 and‐depending on the substitutent in 19 and 20‐the so‐called ortho amination products 23. Analogous reactions of the aceto‐and pivalohydroxamic acids 24 and 25 lead also to the adducts 22 and 23, respectively, in comparable yields. These results demonstrate that the O‐α‐aminoacylation as shown here may be similarily used in model reactions for the activation of carcinogenic aromatic amines as the O‐acetylation.
Untersuchungen zur Chemie von Isoindolen und Isoindoleninen, XXXVII. Symmetrisch substituierte 2‐Alkyl‐2H‐isoindole
Authors: Kreher Richard P. , Sewarte‐Roß Günter , Vogt Günther
Published: July 2007

Studies on the Chemistry of Isoindoles and Isoindolenines, XXXVII1) – Symmetrically Substituted 2‐Alkyl‐2H‐isoindoles

2‐Alkyl‐Rn‐2H‐isoindoles (1; Rn=4,5,6,7‐tetramethyl, 4,5,6,7‐tetrachloro) have been prepared efficiently by the N‐oxide route and characterized by spectroscopic means.
Cyclopentenyliden‐Komplexe aus Alkinylcarben‐Komplexen, Lithiumaryl und H+
Authors: Fischer Helmut , Meisner Thomas , Hofmann Josef
Published: July 2007

Cyclopentenylidene Complexes from Alkinylcarbene Complexes, Aryllithium and H+

[Alkoxy(phenylethynyl)carbene]pentacarbonyl complexes of chromium and tungsten, (CO)5M[C(CCPh)OR] (1) (M  Cr, W, R  Me, Et) react with Li[C6H4R′‐p] (R′  H, Me) and HBF4 ‐ Et2O to give the vinylcarbene complexes (CO)5‐M{C[CHC(Ph)C6H4R′‐p]OR} 2 and two isomeric cyclopentenylidene complexes 3 and 4. The cyclopentenylidene ligand is formed from two carbene ligands of 1, [C6H4R′‐p]− and H+. The structure of 4a (M  W, R  Et, R′  Me) is established by an X‐ray structure analysis. The product ratio strongly depends on the reaction conditions. The complex 3c (M  Cr, R  R′  Me) reacts with ethyl vinyl ether to give the 3,5‐bis(methylene)cyclopentene derivative 8 by metathesis.
Preparation of donor‐acceptor‐substituted vinylcyclobutanes
Authors: Gruseck Ursula , Heuschmann Manfred
Published: July 2007

2‐Methylen‐1,3‐dioxolane (1) and the methyl acrylates or crotonates 2 form [2+2] cycloadducts 3 which are reduced to give alcohols 6. Oxidation of these alcohols at low temperatures leads to unstable aldehydes 7, which either rearrange to dihydropyrans 5 or react with Wittig(‐Horner) reagents to afford donor‐acceptor‐substituted vinylcyclobutanes 8. The cis‐vinylcyclobutane 8g is prepared by [2+2] cycloaddition of dioxolane 1 and methyl (2E,4Z)‐hexadienoate (9). The configurations and preferred conformations of the vinylcyclobutanes 8 have unequivocally been assigned on the basis of 13C‐and 1H‐NMR spectra.
Vinylcyclobutane‐cyclohexane rearrangements: zwitterions as discrete intermediates
Authors: Gruseck Ursula , Heuschmann Manfred
Published: July 2007

Donor‐acceptor‐substituted vinylcyclobutanes 1 rearrange to cyclohexenes 2 at temperatures between 20 and 195°C. In solvents of low polarity, [2+2] cycloreversion competes with ring enlargement. Under acidic conditions, addition of nucleophiles to vinylcyclobutanes 1 with ring opening is observed. Stereospecificity of rearrangement and [2+2] cycloreversion are functions of temperature, solvent polarity and acid catalysis. Strong dependence on solvent polarity is found for the rates of both reactions. The mechanisms of the thermally induced and acid‐catalyzed reactions are discussed on the basis of stereospecificity, kinetic parameters and trapping of intermediates. Two structurally different zwitterions 13 and 14 are proposed as intermediates, one of which is responsible for rearrangement, the other for diastereomerization and [2+2] cycloreversion.
Röntgenstrukturanalyse des dimeren 2,2‐Diphenylcyclopropanthiocarbonsäure‐S‐tert‐butylester‐Lithium‐Enolat · TMEDA‐Komplexes: ein „ganz normales”︁ Ester‐Enolat und ein „ganz normales”︁ Methylencyclopropan‐Derivat
Authors: Hahn Ekkehardt , Maetzke Thomas , Plattner Dietmar A. , Seebach Dieter
Published: July 2007

X‐ray Crystal Structure of the Dimeric tert‐Butyl 2,2‐Diphenylcyclopropanecarbothioate Lithium Enolate · TMEDA Complex: an “Ordinary” Ester Enolate Containing an “Ordinary” Methylenecyclopropane Moiety

After many unsuccessful attempts we now succeded in growing a suitable crystal of a cyclopropanecarbothioate lithium enolate (title compound 11c) for X‐ray crystal structure analysis. 11c crystallizes as a tetramethylethylenediamine (TMEDA) complex in large cubes and contains hexane, is unstable above − 20°C and twinned. 11c is not C‐lithiated, but exhibits features normal for an ester lithium enolate: a double bond with planar trigonal centers, a methylene cyclopropane moiety with bond lengths and angles almost identical with those in corresponding hydrocarbons, a dimeric aggregation with an almost planar Li‐O‐Li‐O ring, with the large hydrocarbon units in a cis arrangement (Figure 1,2). A comparison with other lithiated cyclopropanes is made (Figure 3). The X‐ray crystal structure analysis shows 11c to form a channel structure in which n‐hexane is included. The structure described here is the first one of a thiocarboxylic acid S‐ester lithium enolate.
Unerwartete Diels‐Alder‐ und Oxidations‐Reaktionen von Benzo[c]thiophenen
Authors: Volz Wolfgang , Voß Jürgen , Adiwidjaja Gunadi
Published: July 2007

Unexpected Diels‐Alder and Oxidation Reactions of Benzo[c]thiophenes

The oxidation of thiophenes by peracids to form thiophene S‐oxides could not be carried out with benzo[c]thiophenes. With the sterically hindered compound 1a the quinones 2 and 3 were produced whereas the anisyl‐substituted derivative 1b formed the sulfine 5. Significantly different behaviour of 1a and 1b was also observed for the Diels‐Alder reaction with N‐phenylmaleimide. The unexpected and unusual adduct 6 was the only product formed from 1a, with low yield though, whereas the normal Diels‐Alder adduct was obtained from 1b.
Dimethyldioxirane epoxidation of β‐oxo enol ethers
Authors: Adam Waldemar , Hadjiarapoglou Lazaros
Published: July 2007

The synthesis of the epoxides 2a–f by epoxidation of the β‐oxo enol ethers 2,2‐dimethyl‐3(2H)‐furanone (1a), (Z)‐2(ethoxymethylene)cyclohexanone (1b), and 3‐alkoxy‐5,5‐dimethyl‐2‐cyclohexenones 1c–f with dimethyldioxirane is reported. These labile epoxides (stable below 0°C) were isolated and characterized spectroscopically (IR, 1H, and 13C NMR). Warming up to room temperature led to decomposition to afford complex product mixtures. When the epoxidation of 3‐ethoxy‐5,5‐dimethyl‐2‐cyclohexenone (1c) was conducted above 0°C, the epoxide 2c afforded the rearrangement product 3‐ethoxy‐2‐hydroxy‐5,5‐dimethyl‐2‐cyclohexenone (3).
Organobor‐Schwefel‐Verbindungen mit Bicyclo[x.3.0]alk‐3‐en‐Struktur — Herstellung und Charakterisierung
Authors: Köster Roland , Seidel Günter , Boese Roland
Published: July 2007

Organoboron‐Sulfur Compounds with Bicyclo[x.3.0]alk‐3‐ene Structure — Preparation and Characterisation

The compounds (R  CH3: I: R  C6H5: II) are prepared from (E)ClSi(CH3)2C(R3)C(C2H5)B(C2H5)Cl [R3  CH3; A; R3  C(CH3)CH2: B] with LISR. ‐ A and B react with LiS(CH2)nSLi (n = 2: Li2‐1; n = 3: Li2‐2 n = 4: Li2‐3) to form the bicyclic compounds R3)C(C2H5)B
Cyclopropan‐Derivate, 2. Selbst‐Acylierung der α‐Alkyl‐γ‐lactone zu Herstellung von Bis(1‐alkylcyclopropyl)ketonen über Spiro[4.4]acetale
Authors: Böhrer Gerald , Knorr Rudolf , Böhrer Petra
Published: July 2007

Cyclopropane Derivatives, 2. — Self‐Acylation of α‐Alkyl‐γ‐lactones To Give Bis(1‐alkylcyclopropyl)ketones via Spiro[4.4]acetals

High‐yield synthetic ways are recommended for the title lactones 1.The coupling of two 2‐alkyl‐4‐butanolides is possible in an inter‐(1b, c) or intramolecular fashion (4c) to give spiro[4.4] acetals 8 or 9 respectively, in the absence of hindering substituents. Symmetrically substituted bis(1‐alkylcyclopropyl)ketones 12 and 13 may be prepared by acidic cleavage of those spiro[4.4] acetals lacking 2,7‐substituent.
Cyclopropan‐Derivate, 3. (1‐Alkylcyclopropyl)ketone durch Acylierung von α‐substituierten γ‐Lactonen
Authors: Böhrer Gerald , Böhrer Petra , Knorr Rudolf
Published: July 2007

Cyclopropane Derivatives, 3. — (1‐Alkylcyclopropyl)ketones by Acylation of α‐Substituted γ‐Lactones

The 2‐acylation of 2‐substituted 4‐butanolides 2 is moderately sensitive to steric crowding, whereas the subsequent ring‐ opening of 2‐acyl‐2‐alkyl‐4‐butanolides 4, 11 to give‐chloro ketones 6, 12 by chloride‐transferring acid derivatives be‐comes difficult with bigger lactone substituents. Similar observations pertain to the preparation of y‐chlorobutanoyl chlorides 10 from 2‐alkyl‐4‐butanolides 2. The proper choice of the starting 4‐butanolides (2a, b or 14 but not 2c) provides for an indirect coupling of two different lactones to y,y‐dichloro ke‐tones 12. Dicyclopropyl ketones 13 with variable patterns of substitution may thus be prepared from 4‐butanolides in a direct manner with global yields exceeding 50% and without purification of intermediate products (except for acid chlorides like 10).
Beiträge zur Chemie der Halogensilan‐Addukte, 21. Darstellung, Eigenschaften, Kristall‐ und Molekülstruktur von Dichloro(1,10‐phenanthrolin)bis(trichlorsilyl)silicium, (SiCl3)2SiCl2 · phen
Authors: Kummer Dieter , Chaudhry Subhash C. , Depmeier Wulf , Mattern Günter
Published: July 2007

Contributions to the Chemistry of Halogenosilane Adducts, 21. — Preparation, Properties, Crystal and Molecular Structure of Dichloro(1,10‐phenanthroline)bis(trichlorosilyl)silicon, (SiCl3)2SiCl2 · phen

Si3Cl8 · phen (1) is obtained as a stable solid by the reaction of Si3Cl8 with phen. The structure of 1 in solution and its reactions correspond to that of Si3Cl8 · bipy reported earlier (1H‐NMR and IR studies). Rearrangement of 1 occurs in solution to give bis(silyl)‐substituted 1,2‐dihydrophenanthroline. From THF/C6H6 solution crystalline Si3Cl8 · phen · C6H6 (1a) is obtained. The X‐ray structure determination shows 1a to be monoclinic, space group P21/n (Z = 4). Phenanthroline is coordinated to the central silicon atom of the trisilane with its plane normal to the linear Si3 chain having two tetrahedral terminal SiCl3 groups. The coordination octahedron is regular.
Neuartige basische Liganden für die homogenkatalytische Methanolcarbonylierung, XXXVIII. Synthese, Eigenschaften und fluktuierendes Verhalten von (Ether‐Phosphan)palladium‐Komplexen
Authors: Lindner Ekkehard , Speidel Robert , Fawzi Riad , Hiller Wolfgang
Published: July 2007

Novel Basic Ligands for the Homogeneous Catalytic Carbonylation of Methanol, XXVIII. — Synthesis, Properties and Fluxional Behavior of (Ether‐Phosphine)palladium Complexes

Cl2Pd(COD) (1) (COD = 1,5‐cyclooctadiene) reacts with 1 equiv, of the (ether‐phosphine) ligand Ph2P∼D (2a–c) (D = CH2C4H7O (a), CH2C4H7O2 (b), CH2CH2OCH3 (c)] to give the dimeric complexes [μ‐ClPdCl(Ph2P∼D)]2 (3a–c) (P∼D = η1‐P‐coordinated). According to the field‐desorption mass spectra which show only one peak for the monomeric moieties ClPd(Ph2P∼D), 3a–c have a very weak Pd2Cl2 bridge. trans‐Cl2Pd(Ph2P∼D)2 (4a–c) is obtained either from 3a–c and 2a–c by cleaving the Pd2Cl2 bridge or from 1 and 2 equiv. of the ligands 2a–c. 4c crystallizes in the monoclinic space group P21/c with Z = 2. AgClO4 selectively abstracts one Cl⊖ ligand from 4a–c which results in the formation of the cationic complexes [trans‐(Ph2P∩D)(Ph2P∼D)PdCl]⊕ (5a–c) (P∩D = η2‐D,P‐coordinated) containing one chelated and one η11‐P‐bonded (ether‐phosphine) ligand. 5a–c show fluxional behavior which is demonstrated by temperature‐dependent 31P{1H}‐NMR investigations. The coalescence points have been determined and are at 253 (5a), 303 (5b), and 283 K (5c). The activation enthalpies ΔG‡ are estimated at 48, 58, and 54 kJ/mol. The abstraction of the second Cl⊖ ligand from 5a–c succeeds only in the presence of AgSbF6 yielding the dicationic bis(chelate) complexes [trans‐(Ph2P∩D)2Pd]2⊕ (6a–c). The latter are also obtained from 4a–c) and AgSbF6. The hydrogenating properties of 3a–c and 4a–c toward 1‐hexyne are investigated in comparison with trans‐Cl2Pd(Ph2P‐CH2CH2CH3)2.
Cyclic dinuclear gold(I) complexes: The crystal structure of bis‐μ‐[(diphenylphosphino)(diphenylphosphinoselenoyl)methane]‐digold(I) bis(perchlorate)
Authors: Schmidbaur Hubert , Eschenbach Jennifer Ebner Von , Kumberger Otto , Müller Gerhard
Published: July 2007

[(CO)AuCl] reacts with equimolar amounts of Ph2PCH2P(Se)Ph2 (dpmSe) to afford ClAuPh2PCH2P(Se)Ph2, in which dpmSe is bound to gold in a monodentate fashion by phosphorus. Subsequent reaction of this 1:1 complex with AgClO4 results in the formation of the 10‐membered ring complex 4 which crystallizes in the monoclinic space group P21/n with approximately centrosymmetric dicationic units, in which two gold (I) atoms are doubly bridged by two dpmSe ligands coordinated by phosphorus and selenium. The coordination at the gold atoms deviates from linearity and implies an Au···Au interaction with the gold(I) atoms separated by a distance of 3.020(1) Å.
Isomere Aminoborane und Amin‐Borane mitcis‐BC  CSi‐Gruppierung — Herstellung und Charakterisierung
Authors: Könter Roland , Seidel Günter , Wrackmeyer Bernd
Published: July 2007

Isomeric Aminoboranes and Amine‐Boranes with cis‐BC  CSi Groupings — Preparation and Characterisation

The reaction of the heterocycles ) [R3  CH3: A; R3  C(CH3): CH2: B] with the prim.‐aminohydroxyalkanes H2NROH [R  CH2CH2: 1; CH(C2H5)CH2: rac‐2, R‐2,; [CH2]3 : 3;  [CH2]4 : 4], the prim‐aminophenols H2NC6H4OH [ortho; 5; meta: 6], and the sec.‐aminohydroxyalkanes HN(CH3)  ROH [R  [CH2]2: 7; (R,S)‐CH(CH3)CH(C6H5) : 8; (S,S)‐CH(CH)3)CH(C6H5): 9] leads to elimination of CH3NH2 with formation of the compounds 11a, b, 12–15 and 17–19 as monocyclic aminoboranes B(C2H5) (R1  H, CH3; R3  CH3) and iso‐11a,b, iso‐12‐iso‐15 as bicyclic amine‐boranes . The isomeric compounds 11a and iso‐11a are transformed into one another by crystallisation and by dissolution or distillation, resp. A reacts with the tert.‐aminoethanol (CH3)2NCH2CH2OH (10) to give the acyclic compound (CH3)2N(CH2)2OSi(CH3)2C(CH3  C(C2H5)B(C2H5)O(CH2)2‐N(CH3)2 (20). Further reactions of A with the NH2 compounds HN(CH3)[CH2]2NH2 (21), CH3C(O)NH2, and NCNH2 to the compounds E, 23, and 24, resp., are described. — The compounds (i1) and cis‐HC(C2H5)  C(CH3)Si(CH3)2ORNH2 (i2) are formed as side products by BC(vinyl) fission.
Ein Weg zu neuartigen funktionalisierten Bis(imino)phosphoranen XP( NAryl)NAlkyl
Authors: Niecke Edgar , von der Gönna Volker , Nieger Martin
Published: July 2007

A Route to Novel Functionalized Bis(imino)phosphoranes XP(NAryl)NAlkyl

Chloro(arylimino)phosphane (1) reacts with alkyl azides RN3 (R  tBu, Et3C, 1‐Ad) to form 4,5‐dihydro‐1H‐tetrazaphos‐pholes 2a‐c. The thermal decomposition of these compounds results in the formation of the diazadiphosphetidines 4a–c via the chlorobis(imino)phosphorane intermediates 3a–c, which were detected by NMR spectroscopy. By treating 2a with the lithium salts Li(nBu, C5Me5, NHAryl, OAryl, tBuS) the 4,5‐dihydro‐1H‐tetrazaphosphole intermediates 5a–d are obtained, which by elimination of nitrogen form the bis(imino)phosphoranes 6a–e. The X‐ray structure determination of the phosphane derivative tBu2PP(NCEt3) NAryl (7), obtained by the same procedure, is discussed.
Stereoselective synthesis of alcohols, XXXV. Addition of E‐ and Z‐crotylboronates to chiral α‐substituted aldehydes
Authors: Brinkmann Heinrich , Hoffmann Reinhard W.
Published: July 2007

The direction (Cram/anti‐Cram) and the extent of asymmetric induction on addition of crotylboronates to a range of chiral aldehydes was investigated. A reversal in the sense of the asymmetric induction on changing from the Z‐ to the E‐crotylboronate was found for aldehydes having polar α substituents and for some of the nonpolar chiral aldehydes. Forcefield calculations on transition‐state models reproduced these results in the majority of the cases investigated despite of unaccounted short comings of the method.
(2R)‐5‐Alkyl‐2‐tert‐butyl‐6‐methyl‐4H ‐1,3‐dioxin‐4‐one als Zwischenprodukte zur Herstellung von α,β,β‐trisubstituierten β‐Hydroxycarbonsäuren unter Selbstregeneration des stereogenen Zentrums von (R)‐3‐Hydroxybuttersäure
Authors: Amberg Willi , Seebach Dieter
Published: July 2007

(2R)‐5‐Alkyl‐2‐tert‐butyl‐6‐methyl‐4H‐1,3‐dioxin‐4‐ones as Intermediates for the Preparation of α,β,β‐Trisubstituted β‐Hydroxycarboxylic Acids from (R)‐3‐Hydroxybutyric Acid under Self‐Regeneration of the Stereogenic Center

The exocyclic double bonds of the readily available (2R,6R)‐5‐alkylidene‐2‐tert ‐butyl‐6‐methyl‐1,3‐dioxan‐4‐ones (preceding paper) are shifted to the endocyclic position by treatment with Pd‐C/H2 to give the dioxins 2 ‐ 6 in overall yields of 40‐ 60% (calcd. from the parent tert‐butyl‐methyl‐dioxanone, 4 steps). F3B ‐ OEt2‐mediated Me‐, Bu‐ and Ph‐cuprate additions to the tetrasubstituted double bonds of these dioxinones can be used to prepare the 2‐tert‐butyl‐5,6,6‐trialkyl‐1,3‐dioxanones 7 ‐ 15 (40‐65% yield, 5: 1 to 16: 1 diastereoselectivity) as single isomers. Hydrolysis leads to 5,6,6‐trialkyl hydroxy acids (for instance 16‐18) specified in the title; formally, these compounds are aldol‐type adducts of carboxylic acids to unsymmetrical ketones. — The configurational assignment rests upon NOE measurements and, in one case, upon a chemical correlation. The stereochemical course of the conjugate addition and of the Li enolate protonations, which are responsible for the selective formation of the two new stereogenic centers, is discussed.
[1.1.1]Propellane and maleic anhydride: Face‐specific copolymerization with formation of an alternating 1:1 copolymer
Authors: Gosau Jan‐Michael , Schlüter Arnulf‐Dieter
Published: July 2007

The spontaneous and face‐specific copolymerization of [l.l.l]propellane and maleic anhydride to give the strictly alternating 1:1 copolymer 2 is described. The molecular weight of 2 after transformation into the corresponding diester 5c was determined to be 80.000 (Mn) and 220.000 (Mw), respectively.
Übergangsmetall‐Silyl‐Komplexe, 36 Zur Frage von Gold‐Gold‐Wechselwirkungen bei Ph2P[CH2]1(2) PPh2 verbrückten zweikernigen Gold‐Silyl‐Komplexen
Authors: Piana Hermann , Wagner Herbert , Schubert Ulrich
Published: July 2007

Transition‐Metal Silyl Complexes, 361). — On the Question of Gold‐Gold Interactions in Ph2P[CH2]t(2)PPh2‐Bridged Dinuclear Gold Silyl Complexes

Dinuclear silyl gold complexes of the type dppm(AuSiR3)2 (1) or dppe(AuSiR3)2 (2) are prepared by the reaction of dppm‐(AuCl)2 or dppe(AuCl)2 with two equivalents of LiSi(aryl)3 or LiSi(SiMe3)3 The complex dppe[AuSi(SiMe3)3]2 (2 c) exhibits crystallographic inversion symmetry, and therefore the distance between both gold atoms is a maximum. In dppm‐(AuSiPh3)2 (1b) a gold‐gold interaction between both gold atoms is observed [Au — Au 316.80(3) pm].
Beiträge zur Chemie des Phosphors, 2101,2) Pentaorganyltricyclononaphosphane mit Brexan‐Struktur, b‐P9R5 (R = Me, Et, iPr)
Authors: Baudler Marianne , Arndt Volker
Published: July 2007

Contributions to the Chemistry of Phosphorus, 2101.2). – Pentaorganyltricyclononaphosphanes with a Structure Analogous to Brexane, b‐P9R5 (R = Me, Et, iPr)

The reaction of RPCl2, P4, and magnesium provides two constitutionally isomeric pentaorganyltricyclononaphosphanes. Besides the isomer with a P9 skeleton analogous to that of noradamantane (a‐P9R5), which was already identified, a further isomer of lower relative abundance (b‐P9R5) has now been found. In the case of R = Et (2) it has been isolated as a pale yellow, oily liquid and, in the cases of R = Me (1) and iPr (3), has been highly enriched. According to their 31P{1H}‐NMR spectra, 1 — 3 have a constitution analogous to that of the hydrocarbon brexane, thus being 2,4,5,8,9‐pentaorganyltricyclo[4.3.0.03.7]nonaphosphanes. They are each formed as mixtures of several configurational isomers, which differ in their relative arrangements of the organyl groups.
Asterane, XXII. Synthese eines doppelten Tetraasterans: Nonacyclo[10.8.0.02,11.04,9.04,19.06,17.07,16.09,14.014,19]eicosan
Authors: Hoffmann Volker Thomas , Musso Hans
Published: July 2007

Asteranes, XXII1). — Synthesis of a Double Tetraasterane: Nonacyclo[10.8.0.02,11.04,9.04,19.06,17.07,16.09,14.014,19]eicosane

1,4,5,8‐Tetrahydronaphthalene‐2,3‐dicarboxylic anhydride (9) is dimerized by UV light in dioxane yielding four isomeric [2 + 2] adducts whose methyl ester derivatives are elucidated spectroscopically. The structures of the major products 14 and 16 have been confirmed by X‐ray structure analysis. Degradation of the carboxylic groups of 14 afforded the title compound 5.
Synthesis of 4‐Aminopyrimidines from 1,2,4‐Oxadiazoles, III A Novel Type of Formation of Olefins from Amines
Authors: Korbonits Dezsö , Simon Kálmán , Kolonits Pál
Published: July 2007

On heating at 100°C, 1,2,3,4‐tetrahydro‐6,7‐dialkoxy‐1‐[(acylamidino)methylene]isoquinolines (5) are transformed into 4‐substituted 6,7‐dihydro‐9,10‐dialkoxy‐2H‐pyrimido[6,1‐α]isoquinoline‐2‐imines (6), while at 140°C they undergo a novel prototropic rearrangement via 6 to give 4‐amino‐6‐(4,5‐dialkoxy‐2‐vinylphenyl)‐2‐phenylpyrimidines (7). The structure of 7a has been determined by X‐ray analysis.
Cyclobuten‐Ringöffnung: Eine nützliche Reaktion zur Synthese doppelsträngiger Moleküle
Authors: Godt Adelheid , Schlüter Arnulf‐Dieter
Published: July 2007

Cyclobutene Ring Opening: A Useful Reaction for the Synthesis of Double‐Stranded Molecules

Syntheses and ring‐opening reactions of the compounds endo‐5a – e and 9a – c, all containing cyclobutene rings, are described. From these experiments it is concluded that compound 9a is a useful AB‐type Diels‐Alder monomer for the synthesis of well‐defined double‐stranded molecules. The stereochemistry of the adducts endo‐4b and endo‐5d is determined by X‐ray structure analysis.
Darstellung aromatischer Fluor‐Verbindungen durch nucleophilen Austausch von Nitro‐Gruppen gegen Fluorid
Authors: Effenberger Franz , Streicher Willi
Published: July 2007

Synthesis of Aromatic Fluoro Compounds by Nucleophilic Exchange of Nitro Groups by Fluoride

The synthesis of aromatic fluoro compounds from the respective nitro compounds by nucleophilic substitution of nitrite by fluoride is described. Reasonable yields in case of nonactivated nitro compounds are only obtained if the nitrite formed in the reaction is eliminated by acylation. 1‐Fluoro‐3‐nitrobenzene (2) was obtained from 1,3‐dinitrobenzene (1), and 1‐fluoro‐3,5‐dinitrobenzene (9) as well as 1,3‐difluoro‐5‐nitrobenzene (10) from 1,3,5‐trinitrobenzene (8) in yields up to 92% by reaction of nitro compounds with potassium fluoride in sulfolane at 180 – 200°C in the presence of phthaloyl dichloride (6); 1,2‐difluoro‐4‐nitrobenzene (12) was formed in 58% yield from 2,4‐dinitro‐1‐fluorobenzene (11) in the presence of pyromellitoyl tetrachloride (13).
Neutralization‐Reionization Mass Spectrometry and Matrix Isolation of Some 9‐Silaanthracenes
Authors: Winkel Yvar Van Den , Van Baar Ben L. M. , Bickelhaupt Friedrich , Kulik Willem , Sierakowski Claudia , Maier Günther
Published: July 2007

Neutralization‐reionization mass spectrometry of silaanthracene radical cations, which are generated from the 9,10‐dihydro‐9‐silaanthracenes 1, 3, 8 and 11 under electron‐impact conditions, indicates that silaanthracenes are stable molecues in the gas phase. Flash pyrolysis of the starting compounds mentioned above also yields the silaanthracenes 2, 4, and 10, which may be isolated in an argon matrix at 15 K and exhibit characteristic UV spectra.
Organische Synthesen mit Übergangsmetall‐Komplexen, 50 2H‐Pyrrol‐Komplexe durch stufenweise Insertion von Alkinen und Isocyaniden in MC‐Bindungen von Chrom‐ und Wolfram‐Carbenkomplexen
Authors: Aumann Rudolf , Hinterding Peter
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 501). – 2H‐Pyrrole Complexes by a Stepwise Insertion of Alkynes and Isocyanides into MC Bonds of Carbene Chromium or Tungsten Complexes

2H‐Pyrrole complexes 6a, b are obtained in two step by [1+2+2] cycloaddition reactions of the carbene complex (CO)5WC(OEt)C6H5 (1d), the alkyne EtO‐CCH (2) and isocyanides R1‐NC 4a, b [R1 = CH3, c‐C6H11). LnC(OEt)R 1 [LnM = Cr(CO)5, W(CO)5; R = C6H5, CH3] reacts with 2 to give 1‐metalla‐1,3‐dienes 3a–d. (E)/(Z)‐3d and 4 yield 6a, b via 1‐aza‐1,2,4‐pentatriene complexes 5, which are open‐chain precursors of 6. 2H‐Pyrrole complexes 11 and 14 are synthesized in overall [2+1+2] cycloadditions withe reversed connectivity, or formation of 1‐chroma‐1,3‐dienes 10 and 13 by condensation of the methylcarbene complex 1a with acid amides, and cyclisation again with isocyanides 4.
Umlagerungen von 1,4,4‐ und 2,2,5‐Trimethylbicyclo[3.2.1]oct‐6‐yl‐Kationen
Authors: Kirmse Wolfgang , Mönch Dietmar
Published: July 2007

Rearrangements of 1,4,4‐ and 2,2,5‐Trimethylbicyclo[3.2.1]oct‐6‐yl Cations

1,4,4‐Trimethylbicyclo[3.2.1]oct‐6‐yl cations (18) are generated from the tosylhydrazone 7, by nitrous acid deamination of the amines 6 and 8, and by acetolysis of the brosylates 21 and 24. The product distributions are but slightly affected by the configuration (exo vs. endo) of the leaving groups. The predominant product, 1,4,4‐trimethylbicyclo[3.2.1]octan‐exo‐6‐ol (11) is formed without significant redistribution of a 6‐2H label. The degenerate Wagner‐Meerwein rearrangement of the parent bicyclo[3.2.1]oct‐6‐yl cation is virtually eliminated by the presence of two methyl groups at C‐4. Enhanced conformational strain, raising the barrier to ring flipping, accounts for these observations. Minor products (12, 13) arise from a 7,6‐hydride shift of 18, followed by Wagner‐Meerwein rearrangement. When the 2,2,5‐trimethylbicyclo[3.2.1]oct‐6‐yl cation (19) is generated directly from the tosylhydrazone 17, the tertiary alcohol 13 is obtained as the major product. The conformational barrier to Wagner‐Meerwein rearrangement is compensated by the incipient stabilization of the tertiary carbocation 20.
Umlagerungen von 5,5,6,6‐Tetraalkyl‐2‐norbornyl‐Kationen
Authors: Kirmse Wolfgang , Mrotzeck Uwe , Siegfried Rainer
Published: July 2007

Rearrangements of 5,5,6,6‐Tetraalkyl‐2‐norbornyl Cations

When the 6,6‐dimethyl‐2‐norbornyl cation (9) is generated from the tosylhydrazone 5 by way of the diazonium ion 8, a 2H label is distributed equally between positions 1 and 2 of the exo‐alcohol 10. The degeneracy of 9, previously derived from solvolytic studies, is thus confirmed for the deaminative route. 5,5,6,6‐Tetramethyl‐2‐norbornanone (25) and tetracyclo[4.2.2.12,5.01,6]undecan‐3‐one (31) are prepared by using Diels‐Alder methodology. The corresponding tosylhydrazones 26 and 32 are employed as precursors for the 5,5,6,6‐tetramethyl‐2‐norbornyl and tetracyclo[4.2.2.12,5.01,6]undec‐3‐yl cations (11 and 12). Again, the distributions of 2H labels are close to 1 : 1. The angular distortions expected from repulsive interactions of the methyl groups in 11 and from cyclobutane annulation in 12 do not affect the relative energies of the bridged ions.
Zum Koordinationsverhalten von Alkinylphosphanen RnP(CC–R')3–n
Authors: Lang Heinrich , Zsolnai Laszlo
Published: July 2007

Coordination Ability of Alkynylphosphines RnP(CC – R')3 – n

Alkynylphosphines RP(CC–R')2 (2) react with one equivalent of octacarbonyldicobalt to yield selectively the η2‐μ side‐on‐coordinated alkyne complexes (R)(R' – CC)P[(η2‐CC–R')Co2(CO)6] (6); with another equivalent of Co2(CO)8 the dicoordinated compounds (R)P[(η2‐CC–R')Co2(CO)6]2 (7) are obtained. 7 may also be synthesized directly by the reaction of 2 with two equivalents of Co2(CO)8. However, P(CC–Ph)3 yields with two equivalents of Co2(CO)8 the cyclic Co2P2C2 system {(Ph–CC)(R')P[(η2‐CC–Ph)Co2(CO)5]} 2 (4) [R' = (η2‐CC–Ph)Co2(CO)6]. Decarbonylation of 6a gives the six‐membered cyclic compound {(Ph)(Ph – C  C)P[(η2‐C  C – Ph)Co2(CO)5]}2 (8), while 6b yields the cluster Co3(CO)9(μ3‐PtBu) (9). The structure of (tBu)P[(η2‐C  C – H)Co2)CO)6]2 (7b) is elucidated by an X‐ray analysis.
Cycloadditionsreaktionen von Organometallkomplexen, XII1) Ketenimine aus Isocyaniden und Diazoalkanen: Eine neue Cobalt‐vermittelte C–C‐Verknüpfungsreaktion
Authors: Strecker Beate , Hörlin Gerhard , Schulz Michael , Werner Helmut
Published: July 2007

Cycloaddition Reactions of Organometallic Complexes, XII1). – Ketenimines from Isocyanides and Diazoalkanes: A New Cobalt‐Assisted C–C Bond Forming Reaction

The compounds C5H5Co(CNR)(PMe3) (1–3) react with diaryl‐diazomethanes (X)(Y)CN2 to give the C,C‐bound ketenimine cobalt complexes C5H5Co[η2‐C,C‐RNCCXY] (PMe3) (4–9), while the reaction of 1–3 with 9‐diazofluorene leads to the formation of N,C‐bound ketenimine complexes C5H5Co[η2‐N,C‐RNCC(C12H8)](PMe3) (11–13). The different bonding modes of the ketenimine ligands in 4–9 and 11–13, indicated already by the significantly different spectroscopic data, are shown by the X‐ray structural analysis of 9‐RCoSC (R = CHMePh; X and Y = 4‐ClC6H4) and 12 (R = C6H11). On treatment of compounds 4, 6–9, 11, and 13 with an equimolar amount of iodine, free ketenimines are generated. The by‐product C5H5Co(PMe3)I2 can be transformed into the starting materials 1–3 in two steps via the cations [C5H5Co(CNR)‐(PMe3)I]+ as intermediates.
Metallatome in der Synthese von Metallclustern, II1) Reaktionen von substituierten Cyclopentadienen und Nickelocen mit Nickel‐ und Eisenatomen
Authors: Schneider JöRg J. , Goddard Richard , Krüger Carl , Werner Stefen , Metz Bernkard
Published: July 2007

Metal Atoms in the Synthesis of Metal Clusters, II1). – Reactions of Substituted Cyclopentadienes and Nickelocene with Nickel and Iron Atoms

By vaporizing nickel atoms into solutions of tert‐butyl‐substituted cyclopentadienes in methylcyclohexane mononuclear sandwich compounds (1, 4, and 6 as main products) as well as tri‐ and tetranuclear clusters are prepared. With mono‐ and di‐tert‐butyl‐substituted cyclopentadienes as ligands the new clusters 2 and 5 are obtained. In the reaction with 1,2,4‐tri‐tert‐butylcyclopentadiene 6 is the only observed product. Hindered rotation around the metal‐ligand bond vector is observed for 4 even at room temperature. When treating 1 with nickel atoms cluster 2 is formed, indicating some importance of 1 during the formation of 2 in the above reaction. Clusters 2 and 5 contain hydrido ligands, which could be identified in the case of tris(1,3‐di‐tert‐butyl‐η5‐cyclopentadienyl)trinickel dihydride (5) by a single crystal structure determination as μ3‐H bridges. A tetrahedral structure is found for the cluster 2 by X‐ray crystallography. With the aid of MS, IR, magnetic measurements, and cyclovoltammetric investigations 2 is identified as a mixture of 2a and 2b bearing one or three bridging hydrogens, respectively. In general 2a, 2b, and 5 show a rich redox chemistry with reversible redox couples between –2 and +2. Reaction of iron atoms, nickelocene, and mesitylene in methylcyclohexane at −120°C leads unexpectedly to cluster 3, tetrakis(η5‐cyclopentadienyl)tetranickel trihydride and a not yet identified (η5‐cyclopentadienyl)mesityleneiron complex. Possible formation routes for 1–6 are discussed.
Photocycloadditionen mit α‐ und β‐Naphthaldehyd: Vollständige Umkehr der Diastereoselektivität als Konsequenz unterschiedlich konfigurierter elektronischer Zustände
Authors: Griesbeck Axel G. , Mauder Harald , Peters Karl , Peters Eva‐Maria , Schnering Hans Georg Von
Published: July 2007

Photocycloadditions with α‐ and β‐Naphthaldehyde: Complete Inversion of Diastereoselectivity as a Consequence of Differently Configurated Electronic States

The diastereoselectivity of the [2 + 2] photocycloaddition reaction between aromatic aldehydes and 2,3‐dihydrofuran (3) is completely inverted when changing the electronic configuration of the excited triplet from 3(nη*) to 3(nπ*). Mesitylenaldehyde, which corresponds to the first case, reacts endo‐ selectively, whereas α‐ and β‐naphthaldehyde (with low‐lying ππ* triplets and reactive nπ* singlets) react exo‐selectively. The configuration of the α‐naphthaldehyde adduct is proven by means of X‐ray structure analysis. This type of spin‐correlation effect can be rationalized by comparing the conformation of the reactive biradical intermediates for rapid inter‐system crossing and/or bond closure. In the furan (1) case, this effect cannot be observed. All carbonyl compounds investigated here react exo‐selectively. A possible explanation for this pronounced selectivity is the assumption of a secondary orbital effect.