bluuebunny/crossref_metadata_2025 huggingface dataset:
Regio‐ und stereoselektive Photocycloadditionen aromatischer Aldehyde an Furan und 2,3‐Dihydrofuran
Authors: Griesbeck Axel G. , Stadtmüller Stefan
Published: July 2007

Regio‐ and Stereoselective Photocycloaddition Reactions of Aromatic Aldehydes to Furan and 2.3‐Dihydrofuran

The Paterno‐Büchi reaction between benzaldehyde (1a), tolualdehyde (1b), mesitylaldehyde (1c), and 2,4‐di‐tert‐butyl‐4‐methylbenzaldehyde (1d) and the electron‐rich alkenes furan and 2,3‐dihydrofuran has been investigated. The reaction with furan leads exclusively to exo‐6‐aryl‐2,7‐dioxabicyclo[3.2.0]‐hept‐3‐enes 2a to 2d in yields of 78% to 97% (2a, 2b). In the photoreaction of 2a and 2b with 2,3‐dihydrofuran, however, mixtures of exo‐ and endo‐7‐aryl‐2,6‐dioxabicyclo[3.2.0]heptanes 3a and 4a (7:1) as well as 3b and 4b (15:1) could be isolated. The sterically more hindered aldehydes 1c and 1d give rise to exclusive formation of the endo adducts 3c and 3d. Irradiation of 1d in the presence of 2,3‐dihydrofuran leads to the benzocyclobutenol 5 (Norrish‐type II; up to 45%) as a side product. The regioselectivity observed in these reactions may be explained by comparing the stability of the possible 1,4‐diradical intermediates. The observed stereoselectivity could be rationalized by the geometry of the triplet 1,4‐diradicals during the ISC process and by the life times of the resulting singlet 1,4‐diradicals.
1,1′‐Bis(diphenylphosphino)bicyclopropyl: Synthesis, Properties, Precursors, Derivatives, and Metal Complexes
Authors: Dziwok Klaus , Lachmann Joachim , Wilkinson Dallas L. , Müller Gerhard , Schmidbaur Hubert
Published: July 2007

The title compound 4 has been prepared from readily available 2,3‐bis(diphenylphosphinyl)‐1,3‐butadiene (1) through double cyclopropanation using Me2S(CH2)O to give 1,1′‐bis(diphenylphosphinyl)bicyclopropyl (2), followed by reduction using HSiCl3/NEt3. Addition of sulfur to compound 4 yields the disulfide 5, and reaction with tetrahydrofuran – borane affords the 1:2 adduct with BH3 (6). Quaternization reactions with MeI or CH2I2 give the double quaternary salts 7 and 8, respectively. Single dehydrohalogenation employing nBuLi converts 8 into the cyclic semiylide salt 9. 4 is an excellent ligand for lowvalent late transition‐metal cations. With PdI2 the 1:1 complex LPdI2 (10, with L = 4), and with [(CO)2RhCl]2 the ionic 2:1 complex L2Rh+Cl‐ (11) are obtained. Experiments with (CO)AuCl yield the 1:2 complex L(AuCl)2 (12), X‐ray structure analyses were performed with single crystals of the disulfide 5, as well as the rhodium(I) and gold(I) complexes 11 and 12. 5 has a conformation between s‐cis and s‐trans with the PS functions pointing away from each other at opposite ends of the molecule. By contrast, in the gold(I) complex the ligand approaches an s‐cis conformation, and through rotations about P–C and C–C bonds – as referred to the conformation of 5 – the metal atoms are brought into close contact: Au…Au = 3.085 Å. Through temperature‐dependent NMR investigations of compounds 5 and 12, and by comparison with values calculated or experimentally determined for related bicyclopropyl compounds (available in the literature), the energy of the Au…Au attraction has been estimated to be ca. 6 kcal/mol. Compound 11 features a square‐planar, double‐chelate cation.
Synthesis, Reactions, and Tautomerism of Ketene N,S‐Acetals with Benzothiazoline Ring
Authors: Huang Zhi‐Tang , Shi Xian
Published: July 2007

Ketene dithioacetals 2 react with 2‐aminothiophenol to afford the corresponding substituted 2(3H)‐methylenebenzothiazoles 3. Some compounds 3 react with α,β‐unsaturated esters to give 1H‐pyrido[2,1‐b]benzothiazole derivatives 4 and 5 by an electrophilic addition and cyclocondensation sequence.
Concave Reagents, 5 Bimacrocyclic 1,10‐Phenanthroline Cyclophanes
Authors: Lüning Ulrich , Müller Michael
Published: July 2007

The addition of lithium aryls 3 to 1,10‐phenanthroline (2), functionalization of the rearomatized bisadduct 8b to the tetraphenol 8d, and cyclization of 8d with two equivalents of an α,ω‐ditosylate 9 led to a highly symmetrical, conformer‐free bimacrocyclic 1,10‐phenanthroline 10a in which the basic and coordinating region possesses a concave shielding.
Silicium‐Verbindungen mit starken intramolekularen sterischen Wechselwirkungen, 391) Ein spirocyclisches Silan aus einem 2,2‐Dimesityldisilan
Authors: Weidenbruch Manfred , Pan Youlin , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Silicon Compounds with Strong Intramolecular Steric Interactions, 39. – A Spirocyclic Silane from a 2.2‐Dimesityldisilane

Treatment of 1,1‐Di‐tert‐butyl‐1,2‐dichloro‐2,2‐dimesityldisilane (3) with lithium tert‐butylamide gives the spirocyclic silane 5 by a twofold intramolecular ring formation reaction. The X‐ray structure analysis of 5 reveals strong deviations from the idealized tetrahedral geometry at the spirocyclic silicon atom.
Pentamakrocyclische Tris‐Kronen. – Selektive Bindung von Kationen, Anionen und Neutralverbindungen
Authors: Wallon Alexander , Werner Ute , Müller Walter M. , Vögtle Fritz , Nieger Martin
Published: July 2007

Pentamacrocyclic Tris‐Crown Hosts. – Selective Binding of Cationic, Anionic, and Neutral Guest Compounds

The tris‐crown host compounds 1–4 were synthesized for the first time. The X‐ray crystal structures of 2 and of the 1:3 complex of 1 and KSCN were determined. Whereas in the free crown 2 a less well preorganized molecular cavity is encountered, in the complex of 1 with KSCN one potassium ion is bound to each crown ether unit. One of the three SCN− anions is situated in the interior of the cavity and in addition is disordered in such a way as to be bound to the K+ using partially the S atom of the SCN− ion. Organic guest molecules like 1,2‐, 1,3‐, 1,5‐, 2,6‐, and 2,7‐naphthalenediol as well as β‐naphthol in acidic water solution are bound selectively in the interior of the cavities of the host molecules 2 and 3, but not by 1 and 4, the cavities of which seem to be too small and too large, respectively. In contrast, the binding of α‐naphthol and of smaller phenolic guest molecules like phenol, resorcinol, pyrocatechol, phloroglucinol, pyrogallol, and 1,2,4‐trihydroxy‐benzene with the host 1–4 is much less pronounced (1H‐ NMR highfield shifts).
syn/anti‐Configurational Assignment of sec‐Butalcarbinols Based on 13C‐NMR Spectra
Authors: Hildebrandt Bernhard , Brinkmann Heinrich , Hoffmann Reinhard W.
Published: July 2007

syn or anti configuration1) can be assigned to hte diastereomers of the sec‐butylcarbinols 3 by analysis of diagnostic differences in the 13C‐NMR spectra. Likewise, the 13C‐NMR shifts of the diastereotopic methyl groups in isopropylacarbinols of type 19 have been assigned.
Beiträge zur Chemie der Halogensilan‐Addukte, 20. Hexakoordinierte Verbindungen von Trichlorsilanen. – Darstellung, Kristall‐und Molekülstruktur von RSiCl3·bipy
Authors: Kummer Dieter , Chaudhry Subhash C. , Debaerdemaeker Tony , Thewalt Ulrich
Published: July 2007

Hexacoordinated Compounds of Trichlorosilanes. – Preparation, Crystal and Molecular Structure of BSiCl3·bipy

The octahedral Si complexes CHCl2SiCl3·bipy (1), CCl3SiCl3·bipy (2), and Cl3SiCCl2SiCl3·bipy (3) are obtained by the reaction of the respective trichlorosilanes and 2.2′‐bipyridine (bipy). Their composition is independent of the initial ratio of the components. X‐ray structure determinations show the Si atoms of all three complexes to be octahedrally coordinated with the substituted methyl groups in axial positions. The configurations represent structures of least steric hindrance assuming spheric substituents and demonstrate the usefulness of this structural model for solid compounds (in contrast possibly to dissolved compounds) even for substitutents deviating strongly from this assumption. Bond lengths and angles agree with the presence of hexacoordinated complexes. Deviations from expected values are interpreted in terms of considerable steric interactions. 3 represents a case of strongly hindered coordination requiring interesting steric adjustments.
Lineare Oligophosphaalkane, XXV. Synthese von Ph2PCH2PH2 und (ph2PCH2)2PH durch Phosphinomethylierung von PH3 unter Phasentransferkatalyse
Authors: Langhans Klaus‐Peter , Stelzer Othmar , Weferling Norbert
Published: July 2007

Linear Oligophosphaalkanes, XXV1. – Synthesis of Ph2PCH2PH2 and (Ph2PCH2)2PH by Phosphinomethylation of PH3 with Phase‐Transfer Catalysis

Alkylation of Ph2PH with CH2Cl2 under phase‐transfer conditions in the system dichloromethane/toluene/water affords Ph2P‐CH2Cl in high yields. Depending on the reaction conditions employed Ph2P‐CH2Cl reacts with PH3 in the two phase system under phase‐transfer catalysis (nBu4NCl) to yield the tertiary‐primary methylenebis(phosphane) Ph2P‐CH2‐Ph2 (2) or the PH functional triphosphaalkane Ph2P‐CH2‐PH‐CH2‐PPh2 (3), respectively. Metallation of 2 and 3 with RLi (R = nBu, tBu) and subsequent reaction with Me3siCl yields the silyl derivatives 2e and 3b, respectively. The analysis of the 1H‐ 13C‐ and 31P‐NMR spectra is reported.
Reaktive EC(p‐p)π‐Systeme, XXIII. Unerwartete Isomerisierung des Perfluorisopropylidenphosphans F3CPC(CF3)2 zum Perfluorisopropenylphosphan F3CPF(F3C)CCF2
Authors: Grobe Joseph , Van Due Le
Published: July 2007

Reactive E = C(p‐p)x‐Systems, XXIII. – Unexpected Isomerization of Perfluoroisopropylidenephosphane F3CP = C(CF3)2 to the Perfluoroisopropenylphosphane F3CPF(F3C)C = CF3

Elimination of Me3SnF from the stannylphosphane Me3Sn(F3C)PCF(CF3)2 (2) by gas‐phase pyrolysis at 220°C surprisingly yields the isopropenyl phosphane F3CPFC(CF3)=CF2 (5) instead of the expected isopropylidene derivative F3CP=C(CF3)2 (4). In a similar manner, HF elimination from the phosphane HP(CF3)CF(CF3)2 (3) by passing its vapour over KOH pellets leads to 5. The formation of 5 is due to a spontaneous isomerization of the labile intermediate 4.
π‐Complexes of p‐Block Elements: Synthesis and Structures of Adducts of Arsenic and Antimony Halides with Alkylated Benzenes
Authors: Schmidbaur Hubert , Nowak Reinhold , Steigelmann Oliver , Müller Gerhard
Published: July 2007

1,2,4,5‐Tetramethyl‐and pentamethylbenzene from stable 1:2 complexes with SbCl3 of the type (C6H6‐Men) · 2SbCl3(1,2) with an inverse sandwich structure. The compounds crystallize isotypically and are isostructural to the (hexamethylbenzene)antimony and ‐bismuth complexes.They are thus built of tetrameric chlorine‐bridged Sb4Cl12 units, which are crosslinked at the metal centers with four other tetramers by double‐sided arene coordination (X‐ray structure analysis of 1). The Sb atoms, which are in a distorted trigonal bipyramidal environment, show a slight deviation from a centric (η6) coordination. The same stoichiometry and the same structural principle are found for the complex (C6Me6 · 2 AsCl3 (4), which is obtained from solutions of hexamethylbenzene and AsCl3 in toluene. In 4 the arsenic atoms are η6‐coordinated to the hexamethylbenzene ring from both sides (X‐ray analysis). Treatment of AsBr3 with hexamethylbenzene leads to a product of the composition 5 (C6Me6) · AsBr3. Reaction of hexaethylbenzene with AsCl3 in petroleum ether leads to the formation of the 1:2 complex (C6Et6) · 2 AsCl3 (5), built of discrete inverse sandwich units, which are arranged in strings parallel to the crystallographic c axis. From solutions of AsCl3 (AsBr3), SbCl3 (SbBr3) and hexaethylbenzene in petroleum ether ternary compounds are isolated with an As:Sb ratio of 1:5.2 and 1:1.86, respectively. Single crystal X‐ray structure determinations failed as a consequence of severe disorder.
Zur Lewis‐Acidität von Nickel(0), XII. Dimethylaluminiumhydrid‐Komplexe von Nickel(0)
Authors: Pörschke Klaus‐Richard , Kleimann Wolfgang , Tsay Yi‐Hung , Krüger Carl , Wilke Günther
Published: July 2007

On the Lewis Acidity of Nickel(0). XII. ‐ Dimethylaluminium Hydride Complexes of Nickel(O)

Ni(CDT) reacts with (1‐azabicyclo[2.2.2]octane)dimethylaluminium hydride in pentane to form the yellow crystaline addition compound (C7H13N)(Me2AlH)Ni(CDT) (2c). In its crystal structure 2c exhibits a Ni–H–Al three‐center bond. Displacement of the CDT ligand of 2c with ethene in pentane at 0°C yields light brown crystals of (C sb7H13N)(Me2AlH)Ni(C2H4)2 (4), which is also obtained from Ni(C2H4)3 and (C7H13N)‐Me2AlH). Complex 4 is converted by CO at – 78°C into the colorless carbonyl complex (C7H13N)(Me2AlH)Ni(CO)3 (5). 2c and 4 may be considered as model compounds for intermediates of the nickel(0)‐catalyzed hydroalumination reaction of alkenes.
Organometallic Compounds of the Lanthanides, 57. Pyrrolyl Complexes of Yttrium and Lutetium. Molecular Structure of Dicyclopentadienyl(2,5‐dimethylpyrrolyl)(tetrahydrofuran)lutetium(III)
Authors: Schumann Herbert , Lee Pil Ryul , Dietrich Andreas
Published: July 2007

The reactions of Na(NC4H4) with (C5H5)2LuCl(THF) and (C5Me5)2YCl(THF) result in the formation of the pyrrolyl complexes (C5H5)2Lu(NC4H4) (1) and (C5Me5)2Y(NC4H4)(THF) (2), respectively. Na(NC4H2Me2) reacts with (C5H5)2LuCl(THF) to form (C5H5)2Lu(NC4H2Me2(THF) (3). The 1H‐ and 13C‐NMR spectra of the new compounds as well as the X‐ray single‐crystal structure analysis of 3 are reported and discussed.
Zur Gasphasenpyrolyse von 2‐Ethinyl‐1,3‐butadien und dessen thermischer Cycloisomerisierung
Authors: Remmler Mathias , Zimmermann Gerhard , Ondruschka Bernd , Bader Hubert , Hopf Henning
Published: July 2007

On the Gas‐Phase Pyrolysis of 2‐Ethinyl‐1.3‐butadiene and Its Thermal Cycloisomerization

The gas‐phase pyrolysis of 2‐ethinyl‐1,3‐butadiene (2) has been investigated in the 500‐to‐700°C temperature range. Besides several fragmentation products (≤C4 hydrocarbons) benzene and fulvene (5) are the main products. Under the same conditions 2‐([2‐D1]ethinyl)‐1,3‐butadiene (2a) furnishes the monodeuteriofulvenes 5a–c. The cycloisomerization of 2/2a presumably begins with an acetylene‐vinylidenecarbene rearrangement, which may be followed by a deuterium scrambling mechanism involving either benzvalene (9) or vinylcyclobutadiene (10) intermediates. When 1‐ethinyl‐1‐cyclohexene (6) is employed as a precursor for 2, styrene is produced in significant amounts besides the products observed from 2. Pyrolysis of 1‐([2‐D1]ethinyl)cyclohexene (6a) provides [D1]‐styrene whose isotopic label is scrambled over both the vinyl substituent and the aromatic nucleus.
1‐Oxa‐3‐cyclooctin
Authors: Meier Herbert , Stavridou Evaggelia , Roth Silke , Mayer Winfried
Published: July 2007

1‐Oxa‐3‐cyclooctyne

According to an MNDO calculation, 1‐oxa‐cyclooctyne (13) and 1‐oxa‐3‐cyclooctyne (14) are 8‐membered heterocyclic ring systems with high steric energy (ring strain). On the basis of THF (1) and acetoacetic ester (4), a multi‐step synthesis is described for 14. The triple bond is introduced in the last step by a thermal fragmentation of the 1,2,3‐selenadiazole 12.
Synthesis of New Zwitterionic Pyridazino‐as‐triazines
Authors: Juhász‐Riedl Zsuzsanna , Hajós György , G´cs‐Baitz Eszter , Kollenz Gert , Messmer András
Published: July 2007

Reaction of the furo[2,3‐e]pyrido[l,2‐b]‐as‐triazinium salt 1 with methyl hydrazine gave the zwitterionic 1‐substituted pyrido‐pyridazino‐as‐triazine 4. The neutral 2‐substituted isomer 6 was formed when 1 was treated with 1‐formyl‐1‐methylhydrazine. Reaction of 1 with 1‐acyl‐2‐methylhydrazine gave rise to 1,3,4‐trisubstituted zwitterionic derivatives of the same ring system. Efforts to synthesize aryl‐substituted zwitterions led to simultaneous formation of the desired compound 12 and of a new ring transformation product, the pyrazolopyrido‐as‐triazine derivative 15.
The N‐Substitution of Aliphatic Primary Amines via 1‐[(Alkylamino)methyl]benzotriazoles: Preparation of Secondary Amines
Authors: Katritzky Alan R. , Noble Gloen , Pilarski Boguslaw , Harris Philip
Published: July 2007

A new method has been developed for the selective conversion of primary aliphatic amines into unsymmetrical secondary amines by Grignard reaction of 1‐[(alkylamino)methyl]‐benzotriazoles 1. This method employs simple procedure and mild conditions, and is specific in that only monoalkylation of the primary amines results.
Folgereaktionen von Sulfenen aus Sulfonylchloriden und tertiären Aminen, 1 Über die konkurrierende Bildung von Sulfen–Trialkylamin‐S,N‐ und ‐C,N‐Addukten
Authors: Opitz Günter , Rieth Karlheinz , Ehlis Thomas
Published: July 2007

Secondary Reactions of Sulfenes from Sulfonyl Chlorides and Tertiary Amines, 1. ‐ On the Competing Formation of Sulfene ‐ Trialkylamine S,N‐ and C,N‐Adducts

Phenylmethanesulfonyl chloride (1a) reacts with an excess of triethylamine in acetonitrile solution at ‐40°C to give stilbene episulfone (9a, 95%) via the phenylsulfene–triethylamine S,N‐adduct 1ah. With trimethylamine and quinuclidine the yield of stilbene is reduced by the additional formation of (benzylsulfonyl)phenylsulfene–amines S,N‐adducts 11ag and 11ae and C,N‐adducts 15ag and 15ae which was proven by reaction with dimethylamine to 16 and by hydrolysis to 17–19, respectively. 1d reacts with triethylamine yielding 94% of α‐chloro sulfones 4s and 6d via pentamethylenesulfene–triethylamine S,N‐adduct 5dh, with trimethylamine, however, C,N‐adduct 12dg is obtained which is easily oxidized to 20dg (47%). The air‐sensitive dimethylsulfene–trimethylamine C,N‐adduct 12cg was isolated and characterized.
Synthesen mit 2,4,4‐Trifluor‐1,3‐dithietan‐2‐ylium‐hexafluoroarsenat
Authors: Waterfeld Alfred
Published: July 2007

Syntheses with 2,4,4Trifluoro‐1,3‐dithietan‐2‐ylium Hexafluoroarsenate

The 2‐bromo and 2‐iodo cations ‐X (XBr, I) are prepared as stable salts 3a and 4a from the title compound ‐F AsF‐6 (1a). Salt 1a reacts with BaCS3 to yield the new cyclic thiocarbonyl compound (5). Alkylation of 5 with CF3F/AsF5 produces the trithiocarbenium salt ‐SCH3 AsF‐6 (5a). Difluorothiophosgene (7) and its trimer (F3CS)2CS (8) add to the cation of 1a to form ‐SCF3 AsF‐6 (10a), the perfluorinated analog of 5a. The cation of 10a unlike 5a adds a fluoride ion to give ‐SCF3 (10), a new isomer of 8.
1H‐ und 13C‐NMR‐Konformationsanalysen und Minimal‐Potential‐Energie‐Rechnungen an Desoxyguanosin‐, Guanosin‐ und 5′‐Guanosinmonophosphat‐Addukten des Grenzcarcinogens 4‐Methylanilin
Authors: Meier Chris , Boche Gernot
Published: July 2007

The conformations of the C‐8‐nucleobase adducts of the borderline carcinogen 4‐methylaniline (p‐toluidine) N‐(deoxyguanosine‐8‐yl)‐4‐methylaniline (10), N‐(guanosine‐8‐yl)‐4‐methylaniline (11), and 8‐(4‐methylanilino)‐5′‐guanosinemonophosphate (12) have been investigated by 1H‐, 13C‐NMR spectroscopy and “minimal‐potential‐energy” calculations. As far as the glycosidic bond is concerned, the 1H‐ and 13C‐NMR data show in agreement with the calculations that the nucleoside adducts 10, 11 exist preferentially in the anti conformation while the 5′‐phosphorylated nucleotide adduct 12 exists in the syn conformation. Different conformations are also observed around the backbone C‐4′ – C‐5′ bond. While the nucleoside adducts 10, 11 show a strong preference for the gauche‐gauche conformation (ca. 90%), nucleotide adduct 12 exists mainly in the gauche‐trans/trans‐gauche conformation (ca. 70%). All adducts show a preference for the C‐2′‐endo conformation of the (deoxy)ribose puckering. A comparison of the conformational data of monocyclic arylamine adducts 10, 11, and 12 with the conformations of DNA‐ or oligonucleotide‐bonded 2‐[(deoxyguanosine‐8‐yl)amino]fluorene (6) shows, that the conformational situations in the case of the borderline carcinogen p‐toluidine are similar to that of the strong hepatocarcinogen 2‐aminofluoren (4b). The reasons for the different cancer‐inducing potentials of borderline carcinogens like p‐toluidine and strong carcinogens like 2‐aminofluorene thus seems not to be connected with the conformational changes of the DNA double helix caused by adduct formation but rather with the in vivo metabolization to give the ultimate carcinogen.
Preparation of Dimethyl 7‐Oxobicyclo[2.2.1]heptane‐exo‐2, exo‐3— dicarboxylate. An Easy Route to Functionalized Norbornane Derivatives and Cage Compounds
Authors: Camps Pelayo , Mauleón David , Minguillón Cristina , Parcerisa Xavier , Pérez Francesc
Published: July 2007

A four‐step preparation of dimethyl 7‐oxobicyclo[2.2.1]‐heptane‐exo‐2, exo‐3‐dicarboxylate (4) in satisfactory yield from the readily available 6,6‐dimethylfulvene and maleic anhydride is described. Compound 4 represents a well‐functionalized intermediate for the synthesis of norbornane derivatives which is used for an improved synthesis of the tricyclic diester 7, precursor of the cage compound 8. An alternative approach to diester 7 from dimethyl 7‐isopropylidenebicyclo[2.2.1]heptane‐exo‐2, exo‐3‐dicarboxylate (2) is also discussed.
Intramolecular Metalation of CH Bonds with {cis,cis‐1,3,5‐Tris[(diphenylphosphino)methyl]cyclohexane}rhodium(I) Chloride
Authors: Mayer Hermann August , Kaska William Charles
Published: July 2007

The novel tridentate ligand cis,cis‐1,3,5‐tris[(diphenylphosphino)methyl]cyclohexane (6) has been synthesized and treated with [Rh(COD)Cl]2. Intramolecular metalation of a CH bond of the cyclohexane ring occurs (7). Studies with D2 gas and 6[D6] prove that axial and equatorial CH bonds are metalated and that a mutual exchange occurs in this process. Replacement of the Cl− by the SbF−6 anion in 7 results in a reduced interaction between the metal and the CH bond (8). 7 reacts with CO to form the carbonyl 9 where no such interaction is observed.
Silylierungs‐ und Desilylierungs‐Experimente mit sterisch gehinderten Stannylphosphanen
Authors: Hänssgen Dieter , Aldenhoven Heinz
Published: July 2007

Silylating and Desilylating Experiments with Sterically Hindered Stannyl Phosphanes

MeP(SiMe3)2 reacts with tBu2Cl2 to give the four‐membered ring (tBu2SnPMe)2 (1). Mixed silyl‐stannyl‐substituted phosphanes tBu3SnP(SiMe3)2 (2) and tBu2Sn[P(SiMe3)2]2 (3) are obtained by metathesis of LiP(SiMe3)2 with tBu3SnCl and tBu2SnCl2, respectively. Methanolysis of 2 and 3 yields the corresponding PH compounds tBu3SnPH2 (4) and tBu2Sn(PH2)2 (5). On heating of 5, the four‐membered ring (tBu2SnPH)2 (6) is formed by a condensation reaction. The new compounds are characterized by NMR (1H, 31P, 119Sn) and mass spectroscopy.
Beiträge zur Chemie des Bors, 206. Darstellung und strukturelle Charakterisierung der p‐Formylbenzolboronsäure
Authors: Feulner Herta , Linti Gerald , Nöth Heinrich
Published: July 2007

Contributions to the Chemistry of Boron, 206. — Preparation and Structural Characterization of p‐Formylbenzeneboronic Acid

The Grignard compound prepared from 1‐bromo‐4‐(diethoxymethyl)benzene in tetrahydrofuran reacts with tri‐n‐butoxyborane to produce the title compound in 78% yield after hydrolytic workup. The molecule crystallizes in the triclinic space group P&1bar;, Z  2, its B(OH)2 group showing extensive intermolecular hydrogen bonding. The formyl group is disordered.
Wasserlösliche Metallkomplexe und Katalysatoren, V. 2,2′‐Bipyridin‐5‐sulfonsäure und metallorganische Komplexe: Spektroskopie und Strukturchemie
Authors: Herrmann Wolfgang A. , Thiel Werner R. , Kuchler Josef G. , Behm Joachim , Herdtweck Eberhardt
Published: July 2007

Water‐Soluble Metal Complexes and Catalysts, V. — 2,2′‐Bipyridine‐5‐sulfonic Acid and Organometallic Complexes: Spectroscopy and Structures

Coplanar orientation of the pyridine rings in 2,2′‐bipyridine‐5‐sulfonic acid (1a) and in metal complexes of this ligand is evident from NMR studies. While the free acid 1a exists as a planar zwitter‐ion the rings of the salts 1b–d (Na+, [N(C4H9)4]+,[P(C6H5)4)]+) and sulfonamides 1f–h (tert‐butyl, benzyl, 2‐pyridylmethyl) are twisted. X‐ray crystal structures determined for four complexes 4e, h, 1, and 10b of the sulfonic acid and sulfonamide derivatives of 2,2′‐bipyridine show that there is no influence of the sulfonic acid and the sulfonamide groups (meta‐position) on the complex chemistry of the chelate ligand. Variation of solubility should, therefore, occur without principal changes of reactivity.
Zur Struktur von Trithiatriazinen
Authors: Jaudas‐Prezel Evelyn , Maggiulli Roberto , Mews Rüdiger , Oberhammer Heinz , Stohrer Wolf‐Dieter
Published: July 2007

The Structure of Trithiatriazines

MNDO and ab initio calculations have shown that the structure of trithiatriazines [(RSN)3, where R  F, Cl, {H}] is influenced by the anomeric effect and by antiaromaticity of the ring for electron pairs in axial positions. These calculations are supported by a joint electron diffraction and microwave structure determination of (NSF)3 in the gas phase.
Synthesis and reactions of novel tricyclo[4.3.1.12,5]undec‐3‐en‐10‐ones
Authors: Hoffmann H. Martin R. , Wagner Dagmar , Wartchow Rudolf
Published: July 2007

Sodium iodide/copper mediated intermolecular cyclodehalo‐genation of 2,6‐dibromocyclohexanones in the presence of furan and cyclopentadiene afforded a variety of alkylated tricyclo[4.3.1.12,5]undec‐3‐en‐10‐ones. An alkyl group (methyl or isopropyl) adjacent to the carbonyl carbon atom in the starting 2,6‐dibromocyclohexanone derivative was important for the success of the cycloaddition procedure. Even tricylic ketone 11, containing two quaternary carbon atoms adjacent to the carbonyl carbon atom, was prepared. The α,α'‐dibromoketones derived from either enantiomer of menthone and cyclopentadiene reacted enantioselectively, yielding tricycles (7R)‐7 and (7S)‐7. Since a number of tricyclic ketones 3–11 were sensitive, they were reduced to secondary alcohols 19–25, having an axial, α‐configurated OH group and were also converted into tertiary methylcarbinols 26 and 27 using methyllithium activated with tBuOK. Secondary α‐configurated alcohols 19–25 had an earthy‐mouldy odour, and tertiary carbinols 26 and 27 even more so. Unsaturated alcohols 26 and 27 showed a 4 J coupling of 2 Hz between the rigidly held OH proton and the nearest methyl protons. On hydrogenation of the olefinic double bond (4 → 33, → 34) this long‐range coupling disappeared.
Ein sterisch gehindertes Brückenkopfsystem: 13‐Substituierte 1,4,5,8,9,12‐Hexamethyltriptycene
Authors: Pakusch Joachim , Rüchardt Christoph
Published: July 2007

A Sterically Hindered Bridgehead System: 13‐Substituted 1,4,5,8,9,12‐Hexamethyltriptycenes

The synthetic access to five 13‐X‐substituted 1,4,5,8,9,12‐hexamethyltriptycenes (X  NO2, NC, CN, NH2, NHCHO) is described. Due to steric hindrance of the bridgehead position by the methyl groups in position 1, 8 and 9 it was impossible neither to formylate nor acetylate the 13‐amino compound 23, nor to dehydrate the 13‐formamido compound 22 to the isocyanide 19 by standard methods.
Wittig‐Synthese und Röntgen‐Struktur eines 26‐gliedrigen, zwei Bipyridin‐Einheiten enthaltenden Makrocyclus
Authors: Vogtle Fritz , Hochberg Robert , Kochendörfer Frank , Windscheif Paul‐Michael , Volkmann Martin , Jansenb Martin
Published: July 2007

Wittig Synthesis and X‐Ray Structure of a 26‐Membered Macrocycle Containing two Bipyridine Units

Wittig‐type macrocyclization of bipyridinedicarbaldehyde 5 with bis(phosphonium bromide) 6 leads to the new bipyridinophanes 7 8. The X‐ray structural analysis of 8 reveals a step‐type conformation, which according to 1H‐NMR results is also present in solution.
Metal complexes with tetrapyrrole ligands, LVII. Synthesis, spectra, and structure of nitridorhenium(V) porphyrins
Authors: Buchler Johann W. , Cian André De , Fischer Jean , Kruppa Steffen B. , Weiss Raymond
Published: July 2007

Oxorhenium(V) porphyrins ReO(P)X (X = Cl, Br) or [ReO(P)]2O, or trichlororhenium(V) porphyrins ReCl3(P) (P = OEP, TPP, TTP, TAP, TCIP, TMP)2,3, respectively, are transformed into nitridorhenium(V) porphyrins ReN(P) with hydrazine hydrate in the presence of ethanol, in good yields. The diamagnetic complexes are stable towards hydrolysis and contain pentacoordinate ReV in a square pyramid of nitrogen donor atoms. Their structure is deduced spectrometrically and is proven in the case of ReN(OEP) by X‐ray crystallography. The UV/Vis‐ and 1H‐NMR spectra of the new nitrido complexes are compared with those of the corresponding zinc(II) porphyrins.
Orotate complexes. Synthesis and crystal structure of lithium orotate(—I) monohydrate and magnesium bis[ orotate(—I)] octahydrate
Authors: Bach Ina , Kumberger Otto , Schmidbaur Hubert
Published: July 2007

Neutralization of orotic acid (OrH2) by lithium or magnesium hydroxide in aqueous medium yields the crystalline metal orotate hydrates Li(OrH). H2O (1) and Mg(OrH)2. (H2O)6 (2). By single‐crystal X‐ray diffraction studies it has been shown that 1 (space group P1) forms a layer structure, with lithium in a tetrahedral environment of oxygen atoms from three different orotate( ‐ I) anions (one carboxylate and two uracil oxygen atoms) and the water molecule. 2 (space group P21/c) has been shown to feature a hexaquo complex of magnesium, the Mg(H2O)26 cations being associated with two hydrated OrH⊖ ions only through hydrogen bonds. The anions are also engaged in “base‐pairing” hydrogen bonds between the planar uracil ring systems of different units. The results are relevant for applications of magnesium orotates in magnesium therapy.
Reaktive EC(p‐p)π‐Systeme, XXVI. Einfache Synthese für Methylenphosphane (Phosphaalkene) des Typs HPC(F)NR2 und das Phosphaalkin PC‐N(iPr)2
Authors: Grobe Joseph , Van Duc Le , Lüth Bettina , Hegemann Marianne
Published: July 2007

Reactive EC(p‐p)π‐Systems, XXVI. — Facile Synthesis of Phosphaalkenes of the Type HPC(F)NR2 and the Phosphaalkyne PC‐N(iPr)2

The reaction of trifluoromethylphosphane CF3PH2 with secondary amines in a 1:3 molar ratio leads to the novel methylenephosphanes (phosphaalkenes) HP  C(F)NR2 [R  Me (1), Et (2), Pr (3), piperidine (4)] in yields between 40 and 60%. The analogous deuterium compound DP  C(F)NEt2 (5) is formed by the reaction of CF3PD2 with Et2ND. However, with di(isopropyl)amine the new phosphaalkyne P  CN(iPr)2 (6) is produced instead of the expected phosphaalkene.
Cyclization of a chiral α‐(δ′‐benzyloxyalkyl)acrylate to a novel tetrahydrofuran derivative
Authors: Drewes Siegfried E. , Njamela Owen L. , Roos Gregory H. P.
Published: July 2007

Methyl 3‐hydroxy‐2‐(iodomethyl)‐5‐methyltetrahydrofuran‐2‐carboxylate (4) is synthesized from (3S)‐3‐(benzyloxy)butanal (2) via methyl 5‐(benzyloxy)‐3‐hydroxy‐2‐methylenehexanoate (3a) as intermediate.
Synthese und Struktur der Polycyclohexaphosphane P6(C5Me5)4 und P6(C5Me5)2
Authors: Jutzi Peter , Kroos Rainer , Müller Achim , Bögge Hartmut , Penk Michael
Published: July 2007

Synthesis and Structure of the Polycyclohexaphosphines P6(C5Me5)4 and P6(C5Me5)2

The cyclotriphosphine (PC5Me5)3 (1) decomposes in boiling benzene to give the bicyclo[3.1.0]hexaphosphine P6(C5Me5)4 (2) which yields the tricyclo[3.1.0.02.6] hexaphosphine P6(C5Me5)2 (3) in boiling xylene. The structures of 2 and 3 have been determined by 31P‐, 13C‐, and 1H‐NMR spectroscopy and by X‐ray crystallography. 3 represents the first member of a new class of polyphosphines. The specific thermolysis of 1 and 2 under comparatively mild conditions is based on the easy homolytic cleavage of P — C5Me5 bonds in these compounds.
Kurzmitteilung / Short Communication P  C Bond Activation and η4‐Coordination of Arene: X‐ray Crystal Structure of a Dinuclear μ‐Phosphido μ‐η2:η2‐Phenoxo Zwitterionic Complex of Palladium Trapping an Aggregate of Three Hydrogen‐Bonded Phenol Molecules
Authors: Sommovigo Milena , Pasquali Marco , Leoni Piero , Braga Dario , Sabatino Piera
Published: July 2007

Pd[P(tBu)3]2 reacts photochemically with an excess of phenol in n‐hexane to give the dinuclear complex [{P(tBu)2H}2Pd2{μ‐P(tBu)2}(μ‐η2:η2‐C6H5O)]  3 C6H5OH (1); X‐ray crystallography shows a linear chain of three phenol molecules hydrogenbonded to the phenoxide ligand which is η4‐coordinated to the Pd2 framework. The π coordination of the phenoxide ring is retained in solution, as evidenced by 1H‐NMR spectroscopy.
A New Route to Alkoxy Radicals — Photochemical Reactions with (Alkylperoxy)cobaloximes
Authors: Hartung Jens , Giese Bernd
Published: July 2007

Alkoxy radicals have been generated by photochemical reactions of (alkylperoxy)cobaloximes 1. The occurrence of alkoxy radicals has been proved by characteristic cyclization and β‐scission reactions of the reactive intermediates.
Electrochemical Investigations on Methylenephosphines and Related Systems
Authors: Schoeller Wolfgang W. , Niemann Jürgen , Thiele Rüdiger , Haug Wilfried
Published: July 2007

Electrochemical investigations on a selection of methylenephosphines 1 and related systems are reported. They are shown to possess an irreversible oxidation and reduction wave. An exception is diaminodiphosphene, which reversibly forms a radical anion. A relative ordering of frontier orbitals is possible, based on the redox properties of these systems.
Neue σ2λ3‐PC – O‐Systeme: Stabile nichtkonjugierte Phosphaalkenether – Synthese und Reaktionen
Authors: Heinicke Joachim , Kovacs Ilona , Nyulaszi Laszlo
Published: July 2007

New σ2λ3‐PC – O Systems: Stable Non‐Conjugated Phosphaalkene Ethers – Synthesis and Reactivity

Non‐conjugated cyclic phosphaalkene ethers (2, 4, 6) are obtained by cyclocondensation of (2‐ or 3‐hydroxyalkyl)phosphanes 1, 3 with N‐arylpivalimidoyl chlorides. Hydrolysis of 2, 4 with H2O (→7, 8), addition of hydrogen compounds (HCl, HSPh, MePhPH) (→ 9–12), and oxidation with air (→ 14) are studied. The reactivity of the title compounds and of benzoxaphospholes are compared.
Darstellung von [Dimethylamino(thiocarbonyl)thioamido]titan(IV)‐dihalogeniden – Verbindungen mit kurzen Ti – N‐Bindungen
Authors: Meller‐Rehbein Birgit , Roesky Herbert W. , Noltemeyer Mathias
Published: July 2007

Preparation of [Dimethylamino(thiocarbonyl)thioamido]titanium(IV) Dihalides – Compounds with Short Ti – N Bonds

Reaction of Me2NC(S)SN(SiMe3)2 (1) with TiCl4 and TiBr4 yields (2) and (3). Treatment of 2 and 3 with pyridine (py) leads to the solvates · 3 py [2a (XCl), 3a (XBr)]. These adducts have been characterized by X‐ray structure determination.
Synthese von nichtsymmetrisch substituierten Perylen‐Fluoreszenzfarbstoffen
Authors: Kaiser Harald , Lindner Jörg , Langhals Heinz
Published: July 2007

Synthesis of Nonsymmetrically Substituted Perylene Fluorescent Dyes

A general method for the preparation of perylene‐3,4:9,10‐tetracarboxdiimides 1 with two different substituents at the nitrogen atoms is described: The easily prepared symmetrical tetracarboxdiimides 1 (R1=R2) are transformed into carboxdiimide anhydrides 2 and condensed with primary amines to the corresponding tetracarboxdiimides 1 (R1 ≢ R2). Applications as fluorescent tracers in biochemistry and polymer chemistry are discussed.
Geminale Vinyldiazide, X. 3,3‐Diazido‐2‐cyanacrylsäure‐methylester: Synthese von Vinylaziden, 4,5‐Dihydro‐1H‐tetrazol‐5‐ylidenen, Oxazolen und N‐Cyaniminen
Authors: Saalfrank Rolf W. , Lurz Claus‐Jürgen , Hassa Jürgen , Danion Daniel , Toupet Loic
Published: July 2007

Geminal Vinyl Diazides, X. – Methyl 3,3‐Diazido‐2‐cyanoacrylate: Synthesis of Vinyl Azides, 4,5‐Dihydro‐1H‐tetrazol‐5‐ylidenes, Oxazoles, and N‐Cyanimines

Reaction of methyl 3,3‐diazido‐2‐cyanoacrylate (1) with amines 2 at –30°C yields aminovinyl azides 4. In the presence of equivalent amounts of triethylamine the vinyl azides 4 undergo 1,5′‐ring closure to afford the triethylammonium salts 5. Treatment of 5 with hydrochloric acid gives the corresponding 4,5‐dihydro‐1H‐tetrazol‐5‐ylidene derivatives 6. In contrast thermolysis of 4 leads via azirines 7 to oxazoles 8. Reaction of vinyl diazide 1 with lysine and cystine, respectively, yields bis(vinyl azides) 9. Triethylamine‐induced 1,5′‐ring closure of 9 produces the bis(triethylammonium) salts 10, which can be transformed under acidic conditions into the corresponding bis(4,5‐dihydro‐1H‐tetrazol‐5‐ylidene) derivatives 11. With methyl acrylate (17) oxazole 15 reacts via carbonyl ylide 16 in a 1,3‐dipolar cycloaddition to give pyrroline 18 (X‐ray structure analysis). Thermolysis of the geminal vinyl diazide 1 in the presence of alcohols 19 or primary amines 21 forms the cyanimines 20 and 22, respectively, via methyl 3‐aza‐2,3‐dicyanoacrylate 25. 25 exists as syn/anti isomers which fully agrees with AM1 calculations carried out on cyanimine model systems.
Regio‐ und Stereoselektivität bei anionischen Ringöffnungsreaktionen in 2‐Azabicyclo[3.2.0]heptan‐Derivaten
Authors: Franzisket Ludwig , Heesing Albert
Published: July 2007

Regio‐ and Stereoselectivity in Anionic Ring Opening Reactions of 2‐Azabicyclo[3.2.0]heptane Derivatives

In the regioselective ring opening of 1 via the dianion 1c the intermediacy of 2a is proven by labeling experiments. The regioselective cleavage of the four‐membered ring in 3 by LiAlH4 proceeds stereoselectively both in the ring and the side chain positions of 4 as shown with deuterated compounds. The regioselectivity is kinetically controlled, the transition state 13 being stabilized by the tendency of lithium ions for complexation.
Pseudooxokohlenstoff‐Anionen der Semidreiecksäure
Authors: Landau Andreas , Seitz Gunther
Published: July 2007

Pseudooxocarbon Anions of Semideltic Acid

Novel pseudooxocarbon anions of semideltic acid (2) can easily be obtained by stepwise substitution of the dimethylamino groups of the cyclopropenium perchlorate 8. Treatment of 8 with cyanamide or malononitrile in the presence of triethylamine leads to the triafulvenes 9 and 13. Two cyanoimino groups are successfully introduced into the cyclopropenylium system by treating 9 with excess cyanamide/potassium ethoxide. Under the same conditions malononitrile reacts with 13 to yield the potassium salts 14 and 17. The thioamide 26 of semideltic acid is obtained by treating the triphenylphosphonium salt 24 with H2S/pyridine and subsequent hydrolysis of the intermediate 25. With the anions of cyanamide or malononitrile ring‐opening reaction of the cyclopropenylium system of 24 occurs to yield the push‐pull phosphonium salts 28 and 29.
Cyclische Metall(IV)‐amide
Authors: Herrmann Wolfgang A. , Denk Michael , Albach Rolf W. , Behm Joachim , Herdtweck Eberhardt
Published: July 2007

Cyclic Metal(IV)Amides

Synthesis and structure of cyclic amide complexes of quadrivalent titanium, vanadium, and chromium are described, and their electrochemical behavior is investigated by cyclic voltammetry. The novel amides of formula ML2 {MTi, (3b); MV, (3c); MCr, (3d); L=[(CH3)3SiNCH2CH2NSi(CH3)3]} are formed by reaction of the halide adducts MCl3(THF)3 with the dilithium salt Li2L with concomitant disproportionation. Formation of 3d proceeds via the complex [3 d]⊖ and requires additional oxidation with oxygen or iodine. An X‐ray crystalstructure determination of 3b reveals the titanium atom in strongly distorted tetrahedral environment with approximate symmetry D2d. The amide complexes 3b –d are monomeric, thermally stable, and sublime readily without decomposition; they are very sensitive to water and soluble in all common organic solvents.
Metallkomplexe mit biologisch wichtigen Liganden, LVII. 1‐Selenoglucose als Ligand in Metallkomplexen
Authors: Pill Thomas , Beck Wolfgang , Breu Walter , Wagner Hildebert
Published: July 2007

Metal Complexes of Biologically Important Ligands, LVII. – 1‐Selenoglucose as Ligand in Metal Complexes

Reactions of the in situ‐prepared anion of acetylated 1‐selenoglucose with chloro complexes give the compounds R'3 PAuSeR (R'=Me, El, Ph), cis;‐(Ph3P)2Pt(SeR)2 and (η5C5H5)2Ti(SeR)2 (SeR=2,3,4,6‐tetra‐O‐acetyl‐1‐seleno‐β‐D‐glucopyranosato‐Se). The complexes (η5‐C5H5)(OC)2FeSeR and (OC)3M(μ‐SeR)2M(CO)3 (MFe, Ru) are prepared by the reaction of the diselenide RSeSeR with the dinuclear compound [η5‐C5H5Fe(CO)2]2 and M3(CO)12 (MFe, Ru), respectively.
Synthesis, Structure, and Reactivity of Chiral Rhenium Cycloalkene Complexes of the Formula ; Facile Vinylic Deprotonation of a Coordinated Alkene
Authors: Kowalczyk James J. , Arif Atta M. , Gladysz J. A.
Published: July 2007

Reactions of [(η5‐C5H5)Re(NO)(PPh3)(ClC6H5)]+BF−4 and (n = 5, a; 6, b; 7, c; 8, d) give cycloalkene complexes (6a – d, 94 to 79%). A crystal structure of the methylcyclopentadienyl analog of 6a shows the Re – plane and Re – PPh3 bond to be coplanar, with the vinyl protons syn to the cyclopentadienyl ligand. Reaction of 6a and tBuO−K+ leads to the vinyl complex (9a, 90%) instead of expected allyl complex (10a) Analogous reactions of 6b – d give varying mixtures of 9b – d/10b – d. HBF4 · OEt2 and 9a react to form the cyclopentylidene complex (10+ BF−4, 96%), the stability of which precludes any intermediacy in the deprotonation of 6a. A crystal structure of 11+ PF−6 shows the ReCC planes to be perpendicular to the Re – P bond. Spectroscopic features of compounds 6 are analyzed in detail, and NMR data show a high barrier to cyclopentylidene ligand rotation in 11+ BF−4 (ΔG≢ (110°C) ≥ 19 kcal/mol).
Azaphosphaboriridine und Azadiphosphiridine durch Phosphandiyl‐Transfer
Authors: Streubel Rainer , Niecke Edgar , Paetzold Peter
Published: July 2007

Azaphosphaboriridines and Azadiphosphiridines by Phosphinediyl Transfer Reactions

The azaphosphaboriridines (4a – d) are obtained by the reaction of the corresponding chloro(trimethyl‐silyl)posphines RP(Cl)SiMe3 (1a – d) with the iminoborane 2. Equally, reaction of 1a – c with the iminophosphine 5 leads to the azadiphosphiridines (8a – c) via an imino‐λ3,λ5‐diphosphene intermediate tBuNP(CEt3)=PCH‐(SiMe3)2 (7a).
Undecacarbonyl(μ2‐trifluoromethyl isocyanide)triruthenium, a Derivative of [Ru3(CO)12] with [Fe3(CO)12] Structure
Authors: Lentz Dieter , Marschall Robert , Hahn Ekkehardt
Published: July 2007

[Ru3(CO)10(μ2‐CO)(μ2‐CNCF3)] (1), [Ru3(CO)10(CNCF3)2] (2), and [Ru2(CO)6(μ2‐CNCF3)3] (3) are obtained by the reaction of [Ru3(CO)11(CH3CN)] with CNCF3. An X‐ray crystal structure determination revealed, that 1 has an unusual [Fe3(CO)12] structure, different from most other derivatives of [Ru3(CO)12].
Alkine und Cumulene, XXII. Die thermische Di‐ und Trimerisierung von tert‐Butylallen
Authors: Hopf Henning , Kretschmer Olaf , Ernst Ludger , Witte Ludger
Published: July 2007

Alkynes and Cumulenes, XXII. ‐The Thermal Di‐ and Trimerization of tert‐Butylallene The thermal di‐ and trimerization of tert‐butylallene (4) in the gas phase has been investigated at 220 and 290°C. Whereas the dimers 5 and 6 are the main products at the lower temperature, the trimers 10 and 11 as well as the rearrangement product 12 are obtained at 290°C. The mechanisms of formation of these allene oligomers are discussed.
Zur Struktur von 1‐Azapentadienyllithium‐Verbindungen
Authors: Wolf Gerhard , Würthwein Ernst‐Ulrich
Published: July 2007

On the Structures of 1‐Azapentadienyllithium Compounds

1‐Azapentadienyllithium compounds 2–6 have been prepared by deprotonation of the α,β‐unsaturated imines 1 with lithium diisopropylamide. Their structures in THF solution at various temperatures have been studied by 1H‐ and 13C‐NMR spectroscopy. All N‐alkyl‐substituted derivatives 2 – 5 adopt W conformations of the 1‐azapentadienyl unit. The N‐tert‐butylsubstituted compound 2 shows an (E)‐configurated NC‐ bond, whereas compounds 3 –5 prefer (Z)‐NC configurations. According to NOE experiments, the triphenyl system 6 has a U‐shape structure, probably because of steric interactions of the phenyl substituents. 13C‐shifts of the 1‐azapentadienyl carbon atoms are discussed in terms of HOMO coefficients. The experimental structural results are compared with theoretical data obtained by MNDO and ab initio calculations for the corresponding anions. MNDO results are also given for monomeric 1‐azapentadienyllithium conformers 11.
Ozonolysen von α‐Oxo‐alkenen: Zur Existenz von α‐Oxo‐ozoniden
Authors: Griesbaum Karl , Greunig Hans‐Joachim , Volpp Willi , Jung In‐Chan
Published: July 2007

Ozonolyses of α‐Oxo‐alkenes: On the Existence of α‐Oxo‐ozonides

Ozonolyses of nine acyclic (1a–i) and of two cyclic (14, 29) α‐Oxo‐alkenes on polyethylene or in pentane afforded in eight cases (1d–i, 14, 29) isolable α‐Oxo‐ozonides. α‐Diozonides (9) are obtained from five of the acyclic α‐Oxo‐alkenes (1a, b, d, g, h). All isolated ozonides are labile; the 2,4‐dinitrophenylhydrazones of the α‐Oxo‐ozonides, however, are very stable. Decomposition of the α‐Oxo‐ozonides affords not only the hitherto known fragments, but non‐peroxidic isomers (8) of the ozonides, too.
Zur Bildung von Vinylcyclopropan‐ und Cyclopentenderivaten aus alkenylsubstituierten Chromcarben‐Komplexen: Konkurrenz von formalen [2 + 1]‐ und [3 + 2]‐Cycloadditionen
Authors: Wienand Anette , Rei ßig Hans‐Ulrich
Published: July 2007

Formation of Vinylcyclopropane and Cyclopentene Derivatives from Alkenyl‐Substituted Chromium Carbene Complexes: Competition between Formal [2 + 1] and [3 + 2] Cycloadditions.

The alkenyl‐substituted chromium carbene complexes 1 – 4 were synthesized following the method of Aumann which starts from the corresponding aldehydes. At 80°C the styryl‐substituted complex 1 and electron‐deficient olefins smoothly provide vinylcyclopropane derivatives 6,8, 10, and 12 in good yields. On the other hand, methyl acrylate and the anisyl‐ and furyl‐substituted vinylcarbene complexes 2 and 3 give mixtures of the expected vinylcyclopropanes and of cyclopentene derivatives. The pyrrolyl‐substituted complex 4 and methyl acrylate exclusively afford the cyclopentenes 24a/b which are the result of a hitherto unprecedented formal [3 + 2] cycloaddition of the vinylcarbene complex to the olefin. However, there are strong arguments suggesting the corresponding vinylcyclopropanes as intermediates. The very smooth vinylcyclopropane→cyclopentene rearrangement probably occurs via zwitterionic intermediates that are wellstabilized by donor and acceptor substituents. Hydrolysis of 24a/b to the cyclopentanone derivatives 25a/b demonstrates that this new route to five‐membered carbocycles should have synthetic potential.
Redoxreaktivität Phosphido‐verbrückter Heterodimetallkomplexe
Authors: Lindner Ekkehard , Funk Torsten
Published: July 2007

Redox Reactivity of Phosphido‐Bridged Heterodimetallic Complexes

The metal‐metal bond in (3a,b,e) [LCO: RPh (a), Cy (e); LPMe3: RPh (b)] is cleaved reductively, oxidatively, and by nucleophiles by using Na[HBEt3], bromine or iodine, and PMe3, respectively. The action of PMe3 on 3a affords Me3P(OC)4Mn – PPh2 – Fe(CO)4 (5), which is photolyzed to give 3b. While the reduction of 3a can be regarded as a nucleophilic bond opening functionalizing only manganese, oxidation of 3a,b with halides results in the formation of the complexes XMn(CO)4 – PPh2 – Fe(X)(CO)3L (4a – d) [LCO: XI (a), Br (c); LPMe3: XI (b), XBr (d)], which provide two functionalized metals. To elucidate the redox behavior of 3a cyclovoltammetric investigations were carried out. They indicate a complex reaction scheme including reactions of higher order.
Arsen(III)‐, Antimon(III)‐ und Bismuth(III)‐halogenid‐Komplexe des [2.2.2]Paracyclophans: Vom lockeren van‐der‐Waals‐Addukt zu stark gerichteten π‐Komplexen mit zwei‐ und dreifacher externer η6‐Koordination
Authors: Probst Thomas , Steigelmann Oliver , Riede Jürgen , Schmidbaur Hubert
Published: July 2007

Arsenic(III), Antimony(III), and Bismuth(III) Trihalide Complexes of [2.2.2]Paracyclophane: From Weak van der Waals Coordination to Strongly Directional π Complexation with Single or Double External η6 Coordination

[2.2.2]Paracyclophane forms the adducts C24H24·AsCl3 (1), C24H24·(SbCl3)2·1/2 C6H6 (2), and C24H24·(BiCl3)3·C6H6 (3). For solutions in polar solvents NMR spectra indicate extensive dissociation and/or fluxionality. In the crystals adduct 1 features a weak addition of the AsCl3 molecule to one open side of a paracyclophane molecule with long intermolecular contacts approaching C3v symmetry. – Crystalline 2 shows SbCl3 coordination to two of the benzene rings of the hydrocarbon in a quasi‐centered η6 mode, while one of the benzene rings remains uncoordinated. Chlorine‐bridging between antimony atoms leads to tetrameric units (SbCI3)4 in the lattice. – In the bismuth compound 3 each benzene ring of the hydrocarbon is engaged in centroid (η6)π complexation, with the BiCl3 units crosslinked by chlorine bridges. The average of the Bi–ring distances (3.08,2.98, and 2.99 Å) is shorter than for the Sb–ring distances in 2 (3.047 and 3.050 Å), indicating stronger bonding. The crystal benzene is not coordinating.