bluuebunny/crossref_metadata_2025 huggingface dataset:
1‐Alkynyl Disulfides: Their Characterization and Their 1‐Thiapropargyl — 3‐Thiaallenyl Rearrangements
Authors: Nørkjær Kim , Senning Alexander
Published: July 2007

The synthesis of novel 1‐alkynyl disulfides 1 is described together with their 1‐thiapropargyl — 3‐thiaallenyl rearrangement and a [1,3]‐sigmatropic shift of 1‐alkynyl amino disulfides, followed by rearrangement of the aminothio‐substituted thioketenes so formed.
Contributions to the Chemistry of Boron, 214. Synthesis and Reaction Chemistry of Aminophosphanylboranes
Authors: Dou Danan , Westerhausen Matthias , Wood Gary L. , Duesler Eileen N. , Paine Robert T. , Linti Gerald , Nöth Heinrich
Published: July 2007

Aminochlorophosphanylboranes, (R2N)B(Cl)P(SiMe3)2 (1a — d) and (R2N)B(Cl)PH2 (2a — d), are obtained from elimination reactions between aminochloroboranes and LiP(SiMe3)2 and LiPH2, respectively. Selected reaction chemistry of (i1‐Pr2N)B(Cl)P(SiMe3)2] (1a) with NH3, Me3SiN3, Cr(CO)5 · NMe3, and W(CO)5 · NMe3 is described. The azide (i1‐Pr2N)B(N3)P(SiMe3)2 (12a) is stable at 25°C; however, thermolysis at 80°C provides a novel six‐membered ring compound [(i1‐Pr2N)BN(SiMe3)P(SiMe3)]2 (13a). The reaction of (Ph2N)B(Cl)P(SiMe3)2 (1b) with LiP(SiMe3)2 produces the only isolable bis(phosphanyl)borane (5b), while combination of (R2N)B(Cl)Ph2 with LiPH2 · DME yields new diphosphadiboretanes 6 {(R2N)BPH}2 (R2Ni1‐Pr2N, Ph2N and tmp2,2,6,6‐tetramethylpiperidino) and triphosphatriborinanes 7 {(R2N)BPH}3 (R2N(Me3Si)2N, Me2N and Et2N). Two salts, [(i1‐Pr2N) DME]2 (8a) and [tmpLi · DME]2 (8c) (DMEethylene glycol dimethyl ether) are also isolated. The results of molecular structure determinations for [(i1‐Pr2N)Bn(SiMe3)P(SiMe3)]2 (13a), [tmpBPH]2 (4c), [tmpBPH]2 · Cr(CO)5 (7c), {[(Me3Si)2N]BPH}3 (4d), {[(Me3Si)2N]BPH}3 · Cr(CO)5 (7d), (Ph2N)B[P(SiMe3)2]2 (5b), and [(i1‐Pr2N) · DME]2 (8a) are discussed.
Bis(pentamethylcyclopentadienyl)keton und ‐thioketon: Kohlenstoff‐Verbindungen mit präformierter Diels‐Alder‐Geometrie
Authors: Jutzi Peter , Schwartzen Karl‐Heinz , Mix Andreas , Stammler Hans‐Georg , Neumann Beate
Published: July 2007

Bis(pentamethylcyclopentadienyl) Ketone and Thioketone: Carbon Compounds with Performed Diels‐Alder Geometry

1,2,3,4,5‐Pentamethyl‐1,3‐cyclopentadien‐5‐carbonyl chloride (2) is formed in good yields by the reaction of pentamethylcyclopentadienyllithium (1) with phosgene. The corresponding carbothioyl chloride 3 is synthesized by treatment of 1 with thiophosgene. Both acyl chlorides are stable against air and moisture and difficult to attack in SN2‐type reactions. Treatment of 2 and 3 with trimethyl(pentamethylcyclopentadienyl)stannane in the presence of boron trifluoride — ether leads to bis(1,2,3,4,5‐pentamethyl‐1,3‐cyclopentadien‐5‐yl) ketone (5) and thioketone (6), respectively. Even at room temperature, 5 and 6 tend to intramolecular [4 + 2] cycloaddition reactions. X‐ray crystal structure investigations of 2, 5, and 6 show the steric demand of the pentamethylcyclopentadienyl ligand and explain the untypical chemical behavior of 2 and the easy [2 + 4] cycloaddition reactions of 5 and 6.
(Diphenylphosphanyl)(tetramethylcyclopentadienyl)thallium(I)
Authors: Schumann Herbert , Ghodsi Tahereh , Esser Lothar , Hahn Ekkehard
Published: July 2007

(Diphenylphosphanyl)(tetramethylcyclopentadienyl)thallium(I)

(Diphenylphosphanyl)tetramethylcyclopentadiene (1) reacts with TlOC2H5 to form Tl[C5Me4PPh2] (2). In a transmetallation reaction 2 reacts with InCl to yield the corresponding In[C5Me4PPh2] complex (3). The 1H‐, 13C‐NMR‐and mass spectra as well as the single‐crystal X‐ray structure analysis of the monomeric 2 are reported and discussed.
Preparation and Crystal Structures of Gold(I) Complexes of a Series of Benzenethiolates: Pair Formation by Gold‐to‐Gold Interactions of (Benzenethiolato)(triphenylphosphane)gold(I)
Authors: Nakamoto Masami , Hiller Wolfgang , Schmidbaur Hubert
Published: July 2007

Chloro(triphenylphosphane)gold(I) reacts readily with benzenethiol C6H5SH and a series of sterically hindered (2,4,6‐trialkylbenzene)thiols 2,4,6‐R3C6H2SH in the presence of NEt3 to yield stable gold(I) complexes Ph3PAu(S – 2,4,6‐C6H2R3) [RH (1), Me (2), Et (3), iPr (4)]. The crystal structures of these complexes have been determined by single‐crystal X‐ray diffraction analysis. In all compounds the gold atoms are linearly two‐coordinate with very similar bond lengths and angles. – While complexes 2 – 4 with bulky thiolate ligands are monomeric in the crystal lattice, complex 1 has been found to form pairs of molecules with intermolecular gold – gold contacts of 313.5(5) pm. The Mössbauer spectra of the complexes exhibit large isomer shifts (I.S.), ranging from 3.06 to 3.72 mm s–1, and quadrupole splittings (Q.S.), ranging from 7.90 to 8.68 mm s–1. These data can be attributed to the strong electron‐donating properties of the benzenethiolate ligands. The gold – gold contacts in complex 1 lead to I.S. and Q.S. values which are slightly smaller than those of 2 – 4. The Au – S distances do not show a major influence of the S – Au – P pairing in complex 1 as compared to complexes 2 – 4.
Beiträge zur Chemie des Bors, 215. Darstellung und Reaktionen monomerer Tetraorganylphosphanylborane
Authors: Nöth Heinrich , Staude Siegfried , Thomann Martina , Paine Robert T.
Published: July 2007

Contributions to the Chemistry of Boron, 215[1]. – Synthesis and Reactions of Monomeric Tetraorganyl‐phosphanyl‐boranes

The reaction of diorganyl‐chloroboranes with lithium diorganyl‐or lithium bis(trimethylsilyl)phosphides leads to the monomeric phosphanylboranes tBu2BPtBu2 (1), tBu2BP(SiMe3)2 (2), 9‐BBNPtBu2 (3), 9‐BBNP(SiMe3)2 (4), and Cy2BPtBu2 (5). These species were studied by NMR‐spectroscopic methods. For further characterization reactions of the compounds 1, 3, and 5 have been investigated. Heating of 1 and 5 results in the formation of the dimeric phosphanylboranes tBu(H)BPtBu2 (8) and Cy(H)BPtBu2 (9) by dehydroboration. Dimers 8 and 9 are present as cis‐ and trans1‐isomers as confirmed by X‐ray structure analyses. The trans1‐isomer of 9 shows a planar (BP)2 four‐membered ring, whereas the ring of the cis1‐isomer of 8 is slightly folded. Furthermore, the reaction of 3 with 9H‐9‐BBN yields (μ1‐H)(μ‐tBu2P)[9‐BBN]2 (14), whose bridged structure is proven by a crystal structure analysis. Oxidation of the phosphorus atom in 3 with sulfur leads to the S1‐boryl thiophosphinate tBu2(S)PS‐9‐BBN (16).
Nucleophile Singulett‐Carbene in der [4 + 1]1‐Cycloaddition mit 1,2,4,5‐Tetrazinen: Eine neue Isopyrazol‐Synthese
Authors: Gerninghaus Christian , Kümmell Andreas , Seitz Gunther
Published: July 2007

Nucleophilic Singlet Carbenes in the [4 + 1] Cycloaddition with 1,2,4,5‐Tetrazines: a New Synthesis of Isopyrazoles

A series of 3,6‐disubstituted 1,2,4,5‐tetrazines 6, including C6H5, SCH3, SO2CH3, N(CH3)2, CF3, CO2CH3 groups, has been submitted to [4 + 1] cycloaddition with the nucleophilic singlet carbenes 4, 15, and 20, which are generated from the precursors 1, 11 and 19, resp. In all cases isopyrazoles (4H1‐pyrazoles) 9, 10, 18, and 21 are isolated in good yields. They are formed in a two‐step reaction sequence with the [4 + 1] cycloadducts of type 8 as intermediates which eliminate nitrogen by subsequent [4 + 2] cycloreversion. The acceptor‐substituted isopyrazole 9e is characterized as an electron‐deficient diene by some Diels‐Alder reactions with inverse electron demand leading to the expected azo‐bridged cycloadducts 23, 25, 27, 29, and 31 without acid catalysis or application of higher pressure. With cyclooctyne (32), the [4 + 2] cycloaddition is followed by a [4 + 2] cycloreversion with formation of the cyclopentacyclooctene 34.
Rearrangements of 1‐ and 2‐Cyano‐2‐norbornyl Cations
Authors: Geier Holger , Kautz Cornelia Brigitte , Kirmse Wolfgang , Landscheidt Heinz , Schimpf Iris , Siegfried Rainer
Published: July 2007

Sulfonates of exo‐2‐hydroxynorbornane‐endo‐2‐carbonitrile (2c–e) were found to rearrange exothermally to give sulfonates of exo‐2‐hydroxynorbornane‐1‐carbonitrile (6c–e), solvolysis being a minor side reaction. In contrast, the analogous endo substrates (3c–e) afforded the rearranged alcohol 6a and tricyclo[2.2.1.02,6]heptane‐1‐carbonitrile (4) as the major products. We have not been able to trap 2‐cyano‐2‐norbornyl cations by external nucleophiles or by internal 6,2‐shifts of hydrogen or carbon. On the other hand, there is good evidence for the generation of 1‐cyano‐2‐norbornyl cations from both 3d, e and 6e. The degenerate 6,2‐H shift in these species has been uncovered by means of labeled or optically active precursors. The 1‐CN substituent clearly promotes the 6,2‐H shift relative to the parent 2‐norbornyl cation, but is inferior to 1‐C2F5. Ring expansion of a spiroannelated cyclopropane, involving a 6,2 shift of carbon, was also observed (25, 26 → 27, 28). Our data strongly suggest that 2‐cyano‐2‐norbornyl cations are less stable than 1‐cyano‐2‐norbornyl cations. The reaction rates of 2c versus 6c do not reflect the stability of the incipient carbocations, owing to the large difference in ground state energy.
Tin for Organic Synthesis, 7. New Regioselective Syntheses of Diaryl Sulfones, Arenesulfonamides, and Arenesulfonic Acid Sodium Salts
Authors: Neumann Wilhelm P. , Wicenec Christian
Published: July 2007

The reaction of (trialkylstannyl)arenes 1 with corresponding reagents containing a chlorosulfonyl group leads, by exclusive ipso substitution, to important diaryl sulfones 2a – i, N1‐alkyl‐arenesulfonamides 8a – f, and sodium arenesulfonates 13a – c in high yields under mild conditions. The specific leaving ability of the stannyl group allows, moreover, the preparation of arylsulfonyl isomers which are not accessible under the influence of the conventional directing forces of substituents. With N, N1‐dialkylamidosulfonyl chloride/AlCl3 complexes no destannylation takes place, but the first intramolecular sulfonyltin complex 11 is formed. This result is used to discuss details of the mechanism involved.
Cycloadditionen von 6H‐1,3,4‐Oxadiazin‐6‐onen (4,5‐Diaza‐α1‐pyronen), 12. Dieckmann‐Kondensationen ohne Basen
Authors: Christl Manfred , Lanzendörfer Ulrike , Grötsch Maria M. , Hegmann Joachim , Ditterich Elke , Hüttner Gerhard , Peters Eva‐Maria , Peters Karl , Von Schnering Hans Georg
Published: July 2007

Cycloadditions of 6H‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α1‐pyrones), 12[1]. – Dieckmann Condensations without Bases

Prepared by treatment of methyl 6‐oxo‐5‐phenyl‐6H‐1,3,4‐oxadiazine‐2‐carboxylate (1) with norbornene, norbornadiene, and styrene, respectively, the γ1‐oxoketenes 2, 5, and 7 were allowed to react with methanol. Inter alia, the semiacetals 3, 6, and 10 of 1,2‐cyclopentanedione derivatives were formed. The identity of 3 has been established by an X‐ray structure analysis. The pathway to these compounds seems to be closely related to the mechanism of the Dieckmann condensation. By using [D4]methanol, it has been shown that the semiacetal methoxy group underwent an intramolecular [1,2] migration. Methanol was eliminated from semiacetal 10 by chromatography on silica gel with formation of the enol 11. In addition to 3 and 10, the dimethyl adipates 4 and 9 were observed as the expected methanolysis products of the γ1‐oxoketenes 2 and 7, respectively. The diesters 9 were obtained on a second route from 7. Treatment of 7 with trifluoroacetic acid and subsequent hydrolysis gave rise to the monoesters 12, which were converted into the diesters 9 by conventional esterification.
Monoazadien‐Komplexe elektronenarmer Übergangsmetalle, I. Zirconocen(1‐aza‐1,3‐dien)1‐Komplexe: Synthese, Struktur und Reaktionen
Authors: Scholz Joachim , Nolte Matthias , Krüger Carl
Published: July 2007

Monoazadiene Complexes of Electron‐Deficient Transition Metals, I. – Zirconocene(1‐aza‐1,3‐diene) Complexes: Synthesis, Structure and Reactions[1]

The reduction of Cp2ZrCl2 in THF by Mg in the presence of 1‐aza‐1,3‐dienes 2a–d generates the orange air‐sensitive zirconocene(s‐cis‐1‐aza‐1,3‐diene) complexes 3a–d. 1H‐and 13C‐NMR spectral data of 3a–d indicate that the bonding of the heterodiene ligand has σ2,π1‐metallacyclopentene rather than η4‐1‐aza‐1,3‐diene character. No evidence for s‐trans1‐heterodiene coordination was found in any of the new zirconocene complexes. The molecular structure of 3d has been determined by single‐crystal X‐ray diffraction, confirming the envelope‐shaped σ2,π1‐type structure also in the solid state. 3b slowly reacts with one molar equivalent of acetophenone to give a seven‐membered oxaazametallacycle (4) which has a cis1‐CC bond in the ring. The structure of 4 has been determined by NMR and X‐ray diffraction.
1,3‐Donor/Donor‐substituierte Allene, VII Allencarboxanilide durch Umallenierung oder [2.3]/[3.3]1‐sigmatrope Umlagerungen Bausteine mit vielseitigem intra‐und intermolekularem Synthesepotential
Authors: Saalfrank Rolf W. , Bauer Udo , Hilbig Klaus , Welch Andreas
Published: July 2007

1,3‐Donor/Donor‐Substituted Allenes, VII[1]. – Allenecarboxanilides by Transallenation or [2.3]/[3.3]1‐Sigmatropic Rearrangements – Building Blocks with Versatile Intra‐and Intermolecular Synthetic Potential

Herrn Professor Richard P. Kreher zum 60. Geburtstag gewidmet.

The reaction of 1,3‐bis(alkylarylamino)1‐1,3‐diethoxyallenes 1,2 with disubstituted malonyl chlorides 3 leads to N, N′1‐dialkyl‐N, N′1‐diarylallene‐1,1‐dicarboxamides 4, 5, and 2H1‐pyran‐2,4(3H)1‐diones 6, 7, respectively, with a transallenation reaction being favoured in the case of allene 1. Thermal tandem cyclisation of allene‐1,1‐dicarboxanilide 4c via 2‐quinolone 8 affords phenanthridone 9. Spontaneous acylcycloalkane/cycloenol ether isomerisation of spirane 6b gives pyrane 12. Thermally induced (Z)1‐anilinoacryclic acid/quinolone cyclisation of pyranes 6a, 12, and 7 leads to 4‐quinolones 11, 13, and 14. Propargyl THP ether 15 reacts with carbamoyl chloride 16 to yield alkinol‐N1‐phenylanilides 17. Alkinol 17a reacts with sulfinyl chloride 18 to yield sulfinic ester 19, which on heating undergoes a [2.3]1‐sigmatropic rearrangement to N1‐phenyl‐1‐sulfonylallene‐1‐carboxanilide 20. Reaction of alkinols 17 with sulfenyl chlorides 21 or chlorophosphanes 23, followed by [2.3]1‐sigmatropic shift, affords N1‐phenyl‐1‐sulfinyl‐22 and N1‐phenyl‐1‐phosphorylallene‐1‐carboxanilides 24, respectively. Alkinyl ketene acetal intermediates 26 are formed starting from alkinol 17a and orthoesters 25. Spontaneous [3.3]1‐sigmatropic rearrangement of 26 gives N1‐phenylallene‐1‐carboxanilides 27. Intramolecular Diels‐Alder (IDA) reactions of the allene‐1‐carboxanilides 27 lead to [2.2.2]bicycles 28. Contrarily, the IDA intermediates of 20b and 24 further isomerize to the [3.2.1] bicycles 29 and 30. The allenyl sulfoxides 22 readily undergo Michael‐type reactions with CH‐acidic compounds 31 to give allyl sulfoxides 32. Among these, only 32d can be isolated, whereas 32a–c spontaneously rearrange in a four‐step reaction cascade to butenolides 33a–c. A Michael‐type reaction of (diethoxyphosphoryl)allenes 24 with α1‐hydroxy ketones 34 followed by a Horner‐Emmons reaction leads to alkylidene‐dihydro‐furans 35, which isomerize in the presence of a base to yield furans 36. Analogously, allenes 24 react with 2‐hydroxybenzaldehydes 37 or 2‐pyrrole‐/2‐imidazole derivatives 40 to form alkylidenechromenes 38 and pyrrolizines/pyrroloimidazoles 41, respectively. Benzopyrylium salts 39 are accessible from chromenes 38 and perchloric acid.
Siderophore, III. Neutrale Koordinationspolymere aus Pyrrolinyl‐enolen und Kupfer(II)1‐acetat durch spontane Selbstorganisation – Kristallstruktur von 2D‐[CuL22]n
Authors: Sallfrank Rolf W. , Struck Oliver , Peters Karl , Von Schnering Hans Georg
Published: July 2007

Siderophores, III[1]. – Neutral Coordination Polymers from Pyrrolinyl Enols and Copper(II) Acetate by Spontaneous Self‐Assembly – Crystal Structure of 2D‐[CuL22]n

Contrary to tetrazole 1 (HL1) structurally analogous pyrrolidines 3 (HL2) react with copper(II) acetate to give 2D‐coordination polymers 4 ([CuL22]n), rather than 3D‐coordination polymer 2 ([CuL21]n). The structure of 4a is established by single‐crystal X‐ray diffraction. The formation of 2D‐coordination polymer 4a is understandable if 3a or its enolate is considered as tridentate chelate ligand and if an intermediate formation of the coordinatively unsaturated copper(II) building block 5a is assumed. The monomers 5a are bidentate coordinating with the two CN groups, which leads to linking of monomers and to coordinative saturation at the copper(II) center of 5a with formation of 2D‐4a. Depolymerisation of 2D‐4 with excess pyridine leads to racemic mononuclear tetragonally pyramidally coordinated copper(II) chelate complexes 6 (X‐ray), whereas under the same conditions 3D‐2 yields octahedral bis(pyridine) complex CuL21(Py)2.
Metallorganische Lewis‐Säuren, IL. Bis(acyl)1‐verbrückte heterometallische Komplexe von Rhenium, Molybdän, Ruthenium und Kupfer
Authors: Lippmann Elisabeth , Robl Christian , Beck Wolfgang , Berke Heinz , Kaesz Herbert D.
Published: July 2007

Organometallic Lewis Acids, IL[1]. – Bis(acyl)1‐Bridged Heterometallic Complexes of Rhenium, Molybdenum, Ruthenium, and Copper

The reaction of the metalla‐β1‐diketonate complex [(OC)41‐Re[–C(Me)O]2][NMe4] with various organometallic Lewis acids yields the bis(acyl)1‐bridged bimetallic complexes (OC)4 ‐Re[–C(Me)O–]2Re(CO)4 (1), (OC)4Re[–C(Me)O–]2MoCp(CO)2 (2), (OC)4Re[–C(Me)O–]2Ru(η31‐C3 H5)(nbd) (nbdnorbor‐nadiene) (3), [(OC)4 Re[–C(Me)O–]2Ru(PPh3)2 (CO)2][BF4] (4), and (OC)4 Re[–C(Me)O–]2Cu[–O(Me)C–]2Re(CO)4 (5), respectively. The structures of the compounds 1–5 have been determined by X‐ray diffraction. They show different conformations of the six‐membered ring Re[–C(Me)O–]2[M]. The molecular structure of complex 1 proves a “flipping” of the acyl ligands.
Trimethylsilylcyanid als Umpolungsreagens, XXIII. Umpolungsprodukte aus α,β1‐ungesättigten Aldehyden mit α,β1‐ungesättigten Carbonyl‐Verbindungen: Folgereaktionen
Authors: Hünig Siegfried , Schäfer Matthias , Schweeberg Walter
Published: July 2007

Trimethylsilyl Cyanide – A Reagent for Umpolung, XXIII[1]. – Products from Umpolung of α,β1‐Unsaturated Aldehydes and α,β1‐Unsaturated Carbonyl Compounds: Consecutive Reactions

The unsaturated nitrile 1 is transformed by TiCl4 into chloronitrile 2, whereas reaction with [BzNMe3]+F− and treatment with acids yields cyanocyclopentenone 4. Removal of the umpolung groups from 1 and 5–8 by [BzNMe3]F− results in the unsaturated 1,4‐diketones 9–13 only if the cyanide ions formed are prevented by ZnO from adding to the double bond. Condensation of ketones 9 and 11–13 with tBuOK yields cyclopentenones 14–18 with conjugated vinylic groups. In the presence of [BzNMe3H]+F− α1‐cyano enol silyl ethers 22–24 are smoothly converted in methanol into ϵ1‐oxo‐carboxylic esters 19–21, whereas in pure methanol α1‐hydroxycyclopentanecarboxylic esters 25–27 are produced in high yied.
Maßgeschneiderte Wirtverbindung für Piperazin und verwandte Amine
Authors: Hoss Ralf , Vögtle Fritz
Published: July 2007

Tailor‐Made Host for Piperazine and Related Amines

The 38‐membered bis‐catechol 4b is obtained by cyclisation of the diacyl dichloride 3c with the diamine 2b in 45% yield, whereas a 68‐membered octalactam 7 is formed under similar conditions from 5 and 1b. Bis‐catechol 4b is a selective host compound for piperazine (8) and the structurally related diamine 9. Association constants for the 1:1 complexes have been measured by 1H‐NMR titration experiments. A nucleobase guest (pterine, 24) was extracted into a hydrochloric acid phase by complex formation with the host 4b. The results are compared with solubility and transport experiments obtained by use of analogous macrobicyclic tris‐catechol hosts.
Bimolekulare Radikalbildung durch H‐Transfer, 2. H‐Transferreaktionen mit Phenalen
Authors: Gerst Matthias , Rüchardt Christoph
Published: July 2007

Bimolecular Formation of Radicals by H‐Transfer, 2[1]. – H‐Transfer Reactions of Phenalene

The uncatalysed H transfer from phenalane (7) to α1‐methyl‐styrene (2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10‐dihydroanthracene (1) (DHA) in diphenyl ether at 200–250°C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10‐dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of α1‐methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200–250°C. They allow the determination of the CH bond enthalpy δHdiss of phenalene (7) (65.3 kcal mol–1) at the methylene position.
Monomere flüchtige Alkoxide von Chrom und Bismut
Authors: Herrmann Wolfgang A. , Huber Norbert W. , Anwander Reiner , Priermeier Thomas
Published: July 2007

Monomeric Volatile Alkoxides of Chromium and Bismuth

The β1‐methoxy alcohol HOCMe2CH2OMe (1) yields monomeric (mononuclear), highly volatile and soluble complexes M(OCMe2CH2OMe)3 3a, b of chromium(III) and bismuth(III), respectively, upon treatment with the amide precursors Cr[N(iPr)2]3 (2a) and Bi[N(SiMe3)2]3 (2b). A single‐crystal X‐ray diffraction analysis of 3a was performed because of the novelty of this particular compound being the first thermostable monomeric alkoxide of trivalent chromium. 3a exhibits an octahedral structure with six oxygen atoms surrounding the metal atom. Three chelating O,O′ ligands coordinate to Cr(III) in a mer configuration.
What is Different in Photochemical Reactions of Primary and Secondary Alkylcobaloximes with and without Radical Traps?
Authors: Hartung Jens , Hertel Barbara , Trach Frank
Published: July 2007

Photochemical cyclization and halogen abstraction reactions of secondary alkylcobaloximes1band1dcompared to their primary counterparts1aand1cshow an enhanced reactivity of secondary alkylcobaloximes: Thus, cyclohexylcobaloxime1dreacts 13 times faster with CCl4thann1‐hexylcobaloxime1c, 6‐hepten‐2‐yl‐cobaloxime1brearranges 58 times faster to its cyclopentylmethyl isomer4bthan 5‐hexenylcobaloxime1a. Althoughfreealkyl radicals are reactive intermediates in photolytic conversions of alkylcobaloximes1in organic solvents, the presence of BrCCl3or bromobenzene in photoreactions of primary alkylcobaloximes1aand1cseems to cause a more efficient homolytic cleavage of the Co – C bond.
Preparation and Properties of Alkylbis(dimethylglyoximato)rhodium(III) Complexes
Authors: Giese Bernd , Kesselheim Christoph , Hartung Jens , Lindner Hans Jörg , Svoboda Ingrid
Published: July 2007

Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans1‐dichlororhodium complex 3. X‐ray crystallography of the previously unknown tert1‐butylrhodoxime 1k reveals structural features of this tert‐s̀1‐alkylrhodium compound. Photochemical homolytic cleavage of the Rh – C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
Ligand‐Induced Hydrogen Scrambling and Interligand Carbon – Carbon Bond Formation in the Gas‐Phase Reactions of MCH3+ (MFe, Co) with 1‐Octyne and 1‐Octene
Authors: Schwarz Josef , Schwarz Helmut
Published: July 2007

Evidence is presented that the encounter complexes of MCX3+ (MFe, Co; XH, D) with 1‐octyne, prior to C – H‐and C – C bond activation, undergo interligand C – C bond coupling as well as extensive hydrogen exchange. In distinct contrast, in the related complexes formed by gas‐phase reaction of MCX3+ (MFe, Co; XH, D) with 1‐octene, the metal‐methyl group retains its identity while the alkene ligand is subject to extensive hydrogen scrambling presumably by β1‐hydrogen shift to and from the metal centers.
Methylenphosphanyl‐Komplexe von Chrom, Molybdän, Wolfram, Eisen und Nickel: Synthese und Reaktionen
Authors: Niecke Edgar , Metternich Hans‐Jürgen , Nieger Martin , Gudat Dietrich , Wenderoth Peter , Malisch Wolfgang , Hahner Christoph , Reich Wolfgang
Published: July 2007

Methylenephosphanyl Complexes of Chromium, Molybdenum, Tungsten, Iron and Nickel – Synthesis and Reactivity

Herrn Professor Heinrich Nöth zum 65. Geburtstag gewidmet.

The reaction of the functionalized P/C double bond systems X – PC(R)SiMe3 [RSiMe3 and XCl (1a), Cp* (5a) or RPh and XBr (1b), Cp* (5b)] with alkali carbonylmetallates or carbonyl complexes of group 6, 8, and 10 metals leads to the formation of the transition metal‐substituted phosphaalkenes [{M} – PC(R)SiMe3 3a – j and 4a – i], in which the P – C fragment acts as a one‐electron donor. Depending on the nucleophilicity of the transition metal anion used, but also on the methylene carbon substituents [1a: (SiMe3)2: 1b: (Ph)1‐SiMe3], a different stability of the (methylenephosphanyl)1‐metal complexes is observed, which results in a broad spectrum of reactivities. As demonstrated by the reactions of the (methylenephosphanyl)metal complexes with sulfonic acid derivatives (10a – c), diverse transition metal complexes (11a – c), as well as chalcogenes (14a – c, 15), a change in the reactivity is observed, indicating a transition from an olefinic to a carbenic character of the methylenephosphane. In comparison to the phenyl‐substituted derivatives 4a – i the bis(trimethyl)1‐substituted species 3a – j exhibit an increased reactivity. This is reflected in the easy decarbonylation of 3a – d to the phosphavinylidene complexes 12a – d.
Ein einfacher Weg zur Herstellung von Alkylpalladium‐Verbindungen durch PdO‐Bindungs‐Spaltung in kationischen Bis(ether‐phosphan)palladium(II)1‐Komplexen mit Grignard‐Reagenzien
Authors: Lindner Ekkehard , Dettinger Johannes , Fawzi Riad , Steimann Manfred
Published: July 2007

A Simple Method for the Preparation of Alkylpalladium Compounds by PdO Bond Cleavage in Cationic Bis(etherphosphane)palladium(II) Complexes with Grignard Reagents

Herrn Professor Heinrich Nöth zum 65. Geburtstag gewidmet.

The bis(chelate) complexes [Pd(P∩O)2][ClO4]2 (3a – e) react with methylmagnesium chloride with a concomitant cleavage of two weak PdO bonds to give the methyl complexes trans1‐ClPd(P∼O)2(CH3) (4a – e) (P ∼ O; η1‐P1‐coordinated; P∩O: η21‐O, P1‐chelated; Scheme 1). Diffusion of pentane into the reaction mixture of 4a–e in the presence of the formed magnesium salts yields the cationic complexes trans‐[Ch3Pd(P∼O)1‐(P∩O)][ClO4] (6a, c). The reaction of 3a–e with benzylmagnesium chloride affords the cationic benzyl complexes cis‐[PhCh2Pd(P∼O)(P∩O)][ClO4] (8a–e) in which only one PdO bond has been cleaved. In the presence of carbon monoxide 4a–e adn 6a, c are transformed into the corresponding acyl complexes CH3C(O)Pd(P∼O)2Cl (5a–e and [CH3C(O)Pd‐(P∼O)(P∩O)][ClO4] (7a, c). Whereas at 183 K variable‐temperature 31P{1H}1‐NMR measurements of 6a, c, 7a, c indicate a non‐rigid behavior of the two differently bound ether‐phosphanes, the dynamic process is frozen out for 8a–e. By a lineshape analysis of the spectra the thermodynamic parameters ΔG≢, ΔH≢, and ΔS≢ are obtained. According to a crystal structure analysis 3d and 6c crystallize in the monoclinic space group P21/c with Z4.
Carben‐analoge Amidoosmium‐Komplexe mit OsN‐Doppelbindung: Synthese, Struktur und Reaktivität von [(Mes)Os(=NHR)(PiPr3)]PF6
Authors: Daniel Thomas , Mahr Norbert , Werner Helmut
Published: July 2007

Carbene‐Type Amidoosmium Complexes with an OsN Double Bond: Synthesis, Structure and Reactivity of [(Mes)Os(=NHR)(PiPr3)]PF6*

The reaction of [(Mes)Os(PiPr3)Cl2] (1) (Mes1,3,5‐C6H3Me3) with primary amines RNH2 (RPh, Me, Et) in acetone/water (1:1) gives, after addition of KPF6, the amidoosmium(II) complexes [(Mes)Os(=NHR)(PiPr3)]PF6 (2–4) in 60–80% yield. From 1 and Et2NH, the chloro(hydrido)compound [(Mes)1‐OsH(PiPr3)Cl] (5) is formed. The X‐ray structural analysis of 2 reveals that the geometry around the osmium atom is trigonalplanar (with the midpoint of the mesitylene ring as one coordination site) and that the OsN distance of 1.923(4) Å is in agreement with an OsN double bond. Thermolysis of 4 (REt) at 165°C leads to the formation of the aldimino(hydrido)osmium complex [(Mes)OsH(NHCHMe)(PiPr3)]PF6 (6) by β1‐hydride migration from the NCH2 carbon atom to the metal atom. Protonation of 3 (RMe) with HCl gives the amine complex [(Mes)Os(NH2Me)(PiPr3)Cl]PF6 (7), whereas on treatment of 3 and 4 with CD3NO2 the deuterated derivatives [(Mes)Os(=NDR)(PiPr3)]PF6 ([D1]‐3, [D1]‐4) are almost quantitatively formed. Compound 2 (RPh) reacts with KOtBu by proton abstraction and phosphane elimination to give the dinuclear imidoosmium complex [(Mes)2Os2(μ1‐NPh)2] (8).
Synthese und Struktur von [Rh2(μ1‐NO)(μ1‐H)(PiPr3)4]: Ein chiraler, NO‐und Hydrid‐verbrückter Rhodium(0)1‐Zweikernkomplex
Authors: Wolf Justin , Nürnberg Oliver , Werner Helmut
Published: July 2007

Synthesis and Structure of [Rh2(μ1‐NO)(μ1‐H)(PiPr3)4]: A Chiral, NO‐and Hydride‐Bridged Binuclear Rhodium(0) Complex

The reaction of RhCl3 · 3 H2O, PiPr3, iPrONa / iPrOH and N1‐methyl‐N1‐nitroso‐4‐tosylamide (diazald) yields the binuclear rhodium complex [Rh2(μ1‐NO)(μ1‐H)(PiPr3)4] (3) in 67% yield. 3 is probably formed via [RhH(PiPr3)3] (4) for which an improved preparative procedure is given. The X‐ray structural analysis of 3 proves that two pairs of inequivalent phosphane ligands are present. In solution, 3 shows a fluctional behavior which is reminiscent to that of molecules possessing axial chirality.
Synthesis of 2,6‐Diphenylbarbarlane by Oxidation of Dipotassium 2,6‐Diphenylbicyclo[3.3.1]nonadienediide with 1,2‐Dibromoethane. – Preparative Reversed‐Phase Liquid Chromatography of Hydrocarbons
Authors: Quast Helmut , Carlsen Jürgen , Janiak Rolf
Published: July 2007

The diphenylbicyclo[3.3.1]nonadiene 11 is deprotonated by butylpotassium to afford the black‐red crystalline dipotassium diphenylbicyclo[3.3.1]nonadienediide 12. At low temperatures, 12 is oxidized in tetrahydrofuran solution by 1,2‐dibromo‐ethane yielding the diphenylbarbaralane 13 which is isolated in 57% yield on a 20‐mmol scale after cyclic liquid chromatography on C18 reversed‐phase silica gel with methanol. The packing procedure for suitable columns is also detailed.
A Methyl Group Effect on the Conformation of Methylated [3.2]Metacyclophan‐10‐enes
Authors: Grützmacher Hans‐Friedrich , Neumann Ekkehard
Published: July 2007

The syntheses of 7,13‐dimethyl[3.2]metacyclophan‐10‐ene (5) and 7,10,11,13‐tetramethyl[3.2]metacyclophan‐10‐ene (6) starting from 1,3‐bis(4‐methylphenyl)propane (1) are reported. 5 exists in the anti conformation typical of [3.2]metacyclophan‐enes while 6 prefers the syn conformation because of steric repulsion between the methyl groups at the etheno bridge and at the aromatic rings.
[n + 2]‐Cycloadditionsreaktionen des (Arylimino)phosphenium‐Ions, [P≡NAr]+–kationische PN‐Heterocyclen mit ungewöhnlicher Struktur und Bindungssituation
Authors: David Gabriele , Niecke Edgar , Nieger Martin , Gönna Volker Von Der , Schoeller Wolfgang W.
Published: July 2007

[n + 2] Cycloaddition Reactions of the (Arylimino)phosphenium Ion, [P≡NAr]+–Kationic PN Heterocycles with Unusual Structure and Bonding Situation

The iminophosphenium ion [P≡NAr]+ (Ar=2,4,6‐tBu3C6H2) (1) reacts with aminoiminophosphanes R2N–P=NtBu (R=iPr, Me3Si) (2) and alkyl azides RN3 (R=tBu, Et3C) (6) to yield the corresponding [n + 2] cycloadducts [R2NP (NAr)P(NtBu)+ (3) and [PN(Ar)NNN(R)]+ (7), respectively. Single‐crystal X‐ray diffraction studies show that 3a can be considered as an intramolecular donor‐acceptor complex while 7 can be regarded as a cyclic diaminophosphenium cation coupled to a diimine fragment, which is in accordance with results of ab initio calculations.
Weitere Reaktionen der Iminoborane RB≡NR′ mit Neopentylidentantal‐Komplexen
Authors: Braunschweig Holger , Paetzold Peter , Boese Roland
Published: July 2007

Further Reactions of Iminoboranes RB≡NR' with Neopentylidenetantalum Complexes

The azaboratantalacyclobutanes [–NR≡–BR–CH(tBu)–Ta‐CpCl2–] (3b, d, f, h–1; R/R′=Pr/tBu, iPr/tBu, iPr/iPr, tBuCH2/tBuCH2, Me3SiCH2/Me3SiCH2, tBu/Me, tBu/iPr, tBu/SiMe3) are formed from the corresponding iminoboranes RB≡NR′ and the neopentylidenetantalum complex [tBuHC=TaCpCl2] (2a) by [2 + 2] cycloaddition. The elimination of HCl from 3b, d, f, h and from the four known azaboratantalacyclobutanes 3a, c, e, g [R/R'equals;Et/tBu, Bu/tBu, Ph/tBu, iBu/iBu] gives the azaboratantalacyclobutenes [–NR′–BR–C(tBu)TaCpCl–] (4a–h). X‐Ray structural analyses of 4e, f show these cyclic carbenetantalum complexes to contain short Ta–C and Ta–N bonds and perhaps some transannular Ta–B interaction. The complex [tBuHC=TaCl3(THF)2] (2b) adds iminoboranes RB≡NtBu with unbranched alkyl groups (R=Et, Pr, Bu) in a 1:2 molar ratio to yield the diazoniadiboratatantalacyclohexadienes 5a–c; the product 5a adopts a non‐planar ring structure in the crystal. The 1:2 reaction of 2b with tBuB≡NMes, instead, results in the cyclobutane [–N(Mes)–B(tBu)–N(Mes)–TaCl3(THF)–] (7m).
[ω‐(Phosphanyl)alkyl]cyclopentadienyl Complexes
Authors: Kettenbach Ralf T. , Bonrath Werner , Butenschön Holger
Published: July 2007

The syntheses and characterisation of the [ω‐(phosphanyl)alkyl]cyclopentadienyl anions 2, 3, 6–8, 10, and 11 are described. These anions form metallocenes 12–15 and 17–19 with FeCl2 · 2 THF and with ZrCl4 · 2 THF, respectively. With ICo(CO)4 chelated carbonbyl complexes 23–25, 28, and 29 are formed. The unchelated intermediate 20 has been detected by IR spectroscopy. The carbonyl chelate complexes are thermally stable. Under photochemical conditions, ligand exchange reactions are possible which in the case of 1,5‐cyclooctadiene proceed with decomplexation of the phosphane arm. This does not prevent a reaction at the cobalt(I) atom; treatment of 35 with diphenylethyne gives the corresponding tetraphenylcyclobutadiene complex 36 in good yield, the phosphane arm remaining uncoordinated.
Chemie des η1‐Rhenium‐koordinierten Triphenylcyclopropenyl‐Liganden
Authors: Löwe Christiane , Shklover Valery , William Bosch H. , Berke Heinz
Published: July 2007

Chemistry of the η1‐Rhenium‐Coordinated Triphenylcyclopropenyl Ligand

The s̀‐coordinated pentacarbonyl[η1‐1,2,3‐triphenylcyclopropenyl)rhenium complex 1 is transformed into the green tetracarbonyl(η2‐1,2,3‐triphenylpropenetriyl)rhenium compound 2 with loss of CO by heating or irradiation. In addition, tetracarbonyl(η3‐4‐oxo‐1,2,3‐triphenylcyclobutenyl)rhenium (3a) and Tricarbonyl(η5‐1,2,3,4,5,6‐hexaphenylcyclohexadienyl)‐rhenium (4) were obtained from this reaction. Treatment of 1 with trimethylamine N‐oxide leads under oxygen transfer to tetracarbonyl(η2‐3‐oxo‐1,2,3‐triphenyl‐1‐propenyl)rhenium (5) and tricarbonyl(trimethylamine)(η2‐3‐oxo‐1,2,3‐triphenyl‐1‐propenyl)rhenium (6). The NMe3 ligand in 6 can be substituted either by CO or trimethyl phosphite to yield 5 or tricarbonyl‐(trimethyl phosphite)(η2‐oxo‐1,2,3‐triphenyl‐1‐propenyl)‐rhenium (7), respectively. Complex 1 reacts with trimethyl‐phosphane or trimethyl phosphite to give tetracarbonyl(phosphorus donor)(η1‐4‐oxo‐1,2,3‐triphenyl‐2‐cyclobuten‐1‐yl)rhenium 8b [L = PMe3] or 8c [L = P(OMe)3]. The derivatives Re(CO)3L2‐η1‐C3Ph3CO [L = CO, 8a; L = PMe3, 8d; L = P(O‐Me)3 8e] were obtained by treatment of 3a with CO or two equivalents of PMe3 or P(OMe)3. The formation of 8d and 8e proceeded via the tricarbonyl(phosphorus donor)(η3‐4‐oxo‐1,2,3‐triphenylcyclobutenyl)rhenium compounds 3b and 3c. The unusual η1‐coordination of the cyclobutenone system in 8 was established by an X‐ray structure analysis of 8c. Furthermore, 4 and 5 were characterized by single‐crystal X‐ray diffraction. Reactions of 2 with alkynes led to substituted tricarbonyl(cyclopentadienyl)rhenium derivatives Re(η5‐C5Ph3RR')(CO)3 9 (R = R' = Ph, 9a; R = R' = CO2Me, 9b; R = R' = CO2Et, 9c; R = Ph, R' = H, 9d).
Beiträge zur Chemie des Imidazols, III. 2‐Telluroimidazoline — stabile Tellurocarbonyl‐Verbindungen
Authors: Kuhn Norbert , Henkel Gerald , Kratz Thomas
Published: July 2007

Imidazole Chemistry, III[1]. — 2‐Telluroimidazolines — Stable Tellurocarbonyl Compounds

2‐Telluroimidazolines 6 are obtained as stable solids from the imidazol‐2‐ylidenes 4 and tellurium in good yields. The X‐ray structure of 6c reveals the relevance of the mesomeric structure 5 [d(C1—Te) = 2.087(4) Å] which is confirmed by the upfield shift in the 125Te NMR spectra (dL < —150).
ω‐Hydroxy‐ortho‐quinodimethane: trapping with trifluoroacetone and photocyclization
Authors: Griesbeck Axel G. , Stadtmüller Stefan
Published: July 2007

ω‐Hydroxy‐ortho‐quinodimethane (2), generated by photoenolization of 2‐methylbenzaldehyde (1) in benzene, is quantitatively trapped with trifluoroacetone to give the bicyclic hemiacetal 6 and the hydroxy aldehyde 7. A less effective trapping reaction is observed with benzaldehyde with the formation of the bicyclic hemiacetal 5. The formation of benzocyclobutenol 4 is probable due to a two‐photon process involving electronically excited 2.
Synthesis, Structure, and Antitumour Testing of Platinum(II) and Palladium(II) Complexes of 1,6‐Diaminotetrahydropyrrolo[2,3‐b]pyrrole‐2,5(1H,4H)‐dione
Authors: Borrell José I. , Beti Carlos , Ventosa Nora , García‐Puig Eduard , Planas Carles , Alvarez‐Larena Angel , Piniella Juan F.
Published: July 2007

The syntheses of the platinum(II) and palladium(II) complexes of 1,6‐diaminotetrahydropyrrolo[2,3‐b]pyrrole‐2,5(1H,4H)‐dione (3) are described. These compounds contain a six‐membered chelate ring with four nitrogen atoms. An X‐ray diffraction study of the palladium(II) complex [Pd(3)Cl2] shows a distorted “sofa” conformation for this chelate ring. Both complexes exhibited in the 1H‐NMR spectrum an ABgem system for the amino protons. In vitro ICL50 and ICT50 and in vivo antitumour activities have been determined for these products. The corresponding dicarboxylato complexes have been obtained by the reaction of the platinum(II) complex [Pt(3)Cl2] with silver sulfate followed by the addition of barium hydroxide and oxalic, malonic, hydroxymalonic, and 1,1‐cyclobutanedicarboxylic acid.
Silaheterocyclen, XXV. (Me3SiO)2SiCHCH2tBu: Ein Siloxy‐funktionalisiertes Syntheseäquivalent für Dichlorneopentylsilaethen
Authors: Auner Norbert , Heikenwälder Claus‐Rüdiger , Ziche Wolfgang
Published: July 2007

Silaheterocycles, XXV[1]. — (Me3SiO)2SiCHCH2tBu: A Siloxy‐Functionalized Synthetic Equivalent for Dichloroneopentylsilene

(Me3SiO)2SiCHCH2tBu (4) is obtained by the reaction of (Me3SiO)2Si(Cl)CHCH2 (2) with LitBu. The reaction proceeds via the α‐lithiated species 3, which can be intercepted by trimethylsilyl triflate to give 5. Silaethene 4 dimerizes to the E/Z‐isomers of disilacyclobutane 7 and adds to Me3SiOMe to give 6. The reactivity of 4 resembles that of Cl2SiCHCH2tBu (1): A [4 + 2] cycloadduct is obtained from the reaction with anthracene, and with 1,3‐cyclohexadiene and 1,3‐cycloheptadiene mixtures of monosilacyclobutanes (10 and 12) and bicyclic Diels‐Alder adducts (9 and 11) are available. Exclusive [2 + 2] cycloaddition reactions take place with styrene (formation of 13), 2,3‐dimethyl‐1,3‐butadiene (→19), and 1,3‐butadiene (→21). With quadricyclane only the product (14) originating from a [2 + 2 + 2] cycloaddition is formed, while with 2,5‐norbornadiene the [2 + 2] and [2 + 2 + 2] cycloadducts (14 and 15) are formed. In addition the ene products (16, 18, 20, 22) are isolated in some cases from side reactions. — The tendency of 1 and 4 to preferably participate in [2 + 2] cycloaddition reactions is ascribed to the polarity of the SiC bond and the additional influence of the π donor ligands at silicon. These factors enable a stepwise [2 + 2] reaction in which the primary zwitterionic intermediates B are cyclized to yield the SiC four‐membered ring compounds.
Neue Wege zu Bis[(cyclopentadienyl)cobalt]‐μ‐(η5‐2,3‐dihydro‐1,3‐diborolyl)‐Tripeldeckerkomplexen über Wasserstoff‐Verschiebungsreaktionen in Derivaten des 4,5‐Diisopropyliden‐1,3‐diborolans, des 2,4,5‐Triisopropyliden‐1,3‐diborolans und des Benzo‐1,3‐diborafulvens
Authors: Enders Markus , Gangnus Bernd , Hettrich Ralph , Magos‐Martin Zsuzsanna , Stephan Martin , Pritzkow Hans , Siebert Walter , Zenneck Ulrich
Published: July 2007

New Routes to Bis[(cyclopentadienyl)cobalt]‐μ‐(η5‐2,3‐dihydro‐1,3‐diborolyl) Triple‐Decker Complexes by Hydrogen Shift Reactions in Derivatives of 4,5‐Diisopropylidene‐1,3‐diborolane, 2,4,5‐Triisopropylidene‐1,3‐diborolane, and Benzo‐1,3‐diborafulvene

The 31 VE dicobalt triple‐decker complexes 6, 7a, 7b, c, 8a, b, and 9a, b with bridging 2,3‐dihydro‐1,3‐diborolyl ligands are prepared. The reaction of the 1,3‐diborole 1 with [(C5Me5)‐Co(C2H4)2] leads to the sandwich complex 5, which is treated with [(C5H5)Co(C2H4)2] to yield unsymmetrical 6. The 4,5‐diisopropylidenetrimethyl‐1,3‐diborolane 3 undergoes a metal‐induced 1,5‐hydrogen shift and reacts with [(C5H5)Co(C2H4)2] to form the triple‐decker 7a. The reaction of the 2,4,5‐triisopropylidene‐1,3‐diborolane 4 with [(C5H5)Co(C2H4)2] leads to a mixture of the triple‐deckers 7b/c, formed by intermolecular hydrogen shift. The benzo‐1,3‐diborafulvene derivatives 2b and 2c also react with [(C5H5)Co(C2H4)2] to give the triple‐decker 8b and a mixture of 9a, b. In addition, the trinuclear complex 8c is obtained in low yield. The new paramagnetic triple‐decker complexes have been analyzed by NMR and ESR spectroscopic measurements as well as by electochemistry. The constitutions of 7b/c, 8b, 8c, and 9a/b have been confirmed by X‐ray structure analyses. The complexes are iso‐structural, the Co—Co distances range from 3.277(1) (7b/c) to 3.316(1) Å for 8c.
Chemie der Isoblausäure, 9. Dreikomponenten‐Cycloadditionen mit Cyanokomplexen
Authors: Fehlhammer Wolf Peter , Rieger Dirk , Lotz Sabine , Kernbach Ulrich , Fuchs Joachim
Published: July 2007

Chemistry of Hydrogen Isocyanide, 9[1]. — Three‐Component Cycloadditions with Cyano Complexes

A novel and obviously general reaction of the coordinated cyano ligand in [M(CN)(CO)5]— (M = Cr, W) is reported, viz. its high‐yield one‐step [2 + 1 + 2] cycloaddition with a great variety of isocyanides and ketones resulting in carbenoid metal complexes of five‐membered N,O heterocycles. The structure of the product 1a from [W(CN)(CO)5]—, tert‐butyl isocyanide, and diethyl ketone has been elucidated by X‐ray diffraction and found to contain a C‐bound non‐aromatic 4‐aminooxazoline with an unprecedented π‐delocalization along the magnified imageexo chain which is also evident from severe low‐field shifts of the C‐2 and C‐4 signals in the 13C‐NMR spectra. The heterocycles are cleaved off the metal by oxidative decomposition with KMnO4/Fe(NO3)3 to give the corresponding oxazolinones, e.g. 4, with a high potential for biological activity. The general validity of this reactivity pattern for metal cyanides is further demonstrated by the successful incorporation of cyanoiron(II) and ‐cobalt(III) species in these three‐component cycloaddition reactions.
Verkronte‐Fullerene
Authors: Osterodt Jens , Windscheif Paul‐Michael , Vögtle Fritz , Nieger Martin
Published: July 2007

Crowned Fullerenes

C60 reacts with [15]crown‐5‐substituted diphenylcarbene precursors to give the corresponding benzo‐crowned methano‐fullerenes 7, which were isolated preparatively and characterized. Two isomers 7a and 7b, which equilibrate to 7a upon heating, were detected by HPCL and separated. The [15]crown‐5‐, [18]crown‐6‐, and bis[15]crown‐5‐substituted hydrazones 3b—d have been prepared. The X‐ray structure analysis of the crowned hydrazone 3b shows distinct hydrogen bonding patterns between NH‐ and crown oxygen atoms in dimer‐type arrangements.
Diastereomerically Pure 3‐(Silyloxy)oxetanes by a Selective Paternò‐Büchi Reaction
Authors: Bach Thorsten , Jödicke Kai
Published: July 2007

Diastereomerically pure 3‐[(trimethylsilyl)oxy]oxetanes 3 were prepared in moderate to good yields (45–72%) by the Paternò‐Büchi reaction of silyl enol ethers 2 with benzaldehyde. The photocycloaddition exhibits a high degree of regio‐ and diastereoselectivity. The substituents R in the silyl enol ether have been varied [R = Me, Et, iPr, tBu, Ph, CH(OMe)2, CH(OCH2)2, C(OCH2)2Me], and it was found that steric bulk is mainly responsible for enhanced selectivity (diastereoselectivity from 70:30 up to 95:5). The regiochemical control is perfect (regioselectivity >95:5) except for silyl enol ether 2a (R = Me) in the case of which a 90:10 ratio of regioisomers was observed. Irradiation of the reaction mixture at lower temperature (–25°C) led to a further improvement of diastereoselectivity. The relative configuration of the products obtained was elucidated both by 1H‐NMR spectroscopy and by chemical degradation. As a mechanistic hypothesis to explain the high observed diastereoselectivity we propose that the steric environment in the intermediate diradical 11 determines the selectivity according to two possible reaction pathways, i.e. bond formation and retrocleavage.
Preparation and Conformational Studies of Ethylene‐Bridged Calixarene‐Analogous Macrocyclic Metacyclophanes
Authors: Yamato Takehiko , Saruwatari Yoshiyuki , Doamekpor Louis Korbla , Hasegawa Ken‐Ichi , Koike Masanori
Published: July 2007

The novel macrocyclic compounds hexahydroxy[2.1.2.1.2.1]‐ (7b) and octahydroxy[2.1.2.1.2.1.2.1]metacyclophane (7c) have been prepared from anisole in six steps by using the tert‐butyl function as a positional protective group on the aromatic ring. Base‐catalyzed condensation of 1,2‐bis(5‐tert‐butyl‐2‐hydroxy‐phenyl)ethane (5) with formaldehyde in refluxing xylene does not afford the dimeric product, tetrahydroxy[2.1.2.1]metacyclophane 6a, but furnishes the larger macrocycles 6b and 6c in 70–90% yield. AlCl3/MeNO2‐catalyzed trans‐tert‐butylation of 6b and 6c in toluene gives the desired metacyclophanes 7b and 7c in 60 and 80% yields, respectively, along with tert‐butyltoluene 8b. The conformations of the systems such as trimer 6b and tetramers 6c, 7c have been evaluated from their dynamic 1H‐NMR spectra. The tetramer 6c is fixed to form a “pleated‐loop” conformation like the calix[8]arenes due to the much more stronger intramolecular hydrogen bonding among the hydroxyl groups than in the trimer 6b.
(Ethyl‐, Ethenyl‐ and Ethynylsilyloxy)aluminum Compounds Generated by Heterolytic Cleavage of 1,3‐Disubstituted Disiloxanes
Authors: Bissinger Peter , Paul Martin , Riede Jürgen , Schmidbaur Hubert
Published: July 2007

sym‐Diorganodisiloxanes RH2SiOSiH2R (R = C2H5, 7; C2H3, 8; C2H, 9) are prepared by hydrolysis of organo(bromo)silanes which are available in high yields by the reaction of organo‐(phenyl)silanes with liquid HBr. Asymmetrical cleavage of these disiloxanes with AlCl3 leads to the formation of organo‐(chloro)silanes and aluminosiloxane dimers [RH2SiOAlCl2]2 (R = C2H5, 10; C2H3, 11; C2H, 12). Crystal structure determinations of 11 and 12 reveal a planar centrosymmetrical SiOAl2OSi skeleton with three‐coordinate oxygen atoms and tetrahedral four‐coordinate aluminum atoms. Treatment of 7–9 with Me2AlCl yields volatile dimethylaluminumorganosilyl oxides [RH2SiOAlMe2]x (R = C2H5, 13; C2H3, 14; C2H, 15; x = 2, 3, 4). NMR studies confirm the presence of more than one oligomer in solutions of these compounds. The asymmetrical compound (HC‐CSiH2O)2Me3Al2Cl (16), resulting from small amounts of MeAlCl2 in the Me2AlCl used, is isolated as a byproduct in the synthesis of 15. The crystal structure of 16 shows a disorder of the molecules leading to pseudosymmetry with a center of inversion.