bluuebunny/crossref_metadata_2025 huggingface dataset:
Alkylvanadium‐ und Alkylniobium‐Reagentien, II. Niobium‐induzierte reduktive Carbonyldimerisierung
Authors: Kauffmann Thomas , Kallweit Harry
Published: July 2007

Alkylvanadium and Alkylniobium Reagents, II. — Niobium‐Induced Reductive Carbonyl Dimerisation

NbCl5 reacts with one equivalent of methyllithium or metallic potassium to give a reagent for the transformation of aldehydes, ketones, benzalchloride, and benzotrichloride to symmetrically substituted ethene derivatives (Tab. 1). The reagent NbCl5/K (2) is distinctly more reactive than NbCl5/MeLi (1). For the reductive carbonyl dimerisation with niobium reagents a mechanism is proposed.
Zum Mechanismus der Cyclopropan‐“Walk”‐Umlagerung: Synthese und Eigenschaften eines optisch aktiven Diazoalkan‐Addukts von Toluol; eine hochstereoselektive N2‐Eliminierung
Authors: Klärner Frank‐Gerrit , Band Rudiger , Glock Volker , König Wilfried A.
Published: July 2007

Mechanism of the Cyclopropane “Walk” Rearrangement: Synthesis and Properties of an Optically Active Diazoalkane‐Toluene Adduct; a Highly Stereoselective N2 Elimination

The synthesis and the thermal and photochemical behavior of the optically active 2‐diazo‐1‐methoxypropane‐toluene adduct 3 are reported. The N2 elimination of 3 ocurs with one and the same stereochemical course upon thermolysis as well as direct photolysis: 7‐(Methoxymethyl)‐1,7‐dimethyl‐1,3,5‐cycloheptatriene (1) is formed with retention of configuration at C‐7 and 7‐(methoxymethyl)‐2,7‐dimethyl‐1,3,5‐cycloheptatriene (2) with inversion of configuration at C‐7. These stereochemical findings are explained by an intermediary singlet diradical 1[4] in which the ring closure between C‐1 and C‐7 or C‐5 and C‐7 is faster than the rotation around the single bond between C‐6 and C‐7. In the case of the thermally induced formation of 2 a concerted N2 elimination has to be considered as a competitive pathway. The results presented here are well in accord with the stereochemical analysis of the cyclopropane “walk” rearrangement 1⇋2 reported previously and are therefore a good evidence that the diradical intermediate 4 is also involved in the “walk” rearrangement. In the photochemically induced N2 elimination of 3, sensitized by benzophenone and leading again to 1 and 2, a surprisingly high degree of stereoselectivity is observed. Thus, the intermediary triplet diradical 3[4] must have a much shorter life time than ordinary 1,3‐diradicals in the triplet state.
Novel Transformations of 1,2‐Dioxetanes: β‐Hydroxy Ethers by Addition of Alkyllithium Reagents
Authors: Adam Waldemar , Heil Markus
Published: July 2007

The reaction of 1,2‐dioxetanes with alkyllithium reagents was investigated. The 3,3‐disubstituted dioxetanes 2a,d and their halogen‐substituted analogues 2b,c, which were used as probes to differentiate between the mechanistic alternatives (SN2 reactivity vs. single‐electron transfer), reacted with n‐BuLi to afford the β‐hydroxy ethers 3a—d. Additionally, the epoxide 4 was obtained from dioxetanes 2b,c. The epoxide 5 and a small amount of acetophenone were found in the reaction of dioxetane 2c with triphenylmethyllithium, but only the minor part of the dioxetane‐derived products could be identified. The observation of the epoxides 4 and 5 led to the mechanistic conclusion that nucleophilic attack (SN2 reactivity) is the most prominent process in this reaction.
2‐{[2‐(Dimethylamino)ethyl]methylamino}‐1,3,2‐benzodioxaphosphol als Ligand in Übergangsmetallkomplexen — Kristall‐ und Molekülstruktur eines Tetracarbonylchrom‐Komplexes
Authors: Kaukorat Thomas , Fischer Axel , Jones Peter G. , Schmutzler Reinhard
Published: July 2007

2‐{[2‐(Dimethylamino)ethyl]methylamino}‐1,3,2‐benzodioxaphosphole as a Ligand in Transition‐Metal Complexes. Crystal and Molecular Structure of a Tetracarbonyl Chromium Derivative

Complexes of the zerovalent transition metals chromium, molybdenum, iron, and platinum react with the title phosphorus‐(III)‐compound 3 to give a range of different products: in the coordination compounds 4 and 5, 3 functions as a bidentate ligand, coordinating to the metal through the phosphorus and the nitrogen atom of the dimethylamino group. The structure of 4 was confirmed by a single‐crystal X‐ray analysis, showing a ligand “bite” angle of 91.0, 91.4° in two independent molecules. In the compounds 7 – 9, involving Mo, Fe, and Pt as a central atom, 3 coordinates solely through P(III). For the platinum(O) complex 9 31P‐NMR spectroscopy revealed a dynamic behaviour at room temperature.
Trichloro‐μ3‐[tris(diphenylphosphanyl)methane]‐trigold(I): Auriophilicity in a Triangle of Gold Atoms
Authors: Stützer Albert , Bissinger Peter , Schmidbaur Hubert
Published: July 2007

Trichloro‐μ3‐[tris(diphenylphosphanyl)methane]‐trigold(I) (1) has been prepared by treating the tripod ligand tris(diphenylphosphanyl)methane with three equivalents of chloro(dimethyl sulfide)gold(I) in dichloromethane. 1 is converted into the tribromo (2), triiodo (3), and trimethyl derivatives (4) by treatment of suspensions of 1 in acetone with hydrogen bromide, potassium iodide, and methyllithium, respectively. Polycrystalline 1 has been studied by Mößbauer spectroscopy. From dichloromethane at room temperature cubic crystals of 1 are obtained, whereas at — 30° C a monoclinic dichloromethane solvate of 1 crystallizes. X‐Ray structure analyses have been performed for both forms. They contain essentially the same trinuclear complex with only marginal differences in the molecular dimensions. The striking structural feature of the complex is the triangular all‐cis arrangement of the three gold atoms with rather short Au…Au contacts of 3.201(1) (cubic) and 3.281(1)—3.420(1) Å (monoclinic). This conformation is at variance with the structures of the free ligand (all‐trans) and other adducts of the type HC(PPh2X)3 (cis/cis/trans) and is probably due to specific metal‐metal interactions.
Reaktive E = C(p—p)π‐Systeme, XXXI Erste Vertreter aminosubstituierter 1,2,4‐Diazaphosphole
Authors: Grobe Joseph , Van Due Le , Hegemann Marianne , Krebs Bernt , Läge Mechtild
Published: July 2007

Reactive E = C(p—p)π Systems, XXXII[1]. — First Representatives of Amino‐Substituted 1,2,4‐Diazaphospholes

(Diisopropylamino)phosphaethyne iPr2N—C≡P reacts at 20° C in a [3 + 2] cycloaddition with (trifluoromethyl)diazomethane (2a) or methyl diazoacetate (2b) to yield a mixture of the corresponding regioisomers 1H‐1,2,4‐diazaphospholes (5a or 5b) and 1H‐1,2,3‐diazaphospholes (6a or 6b) in quantitative yields (isomer ratio: 5a/6a = 2:1; 5b/6b = 4:1). X‐ray diffraction studies on 5a and 5b indicate a delicate charge balance in the bonding system of 1H‐1,2,4,σ2‐diazaphospholes under the influence of the exocyclic push/pull substituents iPr2N and CF3 or CO2Me, respectively.
Synthesis and Characterization of O‐Triorganosilyl Selenocarboxylates
Authors: Kato Shinzi , Kageyama Hideki , Kawahara Yasuyuki , Murai Toshiaki , Ishihara Hideharu
Published: July 2007

A series of O‐triorganosilyl selenocarboxylates 2 are prepared by the reaction of sodium or potassium selenocarboxylate 1 with triorganosilyl chlorides. The selenone esters 2 are stable towards heat, but labile towards moisture, and are formed via Se‐triorganosilyl selenocarboxylate 3. In the mass spectrometer, isomerization of 2 to its less stable selenol ester 3 takes place, resembling the Schönberg thione‐thiol rearrangement.
Ringschluß zu organosubstituierten Alkalimetall‐2,5‐dihydro‐1,2,5‐oxadiboratolaten[1]
Authors: Köster Roland , Seidel Günter
Published: July 2007

Ring Formation to Organo‐Substituted Alkalimetal 2,5‐Dihydro‐1,2,5‐oxadiboratolates[1]

The organo‐substituted cis‐1,2‐diborylalkenes cis‐Et2BC(Et)C(R′)BR2 (1: R = Et, R′ = Me; 2: R2 = C8H14, R′ = Me; 3: R,R′ = Et; 4: R2 = C8H14, R′ = Et; 5: R = Ph, R′ = Et; 6: R = Et, R′ = Ph), prepared from Na[Et3BCCR′] and R2BCl, react with alkali metal hydroxides MOH (M = Na, K) in toluene to form the corresponding 1:1 addition compounds (M‐7 to M‐12) quantitatively. On heating to ⩾ 100°C of M‐7, M‐9, and M‐12 1 mol of ethane is split off to yield the salts and with regioisomeric anions [M‐13/M‐iso13: R = Et, R′ = Me; M‐15: R,R′ = Et; M‐19/M‐iso19: R = Et, R′ = Ph) of not yet identified structures. Heating of M‐8 and M‐10 yields the salts (M‐14: R = Me; M‐16: R = Et), whereas M‐11 gives the two salts (M‐17) and (M‐18).
Some Unusual Reactions of 1,2‐Bis(phenylethynyl)benzene with Sulfur, Carbon Monoxide and Alkyl Acetylenedicarboxylates
Authors: Badrieh Yacoub , Greenwald Ayala , Schumann Herbert , Blum Jochanan
Published: July 2007

1,2‐Bis(phenylethynyl)benzene (1) reacts with sulfur, carbon monoxide, and acetylenedicarboxylic esters to give unusual polycyclic products. Under exclusion of air 1 adds sulfur to give 6‐phenylbenz[b]indeno[2,1‐d]thiopyran (3b) and bis(6‐phenylbenz[b]indeno[2,1‐d]thiopyran‐11‐yl) disulfide (4). In the presence of air 3‐benzoyl‐2‐phenyl‐1H‐inden‐1‐one (5) is formed via a sulfur‐containing intermediate. Under phase‐transfer conditions [CH3N(C8H17)3]+ [RhCl4(H2O)2]− promotes reductive carbonylation of 1 to give initially the lactones 3,8‐dihydro‐ and 8,8a‐dihydro‐3‐phenyl‐8‐(phenylmethylene)‐2H‐indeno[2,1‐b]furan‐2‐one (6 and 7) which isomerize to 3‐phenyl‐8‐(phenylmethyl)‐2H‐indeno[2,1‐b]furan‐2‐one (8). Interaction of 1 and MeO2CC≡CCO2Me in the presence of the same rhodium catalyst results in crosscyclooligomerization in which tetramethyl 2‐(phenylethynyl)‐1,1′:2′,1′'‐terphenyl‐3′,4′,5′,6′‐tetracarboxylate (9) is obtained. The H2PtCl6‐Aliquat‐336 catalyst promotes the reaction of 1 with equimolar amounts of RO2CC≡CCO2R (R = Me, Et, Pr) to give the corresponding (Z)‐2‐(10‐phenylindeno[2,1‐α]inden‐5‐yl)‐2‐butendioates (11a–c). The structures of 3b, 4, 5, 8, and 11a have been determined by X‐ray diffraction analyses. Possible routes for the transformation of 1 into the polycyclic products are discussed.
Transition‐Metal Silyl Complexes, 43[1] Preparation and Fluxionality of the Complexes FeH3(PPh2R')3ER3 (E = Si, Sn; R' = Et, nBu)
Authors: Schubert Ulrich , Gilbert Steffen , Mock Stefan
Published: July 2007

The complexes FeH3(PPh2R')3ER3 (R' = nBu: ER3 = SnPh3, SiMePh2; R' = Et: ER3 = SnPh3) were prepared by reaction of Fe(H)2(H2)(PPh2R')3 with HSnPn3 or HSiMePh2. The heavy‐atom skeleton of FeH3(PPh2Et)3SnPh3 shows an approximate C3 symmetry in the crystalline state and a nearly tetrahedral FeP3Sn core. However, the NMR spectra indicate the presence of Fe,H,Si(Sn) three‐center two‐electron bonds at low temperature in solution.
Dithiocarbonsäuren und Derivate aus Carbonsäureestern und Lactonen mit dem Organoborsulfid‐Reagenz (9‐BBN)2S
Authors: Köster Roland , Kucznierz Ralf , Seidel Günter , Betz Peter
Published: July 2007

Dithiocarboxylic Acids and Derivatives from Carboxylic Esters and Lactones with the Organoboron Sulfide Reagent (9‐BBN)2S[1]

Bis(1,5‐cyclooctanediylboryl) sulfide (1) reacts with carboxylic esters to give the dithiocarboxylic 1,5‐cyclooctanediylboryl esters 2a–f in high yields (2a: X‐ray crystal structure analysis). Methanolysis of 2a–f leads to the dithiocarboxylic acids 5a–f, which form the corresponding piperidinium salts in the presence of piperidine. When cyclic esters (γ‐, δ‐lactones) are allowed to react with 1, the boryloxy‐substituted dithiocarboxylic 1,5‐cyclooctanediylboryl esters 3a–c are obtained.
Übergangsmetallkomplexe von Diazenen, XXX. Zur Photoreaktion von Octacarbonyl‐dimetallaheterocyclen mit Bis(phosphanen)
Authors: Kisch Horst , Holzmeier Peter , Knoch Falk
Published: July 2007

Transition Metal Complexes of Diazenes, XXX[1]. – On the Photoreaction of Octacarbonyl Dimetallaheterocycles with Bis(phosphanes)*

Irradiation of (CO)4Cr(μ‐pmd)2Cr(CO)4 (1) (pmd = 3,3‐penta‐methylenediazirine) in the presence of bis(dimethylphosphanyl)methane (dppm) affords (CO)3(μ‐pmd)2(μ‐dppm)Cr(CO)3 (2b) and (CO)4Cr(μ‐pmd)(μ‐dppm)Cr(CO)4 (3b) which both contain boat‐like dimetallaheterocyclic rings as indicated by X‐ray analysis. Contrary to that, in the presence of cis‐1,2‐bis(diphenylphosphanyl)ethene the reaction affords the known Cr(CO)4(cdpe) (4c) by complete cleavage of the dimetalla‐heterocycle.
Isocyanid‐ und Heteroallen‐verbrückte Metallkomplexe, VIII. Dieisenkomplexe mit Acylisocyanid‐ und Iminoacylisocyanid‐Brückenliganden
Authors: Fehlhammer Wolf Peter , Schröder Andreas , Sperber Wilfried , Fuchs Joachim
Published: July 2007

Isocyanide‐ and Heteroallene‐Bridged Metal Complexes, VIII[1,2]. – Diiron Complexes with Bridging Acyl Isocyanide and Iminoacyl Isocyanide Ligands

Acylation (aroylation, carbamoylation, imino acylation) of the terminal cyano ligand in Na[Fe2(CN)Cp2(CO)3] (1) leads to the acyl isocyanide (aroyl, carbamoyl, iminoacyl isocyanide)‐bridged neutral complexes [Fe2Cp2{μ‐CNC( = O)R}(CO)3] (2a–i) and [Fe2Cp2{μ‐CNC( = NPh)Ph}(CO)3] (3). An X‐ray structure analysis has been carried out of the pentafluorobenzoyl isocyanide complex 2 f, important results of which are the cis configuration of the complex, the 163.7° puckering of the central Fe2(μ‐C)2 rhomboid, short [1.892(5), 1.911(5) Å] Fe–μ‐C distances to the acyl isocyanide ligand, the nonplanarity of the latter and the 132° bend at the isocyano nitrogen. The contribution of a μ2‐2‐azaallenylidene form is assumed to explain the bonding.
Catalyzed Enantioselective Alkylation of Aldehydes
Authors: Bolm Carsten , Schlingloff Gunther , Harms Klaus
Published: July 2007

Enantioselective alkylation of a variety of aldehydes with diethylzinc was achieved by using catalytic amounts of optically active pyridines and C2‐symmetric 2,2′‐bipyridines. The products were obtained in good yields with high enantioselectivities. Steric factors of the catalyst structure which govern the stereoselectivity were revealed, and important reaction intermediates were identified by spectroscopic means and singlecrystal X‐ray diffraction. The effect of additives on the optical purity of the product was studied. A strong asymmetric amplification was found with catalysts of low ee′s.
Erste röntgenographische Charakterisierung N‐lithiierter 4‐Alkyliden‐1,4‐dihydropyridine des Typs [{4‐(CH3CR)C5H4N}Li(TMEDA)]2: Vergleich von Kristall‐ und MNDO‐Strukturdaten sowie Untersuchungen zur Lithium‐Koordination in Lösung
Authors: Anders Ernst , Opitz Andreas , Boese Roland
Published: July 2007

The First X‐ray Structures of N‐Lithiated 4‐Alkylidene‐1,4‐dihydropyridines [{4‐(CH3CR)C5H4N}Li(TMEDA)]2: Comparison of the X‐ray and MNDO Geometries and Investigation of Lithium Coordination in Solution

The 4‐ethyl‐ and ‐isopropylpyridines 5a and b were transformed into the lithiated compounds [{4‐(CH3CH)C5H4N}‐Li(TMEDA)]2 (6a) and [{4‐(CH3CCH3)C5H4N}Li(TMEDA)]2 (6b) by reaction with LDA and in the presence of TMEDA. These compounds were recrystallized from a toluene/hexane solution to obtain suitable crystals for X‐ray investigations. Both structures are dimeric containing nonstoichiometric amounts of toluene in the crystals. The structural parameters of the heterocyclic moieties of 6a or b are typical of N‐lithiated 4‐alkylidene‐1,4‐dihydropyridines. MNDO geometries compare quite well with the X‐ray structure of 6a. The lithium atom of 6a in solution prefers the same type of coordination as in the crystal: Two‐dimensional 6Li,1H‐HOESY showed Li contacts only to ortho‐hydrogen atoms (Figure 3). 6a and b react differently with chlorotrimethylsilane (8). The variations of the alkylidene moieties of 6a and b, although seemingly small, are decisive: While the α,α‐dimethyl compound 6b reacts exclusively as an N nucleophile, the α‐methyl compound 6a functions also exclusively as a Cα nucleophile.
The unusual oxidation of a 1,5,2,4‐diazadiphosphorinan‐6‐one with tetrachloro‐ortho‐benzoquinone
Authors: Shevchenko Igor V. , Fischer Axel , Jones Peter G. , Schmutzler Reinhard
Published: July 2007

The oxidation of 2,4‐bis(diethylamino)‐1,5‐dimethyl‐1,5,2,4‐diazadiphosphorinan‐6‐one (1b) with two equivalents of tetrachloro‐ortho‐benzoquinone (TOB) (2) leads to the cleavage of the original heterocycle and to the formation of a mixture of compounds, including the 1,3,2‐diazaphosphetidine 6 (“λ6P‐”) and the spirophosphorane 7. Compound 7 exists as two isomers that undergo slow spontaneous transformation in solution to compound 9, containing a six‐coordinate phosphorus atom. When the oxidation of 1b is carried out in two stages, with the second equivalent of TOB being added after an interval of four days, the cleavage of the original molecule does not occur, and compound 17, containing a seven‐membered ring with two phosphorus atoms of opposite formal charge and different coordination number (“λ4P+,λ6P‐”) is formed. The structures of 6, 7, 9, and 17 were established by low‐temperature X‐ray analysis. Compound 6 displays crystallographic twofold symmetry; the coordination at phosphorus is octahedral, but distorted by the phosphetidine ring. The phosphorus atom in 7 possesses square pyramidal coordination geometry, the pyramid base being defined by the four oxygen atoms. Compound 9 (“λ6P‐”) crystallized with two molecules of CDCl3. Compound 17 crystallized as a dichloromethane solvate. Distorted octahedral and tetrahedral geometries were observed for P1 and P2, respectively. The four‐membered ring is planar. The bridging hydroquinone ligand displays much wider O–C–C(–O) and C–O–P angles than the chelating hydroquinone.
Conversion of ferriosilanes to ferriosilanols by selective oxidation of the sih function by dimethyldioxirane
Authors: Adam Waldemar , Azzena Ugo , Prechtl Frank , Hindahl Kathrin , Malisch Wolfgang
Published: July 2007

The reaction of ferriohydridosilanes Cp(CO)(L)Fe–SiR2H (R = Me, t‐Bu, Ph, o‐Tolyl; L = CO, Ph3P) 1a–e with dimethyldioxirane (as an acetone solution) leads directly to the corresponding ferriosilanols Cp(CO)(L)Fe–SiR2OH 2a–e in moderate to excellent yields.
Benzoanellated centropolyquinanes, 12[1]trifuso‐centrotetraindan – two syntheses of a new centropolyindan
Authors: Kuck Dietmar , Seifert Monika
Published: July 2007

Two independent syntheses of the new centrotetraindan 2, a “trifuso”, Cs‐symmetrical isomer of fenestrindan 1, are described. The first approach is based on the “endo”‐phenyldiindanone 7, which is converted into 2 by benzylation to ketone 8 and subsequent cyclodehydration with polyphoshoric acid. The second, more efficient approach is based on the diindan‐dione 17, which is converted into ketol 19 in two steps, which, in turn, is subjected to a three‐step cyclodehydration‐reduction‐cyclodehydration sequence via 26 and 27 to give 2 in 8% overall yield. Some limits of the cyclodehydration of diindan alcohols and ketones are demonstrated with regard to effects of steric crowding and fragmentation of the carbon skeleton. The steric hindrance of “endo”‐phenyl‐substituted diindans is demonstrated in the case of ketone 26.
Synthese mittlerer und großer Ringe, XXXI[1] Die [6](3,6)Oxepinophan‐[6](2,5)Furanophan‐Ringverengung mit Rutheniumtetroxid
Authors: Tochtermann Werner , Luttmann Kay , Sdunnus Norbert , Peters Eva‐Maria , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Synthesis of Medium and Large Rings, XXXI[1] – The [6](3,6)Oxepinophane‐[6](2,5)Furanophane Ring Contraction with Ruthenium Tetroxide

A one‐pot synthesis of the furanophanes 2a and 2b by ring contraction of the oxepinophanes 1a and 1b is described. Evidence is presented that the reaction proceeds by subsequent oxidation of two double bonds via the intermediates 3 and 4. On treatment with hydrochloric acid cis‐4 gives 2a by 1,4‐elimination of hydrogen peroxide. The oxidation of the [7](3,6)oxepinophane 1c leads to a complex mixture of the products 2d and 6–10. 2a undergoes Diels‐Alder reactions with benzyne and 2,3‐naphthalyne to give 11 and 12. The latter forms the stable iron tricarbonyl complex 13. The structures of 2c, 4, 10, 11, and 13 have been established by X‐ray analyses.
Regioselective preparation of iodinated phloroglucinols
Authors: Schmidt Boris , Hoffmann H. Martin R.
Published: July 2007

A range of mono‐ and diiodinated phloroglucinols with differential protection of two hydroxy groups has been prepared.
Synthese von 3H‐1,2,3,4‐Triazametallol‐Komplexen durch Addition von Azidoameisensäure‐methylester an die Metall – Kohlenstoff‐Dreifachbindung Cyclopentadienyl‐substituierter Carbin‐Komplexe von Molybdän und Wolfram
Authors: Stegmair Claudia M. , Ullrich Waltraud , Schütt Wolfgang , Kiprof Paul , Kreißl Fritz R.
Published: July 2007

Synthesis of 3H‐1,2,3,4‐Triazametallole Complexes by the Addition of Methyl Azidoformate to the Metal–Carbon Triple Bond of Cyclopentadienyl‐Substituted Carbyne Complexes of Molybdenum and Tungsten

N3CO2Me attacks the electron‐rich metal–carbon triple bond in C5H5(CO)2 ‐ n (PMe3)nMCR (M = Mo, W; R = Ph, Tol; n = 0, 1) (1) to provide neutral 3H‐1,2,3,4‐Triazametallole complexes 2.
Mehrfach verbrückte Triphenylmethane
Authors: Berscheid Ralf , Vögtle Fritz , Nieger Zzmartin
Published: July 2007

Multiple‐Bridged Triphenylmethanes

Up to fourfold‐bridged macrocyclic compounds bearing triphenylmethane units which form a large molecular cavity were prepared for the first time. The macrobicyclus 4 crystallizes from acetonitrile as 1:1 adduct and from phenylacetonitrile as 1:3 adduct with the respective solvent. The X‐ray structures of these complexes are compared with the related 1:5 adduct of 13 with benzene.
Übergangsmetall‐substituierte Diphosphene, XXVIII. Synthese und Strukturbestimmung der ersten 1,2‐Diaza‐3,4‐diphosphetidine und (2E,8E)‐1,7‐Dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadiene
Authors: Weber Lothar , Bastian Holger , Boese Roland , Stammler Hans‐Georg , Neumann Beate
Published: July 2007

Transition‐Metal‐Substituted Diphosphenes, XXVIII. – Synthesis and Structures of the First 1,2‐Diaza‐3,4‐diphosphetidines and (2E,8E)‐1,7‐Dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadienes

(η5‐C5Me5)(CO)2FeP  PMes*(Mes*  2,4,6‐tBu3C6H2) reacts with one equivalent of the Δ1‐1,2,4‐triazoline‐3,5‐diones (2a: R = Ph; 2b: R  4‐EtOC6H4) in benzene to give the first 1,2‐diaza‐3,4‐diphosphetidines 3a, b. When the same reaction is performed in diethylether the novel (2E,8E)‐1,7‐dioxa‐3,4,9,10‐tetraaza‐5,6,11,12‐tetraphospha‐2,8‐cyclododecadienes 4a, b are isolated as the sole products. The molecular structures of 3a and 4b are established by single‐crystal X‐ray analysis.
Metal Binding by Amino Acids: Preparation and Crystal Structures of Lithium, Sodium, and Potassium Hydrogen Bis‐L‐pyroglutamate
Authors: Kumberger Otto , Riede Jürgen , Schmidbaur Hubert
Published: July 2007

Lithium, sodium and potassium hydrogen bis‐L‐pyroglutamate [Li(L‐pGlu)(L‐pGluH)], [Na(L‐pGlu)(L‐pGluH)] and [K(L‐pGlu)(L‐pGluH)], respectively, have been prepared by reaction of aqueous solutions of the metal hydroxides with L‐pyroglutamic acid in the molar ratio 1:2, or in methanol. Crystalline samples of the salts could be obtained by slow evaporation of solutions of the salts in methanol. In the solid state, Li(L‐pGlu)(L‐pGluH) adopts a chain structure with the lithium atoms arranged in double strands. Adjacent metal centers are bridged by the carboxylate groups of the L‐pGlu− ligands. The L‐pGluH ligands are attached to the metal centers through the amide oxygen atoms. Na(L‐pGlu)(L‐pGluH) forms a three‐dimensional coordination polymer with two half‐occupied sodium positions, one L‐pGlu− and one L‐pGluH ligand in the asymmetric unit. The carboxyl and carboxylate groups of the L‐pGluH and the L‐pGlu− ligands are bridging the sodium centers, giving rise to eight‐membered rings, which consist of two sodium atoms, a carboxyl and a carboxylate group. The hydrogen atoms of the carboxyl group of the L‐pGluH ligands are involved in strong hydrogen bonds between a carboxyl and an adjacent carboxylate oxygen atom. K(L‐pGlu)(L‐pGluH) adopts a layer structure with strands of potassium atoms. The metal centers are connected through bridging carboxyl and carboxylate groups of the L‐pGluH and L‐pGlu− ligands, respectively. The structure features eight‐membered ring units comparable to those observed for Na(L‐pGlu)(L‐pGluH), again with the hydrogen atom of the carboxyl group engaged in a strong transannular hydrogen bond. The amide oxygen atoms of the L‐pGlu− and the L‐pGluH ligands are coordinated to the metal centers of adjacent coordination chains. The results of 1H‐ and 13CNMR investigations of aqueous solutions of the compounds indicate extensive electrolytic dissociation in dilute solutions.
Carbonyl O‐Oxides and Dioxiranes: The Influence of Substituents on Spectroscopic Properties
Authors: Bucher Götz , Sander Wolfram
Published: July 2007

Triplet 4‐oxocyclohexadienylidenes 6, matrix‐isolated in Ar/ 2% O2 at 10 K, react with triplet O2 on annealing the matrix. Primary reaction products are quinone oxides 4, which have been characterized by IR and UV/Vis spectrometry. They are very photolabile; long‐wavelength irradiation converts them into spiro‐dioxiranes 5, which in turn yield lactones 10 upon irradiation with visible light. Experimental data have been obtained for quinone oxides 4a–g; additionally, ground‐state properties and UV/Vis absorptions of quinone oxides 4a,b and 4e–1 have been calculated by the MINDO‐3/UHF and CNDO/S methods. Since the theoretical and experimental maxima of the π → π* transitions are in good agreement, we conclude that our semiempirical calculations give an adequate picture of quinone oxides 4 which may best be described as dipolar diradicals.
Langgestreckte Moleküle von Dispiro[5.1.5.2]‐Typ
Authors: Boettcher J. , Hartmann R. , Vögtle F.
Published: July 2007

Rod‐Like Dispiro[5.1.5.2] Compounds

A number of symmetrically and unsymmetrically substituted spiro compounds were synthesized starting from the dispiro[5.1.5.2]trione 1. The trans‐trans isomers of 2, 3, 6–10, and 11 were separated from the cis‐cis and cis‐trans isomers. From the trispiro compound 4 derivatives bearing differing substituents were synthesized. The tetraspiro compounds 5 were obtained in one step. Some of the compounds functionalized with flexible sidegroups show narrow liquid‐crystal phases.
Reaktionen von Komplexliganden, IL. Synthese und Struktur fünf‐ und sechsgliedriger Aminocarben‐C,N‐Chelatkomplexe des Chroms
Authors: Dötz Karl Heinz , Rau Alexander , Harms Klaus
Published: July 2007

Reactions of Complex Ligands, IL[1]. – Synthesis and Structure of Five‐ and Six‐Membered Aminocarbene‐C,N‐Chelate Complexes of Chromium

Aminolysis of pentacarbonyl[methoxy(phenyl)carbene]chromium (1) with cyclic diamines affords the aminocarbene complexes 2, 3, and 6 which undergo a thermally or photochemically induced decarbonylation to give (carbene)tetracarbonyl complexes 4, 5, and 7 containing 5‐ or 6‐membered chelate rings. The X‐ray analysis of 5 indicates a half‐chair conformation for the 6‐membered chelate ring.
Sterische Cyclopentadienyl‐Äquivalente in der Chemie der f‐Elemente: Monomere, homoleptische Lanthanid(III)‐tris[N,N′‐bis(trimethylsilyl)‐benzamidinate]
Authors: Wedler Michael , Knösel Friedrich , Pieper Ursula , Stalke Dietmar , Edelmann Frank T. , Amberger Hanns‐Dieter
Published: July 2007

Steric Cyclopentadienyl Equivalents in f‐Element Chemistry: Monomeric, Homoleptic Lanthanide(III) Tris[N,N′‐bis(trimethylsilyl)benzamidinates]

Anhydrous lanthanide trichlorides react with N‐silylated sodium benzamidinates, Na[4‐RC6H4C(NSiMe3)2], (1a–d), to give the monomeric, homoleptic lanthanide(III) benzamidinates [4‐RC6H4C(NSiMe3)2]3Ln (2–23, R = H, MeO, CF3, Ph). The molecular structure of [4‐MeOC6H4C(NSiMe3)2]3Pr (11) has been determined by X‐ray diffraction. Absorption and emission measurements reveal that the three benzamidinate ligands produce an unusually large crystal field which is comparable with that of cyclopentadienyl.
Phosphorus derivatives of anthracene and their dimers
Authors: Wesemann Jodi , Jones Peter G. , Schomburg Dietmar , Heuer Lutz , Schmutzler Reinhard
Published: July 2007

The syntheses of the (9‐anthracenyl)phosphanes 2 to 7 and of the metal carbonyl complexes 8 and 9 are described. Both 1 and 4 undergo [4 + 4] cycloaddition when irradiated, forming the dimers 10 and 11. Only one of the six possible rotamers for 10 is formed. For 11 one additional rotational isomer is observed. The relationship between the [4 + 4] dimerization and steric effects of the PR2 group is discussed. The compounds 6, 8 and 11 were characterized by X‐ray diffraction. The structure of 6 was rendered imprecise by the presence of disordered toluene, but the influence of the bulky anthracenyl groups was clear, with wide CPC angles of 110.4°. The molecule displays imposed threefold symmetry. The two independent molecules of complex 8, which crystallizes as a dichloromethane hemisolvate, are closely similar to each other; the WP bond lengths are 254.3 and 253.4 pm. The WC bonds trans to phosphorus are 4 pm shorter than those cis. The phosphane dimer 11 crystallizes with imposed centrosymmetry. The H atom positions, which could be tentatively identified from difference syntheses, indicate a different rotamer than was formed for the analogous fluorophosphane dimer 10.
Influence of structural factors and enzyme type on the reactivity and enantioselectivity of the enzymatic esterification of bicyclic meso dialcohols
Authors: Asensio Gregorio , Andreu Cecilia , Marco J. Alberto
Published: July 2007

The meso dialcohols 1–7, obtained from the Diels‐Alder adducts furan/maleic anhydride, furan/dimethyl acetylenedi‐carboxylate, and cyclopentadiene/maleic anhydride, were subjected to enzymatic esterification in organic solvents. A mixture of the corresponding chiral monoacetates and the meso diacetates was obtained. It has been found that reaction rate and enantioselectivity markedly depend on substrate structure, temperature, enzyme type, and nature of the solvent. The presence of an oxygen bridge and an exo configuration are the two structural features which lead to the highest enantioselectivity values.
Model studies of the reduction of 3‐phenyl‐6H‐1,2‐oxazines, chemo‐ and stereoselectivity: synthesis of amino alcohols, amino acids, and related compounds
Authors: Zimmer Reinhold , Hoffmann Matthias , Reißig Hans‐Ulrich
Published: July 2007

While palladium‐catalyzed hydrogenation of 3‐phenyl‐6H‐1,2‐oxazine 1 produces primary amine 5 in a nitrogen‐transposition reaction, the reductions of the related 1,2‐oxazines 2, 10, and the 1,2‐oxazin‐6‐one 3 afford the expected amino alcohols 4, 11, and the γ‐amino acid 6, respectively, with low diastereoselectivites. In the presence of acetic acid 3 is reductively converted into γ‐keto carboxylic acid 9 and 1 into the γ‐lactam derivative 12 probably by a ring contraction to a nitrone intermediate. Raney nickel as the catalyst is able to transform 1,2‐oxazine 7 bearing an exo‐methylene unit into 3,4‐dihydro‐2H‐pyrrole 13. The reaction of 6H‐1,2‐oxazine 1 with aluminium amalgam produces pyrrole 14 in moderate yield. Treatment of 1 with sodium in 2‐propanol brings about its transformation into pyrrolidine derivative 15 together with pyrrole 14 and amino alcohol 4 as minor products. The chemoselectivity and stereoselectivity of these reductions are discussed including mechanistic proposals for the multistep processes involved.
Inter‐ and intramolecular hetero diels‐alder reactions, 41. Unusual stereocontrol in intramolecular hetero diels‐alder reactions of 2‐Aza‐1,3‐butadienes. A stereoselective sequential synthesis of annulated tetrahydropyridines
Authors: Tietze Lutz F. , Utecht Jens
Published: July 2007

Condensation of aldehydes 1a–e with 5‐amino‐3‐methylisoxazole (4) gives the corresponding imines 5a–e with a 2‐aza‐1,3‐butadiene moiety, which cyclize selctively, e.g. 5a to form the trans‐fused tetrahydropyridine 7a and 5c to yield the cis‐fused cycloadduct 8c. The astounding difference in the selectivity of these reactions is explained by electronic effects and suggests a change in the dominating interactions of the orbitals in the transition structure. The structure of 7a is elucidated by an X‐ray analysis.
Photoinduced electron transfer in porphyrin‐quinone cyclophanes, 7. Porphyrin‐quinone cyclophanes with gradually varied acceptor strength: Physical properties related to electron transfer
Authors: Staab Heinz A. , Voit Guido , Weiser Jürgen , Futscher Michael
Published: July 2007

Absorption and emission spectra of the doubly quinone‐bridged porphyrin cyclophanes 1–4 with gradually varied acceptor strength as well as of the single‐bridged analogues 5–9 and 10–13 are reported. Reduction and oxidation potentials of these intramolecular porphyrin‐quinone systems have been determined. Based on these data, fluorescence quenching as well as time‐resolved fluorescence lifetime measurements are discussed in terms of photoinduced electron transfer to the charge‐separated zwitterionic state.
Synthesis of N‐ and p‐(Diphenylmethyl)anilines. ESR Study of their Photofragmentation
Authors: Siskos Michael G. , Garas Stylianos K. , Zarkadis Antonios K. , Bokaris Efthymios P.
Published: July 2007

The reaction of N‐substituted anilines 2 with diphenylmethyl halides 1 at room temperature in the presence of AlCl3 affords p‐substituted derivatives 3 in good yields according to an electrophilic aromatic substitution. In contrast, aniline itself is only converted to the N‐substituted compounds 4. A novel rearrangement from Ph3C‐NHPh (4c) to p‐(triphenylmethyl)‐aniline (5) is described. Unexpected photofragmentations of 4a, b are studied by using ESR and ENDOR spectroscopy; e.g., irradiation of 4b with quartz‐ or pyrex‐filtered light leads to the formation of the radicals Ph2C‐SiMe3 (7b) and Ph2C – NHPh (6) respectively, following selective cleavage of the C – N and C – Si bond.
Vielgliedrige Donor‐substituierte Kohlenwasserstoffringe
Authors: Vögtle Fritz , Schmitz Jürgen , Nieger Martin
Published: July 2007

Many‐Membered and Donor‐Substituted Hydrocarbon Rings

The preparation of large rings 2 of the [2n]metacyclophane type by the Müller‐Röscheisen method is described. Yields of cyclic products, potential ligand or host character and ring size can be controlled by intra‐ and extraannular OCH3 groups. The 40‐membered macrocyclus 24 containing eight substituted benzene rings is the largest ring compound of this series isolated so far in pure form. Large substituents OR in position 2 of the starting bis(bromomethyl) compounds lead to higher ring member numbers. The new macrocyclic compounds, with the exception of the “dimer” 7, are all conformationally flexible according to 1H‐NMR spectra. X‐ray structural analyses were performed of the macrocycles 10, 13, 17, and 18; the inclusion of solvent molecules is proven.
Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen, CXX. Niob‐ und Tantalamid–Komplexe sowie neue Cyclocarbodisilazane
Authors: Herrmann Wolfgang A. , Dyckhoff Florian , Herdtweck Eberhardt
Published: July 2007

Multiple Bonds Between Main–Group Elements and Transition Metals, CXX[1]. – Niobium and Tantalum Amide Complexes and New Cyclocarbodisilazanes

The new niobium‐ and tantalum complexes 3a and 3b of formula [(CH3)2 are accesible by the reaction of the oxychlorides MOCl3 with the lithium amide (2) in 30 and 19% isolated yield, resp. The new silazanes cyclo‐[(CH3)2Si(CH2)2Si(CH3)2NH]2 (5) and cyclo‐[(CH3)2Si(CH2)2Si‐(CH3)2NH]3 (6) are prepared from (CH3)2ClSiCH2CH2Si–Cl(CH3)2 and NH3. Their structures – ten‐ and fifteen–membered rings – were determined by single–crystal structure analyses.
Nickel–Zweikernkomplexe mit Ni2E4‐Gerüst (EP, As)
Authors: Scherer Otto J. , Braun Jürgen , Walther Peter , Wolmershäuser Gotthelf
Published: July 2007

Dinuclear Nickel Complexes with Ni2E4 Framework (EP, As)

The photolysis of [Cp4Ni(μ‐CO)]2 (1, Cp4  C5H(iPr)4) and P4 affords [Cp24Ni2P4] (2a) and [Cp4Ni(η3‐P3)] (3a); the thermolysis of 1 and As4 gives [Cp24Ni2As4] (2b) as well as [Cp4Ni(η3‐As3)] (3b). The tetranuclear complex [Cp24Ni2P4{W(CO)5}2] (4) is formed from 2a and [W(CO)5(thf)]. Complexes 2b and 4 have been characterized by X–ray structure analyses.
Preparation and Crystal Structure of Na2[Be(o‐C6H4O2)2] · 5 H2O
Authors: Kumberger Otto , Riede Jürgen , Schmidbaur Hubert
Published: July 2007

Crystalline Na2[Be(o‐C6H4O2)2] · 5 H2O was prepared from beryllium hydroxide and a strongly alkaline aqueous solution of catechol. In an X–ray structure determination the complex was shown to feature dianions [Be(o‐C6H4O2)2]2‐ with two chelating catechol ligands. The 9Be–NMR spectrum of an aqueous solution of the compound shows a singlet at δ  7.5. This signal is shifted considerably from the Beaq2+ reference and indicates persistence of the complexation of the metal ion by the catecholate ligands in alkaline aqueous solution. This result is important in the light of the ubiquitous availability of phenolic groups in many biomolecules, such as e.g. catecholamines.
Preparation and Structure of Hexakis[(trialkylphosphane)aurio(I)]methanium(2+) Salts [(LAu)6C]2+(X‐)2 with LEt3P, iPr3P and XBF4‐, B3O3F4‐
Authors: Schmidbaur Hubert , Brachthäuser Benno , Steigelmann Oliver , Beruda Holger
Published: July 2007

Hexaaurated carbon complexes of the type [(R3PAu)6C](BF4)2, REt (2a), iPr (2b) have been prepared by the reaction of the appropriate (phosphane)gold(I) chlorides R3PAuCl (1a and 1b) with tetrakis(dimethoxyboryl)methane, 13C–enriched at the central carbon atom, in the presence of excess of CsF in HMPT at room temperature. The products 2a and 2b are characterized by standard spectroscopic methods including direct detection of the interstitial C atoms by 13C–NMR spectroscopy. The crystal structure of the compound [(iPr3PAu)6C](B3O3F4)2 · 3 CH2Cl2 (3), obtained from partial (anion) hydrolysis has been determined. It contains dications with a central carbon atom surrounded by six (phosphane)gold(I) units. The edges of the CAu6 octahedron represent short Au–Au contacts (aprox. 3.0 Å), which strongly contribute to the formation and stability of these hypercoordinated species. Attempts to prepare a corresponding hexaauriomethanium dication starting from tBu3PAuCl (1c) failed owing to the bulkiness of the (tri‐tert‐butylphosphane)gold(I) unit. The X–ray structure analysis for 1c verifies an extremely crowded environment of the gold atom with small Au—P—C angles of only 107° leading to efficient shielding of the metal atom by methyl groups.
Ergiebige Herstellung von (R)‐ und (S)‐3,3,3–Trifluormilchsäure und von (R)‐ und (S)‐(Trifluormethyl)oxiran
Authors: Bussche–Hünnefeld Christoph Von Dem , Cescato Claudio , Seebach Dieter
Published: July 2007

Simple Access to (R)‐ and (S)‐3,3,3–Trifluorolactic Acid and to (R)‐ and (S)‐(Trifluoromethyl)oxirane

Ethyl trifluoropyruvate (from hexafluoropropylene oxide) is reduced by NaBH4 to rac‐trifluorolactic acid which is resolved on a 100–g scale by salt formation with (R,R)‐ and (S,S)‐2–amino–1‐phenyl–1,3–propanediol (readily available intermediates of industrial chloroamphenicol synthesis). The enantiomerically pure trifluorolactic acids (>99% ee by GC analysis on cyclodextrin columns) are converted into (R)‐ and (S)‐(trifluoromethyl)oxirane in an overall yield of 73% by the following steps: esterification, THP protection of the OH group, LAH reduction and mesylation to the 2–THP–protected mesylate of 3,3,3–trifluoro–1,2–propanediol, and one–pot deprotection (Dowex 50) and cyclization (NaOCH2CH2OH) in ethylene glycol. The enantiomeric purity of the oxirane (b.p. 39C, isolated on a 10–g scale) was determined by GC to be >99%. Possible synthetic targets are mentioned which should be accessible in enantiomerically pure form from the (trifluoromethyl)oxirane described here.
Thermolabile Kohlenwasserstoffe, 32. Konkurrierende Cope‐;Umlagerung und Homolyse von meso‐ und DL‐3,4‐Di(1‐cyclohexen‐1‐yl)‐2,2,5,5‐tetramethylhexan
Authors: Herberg Clemens , Beckhaus Hans‐;Dieter , Kürtvelyesi Tamas , Rüchardt Christoph
Published: July 2007

Thermolabile Hydrocarbons, 32. — Competing Cope‐;Rearrangement and Homolytic Decomposition of meso‐ and DL‐3,4‐Di(1‐cyclohexen‐1‐yl)‐2,2,5,5‐tetramethylhexane

meso‐ and DL‐3,4‐di(1‐cyclohexen‐1‐yl)‐2,2,5,5‐tetramethylhexane (3a) were prepared by an improved reduction procedure (Li/C2H5NH2) from meso‐ and DL‐2,2,5,5‐tetramethyl‐3,4‐diphenylhexane. Products of two competing thermal transformations, C — C cleavage vs. Cope rearrangement, were isolated and identified. From a kinetic analysis of this system of reactions, characteristic activation enthalpies and entropies were obtained for the competing transformations. The standard heat of formation of meso‐3a (ΔHf0(g) = –58.4 ± 1.2 kcal/mol) was determined by combustion calorimetry and by measurement of its heat of sublimation. A strain enthalpy Hs (meso‐ 3a) = 10.2 ± 1.2 kcal/mol was derived therefrom. Force‐field calculations of the diastereomers of 3a and the Cope products 8a were performed by using MM2, MM2ERW, and MM3 in order to analyse the conformational situation. The calculated ΔHf0(g) values for meso‐3a are higher than the experimental value by 4.4 (MM2), 5.2 (MM2ERW), and 14.5 (MM3) kcal/mol. Obviously, the three computational methods require reliable parameters for highly branched olefins like 3a and 5a. From the experimental heat of formation ΔHt0(g) and strain enthalpy Hs of meso‐3a and its ΔH* of homolysis the stabilization energy of the allylic radical 4 was determined to be 12.6 ± 1.5 kcal/mol.
3a,6‐Dihydro‐3H‐imidazo[1,2‐d]tetrazole aus 1‐ und 4‐Phenacyl‐1H‐tetrazolium‐Salzen und Ammoniak
Authors: Moderhack Dietrich , Bode Dirk‐;Ottfried , Schomburg Dietmar
Published: July 2007

3a,6‐Dihydro‐3H‐imidazo[1,2‐d]tetrazoles from 1‐ and 4‐Phenacyl‐1H‐tetrazolium Salts and Ammonia

Treatment of the tetrazolium salts 1 with aqueous ammonia affords the novel ring system 2 (in certain cases along with the ylides 3). The structure of 2 has been confirmed by an X‐ray analysis of 2a.
Synthesis and Aggregation Properties in Solution of a New Octasubstituted Copper Phthalocyanine: {2,3,9,10,16,17,23,24‐Octakis‐[(dioctylaminocarbonyl)methoxy]phthalocyaninato}copper(II)
Authors: Duro José Antonio , Torres TomáS
Published: July 2007

The synthesis of the octasubstituted phthalocyanine1, highly soluble in organic solvents, is described. Its aggregation properties in different solvents and in the presence of alkaline, alkaline earth, and ammonium salts are studied.
Modellreaktionen zur Verankerung von Molybdän‐und Vanadium‐Oxiden auf Silicium‐Sauerstoff‐Oberflächen
Authors: Gosink Hans‐Jürgen , Roesky Herbert W. , Noltemeyer Mathias , Schmidt Hans‐Georg , Freire‐Erdbrügger Cristina , Sheldrick George M.
Published: July 2007

Model Reactions to Anchor Molybdenum and Vanadium Oxides on Silica‐Oxygen Surfaces

The eight‐and twelve‐membered ring compounds [(tBu)21‐Si(O)2MoO2]2 (1) and [(tBu)2Si(O)2V(O)Cl]3 (2) have been prepared by the reaction of di‐tert1‐butylsilanediol or its dilithium salt with MoO2Br2 or VOCl3, respectively. Single crystal X‐ray structure analyses of 1 · 2 py and 2 have been performed. Crystals of 1 · 2 py contain two molecules of 1 · 2 py and four additional molecules of pyridine in the unit cell.
Monomeric Aldimino‐diorganoboranes and Aspects of Their Chemistry
Authors: Yalpani Mohamed , Köster Roland , Boese Roland
Published: July 2007

The hydroboration of benzo‐, tolu‐, p1‐methoxybenzo‐, or pivalonitriles with bis(9‐borabicyclo[3.3.1]nonane) (9H‐9‐BBN)2 affords the corresponding 9‐aldimino‐9‐borabicyclo[3.3.1]1‐nonanes (1a — d) in about 80% yields. Compounds 1a and 1d readily react with an excess of (9H‐9‐BBN)2 to form the 1:1 adducts 2a or 2d, respectively, containing a NB2H four‐membered ring (X‐ray structure of 2a). The adducts 2 are thermally rather stable. Compound 2a is converted to benzylbis(1,5‐cyclooctanediylboryl)amine (3a) only after 48 h at reflux in mesitylene. Compounds 1a — d are stable towards strong N‐bases. Compound 1d reacts with Et2O · BF3 to form 9‐fluoro‐9‐borabicyclo[3.3.1]nonane (4) and the 1:1 cyclic adduct (5d) of (2,2‐dimethylpropylideneamino)difluoroborane (6d) and 1d.
Übergangsmetallaktivierte organische Verbindungen, XXXVII. über eine neue Aldehyd‐und Ketonreaktion: Synthese und spektroskopische Untersuchung von α1‐Phosphonioalkoxy‐übergangsmetallkomplexen
Authors: Kauffmann Thomas , Abel Thomas , Schwarze Dieter
Published: July 2007

Transition Metal‐Activated Organic Compounds, XXXVII[1]. — A Novel Reaction of Aldehydes and Ketones: Synthesis and Spectroscopic Investigation of α1‐Phosphonioalkoxy Transition Metal Complexes

Herrn Professor Ulrich Schöllkopf zum 65. Geburtstag gewidmet.

By treatment of aldehydes and ketones with one mole equivalent of a Lewis acid (TiCl4, NbCl5, TaCl5) and one mole equivalent of PPh3, or in one case of Ph2PCH2CH2PPh2, the aldehyde derivates [R1CH(P+Ph2R2)–OMCln]Cl– (4–8; MTi, Nb, Ta; R2Ph or CH2CH2PPh2) and the ketone derivatives [R1R2C(P+Ph3)–ONbCl4]Cl– (9–10) were prepared. Complexes 4–10 were isolated as air‐and water‐sensitive solids. According to the NMR spectra some of the obtained aldehyde derivatives 4–8 exist in solution as a mixture of isomers or oligomers, whereas the ketone derivatives 9 and 10 form in solution an equilibrium with the free ketone and the complex NbCl5 · PPh3. The chloride ion of 4–10 is perhaps coordinated to the metal.
Oxidative Desilylation of a 5,6:7,8‐Bis(dimethylsilyldioxy)[4]radialene
Authors: Maas Gerhard , Fronda Antonio
Published: July 2007

The title [4]radialene 1 reacts with N1‐methyltriazolinedione or with the iodine(III) salt PhI+ O+IPh · 2 BF4– in CH2Cl2 by oxidative elimination of only one dimethylsilyl unit to form the functionalized 3,4‐bis(alkylidene)1‐1‐cyclobutene 2 or its hydrolysis products, (Z)‐4 and (E)‐4. When the iodonium salt is used in CCl4, rearrangement of the radialene framework occurs, and the bicyclic fluorodimethylsilyl enol ether 9 is obtained. An X‐ray crystal structure analysis of 9 indicates a weak coordination between a carbonyl oxygen atom and a silyl group.
Reactions of cis1‐Stannyl‐boryl‐alkenes with Sulfur Bis(trimethylsilylimide) and N1‐Sulfinyl(trimethylsilyl)amine – X‐ray Analysis of an 1‐Amino‐1λ41‐thia‐2‐azonia‐3‐borata‐1,4‐cyclopentadiene
Authors: Wrackmeyer Bernd , Wagner Klaus , Boese Roland
Published: July 2007

New heterocyclic systems (1‐amino‐1λ41‐thia‐2‐azonia‐3‐borata‐1,4‐cyclopentadienes 4a and 4b, a 1λ41‐thia‐2‐aza‐3‐bora‐1‐cyclopentanone 7 and a 1‐trimethylstannyloxy‐1λ41‐thia‐2‐azonia‐3‐borata‐1,4‐cyclopentadiene 8) are formed by reaction of (E)1‐2‐diethylboryl‐1‐trimethylstannyl‐1‐butene (1a) and (E)1‐3‐diethylboryl‐2‐trimethylstannyl‐2‐pentene (1b) with sulfur bis(trimethylsilylimide) (2) and N1‐sulfinyl(trimethylsilyl)amine (3). There is a marked influence of other substituents at the CC bond on the product distribution. It appears that all reactions proceed via an intermediate borane adduct A. In A the proximity of the electrophilic site of 2 or 3 to various reactive sites of the alkene derivative opens the way to the final products. The proposed structures are supported by consistent 1H‐, 11B‐, 13C‐, 29Si‐and 119Sn‐NMR data. In the case of compound 4a an X‐ray analysis has been carried out.
Phosphanalkylene, 53. Synthese von α,β1‐ungesättigten Cycloalkanonen aus Bis[(1‐acylalkyliden)1‐triphenylphosphoranen] – Eine Methode zur Überführung von Carbonsäure‐Anhydriden in carbocyclische und heterocyclische Verbindungen
Authors: Bestmann Hans Jürgen , Pichl Rainer , Zimmermann Reiner
Published: July 2007

Phosphane Alkylenes, 53[1]. – Synthesis of α,β1‐Unsaturated Cycloalkanones from Bis[(1‐acylalkylidene)triphenylphosphoranes] – A Method for the Transformation of Acid Anhydrides into Carbocyclic and Heterocyclic Compounds

Alkaline hydrolysis of bis[(1‐acylalkylidene)triphenylphosphoranes] 3 leads to 2‐cycloalken‐1‐ones 6. Intramolecular Wittig reaction of an intermediately formed monoacyl ylide 4 and intramolecular aldol condensation of a diketone 5, resulting from hydrolysis of both ylide functions, are discussed as possible reaction mechanisms. The oxidation of 3 with H2O2 · Ph3PO yields 7‐ and 8‐membered 2‐cycloalkene‐1,4‐diones 12, presumely via mono ylides 11 carrying an aldehyde group in the Ō‐position. The reactions of 3 with aldehydes (molar ratio 1:1) lead to the formation of mono Wittig compounds 15 which can cyclize affording 5‐ and 6‐membered 3‐alkenyl‐2‐cycloalken‐1‐ones 16. Since the ylides 3 are easily available from acid anhydrides the reaction sequences represent versatile approaches for the transformation of acid anhydrides into 2‐cycloalken‐1‐ones.