bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Stereoisomeric Ufolanes
Authors: Boldt Peter , Arensmann Eckart , Blenkle Martin , Kersten Helmut , Tendler Heike , Trog Rolf‐Stefan , Jones Peter G. , Döring Detlev 
Published: July 2007

AbstractThree of the six possible stereoisomers of dodecahydroacenaphthylene, t,t,t‐ufolane (1), c,c,t‐ufolane (3), and c,c,c‐ufolane (5), have been synthesized for the first time. The configurations have been confirmed inter alia by an X‐ray analysis of the precursors 11, 14, and 23 and the bromine adduct 24 of c,c,c‐10‐ufolene (19), the precursor of 5.
Observations on Dibutylstannylene as Template for the Assembly of Macrocyclic Oligolactones
Authors: Bredenkamp Martin W. , Flowers Harold M. , Holzapfel Cedric W. 
Published: July 2007

AbstractDibutylstannylene‐mediated macrolactonization of methyl 4,6‐O‐benzylidene‐&7alpha;‐D‐glucopyranoside (2) with glutaryl and phthaloyl dichloride yields the respective dilactones 6e and 6f and parallel tetralactones 5e and 5f as well as the antiparallel tetralactone 4e in the case of glutarylation. The reaction with malonyl dichloride yields a negligible amount of the parallel tetralactone 5d and that of fumaryl and isophthaloyl dichloride yields polyesters only, a byproduct in all these reactions. The mechanism of stannylene‐medidted macrolactonization is discussed incorporating data pertaining to known hexa‐ and octalactone formation when succinyl dichloride is used. A correlation between stannylene dimer symmetry and tetralactone constitutional isomer selectivity is introduced.
Enantioselective Synthesis of Optically Active Pyridine Derivatives and C2‐Symmetric 2,2′‐Bipyridines
Authors: Bolm Carsten , Ewald Martina , Felder Marcel , Schlingloff Gunther 
Published: July 2007

AbstractOptically active pyridine derivatives 2, 15, 18, 19, 21, 26, and 27 are obtained by enantioselective reduction of the corresponding ketones 5, 7, 11–13, 24, and 25 using the chiral borane reagent chlorodiisopinocampheylborane [(Ipc)2BCl]. Nickel(0)‐mediated coupling of bromopyridines 2, 15, and 31 gives C2‐symmetric 2,2′‐bipyridines (R,R)‐32, (R,R′)‐33, and (S,S)‐38, respectively, which form metal complexes with CoII, PdII, CuI, and AgI. Aryl‐substituted pyridines 26, and 39–41 are synthesized by palladium(0)‐catalyzed cross couplings of 2 and 15 with boronic acids 42–44.
The Molecular Structure of Triasterane: An Experimental and Theoretical Study
Authors: Ahlquist Bjørn , Almenningen Arne , Benterud Birgit , Trætteberg Marit , Bakken Pirkko , Lüttke Wolfgang 
Published: July 2007

AbstractThe molecular structure of triasterane (tetracyclo‐[3.3.1.02,3.02,6]nonane) has been investigated by using the gasphase electron‐diffraction method and by theoretical calculations. The experimental data are in accordance with the molecule having D3h symmetry. The C–C bonds in the three‐membered rings are observed to be slightly shorter than those in the methylene bridges [ra 1.508(5) versus 1.520(4) Å; 2s̀ in parentheses]. The C–C–C angle at the methylene bridges is observed to be 118.9(3)°, while the M–C–CH2 angle is determined to be 123.9(2)° (C–M is bisecting the cyclopropyl ring). Theoretical force‐field, semiempirical, and ab initio calculations of the triasterane molecule have also been carried out. The semiempirical results deviate substantially from the experimentally determined parameters, while the ab initio results, using a 6–31G* basis set, are in excellent agreement with the latter. The steric strain in triasterane has its origin mainly in nonbonded repulsion between the cyclopropyl groups and in torsion at the C–C bonds involving the methylene groups.
Cycloaddition Products from (1‐Diazo‐2‐oxoalkyl)silanes and Cyclopropenes. A Silatropic 2,3‐Diazabicyclo[3.1.0]hex‐3‐ene/1,4‐Dihydropyridazine Equilibrium
Authors: Munschauer Rainer , Maas Gerhard 
Published: July 2007

Abstract(1‐Diazo‐2‐oxoalkyl)silanes 1a–h react with cyclopropene 4 to form 2‐silyl‐2,3‐diazabicyclo[3.1.0]hex‐3‐enes 5 and/or 1‐silyll‐1,4‐dihydropyridazines 6. In most cases, a temperature‐ and solvent‐dependent equilibrium 5 ⇄ 6 maintained by an N →N′ silyl shift exists in solution. With cyclopropene 10, only the 1‐silyl‐1,4‐dihydropyridazines 11 are obtained. None of the 1:1 adducts corresponds to the product expected from a [3 + 2] cycloaddition reaction between the components. Evidence is presented that 1‐diazo‐2‐siloxy‐1‐alkenes 2 are initially formed from 1 by a 1,3‐(C → O) silyl shift and are then trapped by the cyclopropene in a 1,3‐dipolar cycloaddition reaction.
(Tetracyannaphthalocyaninato)eisen(II) mit Isocyaniden als axialen Liganden
Authors: Hanack Michael , Großhans Ronald 
Published: July 2007

(Tetracyanonaphthalocyaninato)iron(II) with Isocyanides as Axial Ligands(Tetracyanonaphthalocyaninato)iron(II) [(CN)4‐2,3‐NcFe; 6] is obtained by treating 2,3,6‐tricyanonaphthalene (5) with iron(II) acetate. Compound 5 is synthesized according to the route given in Scheme 1. The mononuclear bisaxial isocyanide complexes (CN)4‐2,3‐NcFeL2 7–9 with L = tBuNC, cHxNC and AdNC as well as the bridged complex [(CN)4‐2,3‐NcFe(dib)]n (10) are formed as stable compounds by treating 6 with the neat ligands L. The spectroscopic properties of the complexes are described and compared with the analogous compounds (CN)4PcFeL2, 2,3‐NcFeL2, 1,2‐NcFeL2, and with PcFeL2. The bridged complex [(CN)4‐2,3‐NcFe(dib)]n (10) exhibits only poor semiconducting properties as compared to [2,3‐NcFe(dib)]n. The oligomer 10 can be doped with iodine, and the resulting product [(CN)4‐2,3‐NcFe(dib)I1.4]n shows a powder conductivity s̀RT = 2 × 10‐5 S/cm at room temperature.
Herstellung und Umsetzungen von (R,R)‐ und (S,S)‐3‐Trifluormethyloxiran‐2‐carbonsäure‐ethylester, einem vielseitigen, leicht zugänglichen CF3‐haltigen Synthesebaustein
Authors: Bussche‐Hünnefeld Christoph Von Dem , Seebach Dieter 
Published: July 2007

Preparation and Reactions of Ethyl (R,R)‐ and (S,S)‐3‐Trifluoromethyloxirane‐2‐carboxylate, a Versatile, Easily Accessible CF3‐Containing Building Block for SynthesisA facile three‐step route has been elaborated leading from 4,4,4‐trifluoro‐3‐oxobutanoate to the trifluoro glycidic ester 1 mentioned in the title (0.1‐mole scale). Reactions with azide (→ 4, 5) and with organometallic compounds such as cuprates (→ 3, 6), lithium (→ 7, 8), and magnesium derivatives (→ 9–11) furnish novel enantiomerically pure trifluoromethyl‐substituted carboxylic esters, ketones, diols, and epoxy alcohols. The latter ones undergo selective isomerizations by Payne rearrangement (11 → 12) in aqueous NaOH/acetone or tert‐butyl alcohol.
Ketonpyrolyse: Darstellung und Röntgen‐Kristallstruktur eines Oxa[3.2.1]cyclophans
Authors: Breitenbach Jörg , Ott Frank , Vögtle Fritz , Nieger Martin 
Published: July 2007

Ketone Pyrolysis: Preparation and X‐ray Structure Analysis of an Oxa[3.2.1]cyclophaneThe oxa[3.2.1]cyclophane 2 was obtained for the first time in the course of the thermal extrusion of carbon monoxide from the dimethoxy[3.3]metacyclophanedione 1. The X‐ray structure analyses of 1 and 2 are reported. 1 shows a syn‐type conformation.
2‐Oxabicyclo[3.2.1]oct‐7‐yl‐Kationen
Authors: Kirmse Wolfgang , Mönch Dietmar 
Published: July 2007

2‐Oxabicyclo[3.2.1]oct‐7‐yl Cations2‐Oxabicyclo[3.2.1]octan‐7‐one (10) was prepared in five steps, starting from 3‐cyclopenten‐1‐ol (5). The tosylhydrazone 11, derived from 10, was photolyzed in 0.5 N NaOD/D2O to give >99% of 2‐oxabicyclo[3.2.1]octan‐exo‐7‐ol (9) with equal distribution of D at C‐1 and C‐7. In contrast to the parent 6‐bicyclo[3.2.1]octyl cation (1), the oxa analog 14 exhibits the same symmetry as was observed with the 6‐oxa‐2‐norbornyl cation (13). The conformational effects that are evident in 1 are overruled by strong n participation.
Umlagerungen von Tricyclo[3.2.1.12,4]non‐6‐yl‐, Tricyclo[4.2.1.12,5]dec‐3‐yl‐ und Tricyclo[4.2.2.12,5]undec‐3‐yl‐Kationen
Authors: Kirmse Wolfgang , Mönch Dietmar , Müller Katja , Gomann Klaus 
Published: July 2007

Rearrangements of Tricyclo[3.2.1.12,4]non‐6‐yl, Tricyclo[4.2.1.12,5]dec‐3‐yl, and Tricyclo[4.2.2.12,5]undec‐3‐yl CationsThe tricyclic ketones 5, 9, 13, and 24 were prepared by modified or novel routes. The corresponding tosylhydrazones 10, 11, 14, and 25 were photolyzed in 0.5 N NaOH (NaOD) to generate the title cations 2, 15–17, and 28, respectively, by way of diazonium precursors. The distribution of deuterium labels revealed rapid degenerate Wagner‐Meerwein rearrangements of 2 and 28 contrasting the unsymmetrical behavior of the parent bicyclo[3.2.1]oct‐6‐yl cation (1). The virtually irreversible rearrangement of 17 to 15, on the other hand, mirrors the preferred chair conformation of 1. The results with tricyclic carbocations support our previous explanation for the exceptional reactivity of 1.
Investigation of the Enantiomerization Barrier of Homofuran by Computer Simulation of Interconversion Profiles Obtained by Complexation Gas Chromatography
Authors: Schurig Volker , Jung Martin , Schleimer Michael , Klärner Frank‐Gerritt 
Published: July 2007

AbstractBy computer simulation of experimental interconversion profiles, obtained by complexation gas chromatography, rate constants of enantiomerization have been determined for homofuran between 95 and 130°C. Since enantiomerization proceeds at similar rates in the mobile and stationary phase, the rate constants obtained by an Arrhenius plot are in excellent agreement with values determined independently by polarimetry between 60 and 90°C. We thus demonstrate that dynamic chromatography can be an easy means for the rapid determination of enantiomerization (or isomerization) barriers of ca. 70–120 kJ mol‐1 requiring only minute amounts of racemic sample.
Darstellung und Reaktivität von {(η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO)
Authors: Lang Heinrich , Imhof Wolfgang 
Published: July 2007

Synthesis and Reactivity of {(η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO)The synthesis and reactivity of {(η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO) (6) is described. (η5‐C5H4SiMe3)2Ti(CCPh)2 (1a) reacts with equimolar amounts of Ni(CO)4 (5) to afford the dinuclear complex {(η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO) (6) in 95% yield. In 6 both phenylethynyl units are η2‐side‐on‐coordinated to the Ni(CO) moiety. When 6 is treated with HX or X2 (X = Cl, Br) the Ti–C(alkynyl) σ bond is cleaved, and the corresponding titanocene dihalides (η5‐C5H4SiMe3)2TiX2 (7) are formed. With PRR′2 [8a: R = R′ = OMe; 8b: R = C = CPh, R′ = Ph; 8c: R = Ph, R′ = CCPh] 6 reacts by substitution of the nickel‐bonded carbonyl ligand to form {(η5‐C5H4SiMe3)2Ti(CCPh2}Ni(PRR'2) (9). The reactivity of 9b, which contains a noncoordinated phenylethynyl unit, has been investigated by using Co2(CO)8 (10) and Fe2‐(CO)9 (13). With 10 the compounds {η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO) (6), [μ‐(η2‐Ph2PCCPh)]Co2(CO)6 (11) and {[μ‐(η2‐Ph2PCCPh)]Co2(CO)5}2 (12) can be obtained. Complex 11 yields upon heating by decarbonylation and dimerization the six‐membered cyclic compound 12. Whereas, the reaction of 9b with 13 affords {(η5‐C5H4SiMe3)2Ti(CCPh)2}Ni(CO) (6) next to the dinuclear complex Fe2(CO)6‐(μ‐PPh2)[μ‐(η1:η2‐CCPh)] (14).
Hexasilylbenzene, C6(SiH3)6
Authors: Rüdinger Christoph , Beruda Holger , Schmidbaur Hubert 
Published: July 2007

AbstractThe title compound was obtained in a four‐step synthesis starting from (4‐methoxyphenyl)silane. Owing to the presence of activating p‐methoxy groups in the key intermediate hexakis[(4‐methoxyphenyl)silyl]benzene (4), the peripheral aryl groups can be cleaved selectively from the silicon atoms with trifluoromethanesulfonic acid, leaving the Si–C bonds to the central benzene ring intact. LiAlH4 reduction of the resulting hexakis[(trifluoromethylsulfonyloxy)silyl]benzene (5) finally leads to crystalline, sublimable, air‐stable C6(SiH3)6 (6), m.p. 165°C. In the crystals (triclinic, space group P&1macr;) the structure of the centrosymmetrical molecules approaches very closely point group D3d, as predicted from theoretical considerations.
Wasserstoffübertragungen, 21[1] Pericyclische Wasserstoff‐Übertragung von 1,2‐Dihydroarenen auf ein Cycloheptin
Authors: Gerres Thomas , Heesing Albert 
Published: July 2007

Hydrogen Transfer Reactions, 21. – On the Pericyclic Hydrogen Transfer from 1,2‐Dihydroarenes to a CycloheptyneThe aromatization of 1,2‐dihydroarenes by thiacycloheptyne 1 takes place by a pericyclic process. This mechanism is supported by the dependence of the reactivity on the π system, absence of both substituent and solvent effects, a strong negative entropy of activation, high stereoselectivity of hydrogen abstraction, as well as size and consistency of primary isotope effects and semiempirical calculations of the transition state.
Synthesis of new soluble triphenodithiazines and investigation of their donor properties
Authors: Kistenmacher Axel , Adam Martin , Baumgarten Martin , Pawlik Jürgen , Räder Hans‐Joachim , Müllen Klaus 
Published: July 2007

AbstractThe syntheses of 6 and 7, starting from 3,6‐dichloro‐2,5‐bis(2‐thioanisido)‐1,4‐benzoquinone (4), are reported. The solid‐state conformations of 6 and 7 are elucidated by X‐ray structure analysis, and the cyclovoltammetric investigation of 6 and 7 in solution shows low and reversible oxidation half‐waves for both compounds. The relatively high oxidation potentials of 7 compared to 6 are related to their conformational features. EPR measurements on the radical cations derived from 6 and 7 both suggest a planarized conformation of these species. Oxidation of 6 with strong oxidants leads quantitatively to the quinoid triphenodithiazine 8, whereas the charge‐transfer complex formed between 7 and DDQ exhibits semiconducting properties.
Inter‐ and intramolecular hetero diels‐alder reactions, 39. Influence of phenylthio and alkylthio substituents on the reactivity of 1‐Oxa‐1,3‐butadienes in hetero diels‐alder reactions
Authors: Tietze Lutz F. , Fennen Jens , Wichmann Jürgen 
Published: July 2007

AbstractThe synthesis of the cyclic enamino ketones 1–3 bearing an alkylthio or an phenylthio group and their reactivity in hetero Diels‐Alder reactions with enol ethers is described. Only compound 3 with an phenylthio group undergoes a cycloaddition with 16a–d to afford the diastereomeric adducts 17a–d and 18a–d. To estimate the activation by a phenylthio and alkylthio group semiempirical PM3/RHF calculations of the frontier orbital energies and coefficients of different enamine carbaldehydes have been performed.
Alkylierung von Chinonen mit O‐silylierten Ketenacetalen in LiClO4/Ether als Reaktionsmedium
Authors: Ipaktschi Junes , Heydari Akbar 
Published: July 2007

Alkylation of Quinones by O‐Silylated Ketene Acetals in LiClO4/Ether as Reaction MediumO‐Silylated ketene acetals (2, 5) undergo 1,4‐conjugative addition to α,β‐unsaturated carbonyl systems of quinones 1 in the presence of lithium perchlorate in ether to form 2(3H)‐benzofuranones 3
Trimethylsilylcyanid als Umpolungsreagenz, XIX[1] Dreikomponentenreaktionen zur Synthese von ungesättigten γ‐Ketoestern
Authors: Hünig Siegfried , Koch Michael 
Published: July 2007

Trimethylsilyl Cyanide – A Reagent for Umpolung, XIX[1]. – Unsaturated γ‐Keto Esters by Three‐Component ReactionsAddition products 1a–c of α,β‐unsaturated aldehydes and trimethylsilyl cyanide are deprotonated and added to methyl acrylate (2). On alkylation with the allylic bromo dienes 3a, b the intermediate ester enolates yield the final adducts 4aa–4cb (83–95%). Deprotection transforms these adducts into 5aa‐5cb (72–98%), which contain the functionalities of an α,β‐unsaturated ketone, a carboxylic ester group, and a diene in the appropriate arrangement for intramolecular Diels‐Alder reactions. Yields between 64 and 79% of 5 are achieved if the reaction sequence 1 + 2 + 3 → 4 → 5 is performed without isolation of 4.
C,C‐Verknüpfungen mit Schwefel‐stabilisierten Carbanionen, 2[1] Reaktionen des 2‐(Methylthio)thiolan‐Carbanions mit Elektrophilen[2]
Authors: Böge Askan , Brunck Jörg‐Stephan , Schwär Gerhard , Voß Jürgen 
Published: July 2007

C,C Coupling with Sulfur‐Stabilized Carbanions, 2[1]. – Reactions of the 2‐(Methylthio)thiolane Carbanion with Electrophiles[2]The „semicyclic” thioacetal 2‐(methylthio)thiolane (4) is easily prepared from thiolane (tetrahydrothiophene). It is readily deprotonated by butyllithium to give the lithium derivative 5, which reacts with alkyl halides, saturated and α,β‐unsaturated carbonyl compounds, and benzonitrile to form the alkyl derivatives 6, carbinols 7, allyl alcohols 8, and – after hydrolysis – the ketone 9. The diastereoselectivity of the C,C coupling reaction is discussed.
trans‐1‐(Dimethylamino)‐1,3‐butadiene – Concerted and Stepwise (4 + 2) Cycloadditions
Authors: Sustmann Reiner , Rogge Monika , Nüchter Ursula , Bandmann Heinz 
Published: July 2007

Abstracttrans‐1‐(Dimethylamino)‐1,3‐butadiene is allowed to react with methyl acrylate, acrylonitrile, maleo‐ and fumaronitrile, dimethyl maleate and fumarate, as well as with dimethyl dicyanomaleate and dicyanofumarate. In all cases except the two last ones where only a single isomer is obtained mixtures (endo/exo) of cycloadducts are formed. Structures are determined by a combination of one‐ and two‐dimensional NMR spectroscopy. The E/Z isomeric maleo‐ and fumaronitrile add stereospecifically to the diene. Cycloaddition of dimethyl maleate and fumarate leads to the same mixture of isomers in almost the same ratio. The reaction of dimethyl dicyanomaleate and dimethyl dicyanofumarate yields a cycloadduct which seems to be the thermodynamically most stable one. The results are interpreted in such a manner that a concerted cycloaddition takes place with maleo‐ and fumaronitrile, while stepwise reactions, presumably proceeding via zwitterions, are observed with dimethyl maleate, fumarate, the strongly electrophilic dimethyl dicyanomaleate and dicyanofumarate. With increasing capability of the dienophile to stabilize a negative charge the mechanism changes from a concerted to a stepwise reaction.
Reactions of 1,1‐bis(dimethylamino)‐1,3‐butadiene with olefins – (4 + 2) cycloadditions and zwitterion formation
Authors: Sustman Reiner , Rogge Monika , Nüchter Ursula , Bandmann Heinz 
Published: July 2007

Abstract1,1‐Bis(dimethylamino)‐1,3‐butadiene (1) as a strong donor diene (E1/2 = 0.03 V vs. SCE, 1st IPv = 6.94 eV) is treated with acrylonitrile, dimethyl dicyanofumarate, and tetracyanoethylene. Cycloaddition with acrylonitrile is slow and requires elevated temperatures at which elimination of dimethylamine with formation of 1‐cyano‐2‐(dimethylamino)‐1,3‐cyclohexadiene occurs. The reaction of 1 with TCNE at −40°C in acetonitrile is very fast and leads to the zwitterion 5. At T ⩾ −20°C, 5 eliminates hydrogen cyanide to give a highly colored (λmax = 489 nm, lgϵ = 4.716) merocyanine. A zwitterion 9 generated from 1 and dimethyl dicyanofumarate can be isolated in crystalline form. The structural analysis shows that the zwitterions are produced by attack of the olefin at the antiperiplanar conformation of 1. Both zwitterions which can be trapped as crystalline picrates cannot be converted to cycloadducts. These results suggest that cycloaddition is observed if zwitterion formation becomes energetically unfavorable.
The Pagodane Route to Dodecahedranes Scope and Limitation of the Dehydrocyclization Stratagem
Authors: Lutz Georg , Pinkos Rolf , Murty Bulusu A. R. C. , Spurr Paul R. , Fessner Wolf‐Dieter , Wörth Jürgen , Fritz Hans , Knothe Lothar , Prinzbach Horst 
Published: July 2007

AbstractThe stepwise route B from pagodanes to dodecahedranes was completed by double catalytic dehydrocyclization of saturated (alkylated) bisseco precursor substrates (2, 3, 5, 16). Based on pagodane, dodecahedranes (9, 10, 13, 14, 17) were obtained in up to 53% yield. Transannular C,C bond formation at the bisseco stage and partial (C–alkyl) or total (C–OR, C–CO2R) removal of substituent groups under the necessarily forcing reaction conditions constituted preparative limitations. Attempts at alternative ring closure methodologies (homo‐Norrish type II, homoenolization, carbene insertion) have remained unsuccessful.
Metallcarbonyl‐Synthesen, XXI. Einfache Synthese eines präparativ nützlichen Alkoxy(carbonyl)metallats
Authors: Herrmann Wolfgang A. , Mihalios Dimitrios , Öfele Karl , Kiprof Paul , Belmedjahed Fawzi 
Published: July 2007

Metal Carbonyl Syntheses, XXI. – Straightforward Synthesis of a Synthetically Useful Alkoxy(carbonyl)metallateAnionic methoxy complexes are formed upon carbonylation of ammonium perrhenate in methanol at 230–240°C. Thus, the dinuclear ionic complex [N(CH3)4][Re2(CO)6(μ‐OCH3)3] (2) results in 80% yield at CO pressures of ca. 100 bar, while the trinuclear derivative [N(CH3)4][Re3(CO)9(μ3‐OCH3)3(μ3‐OCH3)] (3) is due to lower pressure conditions (ca. 50 bar); 2 yields the bis(carbene) complex 4 of formula fac‐Re(CO)3L2I upon treatment with a bis(imidazolium) iodide, thus demonstrating that carbonylrhenium chemistry not necessarily depends on the availability of Re2(CO)10.
Organische Synthesen mit Übergangsmetall‐Komplexen, 60. Neuartige Benzoanellierung mit Carben‐Komplexen und Alkinen. – 2‐Oxybenzoanellierung von Cycloheptatrien über (Cycloheptatrienylmethyl)‐carben‐Komplexe von Chrom und Wolfram
Authors: Aumann Rudolf 
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 60. – Novel Type of Benzoanellation with Carbene Complexes and Alkynes. – 2‐Oxybenzoanellation of Cycloheptatriene via (Cycloheptatrienylmethyl)carbene Complexes of Chromium and TungstenWe report on a three‐step procedure for the regiospecific 2‐oxybenzoanellation to cycloheptatriene by means of Fischer carbene complexes and alkynes. The first step involves the formation of (cycloheptatrienylmethyl)carbene complexes LnMC(OEt)CH2‐c‐C7H7 [1, LnM  Cr(CO)5 (a), W(CO)5 (b)] from the corresponding methylcarbene complexes and a tropylium salt. 1 reacts with the alkyne Et2NCCMe (2) to give the (E)‐ and (Z)‐1‐amino(1‐alkenyl)carbene complexes LnMC(NEt2)C(Me)C(OEt)CH2c‐C7H7 (3 and 4 resp.). Thermolysis of 3b [LnM = W(CO)5, 100°C, 5 h] finally leads to elimination of W(CO)5(Et2NH) (6b) and the regiospecific formation of the ethoxybenzocycloheptatrienes 5,7, and 8 in 92% total yield. The reaction is kinetically controlled and yields an isomeric ratio of 5:7:8 = 60:12:20% with the thermodynamically less stable isomer 5 predominating.
Cycloadditionen von 6H‐1,3,4‐Oxadiazin‐6‐onen (4,5‐Diazaα‐pyronen), 11. δ‐Chlor‐δ‐lactone aus γ‐Oxoketenen
Authors: Hegmann Joachim , Ditterich Elke , Hüttner Gerhard , Christl Manfred , Peters Eva‐Maria , Peters Karl , Von Schnering Hans Georg 
Published: July 2007

Cycloadditions of 6H‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones), 11. – δ‐Chloro δ‐Lactones from γ‐Oxo KetenesPrepared from 1,3,4‐oxadiazinone 1 with norbornene, cyclopentene, cyclopentadiene, and indene, the γ‐oxo ketenes 2, 5, 6, and 7 have been converted into the δ‐chloro δ‐lactones 3, 8, 9, and 10, respectively, by treatment with hydrogen chloride. The configuration of 10 has been determined by an X‐ray structural analysis. These pseudo chlorides prove to be stable against methanol. Only in the presence of sulfuric acid as catalyst 3 suffers methanolysis to yield diester 4. On thermolysis, the γ‐oxo ketenes are transformed into β‐lactones. In particular, 6 and 7 gave 13 and 12, respectively. Formed also on photolysis of 6, β‐lactone 13 partly isomerized to β‐lactone 14 on prolonged heating.
An Excellent Method for the Mild and Safe Oxidation of N‐Heteroaromatic Compounds and Tertiary Amines
Authors: Kaczmarek Lukasz , Balicki Roman , Nantka‐Namirski Pawel 
Published: July 2007

AbstractSelective, mild and safe N‐oxidation of N‐heteroaromatic compounds and tertiary amines affording high product yields was achieved by using the H2O2‐urea/phthalic anhydride system.