bluuebunny/crossref_metadata_2025_split huggingface dataset:
Darstellung, Struktur und Eigenschaften von harnstoffverbrückten cyclischen Phosphoniumsalzen mit Phosphor‐Phosphor‐, Phosphor‐Arsen‐, Phosphor‐Antimon‐und Phosphor‐Zinn‐Bindung
Authors: Vogt Roland , Jones Peter G. , Schmutzler Reinhard 
Published: July 2007

Preparation, Structure, and Properties of Urea‐Bridged Cyclic Phosphonium Salts with Phosphorus‐Phosphorus, Phosphorus‐Arsenic, Phosphorus‐Antimony, and Phosphorus‐Tin BondsN‐[tert1‐Butyl(phenyl)phosphanyl]‐N,N′‐dimethyl‐N′‐(trimethylsilyl)urea (2) reacts with organodichlorophosphanes with cleavage of the Si – N bond to form the cyclic phosphanylphosphonium chlorides 3a – i containing the grouping [λ3P – λ4P+]Cl–. Evidence was obtained for the existence of an equilibrium in solution between the ionic phosphonium structure 3 and a covalent form. The position of the equilibrium is determined by the nature of the group R at λ3P. Reaction of the phosphonium salts 3a – i with Na[BPh4] furnished the phosphonium tetraphenylborates 4a – i containing the grouping [λ3P – λ4P+][BPh4]–. In the reaction of 2 with organodichloroarsanes the arsanyl‐phosphonium chlorides 5a and 5b with the grouping [λ3As – λ4P+] were formed. By treatment of 5a and 5b with Na[BPh4] the corresponding tetraphenylborates 6a and 6b were produced. Further cyclic phosphonium salts containing a heteroatom‐phosphorus bond with the complex chloro anions [AsCl4]–, [SbCl4]–, and [Me2SnCl4]2– were formed in the reaction of 2 with the chlorides AsCl3, SbCl3 and Me2SnCl2. – The structures of 4h and 6a were confirmed by low‐temperature X‐ray crystal structure determination; the P – P bond length of 4h is 222.3(2) pm, the P – As bond length of 6a 234.6, 234.1(2) pm in two independent cations.
Novel Spherand‐Type Calixarenes – Synthesis, Conformational Studies, and Isomer Separation
Authors: Yamato Takehiko , Hasegawa Ken‐Ichi , Saruwatari Yoshiyuki , Doamekpor Louis Korbla 
Published: July 2007

AbstractThe novel macrocyclic compounds hexahydroxy[1.0.1.0.1.0]‐6b and octahydroxy[1.0.1.0.1.0.1.0]metacyclophane 6c have been prepared in 50–70% yield by base‐catalyzed condensation of 5,5′‐di‐tert1‐butyl‐2,2′‐dihydroxybiphenyl (5) with formaldehyde in xylene. The conformations of trimer 6b and tetramer 6c have been evaluated from their dynamic 1H‐NMR spectra. Methylation of the hydroxyl groups of 6b and 6c with MeI gives the corresponding methoxy[1n]metabiphenylophanes 7b and 7c in good yields. The metacyclophane 7b has been found to consist of two isomers, out of which one was separated pure. The structural characterization of these products is discussed.
Metallabicyclo[3.1.0]hexene und deren Umlagerung zu Vinylmetallacyclobutenen (M=Ti, Zr)
Authors: Binger Paul , Müller Patrik , Langhauser Franz , Sandmeyer Frank , Philipps Petra , Gabor Barbara , Mynott Richard 
Published: July 2007

Metallabicyclo[3.1.0]hexenes and Their Rearrangement to Vinylmetallacyclobutenes (M=Ti, Zr)Alkyne‐metallocene complexes, e.g. the alkynetitanocenes 1a, b, the alkyne(trimethylphosphane)titanocenes 2a, b and the alkyne(trimethylphosphane)zirconocenes 5a–d react readily with 3,3‐dimethylcyclopropene (3a) and 3,3‐diphenylcyclopropene (3b) to give the corresponding bis(η5‐cyclopentadienyl)‐metallabicyclo[3.1.0]hexene derivatives 4a–e, (M=Ti) and 6a–g (M=Zr) in high yields. In an analogous manner, metallabicyclo[3.1.0]hexene derivatives of Ti or Zr can be prepared from 1,2‐diphenylcyclopropene(trimethylphosphane)metallocenes 9 and 10 and 2‐butyne to yield 11 and 12 and from benzyne 3a or 3b to yield 8a and 8b. Some of these metallabicyclo[3.1.0]hexene derivatives rearrange quantitatively to the corresponding 4‐(dimethylvinyl)‐1‐metalla‐2‐cyclobutene derivates 16 and 17a and 4‐(diphenylvinyl)‐1‐metalla‐2‐cyclobutenes 15c and 17a–c when they are heated to 60–80°C for several hours. The 4‐(diphenylvinyl)‐1‐titana‐2‐cyclobutene derivatives 15a–c can also be obtained by reaction of [(2,2‐diphenylvinyl)carbene](trimethylphosphane)‐titanocen (13) with disubstituted alkynes such as tolane, phenyltrimethylsilylacetylene and bis(trimethylsily)acetylene. With other alkynes, e.g. 2‐butyne, 1‐butyne, 1‐propyne or acetylene, 13 reacts by polymerization of these alkynes; the corresponding 4‐vinyl‐1‐titanacyclobutene derivatives could not be detected in the reaction mixture. All new metallacycles are fully characterized by spectroscopic methods, extensive 1H‐ and 13C‐NMR studies provide unambiguous proof of their structures.
Beiträge zur Chemie des Bors, 218[1]. Über die Reaktion von 9‐Fluorenyliden‐tetramethylpiperidino‐boran mit Nitrilen und Isonitrilen: Azaborafluoranthene und Ketenimino‐azaborolidine
Authors: Mayer Erwin P. , Nöth Heinrich 
Published: July 2007

Contributions to the Chemistry of Boron, 218[1].–On the Reaction of 9‐Fluorenylidene‐tetramethylpiperidino‐borane with Nitriles and Isonitriles: Azaborafluoranthenes and Ketenimino‐azaborolidines9‐Fluorenylidene‐tetramethylpiperidino‐borane 1 reacts with nitriles not in a [2 + 2] cycloaddition manner but to form azaborafluoranthenes 3 whose BNC4 ring shows a C–B–N–C element reminiscent to a butadiene unit as revealed by an X‐ray structure analysis of 3a. An unexpected 3:1 reaction occurs between tert‐butyl isonitrile and 1 leading to the keteneimino azaborolidine 10. Its central ring shows an envelope conformation. 1 is fairly inert towards olefins. Out of 5 examples only 1,1‐diethoxyethene gave the [2 + 2] cycloaddition product, i.e. the boretane 4.
Weitere Reaktionen des Amino(imino)borans Me3Si(tBu)N*B*NtBu und des Alkyliden(amino)borans Me3Si(tBu)N=B=CHtBu
Authors: Braunschweig Holge , Paetzold Peter , Spaniol Thomas P. 
Published: July 2007

Further Reactions of the Amino(imino)borane Me3Si(tBu)N*B*NtBu and the Alkylidene(amino)borane Me3Si(tBu)‐N=B=CHtBuThe alkylidenetantalum complexes [tBuHCTaCl3(THF)2] (1b), [PhHCTaCl3(PMe3)2] (1c), and [tBuHCTa(CH2tBu)3] (1d) were treated with the amino(imino)borane Me3Si(t‐Bu)N*B*NtBu (2d). From 1b and 2d, the alkylidene(amino)borane Me3Si(tBu)NBCHtBu (7) is formed by metathesis. The 1:2 reaction of 1c with 2d gives the azadiboracyclobutane [–N(tBu)–B(X)–CHPh–B(X)–] [6d, XMe3Si(tBu)N]. The six‐membered ring compound [–N(tBu)BR–N(tBu)–SiMe2–CH2–TaR(CHtBu)–] (8, R=CH2tBu) is obtained from 1d and 2d; the product 8 crystallizes in the space group P 21/c. The borane 7 is attacked at the BC double bond by Et2NH, tBuCHO, and Me3SiN3 giving the diamino(neopentyl)borane 9 by protolysis, the oxaboracyclobutane 10 by [2 + 2] cycloaddition, and the azaboracyclopropane 11 by cycloaddition and elimination of N2, respectively.
Crown Ether‐Bearing Dihydroazulens[1]: Synthesis and Photochromism of a Benzo[15]crown‐5 Derivative
Authors: Fischer Christian , Daub Jörg 
Published: July 2007

AbstractPhotosensitive crown ether 1 composed of 1,8a‐dihydroazulene as a photodynamic unit and a benzo[15]crown‐5 ether subgroup has been synthesized from C‐7‐substituted cycloheptatriene 8, which has been obtained by nucleophilic addition of 4‐acetylbenzo[15]crown‐5 (6) to tropenylium tetrafluoroborate (7). Dehydrogenation of dicyanovinyl derivative 9 leads to heptafulvene 2 which thermally rearranges to dihydroazulene 1. Attempts to synthesize 1 according to the „[8 + 2]‐cycloaddition route”︁ have been unsuccessful. Crown ether 1 shows photochromic bistability with a photochemically driven forward and a thermal back reaction. The spectroscopic properties of 1 and the photochemical isomerization 1 → 2 have been shown to be almost insensitive to sodium iodide addition. The rate of the thermal back reaction 2 → 1 slightly is affected by sodium iodide addition.
Double‐Layered 1,4‐Distyrylbenzene Chromophores–Synthesis, UV and Fluorescene Spectra
Authors: König Burkhard , Knieriem Burkhard , Meijere Armin De 
Published: July 2007

AbstractThe reaction of [2.2]paracyclophane (1) with liquid bromine affords a 1:1 mixture of only two isomeric products, the pseudo‐para 2 and pseudo‐ortho tetrabromide 3. The structure of the pseudo‐para isomer 2 has been determined by X‐ray structure analysis. Fourfold palladium‐catalyzed coupling with styrenes and with methyl acrylate converts 2 and 3 into double‐layered derivatives as e.g. 6a, 7a, and 7b, respectively. The molecular structure of 7a has been established by X‐ray structure analysis. The UV and fluorescence spectra of a variety of substituted products are reported and compared with those of the parent chromophors 2,5‐dimethyl‐1,4‐distyrylbenzene (16) and 2,5‐diethyl‐1,4‐bis(phenylethynyl)benzene (17), respectively.
Synthese und Komplexierung von Dithiatetrazadiborocinen
Authors: Schmid Günter , Gehrke Helmut , Kolorz Hans‐Ulrich , Boese Roland 
Published: July 2007

Synthesis and Complexation of Dithiatetrazadiborocines(Dialkylamino)dichloroboranes R2NBCl2 react with N,N'‐bis‐(trimethylsilyl)sulfur diimide to give a novel class of compounds, the eight‐membered rings 3,7‐bis(dialkylamino)‐3H,7H‐1λ4,5λ4,2,4,6,8,3,7‐dithiatetrazadiborocines (1). The derivates with R = n‐propyl (1a), isopropyl (1b), and n‐butyl (1c) have been synthesized and characterized. The X‐ray structure analysis of 1b shows the molecule to have a boat‐like configuration with two NSN functions connected via the BNR2 groups. Although the B atoms are linked to three N atoms, only the exocyclic nitrogen is engaged in π bond interactions with the boron. 1b reacts with W(CO)5(THF) to form the dinuclear complex 2, which is also investigated by means of an X‐ray structure analysis. One W(CO)5 fragment is coordinated to a nitrogen atom of one NSN unit, whereas another W(CO)5 group is linked to the S atom of the second SN2 function. However, the original sulfur diimide has changed into a sulfur diamide group HN–S–NH. A similar change of a NSN unit happens on treatment of 1b with Cp(CO)3WH leading to 3. As the X‐ray structure analysis shows, in 3 again one sulfur diimide group retains its original character. The second SN2 unit has turned into a sulfur amide function, where one N atom binds the H atom of Cp(CO)3WH, the other one is linked to one of the CO ligands to form a carbonyl bridge between N and W. Among a series of other complexes only TiCl4 has additionally been found to react with 1b to yield 1b · 2 TiCl4, the structure of which is still unknown.
Preparation of Benzo‐diimidazoles and Benzo‐triimidazoles
Authors: Mataka Shuntaro , Irie Takashi , Ikezaki Youji , Tashiro Masashi 
Published: July 2007

AbstractThe reaction of benzenehexamine (1), benzene‐1,2,3,4‐tetramine (4), and benzene‐1,2,4,5‐tetramine (6) with aryl isocyanate 2 afforded the corresponding hexakis(N'‐arylureido)benzene 3 and the tetrakis(N'‐arylureido)benzenes 5 and 7. Pyrolysis of 3, 5, and 7 at 400°C furnished the benzo‐triimidazoletrione 8 and benzo‐biimidazolediones 10 and 11.
LiClO4‐katalysierte nucleophile Addition an α‐chirale Aldehyde, Aldimine und Oxirane
Authors: Ipaktschi Junes , Heydari Akbar 
Published: July 2007

LiClO4‐Catalyzed Nucleophilic Addition to α‐Chiral Aldehydes, Aldimines, and OxiranesThe diastereoselectivity of lithium perchlorate‐induced addition of trimethylsilyl cyanide and O‐silylated ketene acetals to α‐chiral aldehydes is studied. Whereas aldehyde 1 reacts with the ketene acetal 2 exclusively to form the syn‐ester 3, a divergent selectivity is observed in the case of trimethylsilyl cyanide addition to 5 and 11a–c. Also the reaction of O‐silylated ketene acetals with aldimines 16 in the presence of lithium perchlorate proceeds smoothly to afford the corresponding β‐amino esters 17 in high yields. While the silyl ketene acetal of methyl acetate leads preferentially to the corresponding anti‐diastereomer, in the case of the silyl ketene acetal of methyl isobutyrate a syn‐/anti‐selectivity in the range of 79:21 to 44:56 is observed. In the presence of lithium perchlorate solution in ether the oxiranes 27a–d undergo facile nucleophilic ring opening reactions with 2, 29, and 30.
Metallkomplexe mit biologisch wichtigen Liganden, LXV. Chirale Halbsandwich‐Komplexe von Cobalt(III), Rhodium(III), Iridium(III) und Ruthenium(II) mit α‐Aminosäureamid‐, Glycinnitril‐ und Peptidester‐Liganden
Authors: Krämer Roland , Maurus Michael , Bergs Ralph , Polborn Kurt , Sünkel Karlheinz , Wagner Barbara , Beck Wolfgang 
Published: July 2007

Metal Complexes with Biologically Important Ligands, LXV[1]. — Chiral Half‐Sandwich Complexes of Cobalt(III), Rhodium(III), Iridium(III), and Ruthenium(II) with α‐Amino Amide, Glycinenitrile, and Peptide Ester LigandsCp*Co(CO)I2 (Cp* = η5‐C5Me5), [(η6‐arene)RuCl2]2 (arene = p‐cymene, hexamethylbenzene), and [Cp*MCl2]2 (M = Rh, Ir) react with α‐amino amides and various peptide esters to give the N,O‐chelate complexes [Cp*(I)Co — NH2C(H)(R1)C(NHR2)‐O]+ (1), [(η6‐arene)(Cl)Ru — NH2C(H)(R1)C(NHR2)O]+ (2), and [CP*(Cl)M—NH2CH2C(NHR)O]+ (M = Rh, Ir) (5, in solution), respectively. In the solid state the ligands are η1N‐bonded in 5. By deprotonation of the peptide bond in 2 and 5 the neutral N, N‐chelate complexes (η6‐arene)(Cl)Ru — NH2C(H)(R1)C(O)‐N̊2 (6) and Cp*(Cl)M — NH2C(H)(R1)C(O)NR2 (M = Rh, Ir) (7) have been obtained. Glycinenitrile is η1‐bonded in (η6‐p‐cymene)(Cl)2Ru(NH2CH2CN) (3) and Cp*(Cl)2Rh(NH2CH2CN) (4). Double deprotonated triglycine methyl ester is a N,N,N‐tridentate ligand in (η6‐C6Me6)Ru(NH2CH2C(O)NCH2C(O)‐NCH2CO2Me) (8). The anions of L‐asparagine and of aspartame (L‐aspartyl‐L‐phenylalanine methyl ester) give the complexes 9–12 with tridentate O,N,O‐ or O,N,N‐chelate ligands. The crystal structures of 1d (L = glyglyOEt), 5a (L = glycinamide), 6e (L = glyglyOEt), and 7k (L = glyglyglyOEt) have been determined by X‐ray structural analysis.
Osmiumkomplexe vom Halbsandwichtyp mit Oximen, Iminen und Azavinylidenen als Liganden
Authors: Daniel Thomas , Knaup Wolfgang , Dziallas Michael , Werner Helmut 
Published: July 2007

Osmium Complexes of the Half‐Sandwich Type with Oximes, Imines, and Azavinylidenes as LigandAzavinylideneosmium complexes of the general composition [(arene)Os(NCRR)(L)]X (L = PMe3, PMetBu2, PiPr3) have been prepared by two methods. The first one uses the hydrido compound [C6H6OsHI(PMetBu2)] (2) and oximes HONCRR as starting materials and proceeds via the oxime complexes [C6H6OsH{N(OH)CRR}(PMetBu2)]PF6 (10, 11) as intermediates. They react with Al2O3 with elimination of water to give the final products 6–9. The second method starts with the dichloro‐ or diiodoosmium(II) compounds [(arene)OxX2(PR3)] (14, 16, 19, 21; arene = C6H6, 1,3,5‐Me3C6H3i R = Me, iPr) which upon treatment with HN = CPh2 or imine derivatives XNC(R)Ph (X = Li, SiMe3) afford the azavinylidene complexes 13b, 18, 23, 33. In the reactions with HNCPh2, the corresponding imine complexes [(arene)OsX(NHCPh2)‐(PR3)]X (15, 17, 20, 22) are formed as the primary products. Whereas nucleophilic addition of H– and CH3— to the N=C carbon atom of [C6H6Os(NCPh2)(PMetBu2)]+ (6) gives the imidoosmium(II) compounds [C6H6Os(NCRPh2)(PMetBu2)] (24, 25), the reaction of [C6H6Os(NCPh2)(PiPr3)]PF6 (13 b) with LiAlH(OtBu)3 yields the hydrido(imino) derivative [C6H6OsH(NHCPh2)(PiPr3)]PF6 (26). The bis(azido) complex [C6H6Os(N3)2(PiPr3)] (27), which is prepared either from 13 b or [C6H6OsI2(PiPr3)] (14) and NaN3, undergoes a [3 + 2] cycloaddition reaction with C2(CO2Me)2. Two isomeric (triazole)osmium compounds 28, 29 have been isolated. Treatment of [C6H6Os(NCRPh)(PiPr3)]PF6 with HX (X = O2CCF3) leads to addition of the acid to the OsN bond and, for R = Ph (13 b), by subsequent elimination of HX to the formation of a five‐membered metallaheterocycle 31. The X‐ray structural analysis of [C6H6Os(NCPh2)(PMetBu2)]PF6 (6) reveals an allene‐like arrangement of the ligands and substituents around the OsNC unit.
Beiträge zur Chemie des Bors, 220. Untersuchungen über Diborylmethane
Authors: Ederer Bernd , Metzler Nils , Nöth Heinrich 
Published: July 2007

Contributions to the Chemistry of Boron 220[1]. — Investigations on DiborylmethanesA convenient synthesis and spectroscopic properties of various organyl‐halogen‐substituted diborylmethanes (RXB)2CH2 (2a — e, R = Me, Et, Pr, Ph, Mes) are described. Reaction of bis(dichloroboryl)methane (1 b) with tBuLi in a 1:2 ratio leads to isomerization of the tert‐butyl group, whereas bis(dimethoxyboryl)methane (1a) reacts with 5 equivalents of tBuLi to yield tri‐tert‐butylborane and lithium di‐tert‐butylethyleneborate (9). Borate 9 is characterized NMR‐spectroscopically and by derivatization with Me3SiCl. Bis[alkinyl(dialkylamino)‐boryl]methanes 10a—c are obtained from the bis[chloro(dialkylamino)boryl]methanes 5a, b and LiCCPh or LiCCMe, respectively. 10c is characterized by an X‐ray crystal structure analysis which allows, for the first time, a direct comparison of an sp‐ and an sp3‐carbon atom bound to the same boron atom. Finally, an almost linear relationship between dL13C of the methylene group and dL11B in diborylmethanes has been detected.
Umwandlungen zwischen Ru3‐fixierten Azoalkan‐ und Dialkylhydrazin‐Baueinheiten
Authors: Hansert Bernhard , Vahrenkamp Heinrich 
Published: July 2007

Interconversions Between Ru3‐Bound Azoalkane and Dialkylhydrazine‐Derived Building UnitsReactions involving hydrogen transfer have been investigated starting from the azoalkane‐bridged clusters Ru3(CO)9‐(RCH2NNCH2R) (1a, R = H; 1b, R = Me). In boiling toluene they are isomerized to the hydrazonide‐bridged clusters HRu3(CO)9(RCH2N—NCHR) (2a, R = H; 2b, R = Me). Pd/C‐catalyzed hydrogenation converts both compound types into the hydrazide‐bridged clusters HRu3(CO)9(RCH2N—NHCH2R) (3a, R = H; 3b, R = Me). Hydride attachment to 1 and 2 and deprotonation of 3 yield a common anionic intermediate 4 which is converted into 3 upon protonation. While deuteration experiments and NMR spectra indicate that the anionic intermediate equilibrates between the N—H and Ru—H isomers, aurations of deprotonated clusters with Ph3PAuCl yield the Ru—Au‐connected clusters Ph3PAuRu3(CO)9(EtN—NCHMe) (5) and Ph3PAuRu3(CO)9(MeN—NHMe) (6). The reversible cluster expansion of 2b with Fe(CO)3 fragments which results in the formation of FeRu3(CO)12(μ4‐η2‐N2Et2) (7) involves a reversible reconversion of the hydrazonide ligand to the azoalkane ligand.
Tricarbonylchromium complexes of centropolyindans, 3. Synthesis and structural investigation of tricarbonylchromium mono‐, bis‐, and tris‐Complexes of triptindan
Authors: Ceccon Alberto , Gambaro Alessandro , Manoli Francesco , Venzo Alfonso , Ganis Paolo , Valle Giovanni , Kuck Dietmar 
Published: July 2007

AbstractThe reaction of 9H,10H‐4b,9a([1,2]benzenomethano)indeno[1,2‐a]indene (triptindan, TRIP) with Cr(CO)6 in Bu2O/THF (9:1) affords a monocomplex (A) together with two bis‐Cr(CO)3 complexes (B and C) and one tris‐Cr(CO)3 complex (D). The relative yields of the four complexes as well as their tendency to lose Cr(CO)3 are related to stabilizing intramolecular factors. All the Cr(CO)3 units of the complexes A, B, and D are coordinated in the isoclined orientation with respect to the polar axis of the ligand, whereas complex C bears one isoclined and one anticlined Cr(CO)3 unit. The results of X‐ray measurements support the hypothesis of weak attractive electronic interactions bonds between the oxygen atoms of the carbonyl groups and polarized faces of benzene rings.
Structure and Spectroscopic Properties of p‐Benzoquinone Diazides
Authors: Sander Wolfram , Bucher Götz , Komnick Peter , Morawietz Jens , Bubenitschek Peter , Jones Peter G. , Chrapkowski Axel 
Published: July 2007

AbstractA series of p‐benzoquinone diazides were investigated by 13C‐NMR and IR spectroscopy as well as by semiempirical and abinitio calculations. In addition, X‐ray structure analyses of the parent compound and three derivatives were performed. The electronic structure and effects of substituents can be described in terms of diazoketo and diazonium phenolate resonance structures. While alkyl groups as substituents have only a minor influence on quinone diazides, electron‐withdrawing substituents lead to a larger participation of the aromatic diazonium phenolate structure. Benzoannellation, on the other hand, leads to a decrease of the interaction between the keto and diazo functional group and to properties more reminiscent of “ordinary” ketones and diazo compounds.
A group 4 metallocene template synthesis of β,γ‐unsaturated ε‐hydroxy carboxylic acids
Authors: Berlekamp Martin , Erker Gerhard , Schönecker Bruno , Krieg Reimar , Rheingold Arnold L. 
Published: July 2007

AbstractThe reaction of (butadiene)zirconocene with hexacarbonyltungsten gives the metallacyclic [(π‐allyl)zirconoxy]carbene complex 7. This reagent adds to a variety of ketones to yield chiral nine‐membered metallacyclic ring systems (8). These systems are thus formed by means of 1,4‐selective coupling reactions of 1,3‐butadiene with W(CO)6 and an organic carbonyl compound at the zirconocene template. The ketones subjected to react with 7 include benzophenone, methyl vinyl ketone, cyclopentanone, and 3‐methoxyestra‐1,3,5(10)‐trien‐17‐one (12). The coupling products of 7 with cyclopentanone (8c) and 12 (8d‐A) were characterized by X‐ray crystal structure analyses. Of the four possible diastereomeric nine‐membered metallacyclic coupling products of 7 with 12 a single isomer [8d‐A with (13'S,17'R,2,3,4‐pS) configuration] was formed with ≥98% selectivity and isolated in 95% yield. Treatment of the complexes 8 in tetrahydrofuran with water and pyridine N‐oxide very effectively removed both transition metals with the formation of the corresponding β,γ‐unsaturated ε‐hydroxy carboxylic acids. The overall reaction sequence has thus converted the steroid ketone 12 very selectively to 5‐[3‐methoxy‐17β‐hydroxyestra‐1,3,5(10)‐trien‐17α‐yl]‐(E)‐pent‐3‐enoic acid (10d)
Pseudoazulene als Dienophile in der [4 + 2]‐Cycloaddition mit inversem Elektronenbedarf
Authors: Reimers Uwe , Seitz Gunther 
Published: July 2007

Pseudoazulenes as Dienophiles in the [4 + 2] Cycloaddition with Inverse Electron Demand[4 + 2] Cycloadditions of the pseudoazulenes 2, 6, 13, 18, and 22 to the extremely electron‐deficient s‐cis‐fixed diazadiene system of 3,6‐bis(trifluoromethyl)‐1,2,4,5‐tetrazine (1) are described. Probably according to a two‐step mechanism the pseudoazulenes 2, 6, and 18 react with 1 to form the corresponding cycloadducts followed by elimination of nitrogen and oxidation to furnish the novel 14 systems 5, 12, and 21 in rather high yields. In contrast, with the cyclopenta[d]‐pyridazines 13 and 22 the azines 17 and 26, respectively, are formed exclusively.
Reaktionen eines freien Stannaimins und von Basen‐stabilisierten Stannylenen
Authors: Ossig Günter , Meller Anton , Freitag Stefanie , Herbst‐Irmer Regine , Sheldrick George M. 
Published: July 2007

Reactions of a Free Stannaimine and of Base‐Stabilized StannylenesThe free stannaimine A reacts with methyllithium, 2,6‐diisopropylaniline, and methyl vinyl ketone to give the corresponding 1,2‐addition products (to the SnN bond) 2, 3, and 10. With 2,6‐diisopropylphenyl isocyanate and benzaldehyde [2 + 2] cycloadditions to the CO bonds lead to 4 and 5, while with benzonitrile oxide and acroleine [2 + 3] and [2 + 4] cyclo‐additions produce 8 and 9. The pyridine adducts bis‐[bis(trimethylsilyl)amino]stannylene and ‐germylene react with aryl azides to give the corresponding derivatives of tri‐amino‐2‐pyridylstannane 11 and ‐germane 12. Bis[2‐pyridyl‐bis(trimethylsilyl)methyl]stannylene upon treatment with aryl azides form the 1‐aza‐8‐stannabicyclo[3.2.0]octa‐2,4,6‐triene systems 13 and 14 via stannaimine intermediates. X‐ray structure analyses are presented for 3, 11, and 13.