bluuebunny/crossref_metadata_2025 huggingface dataset:
A Second Modification of Potassium Fluorenide and the Structure of Potassium 9‐tert‐Butylfluorenide: Effect of Crystallization Conditions and Substituents on Solid‐State Contact Ion Pair Interactions
Authors: Janiak Christoph
Published: July 2007

Crystallization of potassium fluorenide or 9‐tert‐butylfluorenide [formed from potassium metal and fluorene or 9‐tert‐butylfluorene in tetramethylethylenediamine (tmeda)] from a mixture of tmeda, tetrahydrofuran (THF) and diethyl ether yields [K(tmeda)2][C13H9] (1) or {[K(THF)2][μ‐C13H8(tBu)][K(tmeda)][μ‐C13H8(tBu)]}∞ (2). Compound 1 is a monomeric solvated ion pair with one η5‐coordinated fluorenyl and two chelating tmeda ligands and crystallizes in the monoclinic space group C2/c. Compound 1 is an example of polymorphism in organo‐potassium compounds, as a polymeric structure of 1 obtained under slightly different crystallization conditions has been reported earlier. Compound 2 forms a polymeric chain with potassium coordinated to two anellated six‐membered rings from two bridging 9‐tert‐butylfluorenyl systems and alternatingly solvated by one chelating tmeda or two THF. The crystal system for 2 is monoclinic, space group P21/c. A comparative AM1 study on the fluorenyl and 9‐tert‐butylfluorenyl anion suggests a steric origin for the haptotropic potassium shift in 2. 1H‐ and 13C‐NMR data for 1 and 2 as well as for 9‐tert‐butylfluorene are reported.
Thioalkylierung der Metall–Kohlenstoff‐Mehrfachbindung in Carbin‐ und Carben‐Komplexen von Molybdän und Wolfram
Authors: Kreißl Fritz R. , Schütt Wolfgang , Stegmair Claudia M. , Ullrich Norbert , Keller Hans , Ostermeier Josef , Herdtweck Eberhardt
Published: July 2007

Thiomethylation of the Metal–Carbon Multiple Bond of Carbyne and Carbene Complexes of Molybdenum and Tungsten

Carbyne complexes of molybdenum and tungsten react with dialkyl(methylthio)sulfonium tetrafluoroborate in a stepwise addition of the alkylthio cation to the metal–carbon multiple bond yielding dicationic η3‐dithiomethyl complexes.
Metallorganische Clusterkomplexe mit flächenüberbrückenden Aren‐Liganden, 5[1a]. C–H‐Aktivierung und Bildung eines μ3‐Aren‐Komplexes: Konkurrenzreaktionen beim Aufbau von (CpCo)3‐Clusterkomplexen mit Vinylbenzolen als Liganden
Authors: Wadepohl Hubert , Borchert Till , Büchner Klaus , Pritzkow Hans
Published: July 2007

Organometallic Clusters with Face‐Capping Arene Ligands, 5[1a].–C–H Activation and Formation of a μ3‐Arene Complex: Competing Reactions During Assembly of (CpCo)3Cluster Complexes with Vinylbenzenes as Ligands

A number of ring‐substituted styrenes R(C6H4)C2H3(R=CH3, F) reacts with [CpCo(C2H4)2] (1) to give both the cluster complexes [(CpCo)3{μ3‐η2:η2:η2‐(C6H4R)C2H3}] [2a(R=p‐CH3),2c(R=m‐F),2d(R=p‐F)} with Co3face‐capping arenes and [(μ2‐H)(μ3‐H)(CpCo)3{μ3‐1‐s̀:2‐s̀:η2‐HCC(C6H4R)}] [7a(R=p‐CH3),7b(R=o‐F),7c(R=m‐F),7d(R=p‐F)] with Co3face capping alkynes derived from dehydrogenation of the vinyl group. The X‐ray structure analysis of7aconfirms the 1‐s̀:2‐s̀:η2coordination of the bridging alkyne ligand. In solution the complexes7are fluxional and exhibit migration of the alkyne and hydride ligands on the Co3cluster.
Ring Opening of (η5‐Bicyclo[3.2.0]hepta‐1,3‐dienyl)‐(η4‐tetraphenylcyclobutadiene)cobalt(I) Followed by Cycloaddition
Authors: Butenschön Holger
Published: July 2007

The title reaction, which was detected by a comparison of the DSC analysis of title compound 2 with that of the corresponding bicyclo[3.3.0]octa‐1,3‐dienyl complex 3, takes place at 200°C with various dienophiles (dimethyl fumarate, dimethyl maleate, diphenylethyne, N‐methylmaleinimide). 3,4‐Dimethylenecyclopentenyl complex 12 most likely is the key intermediate of the reaction.
Über (Pentafluorphenyl)thiocarbonyl‐Verbindungen sowie die Synthese und Struktur von (Pentafluorphenyl)phenylsulfin
Authors: Hasserodt Jens , Pritzkow Hans , Sundermeyer Wolfgang
Published: July 2007

(Pentafluorophenyl)thiocarbonyl Compounds, Synthesis and Structure of Pentafluorophenyl Phenyl Sulfine

The C6F5‐substituted thiocarbonyls C6F5–CS–R [R=C6H5 (2), CH3 (4)] are synthesized from the corresponding carbonyl compounds by using in situ formed B2S3. The corresponding highly reactive thioaldehyde (R=H) is trapped with anthracene as Diels‐Alder adduct 7. By oxidation of 2 sulfine 10 is generated which dimerizes in the crystal lattice. An X‐ray crystal structure determination of a trithiaphosphinane 9 was carried out for the first time. The bis‐para‐substituted compound 12 is obtained from perfluorobenzophenone and hydrazine hydrate in a fast reaction.
Konkave Makroheterocyclen
Authors: Mekelburger Hans‐Bernhard , Groβ Jens , Schmitz Jürgen , Nieger Martin , Vögtle Fritz
Published: July 2007

Concave Macroheterocycles

Macrocyclic compounds of the general type 2 having a spherical shape and a molecular cavity have been synthesized. A „fold and paste”︁‐type cyclization step generates the macroheterocycles 4, 10, 11, 14, and 21. Since this approach is difficult to apply for O‐substituted derivatives, the „spheriphane”︁ 24 was synthesized by intermolecular cyclizaiton. The X‐ray structure analysis of 11 shows intermolecular interactions („dimer formation”︁) in the crystal.
Reaktionen der Borhydride B3H7 und B5H9 mit den ungesättigten Bor‐Stickstoff‐Verbindungen NBtBu2 und NB2tBu3
Authors: Küpper Stefan , Paetzold Peter , Boese Roland
Published: July 2007

Reactions of the Boron Hydrides B3H7 and B5H9 with the Unsaturated Boron‐Nitrogen Compounds NBtBu2 and NB2tBu3

THF · B3H7 reacts with RB≡NR (1, R = tBu) to yield the μ‐amino‐diborane(6) B2H4R(NHR) (5), which crystallizes in the triclinic space group Pī. The reaction of B3H7 with the azadiboriridine NB2tBu3 (2, R = tBu) leads to the known NB2R3 · BH3 (4) and the novel (NB2R3)2B2H4 (6). Product 6 is considered to represent a diaza‐arachno‐octaborane derivative. The iminoborane 1 reacts with B5H9 in the presence of lutidine (L) to give the ionic product [L – BR = NHR][B9H14] (7); our earlier report on the formation of the aza‐arachno‐heptaborate [LH][NB6H8R2] has to be revised. The products from the reaction of B5H9 with NB2R3 are 4 and 6.
Koordinationschemie Perhalogenierter Cyclopentadine und Alkine, XV. Systematischer Aufbau von fünffach ringsilylierten Cyclopentadienyl‐mangan‐Komplexen aus [C5Br5]Mn(CO)3. Molekülstruktur von [C5Br3(SiMe3)2]Mn(CO)3
Authors: Sünkel Karlheinz , Hofmann Julian
Published: July 2007

Coordination Chemistry of Perhalogenated Cyclopentadienes and Alkynes, XV[1]. – Systematic Generation of Fivefold Ring‐Silylated Cyclopentadienyl Manganese Complexes from [C5Br5]Mn(CO)3. Molecular Structure of [C5Br3(SiMe3)2]Mn(CO)3

[C5Br5]Mn(CO)3 reacts in a sequence of alternate bromine‐lithium exchange reactions and electrophilic silylations by SiMe3Cl or SiMe3OSO2CF3 to give [C5Br5‐n(SiMe3)n]Mn(CO)3, where n = 1 (1), 2 (2), or 3 (3). A crystal structure determination of 2 shows the two silyl substituents in the relative 1,3‐orientation. Addition of one or two equivalents of BuLi and SiMe2HCl to a solution of 3 yields [C5Br2‐n(SiMe3)3‐(SiMe2H)n]Mn(CO)3 with n = 1 (4) and 2 (5), respectively. If 1 is treated twice with 2 eq. of BuLi and then 2 eq. of SiMe2HCl, a further pentasilylated compound, [C5(SiMe3)(SiMe2H)4]‐Mn(CO)3 (6), is obtained. In situ chlorination of [C5(SiMe2H)5]Mn(CO)3 or 6 with PdCl2, followed by addition of MeMgCl, yields after chromatography an inseparable mixture of [C5(SiMe3)4X]Mn(CO)3 compounds, where X = H (7a), SiMe2H (7b), and SiMe3 (7c).
Metallkomplexe mit funktionalisierten Schwefel‐Liganden, VI[1]. Stabilisierung von 1‐Alkin‐1‐thiolato‐Liganden [R–C≡C–S–; R = SiMe3,(η5‐C5H4)Fe(η5‐C5H5)] in Ru(II)‐ und Pt(II)‐Komplexen. Kristallstrukturanalyse von cis‐(Ph3P)2Pt[C≡C–(η5C5H4)Fe(η5‐C 5H5)]2
Authors: Weigand Wolfgang , Robl Christian
Published: July 2007

Metal Complexes of Functionalized Sulfur‐Containing Ligands, VI[1]. – Stabilization of 1‐Alkyne‐1‐thiolato Ligands [R–C≡C–S–; R = SiMe3, (η5‐C5H4)Fe(η5‐C5H5)] in Ru(II) und Pt(II) Complexes. X‐ray Structure Analysis of cis‐(Ph3‐P)2Pt[C≡C–(η5‐C5H5)]2

The 1‐alkyne‐1‐thiolates R–C≡C–SLi [1: R = SiMe3, 3: (η5‐C5H4)Fe(η5‐C5H5)] react with (Ph3P)2PtCl2 and CpRu(PPh3)2Cl to give the complexes trans‐(Ph3P)2Pt(S–C≡C–SiMe3)2 (4a), CpRu(PPh3)2(S–C≡C‐SiMe3) (4b), and cis‐(Ph3P)2Pt[S–C≡C–η5‐C5H4)Fe(η5‐C5H5)]2 (5). The Pt(II) bis(acetylide) complex cis‐(Ph3P)2Pt[C≡C–(η5‐C5H4)Fe(η5‐C5H5)]2 (6a) was isolated after chromatography of 5. The trans‐configurated compound 6b is obtained by the reaction of [LiC≡C–(η5‐C5H4)]Fe(η5‐C5H5) with (Ph3P)2PtCl2. The complexes are characterized by IR, 1H‐, 13C‐, and 31P‐NMR spectroscopy, FAB mass spectrometry and X‐ray diffraction (6a).
Small Rings, 76[1]. – Intermediates on the Way to Tetramethyl Cyclopentadienonetetracarboxylate
Authors: Maier Günther , Wilmes Rolf
Published: July 2007

„Potassium salt”︁ 6, already described by Cookson, reacts with suitable electrophilic reagents to yield the enol esters 8–10. A base‐catalyzed acylation of the hydroxy group in 8–10 cannot be achieved because deprotonation is immediately followed by a [1,5] ester migration. The same reaction occurs upon heating 8–10 to 80°C, leading to the 1,3‐keto enols 11, 12, and 14. Upon treatment of „alcohol”︁ 7 with acetyl chloride only the dimer 3 of cyclopentadienone 2 can be isolated.
Kleine Ringe, 77[1]. Erzeugung und Abfangreaktionen von Cyclobutadientetracarbonsäure‐tetramethylester
Authors: Maier Günter , Wilmes Rolf , Fuchs Hansjörg , Leinweber Matthias
Published: July 2007

Small Rings, 77[1]. – Generation and Trapping Reactions of Tetramethyl Cyclobutadienetetracarboxylate

Dibromocyclobutane derivates 6 and 7 serve as precursors for the generation of the title compound 1. In the presence of suitable reagents 1 can be trapped in Diels‐Alder additions. Photocyclization of the adducts can be used for the construction of polyfunctionalized cage compounds.
Cycloadditions, 43[1]. Cyclobutanones via Photoreactions of Chromium‐Carbene Complexes with Olefins and Dienes – A Comparison with the Traditional Ketene Method
Authors: Köbbing Stephan , Mattay Jochen , Raabe Gerhard
Published: July 2007

Photolysis of chromium‐carbene complexes 1 in the presence of olefins and dienes yields cyclobutanones 4 and 5 with varying stereoselectivity. Under oxidative conditions lactones 6, 7, 8, and 10 are obtained as byproducts. Thermal reactions of ketenes 3 with olefins and dienes yield the same cyclobutanones with usually equal selectivities. In the case of 2,3‐dihydro‐1,4‐dioxin as olefin, diene 9 is obtained as a byproduct. Cycloaddition reactions of 1a or 3a with 1,2‐dimethylenecyclopentane (11) yield the spirocyclic cyclobutanones 12 and 13. The symmetric ketone 16 and the ketene dimer 17 are formed as additional products upon cycloaddition of ketene 3b to tetraethoxyethylene. Novel α‐(butylthio)cyclobutanones 4j, k, l, m and 5k, l are formed by cycloaddition reactions of the newly prepared compounds 1c and 3c. The ketene dimer 20 is formed by thermal reactions of 3a with olefins. Unusually low stereoselectivities are observed in the case of photolytic reactions of 1c with dienes.
α‐Oxygen‐Substituted Organolithium Compounds and their Carbenoid Nature: Reactions with RLi and Other Nucleophiles, Experimental and IGLO‐Calculated 13C‐NMR Shifts of the Carbenoid C Atom
Authors: Boche Gernot , Bosold Ferdinand , Lohrenz John C. W. , Opel Achim , Zulauf Peter
Published: July 2007

In addition to the earlier[1] demonstrated C–O bond elongation between the anionic carbon atom and oxygen in α‐lithiated ethers which indicates a carbenoid character of these compounds we provide further evidence for this property in this publication. Thus, α‐lithiated ethers RCH(Li)–OR' react as electrophiles with nucleophiles R' Li to give RCH(Li)–R' + LiOR', and the 13C‐NMR signal of the carbenoid C atom is shifted downfield (compared to the 13C signal of the corresponding non‐lithiated compound). Since the latter two observations are also made in the Li/Hal carbenoid series, α‐lithiated ethers indeed are Li/oxygen carbenoids. Furthermore, for the first time we have calculated the 13C shifts of carbenoid C atoms in the Li/oxygen carbenoid series by means of the IGLO method: the calculated data agree nicely with the experimental ones. They even allow the preferred bridged structure in solution to be determined.
Dihydroselenapyrans by [4 + 2] Cycloaddition of Diaryl Selenoketones
Authors: Hock Regina , Hillenbrand Stefanie , Erker Gerhard , Krüger Carl , Werner Stefan
Published: July 2007

The phosphorus ylides Ph3PCAr1Ar2 5 [Ar1 = Ph, Ar2 = 4‐CH3C6H4 (c); Ar1 = Ar2 = Ph (d); 4‐ClC6H4 (e); 4‐FC6H4 (f); 3‐CF3C6H4 (g); Ar1 = Ph, Ar2 = 4‐ClC6H4 (h)] were allowed to react with elemental selenium at ca. 75°C in toluene in the presence of an excess of 2,3‐dimethylbutadiene. The diaryl selenoketones 1 thus generated in situ by means of the „Staudinger chalcogenation”︁ reaction were trapped by the added conjugated diene to give the 2,2‐diaryl‐3,6‐dihydro‐4,5‐dimethyl‐2H‐selenapyrans 7 in high yield. Similarly, the ylides 5c–f and 5h were treated with selenium, and the resulting diaryl selenoketones 1 added to 1,3‐butadiene to give the corresponding 2,2‐diaryl‐3,6‐dihydro‐2H‐selenapyrans 8. Selenobenzophenone, synthesized analogously, was employed in a [4 + 2] cycloaddition reaction with 2,3‐dimethoxybutadiene to yield 3,6‐dihydro‐4,5‐dimethoxy‐2,2‐diphenyl‐2H‐selenapyran (9), which was characterized by an X‐ray crystal structure analysis. Compound 9 crystallizes in the space group P21/n. In the crystal the dihydro‐2H‐selenapyran adopts a distorted half‐chair conformation.
Rearrangements of Free Radicals, XIII[1]. Thermal and Photochemical Rearrangements of Cyclic C8H9 Radicals in Adamantane Matrix
Authors: Korth Hans‐Gert , Sustmann Reiner , Sicking Willi , Klärner Frank‐Gerrit , Tashtoush Hasan I.
Published: July 2007

The ESR spectra observed after X‐irradiation of bicyclo‐[5.1.0]octa‐2,5‐diene (homotropylidene) (12) in a [D16]adamantane matrix at 210 K have been identified to be mainly due to the cyclooctatrienyl radical (8), formed by thermal ring opening of the initial bicyclo[5.1.0]octa‐2,5‐diene‐4‐yl (homotropylidenyl) radical (7). The same spectrum has also been observed in X‐irradiation of bromocyclooctatriene and a mixture of bromocyclooctatriene and 7‐bromobicyclo[4.2.0]cycloocta‐2,4‐diene in a [D16]adamantane matrix. In all cases, UV irradiation of the matrix caused an irreversible transformation of radical 8 (and probably 7) into the bicyclo[3.3.0]octa‐2,6‐diene‐4‐yl radical (17). Tricyclo[3.3.0.02,4]oct‐6‐en‐7‐yl radical (19), generated by X‐irradiation of tricyclo[3.3.0.02,4]oct‐2‐ene (20) in adamantane, is thermally stable up to 370 K, but also undergoes a facile rearrangement to the radical 17 on UV irradiation. This process is reasonably explained to occur stepwise via radicals 7 and 8. The postulated reaction paths and the spectral assignments are supported by semiempirical (AM1, PM3), abinitio (UHF/3‐21G*), and molecular mechanics (MM2ERW) calculations, which are in accord with the finding that 8 is energetically more stable than 7. The quantum mechanical calculations predict that a degenerate sigmatropic circumambulation of the cyclopropane ring in radical 7 should favorably compete with its ring opening.
Relationship between Dominant Conformation and Diastereoselectivity of O‐Acetal Formation of Saturated 2H‐3,1‐Benzothiazine‐2‐thiones
Authors: Perjési Pál , Batta Gyula
Published: July 2007

Stereospecific formation of O‐acetals 4, 5 of the isomeric octahydro‐8a‐hydroxy‐4‐phenyl‐2H‐3,1‐benzothiazine‐2‐thiones 1–3 is reported. The stereoselectivity of the reaction is determined by the dominant conformations. During all reactions the phenyl substituent retains its equatorial position.
Alkylierungsreaktionen mit Alkoholen und Kohlenmonoxid: Eine breit anwendbare Synthese von Thioethern und von Coffein aus Theophyllin
Authors: Bott Kaspar
Published: July 2007

Alkylation Reactions by Means of Alkanols and Carbon Monoxide: An Efficient Synthesis of Thioethers and of Caffeine from Theophylline

The reaction of sodium or potassium thiolates with alkanols and carbon monoxide provides a versatile route to produce thioethers in excellent yields. By analogy, the potassium salt of theophylline suffers a nearly quantitative conversion to caffeine when heated with methanol under CO pressure. The mechanism of these alkylation reactions is discussed.
Beiträge zur Chemie des Bors, 219. (Di‐tert‐butylphosphanylimino)(2,2,6,6‐tetramethylpiperidino)boran: ein BNP‐1,3‐”︁Dipol”
Authors: Kroner Jürgen , Nöth Heinrich , Polborn Kurt , Stolpmann Holger , Tacke Matthias , Thomann Martina
Published: July 2007

Contributions to the Chemistry of Boron, 219[1]. – (Di‐tert‐butylphosphanylimino)(2,2,6,6,‐tetrametylpiperidino)borane: a BNP 1,3‐„Dipole”

In contrast to amino‐imino‐boranes R2N–BN–R', which are susceptible to [2 + 2] cycloadditions, the amino(phosphanyl‐imino)borane 2 [R = P(tBu)2] performs [3 + 2] cycloadditions with heteroallenes XCY or nitriles to yield the novel five‐membered heterocycles 3a–g, 6, 7, and 8. The reactions of 2 are dominated by the phosphorus atom as the nucleophile attacking the carbon atom in XCY and R–CN, respectively. The driving force for the formation of the new heterocycles is obviously provided by the formation of an iminophosphorane structure and a three‐coordinated environment at the boron atom. The X‐ray‐structures of 3a, 3c, 3e, and 3g demonstrate planer heterocyclic rings.
Reaktionen der Hydrazid‐verbrückten Cluster HRu3(CO)9(RN—NR2) mit Alkinen
Authors: Hansert Bernhard , Vahrenkamp Heinrich
Published: July 2007

Reactions of the Hydrazide‐Bridged Clusters HRu3(CO)9(RN—NR2) with Alkynes

The clusters HRu3(CO)9(RN—NR2) (1) with triply bridging hydrazide ligands (RN—NR2 = MeN—NHMe, HN—NHMe, HN—NMe2) undergo reactions with the alkynes HCCPh and PhCCPh to yield three cluster products in each case. One of them (2) is presumed to result from Ru—H insertion with concomitant cluster opening. The second (3) contains an open Ru3 cluster bridged by a unique μ3‐η2‐vinyl ligand, as shown by a structure determination. The third (4) represents the expected simple reaction product with a s̀,‐bound vinyl ligand, again proved by a structure determination. Cluster type 3 is converted to cluster type 2 by CO addition.
Alkoxy‐substituted N‐acyliminium salts — synthesis, structure, reactivity
Authors: Funke Wolfgang , Hornig Knut , Würthwein Ernst‐Ulrich , Möller Manfred H.
Published: July 2007

Alkylation of aliphatic imides 5 by use of oxonium salts takes place at one of the carbonyl oxygen atoms, leading to alkoxy‐substituted N‐acyliminium salts 1. These new reactive intermediates are fully characterized by IR, 1H‐ and 13C‐NMR spectroscopy and X‐ray analysis. The stereochemical and dynamical properties of the model compounds 6, 7 are investigated by ab initio model calculations (MP2/6–31G*//6–31G*). The barrier of rotation around the central C—N bond in 6 is calculated to 10.2 kcal/mol. The reaction with CH acids 8 yields new types of enamides (9); primary amines 10 are converted to N‐acylamidines 11. Primary amidines 12 react with 1 to form new 1,3‐diazabutadiene derivatives 13. The reaction with primary amides 14 gives N,N‐bisacylamidines 15. With primary N‐acylamidines 16 new doubly azavinylogous imides 17 (1‐oxa‐3,5‐diazahexatriene derivatives) are formed.
Studies on thiazolidine‐4,5‐dithiones. Synthesis of 5‐hydrazonothiazolidine‐4‐thiones and 5‐unsubstituted thiazolidine‐4‐thiones
Authors: Kibbel Hans Ulrich , Blödorn Hartmut , Ketcham Roger , Schaumann Ernst
Published: July 2007

In attempts to generate dithiones 3, 4‐thioxothiazolidin‐5‐ones 2a — c were converted into hydrazones 4a — c, which, however, could not be thiolyzed. Also thionation of 2a, b did not provide 3, but resulted in reduction to thiazolidine‐4‐thiones 7a, b.
Organomolybdän‐ und Organowolfram‐Reagenzien, V. über die additive, reduktive Carbonyldimerisierung (ARCD‐Reaktion)
Authors: Kauffmann Thomas , Jordan Jan , Voβ Karl‐Uwe , Wilde Heinz‐Wilhelm
Published: July 2007

Organomolybdenum and Organotungsten Reagents, V[1]. – On the Additive, Reductive Carbonyl Dimerization (ARCD Reaction)

Reagents of the type R4(PrO)4(μ‐PrO)2W2 (3; R = Me, Et, Pr, Bu, sBu, iBu, Hex, Me3SiCH2, Ph) prepared in situ by the action of organolithium or Grignard compounds on (PrO)4(μ‐PrO)2‐W2Cl4 (2), react with aromatic aldehydes or ketones and with the α,β‐unsaturated ketone benzylidene acetone in a novel reaction, called the ARCD reaction, to give products 4 of the type RRRC—CRRR with mostly good yields. In the case of benzylidene acetone and furfural besides the ARCD products the rearranged products 27 and 29 are formed. With the reagent Ph4(PrO)4(μ‐PrO)2W2 (3b) ARCD reactions are also possible in moderate yields with aliphatic aldehydes and ketones. The more closely investigated reagent Me4(PrO)4(μ‐PrO)2W2 (3a; decomposition at about — 45C) tolerates the aromatic bound functional groups Cl, F, OH, OMe, and NMe2 in the substrates, but not the NO2 and CO2Et substituents. It reacts with PhCOX (X = OEt, Cl, OCOPh) via acetophenone to give PhCMe2—CMe2Ph. — For the ARCD reactions a radical mechanism (Scheme 7) is postulated.
Alkylvanadium‐ und Alkylniob‐Reagenzien, III. über zwei unkonventionelle Methoden zur Charakterisierung labiler Organoübergangsmetall‐Komplexe; Anwendungen auf Allylderivate von VIII, VV, CrIII und MnII
Authors: Kauffmann Thomas , Bonrath Werner , Beirich Christoph , Li Weichang , Pahde Claudia , Raedeker Susanne , Wichmann Barbara , Wingbermühle Dorothea
Published: July 2007

Alkylvanadium and Alkylniobium Reagents, III[1]. – Two Unconventional Chemical Methods for the Characterisation of Labile Transition Metal Complexes; Application to Allyl Derivatives of VIII, VV, CrIII, and MnII

Two little known chemical methods, the “Competition Constant Method” and the production of “Ligand Concentration/Product Yield Diagrams”, are suitable for the characterisation and identification of allyl and crotyl transition metal species prepared in solution. These methods (Figures 1 – 6) gave the following results: by transmetallation of 1 or 2 equivalents of allylMgBr with 1 equivalent of VCl3, CrCl3, or MnCl2 and subsequent reaction with ketones, a diallyl (2, 23, 25) and not a monoallyl derivative of the transition metal reacts with the ketones, suggesting that the equilibrium: 2 allylMCI (allyl)2M + MCl2 (M = VCl, CrCl, Mn) lies far to the right hand side. This assumption was confirmed by the IR spectrum in the case of vanadation of 1 and 2 equivalents of allylMgBr with VCl3 and corresponds with the observation that by chromation of allylMgBr with 1 equivalent of CrCl3 ca. 50% of the CrCl3 remain unaffected although the allylMgBr is completely consumed. Conversely, according to the results of the “Competition Constant Method” vanadation of 1, 2, or 3 equivalents of allylMgBr with VOCl3 gives three different allyl complexes which are believed to be allylVOCl2 (5), (allyl)2VOCl (6), and (allyl)3VO (7). Vanadation of 1 or 2 equivalents of crotylMgBr with 1 or 2 equivalents of VCl3 gives analogous results to the corresponding reactions with allylMgBr.
Structures of tris(donor)‐tris(acceptor)‐substituted benzenes, 5. Organization and reorganization of the π system in a symmetric tris(alkylamino)trinitrobenzene: balance between cyanine and quinoid structures
Authors: Jens Wolff J. , Irngartinger Hermann , Gredel Frank , Bolocan Ion
Published: July 2007

The π system of 1a may adopt markedly different electronic structures with concomitant strong conformational preferences for the six‐membered ring. Neutral 1a can exist either in a quinoid boat form or as a twist boat, formally resulting from the coupling of an anionic with a cationic trimethinecyanine. Deprotonation gives a rigid quinoid boat structure; protonation occurs at a ring atom to form an equally rigid cyanine.
Dendrimere Polyamine
Authors: Moors Rolf , Vögtle Fritz
Published: July 2007

Dendrimeric Polyamines

The dendritic amines 2, 3, 4 and the imine 6 are synthesized by a divergent strategy. The formerly problematic reduction of polynitriles is achieved by the use of diisobutylaluminium hydride in high yield. The functional imine dendrimer 6 is converted into its tricobalt complex 7.
Iminophosphane und Azadiphosphiridin‐imine
Authors: Barion Detlef , Gärtner‐Winkhaus C. , Link Manfred , Nieger Martin , Niecke Edgar
Published: July 2007

Iminophosphanes and Azadiphosphiridine Imines

A variety of bis(alkyl)iminophosphanes R—PN—R' 3a—e (R = CMe2Et, CMeEt2, CEt3; R' = CMe3, CEt3) and arylimine‐substitued derivatives [R' = 2,4,6‐tBu3C6H2, R = CEt3 (3f), R = PhCHCH (3g)] are obtained by base‐induced dehydrochlorination from the corresponding amino(chloro)phosphanes R—P(Cl)—N(H)R' 2a—g. Depending on the steric demand of the substituents, the iminophosphanes 3a—d undergo a reversible [2 + 1] cyclodimerization to give the azadiphosphiridine imines R—P(NR')—P(R)—N—R' 4a—d. The same ring system is obtained in the reaction of 3c with the (arylimino)‐phosphanes R—PN—aryl (R = PhCHCH, Et, Me). However, this cycloaddition results in the formation of diastereomers 4e—g and 4'e—g, respectively. The reaction of Et—PN—aryl with R—PN—aryl (R = PhCHCH, Cl) furnishes (phosphanylamino)iminophosphanes Et(R)P—N(aryl)—PNaryl 5a, b. The compounds 3f, 4e, f, and 5a have been characterized by X‐ray structure analyses.
Organosubstituted Heterocycles with CBOBCCN, OPBCCB, and BOBCC Skeletons — Preparation, Characterisation in Solution and in the Solid State[1]
Authors: Köster Roland , Seidel Günter , Müller Gerhard
Published: July 2007

The salts K[magnified imageEt] [A: R2–4 = Et; B: R2,3 = Et, R4 = Ph; C: R2,4 = Et, R3 = Ph; D: R22 = C8H14, R3,4 = Et] react with [Me2NCH2]Br in THF to form the saturated bicyclic amine—tetraalkyldiboroxanes Et(R7)magnified image‐Me2 [1a (X‐ray crystal structure analysis): R1,4,7 = Et; 1b/1b': R1,4 = Et, R7 = syn/anti‐Ph; 1c: R1,7 = Et, R4 = Ph, and 1d/1d': R1,7 = syn/anti‐C8H14, R4 = Et]. A—D react with ClPPh2 to give the six‐membered monocyclic magnified imageEt [2a: R3–5 = Et; 2b: R3,5 = Et, R4 = Ph; 2c: R3,4 = Et, R5 = Ph; 2d (X‐ray crystal structure analysis): R23 = C8H14, R4,5 = Et]. From A—C and ClAsPh2 the 1,2,5‐oxoniadiboratoles magnified imageEt2 [3a: R3,4 = Et; 3b: R3 = Et, R4 = Ph; 3c: R3 = Ph, R4 = Et] are obtained, which rearrange to the 1,2,5‐oxadiborolanes magnified imageEt [4a: R3,4 = Et; 4b/4b': R3 = Et, R4 = Ph; 4c: R3 = Ph, R4 = Et].
1,1‐Organoboration of Di‐1‐alkynylsilanes with Alkynyl Groups of Different Reactivity: New Organometallic‐Substituted Siloles
Authors: Wrackmeyer Bernd , Kehr Gerald , Süβ Jürgen
Published: July 2007

The synthesis of alkynyl[(trimethylstannyl)ethynyl]dimethylsilanes 4 [alkynyl R1—C≡C: R1 = Bu (b), tBu (c), iPent (d), Ph (e), SiMe3 (f)] is reported. The intermolecular 1,1‐ethyloboration of 4 with triethylborane takes place selectively at the Sn—C≡ bond to give first the alkenyl(alkynyl)dimethylsilanes 5 and 6. There exists an equilibrium between 5 and 6, and compound 6 has the suitable stereochemistry for the final intramolecular 1,1‐vinyloboration to form the 4‐(diethylboryl)‐2‐(trimethylstannyl)siloles 7. Protodeborylation of 7 with water gives the 2‐(trimethylstannyl)siloles 8, and protodeborylation and protodestannylation with an excess of acetylacetone affords the siloles 9. Multinuclear NMR (1H‐, 11B‐, 13C‐, 29Si‐, and 119Sn‐) serves for monitoring the reactions and for the characterization of the products.
Strukturen und Moleküleigenschaften sterisch überfüllter Moleküle, 37. Hexakis(trimethylsilylmethyl)benzol C6[CH2Si(CH3)3]6
Authors: Bock Hans , Meuret Jochen , Ruppert Klaus
Published: July 2007

Structures and Molecular Properties of Sterically Overcrowded Molecules, 37[1]. — Hexakis(trimethylsilylmethyl)benzene C6[CH2Si(CH3)3]6

Both the low first vertical ionization energy of only 7.40 eV, determined by PE spectroscopy for C6[CH2Si(CH3)3]6, and the blocked substituent rotation in its radical cation as proven by ESR/ENDOR spectroscopy suggest considerable steric over‐crowdedness. To further substantiate this interpretation of the molecular properties, the crystal structure (hexagonal R3, Z = 2) has been determined at 100 K. Accordingly, the bulky trimethylsilyl groups are arranged alternatingly above or below the C6‐ring plane, out of which the methylene C centers are twisted by ±9°. Due to the angles CCSi widened to 115°, however, the intramolecular distances C(H)(H)C between non‐neighboured methyl groups of 443 and 452 pm even slightly exceed their van der Waals radii sum of 400 pm and thus avoid severe spatial congestion.
Synthese, Struktur und Umlagerung von Chlorbis(2,4,6‐tri‐tert‐butylphenyl)gallan
Authors: Meller Anton , Pusch Stefan , Pohl Ehmke , Häming Ludger , Herbst‐Irmer Regine
Published: July 2007

Synthesis, Structure, and Rearrangement of Chlorobis(2,4,6‐tri‐tert‐butylphenyl)gallane

The title compound 1 is easily obtained from GaCl3 and 2 equvialents of supermesityllithium. According to an X‐ray structure analysis one of the supermesityl rings shows a large deviation from planarity. Heating of 1 in vacuo gives mainly two products: an isomer of 1 in which one of the supermesityl groups is bound to Ga by one of its tert‐butyl groups (2) and a benzo[b]gallolane (3) formed by elimination of HCl, X‐ray structure analyses and full NMR (1H, 13C) data are provided for 1 and 2, MS and characteristic NMR (1H, 13C) data for 3.
New Organophosphorus Ligands: 1,1,2‐Tris(diphenylphosphanyl)cyclopropane and Its Derivatives
Authors: Schmidbaur Hubert , Manhart Stefan , Schier Annette
Published: July 2007

Cyclopropanation of 1,1,2‐tris(diphenylphosphanyl)ethene with dimethylsulfonium methylide affords the title compound 1. The trifunctional phosphane is transformed into the trioxide 2 and trisulfide 3 by oxidation with hydrogen peroxide or elemental sulfur, respectively. With the tetrahydrofuran — borane complex the tris(phosphane—borane) 4 is obtained. The crystal structure of compound 1 has been determined by single‐crystal X‐ray diffraction.
Electronic Interactions in Saturated and Unsaturated [1.1.1]‐, [2.1.1]‐, [2.2.1]‐, and [2.2.2]Triblattanes — PE‐Spectroscopic Investigations
Authors: Gleiter Rolf , Sigwart Christoph , Fessner Wolf‐Dieter , Müller‐Bötticher Hermann , Prinzbach Horst
Published: July 2007

The He(I)‐PE spectra of the parent [1.1.1]‐, [2.1.1]‐, [2.2.1]‐, and [2.2.2]triblattanes 1–4, of their unsaturated or ketonic congeners 5–13 and benzo derivatives 14–20 have been recorded. For 1–4, the energy difference between the highest occupied orbitals (e” and a' mainly localized at the central bicyclo‐[2.2.2]octane unit) and the subsequent MOs increases with increasing number of ethano bridges. This observation is rationalized by using a first‐order perturbation‐theoretical approach. The analysis of the PE spectra of the exo‐methylene (5–7), ketone (8–10), and endo‐olefinic derivatives (11–13) unveils a strong π/σ mixing. The splitting of the π‐bands in 7 (0.95 eV) and 13 (1.0 eV), respectively, is traced back to a stronger π/σ mixing of the e MOs as compared to the a2 MOs. An analogous interaction causes the splitting of the first bands of the ketones 8–10 (0.45–1.49 eV). For the benzo derivatives 14–20 the split of the π‐bands is relatively small (0.35–0.7 eV).
Thermisch induzierte formale [3 + 2]‐Cycloadditionen von 3,3‐Dimethoxycyclopropen an Triazine, eine neue Synthese von Pyrrolo[1,2‐d][1,2,4]triazinen
Authors: Rischke Monika , Seitz Gunther , Frenzen Gerlinde
Published: July 2007

Thermally Induced Formal [3 + 2] Cycloadditions of 3,3‐Dimethoxycyclopropene to Triazines, a Novel Synthesis of Pyrrolo[1,2‐d][1,2,4]triazines

Formal [3 + 2] cycloaddition reactions of the π‐delocalized singlet vinylcarbene/three‐carbon 1,3‐dipole 8, generated in a reversible, thermal ring opening of the cyclopropenone ketal 7, with a variety of substituted triazines lead to the novel pyrrolo[1,2‐d][1,2,4]triazines 9 or 10. Compound 10c is protonated at N‐2 by HClO4/HOAc to yield the salt 17c and alkylated at the same position by Meerwein reagent [O(CH3)3BF4] to give 18. 10c reacts smoothly with dimethyl acetylenedicarboxylate to provide the pyrido[2,1‐f]pyrrolo[1,2‐d][1,2,4]triazines 19 and 20. The pyrrolotriazine 14 in the presence of oxygen, daylight, and silica gel is readily oxidized to the triazine N‐oxide 22. The crystal structures of 14, of the protonated species 17c and of the N‐oxide 22 have been determined by X‐ray diffraction methods.
Organische Synthesen mit übergangsmetall‐Komplexen, 66. 2‐Aminopyrrole durch Metathese von (β‐Aminovinyl)carben‐Chrom‐ und ‐Wolfram‐Komplexen mit Isocyaniden
Authors: Aumann Rudolf
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 66[1]. — 2‐Aminopyrroles by Metathesis of (β‐Aminovinyl)carbene Complexes of Chromium and Tungsten with Isocyanides

(β‐Aminovinyl)carbene complexes LnMC(OEt)—CHC(Ph)‐NHR (Z)‐3a—d [LnM = (CO)5Cr, (CO)5W; R = Ph, iPr, CH2Ph] react with two equivalents of isocyanides R1—NC 5 (R = c‐C6H11, t‐C4H9) to give 2‐amino‐3‐ethoxypyrroles 7a—e and isocyanide complexes LnM(R1—NC) 6. The reaction involves the formation of ketenimine complexes by metathesis. These are key intermediates. The pyrroles 7 are easily oxidized by air to give amidines PhN(R1NH)C—C(OEt)CH—COPh 9 (R = c‐C6H11, t‐C4H9). 7a forms a Michael adduct 10a as well as a Diels‐Alder adduct 11a with N‐phenylmaleimide. A 1‐amino‐2‐ethoxybenzene 12a is obtained from 11a by elimination of aniline.
The Photoelectron Spectra of Dimethoxysulfane and Dimethoxydisulfane
Authors: Gleiter Rolf , Hyla‐Kryspin Isabella , Schmidt Heinar , Steudel Ralf
Published: July 2007

The He(I) photoelectron spectra of dimethoxysulfane (1) and dimethoxydisulfane (2) have been recorded. The lowest energy ionizations in the PE spectrum of 1 can be explained by assuming C2 symmetry. They can be described as arising from linear combinations between the 3p lone‐pair at sulfur and 2p lone‐pairs at the oxygen atoms. A comparison between the calculated MO sequence of 2 for different conformations and the first PE bands shows a good agreement with an OSSO torsional angle near 90°. The highest occupied MOs of 2 can be described as linear combinations between the 3p MOs of the S2 unit and linear combinations between the 2p AOs of the oxygen atoms.
Verknüpfung von Cyanamiden mit einem Carbinliganden – Bildung von η2‐(C,N)‐Imidazolium‐ und Ansa‐Carben‐Komplexen
Authors: Fischer Helmut , Troll Carsten
Published: July 2007

Coupling of Cyanamides with a Carbyne Ligand – Formation of η2‐(C,N)‐Imidazolium Complexes and Ansa‐Carbene Complexes

Herrn Prof. Dr. Ernst Otto Fischer zum 75. Geburtstag gewidmet.

Dicarbonyl(cyclopentadienyl)(phenylcarbyne)manganese complexes [Cp(CO)2Mn≡CPh]+X‐ (1‐X) (X = BF4, BCl4) react with dimethyl‐ (2a), diethyl‐ (2b), and diisopropylcyanamide (2c) in five‐fold excess by a head‐to‐tail cyclization of two cyanamides with the carbyne ligand to give η2‐(C,N)‐imidazolium complexes (3a–c–X). As byproducts ansa‐amino(alkylide‐neamino)carbene complexes (4a–c) are formed in which a N=C(Ph) group bridges the carbene carbon and the Cp ring. With increasing excess of the cyanamide the product ratio 3‐X: 4 increases. Among the products of the reaction of 1‐X with the cyanamides N≡CNR2 [NR2 = N(iBu)2, N(Bzl)2, N(Me)Ph] no imidazolium complexes 3‐X are detected, only ansa‐carbene complexes 4 are isolated. PMe3/H2O or pyridine/H2O displaces the heterocyclic ligand from 3a‐BF4. The structure of 3a‐BF4 is established by an X‐ray analysis.
New Organophosphorus Ligands: 1,1,4,4‐Tetrakis(diphenylphosphanyl)butatriene and Its Tetrasulfide
Authors: Schmidbaur Hubert , Manhart Stefan , Schier Annette
Published: July 2007

Treatment of bis(diphenylphosphanyl)ethyne with potassium diphenylphosphide in tetrahydrofuran leads to the formation of tetraphenyldiphosphane Ph2P–PPh2 and the title compound (Ph2P)2C=C=C=C(PPh2)2 (1). A mechanism is proposed for this process. Compound 1 reacts with elemental sulfur to give the tetrasulfide [Ph2(S)P]2C=C=C=C[P(S)Ph2]2 (2). The crystal structures of 1 and 2 have been determined by single‐crystal X‐ray diffraction. In both cases the linear butatriene unit shows strongly alternating C=C bond lengths as predicted in theoretical studies.
A Dynamic Equilibrium of Oxaphosphetanes
Authors: Geletneky Christian , Försterling Frank‐Holger , Bock Willi , Berger Stefan
Published: July 2007

The course of the Wittig reaction was investigated by rapid injection NMR spectroscopy. Rate constants for the formation of oxaphosphetanes were determined. A new dynamic equilibrium of oxaphosphetanes was observed for the first time. The solvent and substituent dependence of the new effect was investigated. By labeling various oxaphosphetanes with 13C and 17O the lithium salt dependence of the new equilibrium was shown. A lithium adduct of oxaphosphetanes under these conditions is proposed.
Facile Synthesis of Ferrocene Biscrown Ethers and Ferrocene Cryptands: NMR Complexation Studies and the Redox‐Switched Bonding of H+ and Na+
Authors: Plenio Herbert , El‐Desoky Hanaa , Heinze Jürgen
Published: July 2007

The reaction of 1,1′‐ferrocenylene‐bis(methylenepyridinium) tosylate chloride (1) with aza‐x‐crown‐y (x/y = 12/4; 15/5; 18/6) gives the three novel ferrocene biscrown ethers 1,1′‐ferrocenylene‐bis(methylene‐aza‐x‐crown‐y) (x/y = 12/4, 2; 15/5, 3; 18/6, 4). The reaction of 1 with diaza‐18‐crown‐6 represents a new and simple route to the known ferrocene cryptands 1,1′‐zacyclooctadecane)] (5) and 1,1″:1′,1″‐bisferrocenylene‐bis‐[bis‐7,16‐methylene(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane)] (6). The solid‐state structure of 5 is described. The ferrocene bridge compresses the diaza crown ether leading to an internitrogen distance of 458 pm. The stoichiometry of Na+ and K+ complexes with 2 and 3 in CD3CN determined in NMR titration experiments suggests the formation of Na+ and K+ crown ether sandwich complexes in solution. Cyclic voltammograms of 2 and 5 in the presence of varying amounts of H+ and Na+ have been recorded. The redox potential of ferrocene is shifted by +180 mV in the case of 5 · Na+ and up to +600 mV in the case of 5 · H+H+ relative to 5, but only by + 70 mV with 2 · Na+ and 2. The protonation of 5 give rises to several isomers (exo and endo protonation) which differ significantly in their redox potential. The extremely large positive shift of the oxidation potential of the diprotonated ferrocene cryptand corresponds to an increase in the acidity of 5 · H+H+ upon oxidation by more than ten orders of magnitude and makes this system a candidate for the directed membrane transport of protons.
Zur Existenz des Hexahydroxoperiodonium‐Ions — Kristallzüchtung und Strukturanalyse von α‐ und β‐H6IO6HSO4
Authors: Kraft Thorsten , Jansen Martin
Published: July 2007

On the Existence of the Hexahydroxoiodine(VII) Cation – Crystal Growth and Structure Analysis of α‐ and β‐H6IO6HSO4*

Periodic acid H5IO6 dissolves at 50°C in 90–97% H2SO4 to give the hexahydroxoiodine(VII) cation H6IO6+. Depending on the concentration of the sulfuric acid, two modifications of H6IO6HSO4 can selectively and reproducibly be precipitated. The crystal structures determinations prove the existence of H6IO6+ in the solid state. The crystal structures and Raman spectra of α‐H6IO6HSO4 (1a) and β‐H6IO6HSO4 (1b) are discussed and compared. The temperature‐dependent behaviour of 1a and 1b is studied by means of DTA, temperature‐dependent X‐ray powder diffraction, and Raman spectroscopy.
Metallkomplexe mit biologisch wichtigen Liganden, LXVIII. Metallorganische Asparaginato‐Cobaltkomplexe als Liganden für Alkali‐Ionen
Authors: Bergs Ralph , Sünkel Karlheinz , Beck Wolfgang
Published: July 2007

Metal Complexes of Biologically Important Ligands, LXVIII[1]. – Organometallic Asparaginato Cobalt Complexes as Ligands for Alkaline Ions

The trischelate complexes of the dianion of aspartic acid and β‐methylaspartic acid (η5‐C5Me5)magnified image] (R = H, Me) form adducts with alkali iodides MI (M = Li, Na, K). The polymeric structure of (η5‐C5Me5)Co(L‐asp.–2H+)KI (1c) was determined by X‐ray diffraction. In the crystal of 1c the potassium ions are surrounded by five oxygen atoms of the carboxylate groups whereby two oxygen atoms form bridges between two K+ ions. Similarly, trischelate complexes 4 and 5 have been obtained from (η5‐C5Me5)Co(CO)I2 and 2,3‐diaminopropionic, 2,4‐diaminobutyric acid, and asparagine, respectively.
Reaktionen von (Fluorsulfonylimino)‐λ6‐schwefeltetrafluorid FSO2N=SF4
Authors: Meier Thomas , Mews Rüdiger
Published: July 2007

Reactions of (Fluorosulfonylimino)‐λ6‐sulfur Tetrafluoride FSO2N=SF4

Herrn Professor Pedro J. Aymonino zum 60. Geburtstag gewidmet.

FSO2N=SF4 (1) reacts with CsF, HF and CIF to form Cs+N(SO2F)SF5– (2), HN(SO2F)SF5 (3) and ClN(SO2F)(SF5) (5); 5 adds to ethylene to give ClCH2CH2N(SO2F)SF5 (6).
Synthese optisch aktiver 2‐Siloxycyclopropancarbonsäureester durch asymmetrische Katalyse, I. Katalysatoreinfluß auf die Cyclopropanierung von (Z)‐1‐Phenyl‐1‐(trimethylsiloxy)prop‐1‐en
Authors: Dammast Franziska , Reißig Hans‐Ulrich
Published: July 2007

Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, I. – Influence of the Catalyst on the Cyclopropanation of (Z)‐1‐Phenyl‐1‐(trimethylsiloxy)prop‐1‐ene

The cyclopropanation of silyl enol ether 1a with methyl diazoacetate (2a) and diazoesters 2b–d in the presence of optically active copper salicylimine complexes 4‐Cu was systematically studied. Up to 88% enantiomeric excess in products 3 were obtained by employing the appropriate reaction conditions and the optimal catalyst ligands. Thus, for the first time respectable optical yields were achieved in asymmetric cyclopropanations of silyl enol ethers with easily available copper‐Schiff base catalysts. The ring opening of the separated diastereomers of 3a employing nBu4NF provided methyl γ‐oxocarboxylate 6a in good optical purity. This demonstrates that this process occurs without racemization and also that 3a is formed with the same absolute configuration at C‐1.
Neue [m.n]Cyclophane durch sukzessive Ketonpyrolyse
Authors: Schmohel Erich , Ott Frank , Breitenbach Jörg , Vögtle Fritz , Nieger Martin
Published: July 2007

New [m.n]Cyclophanes by Successive Ketone Pyrolysis

The new cyclophane ketones 7, 10, 11, 13, 14, and 16 and the known hydrocarbons 8 and 15 are obtained by successive thermal elimination of carbon monoxide with C–C bond formation from the known [3n]cyclophane(ones)n and the new terphenylophanedione 4. X‐ray structure analyses of the ketones 3 and 4 and the anti‐isomer of the ketone 7a are performed.
Medium‐Sized Cyclophanes, 29. Synthesis and Desulfurization of 2,11‐Dithia[3]metacyclo‐ and 2,11‐Dithia[3]paracyclo[3](4,9)pyrenophanes
Authors: Yamato Takehiko , Miyazawa Akira , Tashiro Masashi
Published: July 2007

2,11‐Dithia[3]metacyclo‐ (14b) and 2,11‐dithia[3]paracyclo[3]‐(4,9)pyrenophane (14c) were obtained by the coupling reactions of 4,9‐bis(chloromethyl)pyrene (12) with the corresponding bis(mercaptomethyl)benzenes (13b, c). Attempted pyrolysis of the disulfones 18b, 18c to afford [2]metacyclo‐ (19b) and [2]paracyclo[2](4,9)pyrenophane (19c) failed. Only the ring cleavage products 16 and 20 were obtained. The sulfur dioxide extrusion by vapor‐phase pyrolysis of the corresponding disulfone 18 to the highly strained 19 clearly demonstrates the limits of these preparative ring contraction method. The photolytic desulfurization of 14c afforded the [2](1,5)naphthal‐eno[2]paracyclophane analogue 21 instead of [2]paracyclo[1]‐(4,9)pyrenophane 21′. The mechanism of the pyrolysis and photolysis reactions is discussed.
Flow‐Vacuum Pyrolysis of Polycyclic Compounds, 6. Pyrolysis of Dibenzo [CH]8 Hydrocarbons
Authors: Banciu Mircea D. , Stanescu Michaela D. , Parvulescu Luminitza , Petride Aurica , Pop Mircea
Published: July 2007

The flow‐vacuum pyrolysis of dibenzo [CH]8 hydrocarbons 2,3,4, and 5 are studied at 1 Torr and in the temperature range between 400 and 650°C. The following new transformations have been observed: 2⇆4, 2→5, 3→5, 3⇆4, 3→2, 5→11, the last three presenting analogies in the [CH]8 and/or benzo [CH]8 series. A reaction mechanism is suggested.
On the Reaction of 1‐Aza‐2‐azoniaallene Salts with Carbodiimides
Authors: Wang Quanrui , Troll Carsten , Fischer Helmut , Jochims Johannes C. , Amer Atef
Published: July 2007

1‐Aza‐2‐azoniaallene cations 3, prepared in situ from geminal (chloroalkyl)azo compounds 2, react with carbodiimides 4 to give 4,5‐dihydro‐5‐imino‐1H‐1,2,4‐triazolium salts 7. An X‐ray structural analysis was carried out for 71. According to AM1 calculations the cycloaddition of carbodiimides to 1‐aza‐2‐azoniaallene cations occurs in a nonconcerted manner via cyanamidium cations 5 as intermediates. Hetero‐Wagner‐Meerwein rearrangements of the primary cycloadducts 6 provide the final products 7.
Coordinated 1‐Aza‐1,3‐butadienes: Stable Intermediates in the Formation of Pyridines from [(β‐Aminoethenyl)carbene]chromium Complexes
Authors: Duetsch Michael , Stein Frank , Funke Frank , Meijere Armin De , Pohl Ehmke , Herbst‐Irmer Regine
Published: July 2007

[(β‐Aminoethenyl)carbene]chromium complexes 3a–c rearrange to coordinated 1‐aza‐1,3‐butadienes 6a–c, which undergo cycloadditions with alkynes 7a, c to pyridines 9a, 10a–c.
Ligand Effects on the Gas‐Phase Reactions of (π‐L)FeI Complexes with n‐Pentanenitrile
Authors: Stöckigt Detlef , Sen Semiha , Schwarz Helmut
Published: July 2007

The gas‐phase ion chemistry of the previously studied system Fe(n‐pentanenitrile)+ is dramatically changed, when the metal ion bears substituents L (L = C2H4, C3H6, C4H6, i‐C4H8, 1‐C4H8, 2‐C4H8, and C6H6), and the major ion‐molecule reactions of Fe(L)+ with RCN (R = n‐C4H9) are as follows: (i) Ligand substitution Fe(L)+ + RCN → Fe(RCN)+ + L is observed for all L studied except L = C4H6, C6H6; (ii) the formation of association complexes Fe(L)(RCN)+ takes place for all ligands L, except L = C2H4; (iii) dehydrogenation of the L is confined to L = 1‐C4H8 and 2‐C4H8; (iv) carbon–carbon and carbon–nitrogen bond activation of the nitrile, typical for the behaviour of bare Fe+, are absent in the reactions of all Fe(L)+ with RCN, Dehydrogenation of the nitrile is observed only for L = 1‐C4H8 and 2‐C4H8, and the molecular hydrogen originates exclusively from the γ/δ‐position of the alkyl chain following the well‐established “remote functionalization” concept. In contrast to the reaction of bare Fe+ with n‐pentanenitrile, dehydrogenation in the Fe(L)(RCN)+ system is not preceded by a degenerate isomerization of RCN, bringing about equilibrations of the C(α)/C(γ) positions. Rate constants were derived and compared with those calculated by the ADO and CAP theories. All reactions of the ligated Fe(L)+ ions were found to occur with collision rate, again in contrast to the bare Fe+. Based on the ADO formalism, the dipole locking constant “c” of n‐pentanenitrile was redetermined to c = 0.47.
Zur Energiedelle von Diradikalen, IV[1]. 2‐Methylen‐1,4‐cyclohexadiyl
Authors: Roth Wolfgang R. , Wollweber Detlef , Offerhaus Rolf , Rekowski Volker , Lennartz Hans‐Werner , Sustmann Rainer , Müller Wolfgang
Published: July 2007

The Energy‐Well of Diradicals, IV[1]. – 2‐Methylene‐1,4‐cyclohexadiyl

The energy surface of the title compound 2 is derived from the kinetics of its precursors 5, 6, 7, and 8, the oxygen dependance of its trapping rate, and heat of hydrogenation measurements of 5, 6, 7, and 15. These data lead to a heat of formation for the diradical 2 of 69.8 kcal/mol and an energy well of 8.2 kcal mol–1. From the Curie plot of the ESR spectrum and oxygen trapping experiments a singlet‐triplet splitting of 1.4 kcal mol–1 is indicated, with the triplet being the ground state.