bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carben‐Reaktionen mit Oxetan und mit Oxetan/Methanol‐Gemischen
Authors: Kirmse Wolfgang , Lelgemann Rudolf , Friedrich Klaus 
Published: July 2007

Reactions of Carbenes with Oxetane and with Oxetane/Methanol MixturesEthoxycarbonylcarbene, bis(methoxycarbonyl)carbene, phenylcarbene (17a), diphenylcarbene (17b), fluorenylidene (17c), 2‐furylcarbene (31a), 2‐furyl(phenyl)carbene (31b), 4‐oxo‐2,5‐cyclohexadienylidene (40), and 4,4‐dimethyl‐2,5‐cyclohexadienylidene (53) were generated by photolysis of the appropriate diazo compounds. With neat oxetane, most of these carbenes react by competitive C – H insertion (B → A, Scheme 1) and ylide formation (B → C). 31a and 40 do not insert into C – H bonds; 31b does not attack oxetane but rearranges exclusively with formation of 26. The ylides undergo Stevens rearrangement to give tetrahydrofurans (C → D) and α´,β‐elimination, leading to allyl ethers (C → E). With oxetane/methanol mixtures, the intervention of oxonium ions (H) is indicated by the formation of 1,3‐dialkoxypropanes (I). The oxonium ions arise either by protonation of the ylides (C → H) or by protonation of the carbenes (B → G), followed by electrophilic attack of the carbocations (G) at oxetane (G → H). The former route is followed by the alkoxycarbonylcarbenes and by 40; the ylides derived from the remaining carbenes do not react with methanol, owing to their rapid Stevens rearrangements. Protonation of the carbenes 17b, 31, and 53 is clearly indicated by their product ratios and, for 31, by the formation of isomeric ethers (33, 36). The more electrophilic carbenes discriminate but slightly between oxetane and methanol while the more nucleophilic carbenes (17b, 31,53) prefer the protic methanol strongly over the aprotic oxetane.
Activation and Control of the Reaction of Dioxastannolane with Carbon Disulfide and Phenyl Isothiocyanate by the Addition of Bases
Authors: Yano Katsunori , Baba Akio , Matsuda Haruo 
Published: July 2007

Abstract1,3‐Dioxa‐2‐stannolanes 1 are readlily activated by Lewis bases such as Bu3P and Et3N to give cycloadducts on reaction with carbon disulfide or phenyl isothiocyanate under mild conditions. In particular, bases play a characteristic role in the reaction with carbon disulfide to produce 1,3‐dioxolane‐2‐thiones 2 in good yields, while spiro compounds 3 (1:2 adducts) are predominantly obtained in the absence of bases.
Molecular Structure of Trisilylmethane and Synthesis of 1,1,1‐Trisilylethane
Authors: Schmidbaur Hubert , Zech Joachim , Rankin David W. H. , Robertson Heather E. 
Published: July 2007

AbstractAs a precursor for trisilylmethane, tris(phenylsilyl)methane is prepared by a Merker‐Scott reaction of chlorophenylsilane, bromoform, and magnesium turnings in boiling tetrahydrofuran. Chlorophenylsilane is formed in a new synthesis starting from phenylsilane and hydrogen choride/AlCl3 in diethyl ether. The gas phase structure of trisilylmethane (H3Si)3CH, obtained from (PhSiH2)3CH via (BrSiH2)3CH, has been determined by electron diffraction. Data refinement confirmed a model of C3 molecular symmetry, with local C3v symmetry for the silyl groups. — As a precursor for 1,1,1‐trisilylethane, 1,1,1‐tris(phenylsilyl)ethane has been prepared similarly from chlorophenylsilane, 1,1,1‐trichloroethane and magnesium and converted via 1,1,1‐tris(bromosilyl)ethane into CH3C(SiH3)3.
Thermolabile Kohlenwasserstoffe, 31 Stereoselektive Bildung und Spaltung der Dimeren des 1‐(5,6,7,8‐Tetrahydro‐1‐naphyl)neopentyl‐Radikals
Authors: Peyman Anuschirwan , Beckhaus Hans‐Dieter , Kramer Dirk , Peters Karl , Schnering Hans Georg Von , Rüchardt Christoph 
Published: July 2007

Thermolabile Hydrocarbons, 31. – Stereoselective Formation and Cleavage of the Dimers of the 1‐(5,6,7,8‐Tetrahydro‐1‐naphthyl)neopentyl RadicalThe 1,2‐diaryl‐1,2‐di‐tert‐butylethanes meso‐ and DL‐6 are synthesised by partial catalytic hydrogenation of the parent dinaphthylethanes 5. The crystal structure of meso‐6 was obtained experimentally and calculated by molecular mechanics methods (MM2). It is shown, that 1‐(5,6,7,8‐tetrahydro‐1‐naphthyl)neopentyl radical 8 forms its dimers 6 with high stereoselectivity, e.g. DL‐6: meso‐6 = 45 (at ‐20°C) and 7.07 (at 100°C). The selectivity was measured over a range of 300 K by using several radical precursors. The difference of the enthalpy of activation has been derived for the two dimerisation reactions: δH†dim(DL – meso) = –2.8 ± 0.2 kcal/mol. The cleavage of DL‐6 and of meso‐6 into 8 was measured kinetically, and the enthalpies of activation δH†dis = 46.2 ± 0.6 (DL‐6) and 52.6 ± 1.3 kcal/mol (meso‐6) and the entropies of activation δ†dis = 8.4 ± 0.6 (DL‐6) and 20.0 ± 2.5 e.u. (meso‐6) have been obtained. A complete thermodynamic cycle is constructed by using the calculated (MM2) heats of formation δH°f = –27.6 (DL‐6) and –30.0 kcal/mol (meso‐6). Thus, the diastereomer (DL‐6), which is formed preferentially, appears to be the thermodynamically and kinetically less stable one. It turns out, that the high stereoselectivity of the dimerisation of 8, compared to the parent 1‐phenyl‐neopentyl radical (2a), is mainly caused by the steric repulsions between the approaching radicals.
5,6,7,8‐Tetramethylenebicyclo[2.2.2]oct‐2‐ene as “Bis(diene)” in Repetitive Diels‐Alder Reactions
Authors: Wegener Stefan , Müllen Klaus 
Published: July 2007

AbstractThe synthesis of ladder‐type oligomers by repetitive Diels‐Alder reactions is described. The title compound 1 has been treated with the “bis(dienophile)” 2 at high pressure (7.5 kbar). Under these conditions the formation of oligomers with up to 33 laterally anellated six‐membered rings has been achieved. An attempt has been made to analyze the complex stereochemistry of the cycloadditon by using the model compounds 5a, 5b.
2‐Chloro‐4,5‐dihydroimidazole, VI. Annulation by Means of 4‐(Dimethylamino)pyridine in the Presence of C — H Acids
Authors: Sączewski Franciszek 
Published: July 2007

Abstract2‐Chloro‐4,5‐dihydroimidazole (1) reacts with 4‐(dimethylamino)pyridine to yield the stable pyridinium salt 2, which on treatment with some C — H acids produces 1,2,3,5‐tetrahydroimidazo[1,2‐α]pyrimidines 6.
Simple Entry into Tricyclo[3.3.0.03,7]octanes
Authors: Hoffmann H. Martin R. , El‐Khawaga Ahmed M. , Oehlerking Hans‐Heinrich 
Published: July 2007

Abstract1,5‐Dimethylbicyclo[3.3.0]octan‐3,7‐dione (2) was converted into 1,5‐dihydroxy‐3,7‐dimethyltricyclo[3.3.0.03,7]octane (3) in the presence of Sml2 in 76% yield.
Mono‐, Di‐ und Trikomplexierung von 9,10‐Dihydro‐9,10‐dimethyl‐9,10‐diboraanthracen mit Fe(CO)3‐Komplexfragmenten
Authors: Schulz Hartmut , Pritzkow Hans , Siebert Walter 
Published: July 2007

Mono‐, Di‐, and Tricomplexation of 9,10‐Dihydro‐9,10‐dimethyl‐9,10‐diboraanthracene with Fe(CO)3 Complex FragmentsReaction of 9,10‐dihydro‐9,10‐dimethyl‐9,10‐diboraanthracene (1c) with (CO)3Fe(C8H14)2 gives green (CO)3Fe(η6‐1c) (2c), red [(CO)3Fe]2(η4,η6‐1c) (3c), and orange [(CO)3Fe]3(η4,η4,η6‐1c)(4c). The constitutions of 2c, 3c, 4c are derived from NMR and MS data and confirmed by X‐ray structure analyses. In 2c the Fe(CO)3 group is η6‐bonded to the heterocycle of planar 1c. 3c is formed from 2c by complexation of the diene of the benzo ring in anti position. In 4c both benzo rings of 2c are η4‐bonded to the Fe(CO)3 groups anti to the η6‐bonded Fe(CO)3 group.
Synthese und Struktur von Schwefel‐, Schwefelmonoxid‐ und Schwefeldioxid‐ verbrückten dimetallischen Komplexen des Typs [M(CO)(dppm)]2(μ‐S)(μ‐L) und [(CO)3M'(dppm)2MX](μ‐L') (M = Rh, Ir; M' = Mo, W, Mn; L = SO, SO2; L' = S, SO2; X = Cl, CO)
Authors: Heyke Olga , Hiller Wolfgang , Lorenz Ingo‐Peter 
Published: July 2007

Synthesis and Structure of Sulfur‐, Sulfur Monoxide‐, and Sulfur Dioxide‐Bridged Dimetallic Complexes of the Type [M(CO)(dppm)]2(μ‐S)(μ‐L) and [(CO)3M'(dppm)2MX](μ‐L') (M = Rh, Ir; M' = Mo, W, Mn; L = SO, SO2; L' = S, SO2; X = Cl, CO)The homo‐ and heterodimetallic complexes [M(CO)(dppm)]2‐(μ‐S)(μ‐SO2) (M = Rh, Ir) (2a, b), [(CO)3M'(dppm)2MCl](μ‐SO2) (M' = Mo, W; M = Rh, Ir) (4a – c), and [(CO)3Mn(dppm)2‐ Rh(CO)] (6) by passing sulfur dioxide through their solutions. The X‐ray structure analysis of 5a shows the SO2 ligand in a bridging position, whereas one CO ligand is semibridging. Treatment of the same starting materials with thiirane S‐oxide does not lead to the corresponding SO‐bridged dimers, with the only exception of 1b, which yields the new SO complex [(Ir(CO)(dppm)]2(μ‐S)(μ‐SO) (3b). Passing H2S through a solution of 6, the sulfur‐bridged complex [(CO)3Mn(dppm)2‐ Rh(CO)](μ‐S) (8) is formed, accompanied by H2 elimination.
Half‐Sandwich Pentamethylcyclopentadienyl Iridium Complexes Containing Sulfido and Selenido Ligands X‐Ray Crystal Structures of Cp*Ir(PMe3)(S6) and Cp*Ir(PMe3)(Se4)
Authors: Herberhold Max , Ji Guo‐Xin , Rheingold Arnold L. 
Published: July 2007

AbstractCp*Ir(PMe3)Cl2 (1) reacts with chalcogenide ligand sources such as (NH4)Sx (x ≈︁ 10), (NEt4)2Se6, and H2Se to yield the half‐sandwich complexes Cp*Ir(PMe3)(Sn) [n = 4 (2a), 6 (4a)] and Cp*Ir(PMe3)(Sen) [n = 2 (5b), 4 (2b)]. Desulfurization of 4a by PPh3 leads to Cp*Ir(PMe3)(S5) (3a), while both 4a and 3a react with excess P(nBu)3 to give 2a. The geometries of the cyclo‐oligochalcogenide ligands in 4a and 2b have been determined by X‐ray crystallography.
Bis(tetraphenylimidodiphosphinato)tin(II) and ‐tin(IV) Dihalides. Conversion of Pseudo Trigonal Bipyramidal to Octahedral Geometry
Authors: Day Roberta O. , Holmes Robert R. , Schmidpeter Alfred , Stoll Karl , Howe Lori 
Published: July 2007

AbstractThe tetraphenylimidodiphosphinate [N‐(P,P‐diphenylphosphinoyl)‐P,P‐diphenylphosphinimidate] ion forms stable bis‐chelates with SnII and SnIV. The SnII compound [N(Ph2PO)2]2Sn (3) displays a distorted Ψ‐tbp structure in the solid state and is fluxional in solution. The bis(imidodiphosphinato)tin dihalides 6 are cis‐structured. A comparison of the X‐ray structures of 3 and the diiodide [N(Ph2PO)2]2SnI2 (6c) indicates the presence of a lone‐pair stereochemical effect in 3 which is absent in 6c.
1,2,3,4,5,6‐Hexa(eq)alkylcyclohexan‐Modellverbindungen für Struktur‐Eigenschafts‐Vergleiche gesättigter discotischer Flüssigkristalle
Authors: Praefcke Klaus , Psaras Panicos , Kohne Bernd 
Published: July 2007

1,2,3,4,5,6‐Hexa(eq)alkylcyclohexane Model Compounds for Structure‐Property Comparisons of Saturated Discotic Liquid CrystalsThe new hydrocarbon (1α, 2β, 3α, 4β, 5α, 6β)‐hexahexylcyclohexane (19) and a number of new and differently functionalized scyllo‐hexaalkylcyclohexane derivatives (16a, b, 18a – c) with identical stereochemistry were synthesized stereospecifically starting from simple chemical materials. In comparison to the known scyllitol hexaester 1 and the hexaether 2 none of the novel compounds 16, 18, and 19 were thermomesomorphic. This extreme difference in the thermotropic liquid‐crystalline behaviour of the hexa(eq)hydroxycyclohexane (scyllitol) derivatives 1 and 2 on the one hand and of our varied hexa(eq)alkylcyclohexans 16, 18, and 19 on the other obviously is a function of the presence and the position of the element oxygen within the side chains of these symmetric star‐/disc‐shaped compounds. Details concerning this oxygen effect are discussed briefly.
Organische Synthesen mit Übergangsmetall‐Komplexen, 56 Homopyrrole und Dihydropyridine aus N‐Vinylaminocarben‐Eisenkomplexen und Alkinen durch Cyclisierung intermediärer 5‐Aza‐1‐metalla‐1,3,6‐triene
Authors: Aumann Rudolf , Trentmann Beate , Krüger Carl , Lutz Frank 
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 561). – Homopyrroles and Dihydropyridines from N‐Vinylamino‐carbene Iron Complexes and Alkynes by Cyclisation of Intermediate 5‐Aza‐1‐metalla‐1,3,6‐trienes2,3‐Homopyrroles 5 and dihydropyridines 7, 8 are obtained by the light‐induced addition of alkynes 4a – d (RC = CR1; R, R1 = H, CH3, C6H5, CO2CH3) to the N‐vinylaminocarbene iron complex (= 3‐aza‐1‐ferra‐1,4‐diene) 3. The formation of the N‐heterocycles 5 and 7 as well as that of the pyrrolium carbonylferrates 6 can be explained by assuming the chelated 5‐aza‐1‐ferra‐1,3,6‐trienes A to be key intermediates in this reaction. Stereochemical considerations lead to the conclusion that the ring expansion of the 4 1/2‐membered ring of 3 to the 6 1/2‐membered ring of A occurs without prior ≡ decomplexation by the insertion of a C = C unit into the M = C bond. NMR measurements and MNDO calculations suggest that the bicyclic homopyrroles 5 are in equilibrium with the novel monocyclic homopyrrole species 9. The structure of 6c has been established by X‐ray diffraction analysis.
Neue Cyclooctatetraen‐Komplexe des Niobs(1)
Authors: Herberich Gerhard E. , Englert Ullrich , Roos Peter 
Published: July 2007

New Cyclooctatetraene Complexes of Niobium[1]The (butadiene)niobium complexes Cp′Nb(C4H6)2 and Cp′Nb(C4H6)(PMe3)2 (Cp′C5H4Me) react with cyclooctatetraene (COT) to give Cp′Nb(C4H6)(COT) (2), Cp′Nb(COT)2 (3), and Cp′Nb(PMe3)2(COT) (5) with fluxional COT ligands. The structure of 3 exhibits a prone‐η3‐ and a supine‐η4‐COT ligand which interchange their role at elevated temperature. That of 5 shows a supine η3‐COT ligand.
Synthesis, X‐Ray Crystal Structure, and Fluxional Behaviour of fac‐[Ru(CH3CO2)2(PPh3)3] · 2 CH3CO2H
Authors: Lindner Ekkehard , Fawzi Riad , Hiller Wolfgang , Carvill Andrew , McCann Malachy 
Published: July 2007

Abstract[Ru2(μ‐O2CCH3)4(O2CCH3)] reacts with excess triphenylphosphane in acetic acid to give fac‐[Ru(O2CCH3)2(PPh3)3] · 2CH3CO2H (1), which crystallizes in the triclinic space group P 1− with Z=2. The three phosphane ligands are in the sterically congested facial configuration, and the distorted octahedral geometry around the metal is completed by a unidentate and chelating acetate. A variable temperature 31P{1H}‐NMR study of the complex in CH2Cl2 showed the three phosphanes to be inequivalent at low temperature. On raising the temperature two separate coalescence processes are observed, ultimately making all of the phosphanes equivalent at room temperature. Complex 1 shows slight catalytic activity for the ring‐opening polymerization of bicyclo[2.2.1]hept‐2‐ene (norbornene).
Zur Energie‐Delle von Diradikalen; III1) 2,3,5,6‐Tetramethylen‐1,4‐cyclohexadiyl
Authors: Roth Wolfgang R. , Langer Reinhard , Ebbrecht Thomas , Beitat Arndt , Lennartz Hans‐Werner 
Published: July 2007

Energy Well of Diradicals, III1). – 2,3,5,6‐Tetramethylene‐1,4‐cyclohexadiylGasphase thermolysis of ketone 1 leads to title diradical 3, which in the presence of oxygen yields 5 and peroxides. Assuming that the trapping reaction is collision‐controlled, from the temperature dependence of the competing processes an activation enthalpy of 23 kcal/mol is derived for the recombination of the diradical. By the same technique starting from 5 the heat of formation of the diradical has been determined, ΔH°f(g)=100.8 kcal/mol.
Über die Konformation eines trinuclearen [1.1.1]Tetramethinium‐Cyaninfarbstoffs mit Indolin‐Endgruppen
Authors: Reichardt Christian , Schäfer Gerhard , Knecht Josef , Gärtner Ralf , Allmann Rudolf , Krestel Magda 
Published: July 2007

Conformation of a Trinuclear [1.1.1]Tetramethinium Cyanine Dye with Indoline End GroupsAccording to its ESCA spectrum (Figure 1) and an X‐ray structural analysis (Figure 2), the [1.1.1]tetramethinium cyanine dye 2 exists in the crystalline state and probably also in solution as methinylogous propeller‐like guanidinium ion 2a with approximate C3 symmetry, and not as vinylogous amidinium ion 2b corresponding to a linear β‐substituted trimethine cyanine dye.
Aldol‐ und Michael‐Additionen fluorierter Nitroalkane an Aldehyde, Ketone und α,β‐ungesättigte Carbonylverbindungen1,2)
Authors: Beck Albert K. , Seebach Dieter 
Published: July 2007

Aldol and Michael Additions of Fluorinated Nitroalkanes to Aldehydes, Ketones, and α,β‐Unsaturated Carbonyl Compounds1,2)2,2,2‐Trifluoronitroethane (1) and 3,3,3‐trifluoro‐2‐nitropropane (2), despite their great propensity to undergo HF elimination with base, can be added to aldehydes with KF or neutral alumina (nitroaldol products 7–15). With basic alumina (neat components) they even add to α,β‐unsaturated aldehydes, ketones, esters, and nitriles (γ‐nitro carbonyl derivatives and nitrile 27–35). Doubly lithiated difluoro and trifluoro nitro derivatives (H, L) can be generated from the corresponding nitroethanes and ‐propanes (1–3) with butyllithium (THF, — 100 to −70°C) and added to aldehydes and ketones to give nitroaldols (nitroethanols 11, 12, 16–21) and “homonitroaldols” (nitropropanols 36–38). In essentially all cases, mixtures of diastereoisomers are formed. Through O‐silyltrifluoronitroaldols (22–26) it is possible to enrich one of the diastereoisomers by 3:1 (Scheme 4). Some transformations of the nitro compounds obtained lead to CF3‐substituted aminoethanols (39–46, by catalytic hydrogenation on Raney nickel), a nitrobutanol (30 → 48, with Et3SiH), and a ketone (30 → 49, with Bu3SnH).
Synthesen neuer bororganischer Ringe mit zwei Bor‐Atomen durch Borylierung des Trimethylenmethan‐Dianions
Authors: Herberich Gerhard E. , Englert Ulli , Ganter Christian , Wesemann Lars 
Published: July 2007

Syntheses of New Organoboron Rings with two Boron Atoms by Borylation of the Trimethylenemethane DianionBorylation of Li2[C(CH2)3] (1) provides a versatile starting point for the synthesis of 5‐, 6‐, 7‐, and 8‐membered ring systems with two boron atoms and leads to 1,5‐bis(dialkylamino)‐3,7‐dimethylene‐1,5‐diboracyclooctanes 2a, b (a: R=Et; b: R=iPr), 1,3‐bis(dialkylamino)‐5‐methylene‐1,3‐diboracyclohexanes 8a, b, 1,3‐bis(diethylamino)‐5‐methyl‐1,3‐dibora‐4‐cyclo‐hexene (10), and 1,4‐bis(dialkylamino)‐6‐methylene‐1,4‐dibora‐2‐cycloheptenes 11a, b. The compounds 2b, 8b, and the 2,3‐biboratafulvene derivative [Li(TMEDA)]2[CH2C(CHB)2‐(NiPr2)2] are characterized by X‐ray diffraction analysis. It is shown that for trigonal boron B—C(allyl) bond distances (typically 160 ± 1 pm) are significantly larger than B—C(alkyl) distances (typically 158 + 1 pm).
Metalle in Biologie und Medizin, III. Bismutlactat: Darstellung und Strukturchemie eines Hydroxycarboxylat‐Komplexes
Authors: Kiprof Paul , Scherer Wolfgang , Pajdla Liba , Herdtweck Eberhardt , Herrmann Wolfgang A. 
Published: July 2007

Metals in Biology and Medicine, III. — Bismuth Lactate: Synthesis and Structure of a Hydroxycarboxylate ComplexAs a compound of medical relevance, bismuth (S)‐lactate was synthesized and structurally characterized (single‐crystal X‐ray diffraction). Exploiting the versatile coordination chemistry of carboxylate groups (chelating and bridging ligands), the crystal structure is based upon a three‐dimensional network, showing bismuth in a high coordination number environment.
Darstellung neuartiger monomerer, oligomerer und polymerer Silyltriflate
Authors: Uhlig Wolfram 
Published: July 2007

Preparation of New Monomeric, Oligomeric, and Polymeric Silyl TriflatesThe highly reactive silyl triflates R3SiOSO2CF3 are valuable reagents in organosilicon chemistry. New triflate derivatives of mono‐ and oligosilanes have been prepared by substitution of phenyl groups or hydrogen atoms for the trifluoromethanesulfonyl group. The presence of the electron‐withdrawing triflate group leads to a strong deactivation of the other substituents at the silicon atom, and the displacement of a second phenyl group at the same silicon atom is much slower than the first step. For this reason in the case of phenylated oligosilanes stepwise monosubstitution of the silicon atoms has been found. Other new oligomeric silyl triflates are obtained by reaction of silanediyl(triyl) bis(tris)(trifluoromethanesulfonates) with lithium derivatives of organosilicon compounds. Finally, the cleavage of silicon–phenyl bonds of poly[methyl(phenyl)silanes] by CF3SO3H leads to triflate derivatives of polysilanes.
Synthese, Struktur und Isomerisierung von Diazaphosphiridinoxiden
Authors: Niecke Edgar , Link Manfred , Nieger Martin 
Published: July 2007

Synthesis, Structure, and Isomerization of Diazaphosphiridine OxidesHerrn Professor Joseph Grobe zum 60. Geburtstag gewidmet.
The 1,2‐Bis(alkyl)iminophosphane, Et3C — P=N — tBu (1), reacts with nitroso compounds, RNO (R=tBu, Ph), to form the diazaphosphiridine oxides, Et3C — YYP(=O) — NtBu — NYYR, 4a, b. While 4a (R=tBu) is thermally stable, 4b (R=Ph) isomerizes with formation of the benzodiazaphosphole oxide Et3C — YYP(= O) — NH — C6H4 — NYYtBu (5). The corresponding phospholimine Et3C — YYP(=NtBu) — NH — C6H4 — NYYtBu (7) has been obtained from 1 and azobenzene. The three‐membered phosphorus heterocycle 4a has been characterized by X‐ray structure analysis, which reveales some remarkable features.
Alkyleisen‐ und Alkylcobalt‐Reagenzien, III. Nichtstabilisierte Eisenalkyle: Bildung, Nachweis und Chemoselektivität
Authors: Kauffmann Thomas , Laarmann Barbara , Menges Detlef , Neiteler Gabriele 
Published: July 2007

Alkyliron and Alkylcobalt Reagents, III. — Nonstabilized Ironalkyls: Formation, Detection, and ChemoselectivityThe crystalline ate complex Me4FeLi2(Et2O)2 (1 d) described in the literature as well as the complexes MeFeCl (1a), Me2Fe (1b), Me3FeLi (1c), nBu2Fe (2 a), nBu4FeLi2 (2b), nOct2Fe (3a), nOct3FeLi (3b), and nOct4FeLi2 (3c) are prepared in situ by transmetallation of MeLi, nBuLi, and nOctLi with FeCl2 (readily available by in situ reduction of FeCl3 with MeLi). All these complexes have been subjected to reaction with organic substrates for the first time. Evidence for this transmetallation has been furnished by a novel test (referred to as “β‐bromostyrene‐ketone test”). In this test, involving addition of β‐bromostyrene (4) and 4‐methylpentan‐2‐one (5), the alkyllithium compounds alkylate selectively only the ketone and the alkyliron compounds almost exclusively the β‐bromostyrene. The high preference of the alkyliron reagents for the alkylation of the β‐bromostyryl residue has been utilized for regioselective butylations and octylations of 1‐{4‐[(Z)‐2‐bromoethenyl]phenyl}‐ethanone (6). Moreover, in competition reactions with benzaldehyde/4‐methylpentan‐2‐one the alkyliron reagents have been found to react usually specifically with aldehydes. The decomposition temperatures of the reagents 1a,b,c and 2b in THF have been determined to be 0, −10, 25, and −20°C, respectively.
Organische Synthesen mit Übergangsmetall‐Komplexen, 57. 4,5‐Homotropilidene durch intramolekulare Cyclopropanierung von (Cycloheptatrienylmethyl)carbenchrom‐ oder ‐wolfram‐Komplexen
Authors: Aumann Rudolf , Runge Martina 
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 57[1]. — 4,5‐Homotropilidenes by Intramolecular Cyclopropanation of (Cycloheptatrienylmethyl)carbenechromium or ‐tungsten Complexes(Cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)‐CH2C7H7 [3: LnM=Cr(CO)5 (a), W(CO)5 (b)] are obtained in yields of 80% by the reaction of the corresponding methylcarbene complexes LnM=C(OEt)CH3 1 with tropylium tetrafluoroborate (2) in THF/Et3N. Alkylation of 3 with 2 gives [bis(cycloheptatrienyl)methyl]carbene complexes LnM=C(OEt)CH(C7H7)2 [4: LnM=Cr(CO)5 (a), W(CO)5 (b)]. Thermolysis of 3 leads to the formation of an equilibrium mixture of the 4,5‐homotropilidenes 5 and 6. According to NMR measurements and AM1 calculations the formation of 6 is strongly favored. An equilibrium between 4,5‐homotropilidene complexes is significantly different from that of the metal‐free ligands. By the reaction of 5/6 with bis(ethylene)rhodium 1,3‐pentanedionate (8) the complexes 9 and 10 of both 4,5‐homotropilidenes 5 and 6 are obtained in a 1:3 ratio. The (1,5‐diene)rhodium(I) complexes 9 and 10 are nonfluxional and configurationally moderately stable at 20°C. The reaction of 5/6 with Fe2(CO)9 gives the π‐allyl,σ complexes 11 and 12 in a 10:3 ratio, both of which may be derived from the minor 4,5‐homotropilidene isomer 5. In 11 a vinylcyclopropane unit of 5 serves as a four‐electron donor for a Fe(CO)3 group. In 12 the 4,5‐homotropilidene unit is coordinated as a six‐electron donor to a Fe2(CO)6 unit.