bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and reactivity of naphthalene sandwich complexes of molybdenum. X‐ray structure of [Mo(η6‐naphthalene) {P(OMe)3}3] and [Mo(H)(η6‐naphthalene){P(OMe)3}3][BF4]
Authors: Thi Ngoc Phan Do , Spichiger Serge , Paglia Patrick , Bernardinelli Gérald , Kündig E. Peter , Timms Peter L. 
Published: December 2004

AbstractThe sandwich complexes bis(η6‐naphthalene)molybdenum(0) (1), bis(η6‐1‐methylnaphthalene)molybdenum(0) (2), and bis(η6‐1,4‐dimethylnaphthalene)molybdenum(0) (3) are synthesized by cocondensation of Mo‐atoms with the naphthalene ligands. Complexes 1–3 are also obtained by reduction of MoCl5 or MoCl4. 2THF with highly activated Mg in the presence of the naphthalene ligands. Mg was activated by sublimation of the metal in a simple rotating solution reactor. Complex 2 exists as a mixture of regio‐ and stereoisomers. Three regioisomers, 3a–c, are formed in reactions of Mo‐atoms with 1,4‐dimethylnaphthalene, whereas 3a, the isomer with the Mo‐atom coordinated to the unsubstituted rings, is formed selectively via the reductive method. The ligands in 1–3 are highly labile. CO displaces both naphthalene rings in 2 and 3 to give [Mo(CO)6], while PF3, P(OMe)3, and PMe3 displace only one coordinated naphthalene in 1 to yield the [Mo(η6‐naphthalene)L3] complexes 4–6. In toluene, arene exchange is a competitive process in reactions of 1 with PF3. Complexes 5 (L = P(OMe)3) and 6 (L = PMe3) react with HBF4 to give the cationic metal hydride complexes 8 and 9. The X‐ray crystal structures of [Mo(η6‐naphthalene) {P(OMe)3}3] (5) and [Mo(H)(η6‐naphthalene) {P(OMe)3}3][BF4] (8) are reported.
Structural Chemistry of Chiral Complexes. NMR and X‐ray studies on Rh1 compounds of (S)‐1‐[bis(p‐methylphenyl)phosphino]‐2‐[(p‐methoxybenzyl)amino]‐3‐methylbutane
Authors: Berger Heinrich , Nesper Reihnard , Pregosin Paul S. , Rüegger Heinz , Wörle Michael 
Published: December 2004

AbstractThe Rh1(diolefin)complexes [Rh(nbd)(2)][PF6] [Rh(1,5‐cod)(2)][PF6], and [Rh((Z)‐α ‐acetamidocinnamic acid)(2)][PF6] (2 = the chiral P,N‐ligand (S)‐1‐[bis(p‐methylphenyl)phospino]‐2‐[p‐methoxybenzyl)amino]‐3‐methylbutane have been prepared and characterized. These complexes exit as a mixture of isomers arising from different five‐membered‐ring conformations and diastereoisomers due to both the prochiral nitrogen and olefin ligands. The three‐dimensional solutions structures of these complexes have been studied with the specific aim of understanding how the chiral pocket is built. Aspects of the exchange dynamics and their possible relevance to homogeneous hydrogenation are discussed The solid‐state structure for the nbd complex, [Rh(nbd)(2)][PF6], as well as detailed one‐ and two‐dimensional 31P‐, 13C‐, and 1H‐NMR results are presented.
Degradation of Cephaloridine on Alkaline Hydrolysis
Authors: Vilanova Bartolomé , Muñoz Francisco , Donoso Josefa , Garcia‐Blanco Francisco 
Published: December 2004

AbstractA kinetic study on the alkaline hydrolysis of cephaloridine (1) at pH 10.5 and 37° was carried out using ion‐pair reversed‐phase HPLC. The main resulting degradation products, the 7‐epimer 2 of 1, the Δ2‐isomer 3 of 1, and the 3‐methylidene compound 4 were identified. The presence of a pyridinio group at C(31) results in a slightly increased formation constant for the 3‐methylidene compound 4 and the 7‐epimer 2, and introduces a new reaction: the isomerization of the double bond at C(3) in the dihydrothiazine ring to C(2).
Introduction of a New Class of Ligands for the Metal‐Catalyzed Enantioselective Synthesis
Authors: Spescha Maurus 
Published: December 2004

AbstractProtected thiosugars were prepared as ligands for the metal‐catalyzed enantioselective synthesis. The protecting groups in these ligands were varied to test a proposed new concept for the metal‐catalyzed enantioselective synthesis. This new concept centres on the use of a stair‐like ligand with a large substituent on one side and a small substitutent on the other rather than the commonly employed ligands which have C2 symmetry (see Fig.3). In such a ligand, both substituents should have a major influence on the coordination of a prochiral substrate. To test this proposal, 3‐thio‐α‐D‐glucofuranose derivatives with the following substituents were synthesized: 1,2‐O‐isopropylidene‐5,6‐O‐methylidene (see 24), 1,2:5,6‐di‐O‐isopropylidene (see 2), 5,6‐O‐cyclohexylidene‐1,2‐O‐isopropylidene (see 23), 1,2‐O‐cyclohexylidene‐5,6‐O‐isopropylidene (see 14), 1,2:5,6‐di‐O‐cyclohexylidene (see 13), 5,6‐O‐(adamantan‐2‐ylidene)‐1,2‐O‐isopropylidene (see 21), and 1,2:5,6‐di‐O‐(adamantan‐2‐ylidene) (see 25, Table 2). As a representative of the allofuranoses, 1,2:5,6‐di‐O‐isopropylidene‐3‐thio‐α‐D‐allofuranose (6) was chosen. The following derivatives of 1,2‐O‐isopropylidene‐α‐D‐xylofuranose were also synthesized: 1,2‐O‐isopropylidene‐5‐deoxy‐3‐thio‐α‐D‐xylofuranose (29), 1,2‐O‐isopropylidene‐3‐thio‐α‐D‐xylofuranose (28) and 5‐O‐[(tert‐butyl)‐diphenylsilyl]‐1,2‐O‐isopropylidene‐3‐thio‐α‐D‐xylofuranose (15, see Table 2). The proposed concept was tested using the copper‐catalyzed 1,4‐addition of BuMgCl to cyclohex‐2‐en‐1‐one. The enantioselectivity was very dependent on the ligand used and was up to 58%.
‘One‐Pot’ Synthesis of Raumacline from Ajmaline
Authors: Endress Susanne , Stöckigt Joachim 
Published: December 2004

AbstractFor the alkaloid raumacline (2), which is a biotransformation product of ajmaline (1) in Rauwolfia serpentina cell cultures, an efficient ‘one‐pot’ synthesis was developed using a NaBH4/riboflavin/light‐mediated transformation of 1 into 2 with a total yield of 86%.
Solution Equilibria in Trialkyl‐Phosphite Derivatives of [Ir4(CO)12]. Crystal Structure of [Ir4(CO)11{P(OCH2)3CEt}]
Authors: Besançon Katya , Laurenczy Gábor , Lumini Tito , Roulet Raymond , Gervasio Giuliana 
Published: December 2004

AbstractThe monosubstituted [Ir4(CO)11L] clusters (L = P(OPh)3, 1; L = P(OMe)3, 2; L = P(OCH2)3CEt, 3) were obtained in good yields by the reaction of [Ir4(CO)11I]− with the corresponding phosphite. In the solid state, cluster 3 has a Cs geometry with all terminal ligands as shown by an X‐ray analysis. Three isomers are present in solution: one with terminal ligands (A) and two with three edge‐bridging CO's and with L in axial (B) or radial (C) position (see Scheme). The thermodynamic and kinetic parameters of isomerisations B ⇌ A and A ⇌ C were determined by simulation of the variable‐temperature 31P‐NMR spectra. The three isomers correspond to three minima on the kinetic pathway of CO scrambling, whose relative energies vary independently within a small range (1–9 kJ mol−1 at 298 K). At low temperature, isomer C is always the least stable and is not observed for 1 which bears the most bulky phosphite ligand. The isomerisations are due to two intramolecular merry‐go‐rounds of CO groups about two unequivalent faces of the unbridged species A.
Synthesis and Spectroscopic Characterization of N2‐(N‐Acetyl‐6‐O‐stearoyl‐α‐D‐muramoyl)‐L‐alanyl‐D‐isoglutamine
Authors: Dick Fritz , Jenny Titus A. 
Published: December 2004

AbstractTitle compound 1 was synthesized by a published route which had to be modified (seven steps from readily obtainable starting materials). Characterization of 1 was achieved by spectroscopic means (FAB‐MS, 1H‐NMR, including 2D‐COSY). Furthermore, commercially available reference material purchased for comparison, was unequivocally established to be 10, i.e. incompletely deprotected 1.
Simultaneous Formation of 8H‐Isoquino[2,1‐b][2,7]naphthyridin‐8‐ones and 13H‐Pyrido[4′,3′:3,4]pyrrolo[2,1‐b][3]benzazepin‐13‐ones, a Novel Potential Alkaloidal System
Authors: Nagarajan Kuppuswamy , Rodrigues Patrick J. , Nethaji Munirathinam , Vöhler Markus , von Philipsborn Wolfgang 
Published: December 2004

AbstractCondensation of 3,4‐dihydro‐6,7‐dimethoxyisoquinoline (4) with 4‐methylnicotinoyl chloride (12) in refluxing pyridine gives 5,6,13,13a‐tetrahydro‐2,3‐dimethoxy‐8H‐isoquino[2,1‐b][2,7] naphthyridin‐8‐one (11), along with some of its 13,13a‐didehydro derivative 7. A similar reaction of 4 with 4‐(chloromethyl)nicotinoyl chloride (14) affords, in addition to 7, the isomeric product 10,11‐dihydro‐7,8‐dimethoxy‐13H‐pyrido[4′,3′:3,4]pyrrolo[2,1‐ b][3]benzazepin‐13‐one (3). Analogous pairs of products are obtained from 3,4‐dihydro‐6,7‐(methylenedioxy)‐ and 3,4‐dihydro‐6,7,8‐trimethoxy‐isoquinolines (15 and 18, resp.). The structure of 3 was established by extensive NMR data and confirmed by single‐crystal X‐ray studies. Structure 7 has the ring system of the Alangium alkaloids like alangimarinc (1), while the isomeric ring system 3 is predicted to be present in nature on biogenetic reasoning.
Azidinium‐Salze. 25. Mitteilung. Symmetrische Azopyridinon‐Farbsalze: Synthese, spektrophotometrische und acidobasische Eigenschaften, Metallkomplex‐Bildung und kinetische Untersuchung der Azo‐Kupplung
Authors: Balli Heinz , Chaquime Lucy , Hellrung Bruno , Misun Marian 
Published: December 2004

Symmetrical Azopyridinone Dyes: Synthesis, Spectrophotometrical and Acidobasic Properties, Metal‐Complex Formation and Kinetical Investigation of the Azo‐Dye FormationThe 13 substituted symmetrical azopyridinone dyes 2a–n were synthesized and their VIS spectra measured. The pK*a values of some dyes and of pyridinone coupling components were determined in MeOH/H2O 64:36. The metal‐complex formation of the dyes with Cd2+, Zn2+, Co2+, Ni2+, and Cu2+ was investigated, and complex‐formation constants of the 1:1 complexes were determined in H2O for 2k (Table 2) and in dimethylformamide/H2O 1:1 for some other azopyridinone dyes (Table 3). The mechanism of the azo‐dye formation was investigated and found to be much more complicated than expected. A mechanism of the coupling reaction was developed (see Scheme 4) and fitted by least‐squares calculations.
Nucleosides. Part LV. Efficient synthesis of arabinoguanosine building blocks
Authors: Resmini Matthias , Pfleiderer Wolfgang 
Published: December 2004

AbstractFrom guanosine (1) as starting molecule, protected arabinoguanosine derivatives such as phosphoramidite precursors and arabinoguanosine (18) itself were prepared in high yields. Inversion of the configuration at C(2′) was achieved by introduction of the (trifluoromethyl)sulfonyl residue and subsequent displacement by nucleophiles like acetate, bromide, and azide. The guanine moiety was protected at the amide function by the 2‐(4‐nitrophenyl)ethyl (npe) group on O6 and at the NH2 function by the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) group.
Metabolic Products of Microorganisms. Part 269. 5‐Phenylpentadienoic‐acid derivatives from Streptomyces sp.
Authors: Potterat Olivier , Zähner Hans , Metzger Jörg W. , Freund Stefan 
Published: December 2004

AbstractTwo new phenylpentadienamides isolated from the culture filtrate of Streptomyces sp. were assigned the structures 5‐(4‐aminophenyl)penta‐2,4‐dienamide (2) and N2‐[5‐(4‐aminophenyl)penta‐2,4‐dienoyl]‐L‐glutamine (3). In addition, 5‐(4‐aminophenyl)penta‐2,4‐dienoic acid (1) has been isolated, and its spectroscopic characteristics are reported for the first time. Compounds 1–3 exist in both the (2E,4E)‐ and (2E,4Z)‐configurations. Electrospray and tandem MS, and HPLC/MS proved to be particularly suitable for the characterization of these metabolites.
Synthese des Pyrrolizidin‐Alkaloides (±)‐Trachelanthamidin
Authors: Horni Albert , Hubáček Ivana , Hesse Manfred 
Published: December 2004

Synthesis of the Pyrrolizidine Alkaloid (±)‐TrachelanthamidineThe important intermediate in the synthesis of the title compound 8 is the diastereoisomer mixture of ethyl 2‐[2‐(1,3 dioxolan‐2‐yl)ethyl]‐5‐oxopyrrolidine‐3‐carboxylate (3a/3b) which was prepared from nitromethane, acrylaldehyde, and diethyl fumarate (Scheme). Its reduction (NaBH4, t‐BuOH, MeOH) gave exclusively the trans‐alcohol 4a, which was converted to the protected pyrrolidine derivative 6. The deprotection and reduction of 6 gave the pyrrolizidine alkaloid 8, characterized as its hydrochloride.
α,α‐Disubstituted Allyl Sulfones: An approach to the synthesis of vinyl‐branched pheromone analogues
Authors: Hoskovec Michal , Koutek Bohumír , Lazar Josef , Streinz Ludvík , Brožová Eva , Kalinová Blanka , Vrkoč Jan 
Published: December 2004

AbstractThe two‐step alkylation of phenyl prop‐2‐enyl sulfone (1) with protected ω‐bromoalkanols and 1‐iodoalkanes (→3; see Scheme 1) followed by a Pd‐catalyzed desulfonylation with LiBH4 affords a 96:4 mixture of vinylbranched, protected alcohols and corresponding ethylidene‐branched isomers (see Scheme 2; 4 and 5, respectively). By utilizing the large difference in reactivity of mono‐ and trisubstituted CC bonds towards singlet oxygen, the ethylidene derivatives are easily removed from the mixture by photo‐oxygenation. The vinyl‐branched compounds are inert to this reaction and can be conveniently isolated in highly pure form (99.5%) and ca. 45% overall yield.
Glycosylidene Carbenes. Part 18. Insertion of glycosylidene carbenes into the SnH bond of tributyl‐ and triphenylstannane: A synthesis of stannoglycosides
Authors: Uhlmann Peter , Nanz Daniel , Bozó Eva , Vasella Andrea 
Published: December 2004

AbstractInsertion of the glycosylidene carbenes, derived from the gluco‐ and the manno‐diazirines 1 and 2, into the SnH bond of R3SnH (R = Bu or Ph) leads to the fully substituted stannoglycosides 3–8 (53–77%). The 1,2‐cis‐configurated products are formed preferentially (α‐D/β ‐D ranges from 2.5:1 to 5.1:1 with 1, and 1:1.3 to 1:4.2 with 2). Relative to CH2Cl2, THF favors formation of the equatorial Sn‐glycosides. The stannylated (benzyloxy)glucals 9 and 10 were isolated as side products. The reaction of 1 with (Bu3Sn)2 yielded 9 (17% in CH2Cl2; 36% in CCl4) together with the azines 11 and the benzyloxyglucal 12. NMR Data of the Sn‐glycosides 3–8 show evidence for an anomeric effect, 1J(C(1),H) being larger in the axial and 1J(Sn,C(1)) larger in the equatorial anomers.
Crystal Structure and Packing of 1‐(4, 6‐Diamino‐1, 3, 5‐triazin‐2‐yl)guanidinium nitrate
Authors: Venugopalan Paloth , Bürgi Hans Beat 
Published: December 2004

AbstractThe title compound is a condensation product of four guanidinium ions formed during crystallization of guanidinium nitrate. The crystal structure consists of infinite molecular ribbons stacked into layers which are rotated 58.5° with respect to each other and connected by two different networks of hydrogen bonds.
Strukturen und Molekül‐Eigenschaften ladungsgestörter Moleküle. 52. Mitteilung. 2, 3‐Diphenylchinoxalin‐Radikalanionen in Lösung und im Kristall
Authors: Bock Hans , John Andreas , Näther Christian , Ruppert Klaus 
Published: December 2004

Structures and Molecular Properties of Charge‐Pertubed Molecules. 2, 3‐Diphenylquinoxaline Radical Anions in Solution and in CrystalsThe Na⊕ and K⊕ radical‐ion salts of 2, 3‐diphenylquinoxaline seem to be (according to a structural database search) among the first ones of N‐heterocyclic radical anions in crystals. The one‐electron reduction in aprotic 1, 2‐dimethoxyethan (DME) solution at metal mirrors and the crystallization under Ar have been preceded by cyclovoltammetric (CV) and ESR/ENDOR measurement. The first electron insertion at −1.63 V proves to be reversible, whereas the irreversible second step, which is accompanied by an overcrossing of the CV line, can be rationalized by an ‘ECE‐DISP’ mechanism via a dianion redox disproportionation. The ENDOR spectrum resolves four 1H couplings and allows to simulate the ESR spectrum including the 14N hyperfine splittings. Both dark‐blue single crystals of the radical ion salts \documentclass{article}\pagestyle{empty}\begin{document}$[2,3{\rm - diphenylquinoxaline}^{{.} \ominus} {\rm Met}^ \oplus ({\rm DME})]^.$\end{document} show unexpected similarities for Met⊕ = Na⊕, K⊕ despite the 36‐pm difference in their ionic radii. The largest structural changes inflicted by the one‐electron reduction of the N‐heterocyclic molecule are observed in the vicinity of the N‐centers bearing the highest effective nuclear charge. The DME‐chelated metal cations coordinate at the N electron pairs and form Met⊕(DME)‐bridged polymer chains of the radical anion, which are differently ondulated in the Na⊕ and K⊕ radical anion salts. The take‐home lesson suggests that many more N‐heterocyclic molecules might be analogously reduced under optimized conditions and isolated as single crystals.
Enantioselectivity and cis/trans‐Selectivity in Dirhodium(II)‐Catalyzed addition of diazoacetates to olefins
Authors: Müller Paul , Baud Corine , Ené Doïna , Motallebi Sharokh , Doyle Michael P. , Brandes Bridget D. , Dyatkin Alexey B. , See Marjorie M. 
Published: December 2004

AbstractThe Rh11‐catalyzed carbenoid addition of diazoacetates to olefins was investigated with [Rh2{(4S)‐phox}4] (1;phox = tetrakis[(4S)‐tetrahydro‐4‐phenyloxazol‐2‐one]), [Rh2{(2S)‐mepy}4] (2; mepy = tetrakis[methyl (2S)‐tetrahydro‐5‐oxopyrrole‐2‐carboxylate]), and [Rh2(OAc)4] (3). While catalysis with 2 and 3 afford preferentially trans‐cyclopropanecarboxylates, the cis‐isomers are the major products with 1. In general, the enantioselectivities achieved with 1 and 2 are comparable. Additions catalyzed by 1 are strongly sensitive to steric effects. Highly substituted olefins afford cyclopropanes in only poor yield. The preferential cis‐selectivity observed in reactions catalyzed by 1 is attributed to dominant interactions between the ligand of the catalyst and the substituents of both olefin and diazoacetate, which overrule the steric interactions between olefin and diazoacetate in the transition state for carbene transfer.
Metal Complexes with Macrocyclic Ligands. Part XXXVIII. Steric effects in the copper(II) and nickel(II) complexes with tetra‐N‐alkylated 1,4,8,11‐tetraazacyclotetradecanes
Authors: Oberholzer Martin R. , Neuburger Markus , Zehnder Margareta , Kaden Thomas A. 
Published: December 2004

AbstractA series of tetra‐N‐alkylated 1,4,8,11‐tetraazacyclotetradecanes have been synthesized and their complexation potential towards Ni2+ and Cu2+ studied. In the case of sterically demanding alkyl substituents, such as i‐Pr, PhCH2, or 2‐MeC6H4CH2, no metal complexes are formed, whereas for substituents such as Me, Et, and Pr, the metal ion is incorporated into the macrocycle. The spectroscopic properties of the Ni2+ and Cu2+ complexes in aqueous solution indicate that, depending on the sterical hindrance of the N‐substituents, the complexes are either square planar or pentacoordinated. All these Ni2+ and Cu2+ complexes react with N to give ternary species, the stability of which have been determined by spectrophotometric titrations. The tendency to bind N decreases with increasing steric hindrance of the alkyl substituents. The X‐ray studies of the Ni2+ complex with the macrocycle 11, substituted by two Me and two Pr groups, and that of the Cu2+ complex with the tetraethyl derivative 8 show that in the solid state, the metal ions exhibit square planar coordination with a small distortion towards tetrahedral geometry.
Synthesis and 15N‐ and 17O‐NMR Spectra of 5‐Methyl(15N2)[O2,O4‐17O2]uridine (= (15N2)[O2,O4‐17O2]Ribosylthymine)
Authors: Amantea Antonio , Walser Markus , Séquin Urs , Strazewski Peter 
Published: December 2004

AbstractThe 5‐methyl(15N2)[O2,O4‐17O2]uridine (= (15N2)[O2,O4‐17O 2]ribosylthymine; 15) was synthesized and analyzed by 15N‐ and 17O‐NMR spectroscopy. (15N2)Urea was condensed with 2,3‐dibromo‐2‐methylpropanoyl chloride (3) and cyclized to form (15N2)thymine (5). After glycosidation, the 17O isotopes were introduced in two separate steps: hydrolytic ring opening of 2,5′‐anhydro derivative 9 and hydrolysis of 3‐nitro‐1H‐1,2,4‐triazole derivative 12 with labelled water in the presence of a strong base. The 15N‐ and 17O‐NMR spectra (Fig.) of 15 in phosphate‐buffered water serve as references for heteronuclear NMR spectra of labelled RNA fragments.
Solution‐Structure and Aggregation Behavior of Two Dilithiostyrene Derivatives
Authors: Günther Harald , Eppers Oswald , Hausmann Heike , Hüls Dietmar , Mons Hans‐Egbert , Klein Klaus‐Dieter , Maercker Adalbert 
Published: December 2004

AbstractThe solution structure and the aggregation behavior of (E)‐2‐lithio‐1‐(2‐lithiophenyl)‐1‐phenylpent‐1‐ene (1) and (Z)‐2‐lithio‐1‐(2‐lithiophenyl)ethene (2) were investigated by one‐ and two‐dimensional 1H‐, 13C‐, and 6Li‐NMR spectroscopy. In Et2O, both systems form dimers which show homonuclear scalar 6Li,6Li spin‐spin coupling. In the case of 2, extensive 6Li,1H coupling is observed. In tetrahdrofuran and in the presence of 2 mol of N,N,N′,N′‐tetramethylethylylenediamine (tmeda), the dimeric structure of 1 coexists with a monomer. The activation parameters for intra‐aggregate exchange in the dimers of 1 and 2 (1 (Et2O): ΔH≠ = 62.6 ± 13.9 kJ/mol, ΔS≠ = 5.8 ± 14.0 J/mol K, ΔG≠(263) = 61.1 kJ/mol; 2 (dimethoxyethane): ΔH≠ = 36.9 ± 6.5 kJ/mol, ΔS≠ = −61 ± 25 J/mol K, ΔG≠(263) = 54.0 kJ/mol) and the thermodynamic parameters for the dimer‐monomer equilibrium for 1 (ΔH°; = 26.7 ± 5.5 kJ/mol, ΔS° = 63 ± 27 J/mol K), where the monomer is favored at low temperature, were determined by dynamic NMR studies.
Ein neues 3‐Amino‐2H‐azirin als Aib‐Pro‐Baustein: Synthese des C‐terminalen Nonapeptids von Trichovirin I 1B
Authors: Luykx Roeland , Bucher Christoph B. , Linden Anthony , Heimgartner Heinz 
Published: December 2004

A New 3‐Amino‐2H‐azirine as an Aib‐Pro Synthon: Synthesis of the C‐Terminal Nonapeptide of Trichovirin I 1BThe synthesis of methyl N‐(2,2‐dimethyl‐2H‐azirin‐3‐yl)‐L‐prolinate (3), a novel 3‐amino‐2H‐azirine, is described (Scheme 2). It is shown that the reaction of COCl2 with thioamide 5 is remarkably faster than with the corresponding amide 4, and the yield of 3 is much better in the synthesis starting with 5. The 3‐amino‐2H‐azirine 3 has been used as a building block of the dipeptide moieties Aib‐Pro in the synthesis of nonapeptide 17 (Schemes 4 and 5), the C‐terminal 6–14 segment of the peptaibole trichovirin I 1B. The structure of 17 was established by single‐crystal X‐ray crystallography (Figs.1 and 2).
Extrem aufgeweitete Tetrathiafulvalene mit Polyen‐Spacern. Carotinoide Tetrathiafulvalene. Polymethin‐tetracyanotetrathiafulvalen‐Radikalkationen, eine neue Klasse von Violenen
Authors: Märkl Gottfried , Pöll Andreas , Aschenbrenner Norbert G. , Schmaus Corinna , Troll Theodor , Kreitmeier Peter , Nöth Heinrich , Schmidt Martin 
Published: December 2004

Extremely Expanded Tetrathiafulvalenes with Polyene Spacers. Carotinoid Tetrathiafulvalenes. Polymethin‐Tetracyanotetrathiafulvalene Radical Cations, a New Class of ViolenesThe synthesis of extended tetrathiafulvalenes11with di‐, tetra‐, hexa‐, octa‐, deca‐ and dodecamethine spacers is described by a PPh3‐inducedWittig‐reaction‐like condensation of the corresponding polyenedials10with 2‐thio‐1,3‐dithiole‐4,5‐dicarbonitrile (9). By the same procedure, the dimethyloctamethine‐ and the tetramethyl‐hexadecamethine‐tetrathiafulvalenes14and15, respectively, were obtained. The extended tetrathiafulvalenes represent multistep vinylogous redox systems of the ‘violene type’. They can be oxidized to give the cyanine‐like radical cations,e.g.11sem,14sem, and15sem, and the dications,e.g.11ox,14ox, and15ox; their UV/VIS/NIR spectra are reported. The crystal and molecular structure of (all‐E)‐2,2′‐(octa‐2,4,6‐trien‐1,8‐diylidene)bis[1,3‐dithiole‐4,5‐dicarbonitrile] (11e) was determined: it is a rod‐like, planar molecule; in the crystal, it forms staples along the longest molecule axis. The CV measurements confirm that the redox potentials of11, 14, and15decrease asymptotically with the increasing length of the spacer. Because of the close relationship of the extended tetrathiafulvalenes (ETTF's) to the carotinoids, they are named ‘caroviologenes’; they formally belong to the class of molecular wires.