bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic Palladium(II), Platinum(II), and Rhodium(I) Complexes as Acetalisation Catalysts
Authors: Gorla Fabrizio , Venanzi Luigi M. 
Published: December 2004

AbstractThe use of [Pd(H2O)2(Ph2PCH2CH2PPh2)] (CF3SO3)2 as a catalyst for the acetalisation of a variety of aldehydes and ketones and for trans‐acetalisation is described. It is also shown that Pt(H2O)2(PH2PCH2CH2PPh2) (CF3SO3)2 is at least as effective as the corresponding Pd compound, while much lower reaction rates are observed with [Rh(MeOH)2(Ph2PCH2CH2PPh2)] [BF4].
Pd‐katalysierter Deuterium‐Austausch am Octa(silsesquioxan)H8Si8O12 zu D8Si8O12
Authors: Bürgy Heribert , Calzaferri Gion 
Published: December 2004

Pd‐Catalyzed Deuterium Exchange of Octa(silsesquioxane) H8Si8O12 to D8Si8O12Deuterium exchange on octa(silsesquioxane) H8Si8O12 to D8Si18O12 catalyzed by palladium on carbon is reported.
Metal complexes of macrocyclic ligands. Part XXXIII. Effect of the side‐chain length on the on/off equilibrium in the Ni2+ and Cu2+ complexes of 11‐(2‐aminoethyl)‐ and 11‐(3‐aminopropyl)‐1,4,7,11‐tetraazacyclotetradecane
Authors: Schiegg André , Kaden Thomas A. 
Published: December 2004

AbstractAlkylation of 1,4,7‐tritosyl‐1,4,7,11‐tetraazacyclotetradecane with CH2O/KCN or acrylonitrile gave the corresponding cyanomethyl or 2‐cyanoethyl derivatives, which, by treatment with Na in BuOH, were detosylated and reduced to the macrocyclic pentaamines 1 and 2. The Ni2+ and Cu2+ complexes with 1 and 2 show a reversible pH‐dependent change in geometry, in which the side‐chain amino group is either coordinated to the metal ion (basic form) or protonated and, thus, non‐coordinated (acidic form). The length of the side chain determines the log Ka values of these protonation/deprotonation equilibria: 1.89 and ∼ 2.0 for the Cu2+ and Ni2+ complexes of ligand 1 with the 2‐aminoethyl side chain, and 6.17 and 7.43 for the Cu2+ and Ni2+ complexes of ligand 2 with the 3‐aminopropyl side chain.
Synthesis, Structure, and 2D‐NMR Studies of Novel Chiral (η3‐Allyl)palladium(II) Complexes Containing the Bidentate Ligand Sparteine
Authors: Togni Antonio , Rihs Grety , Pregosin Paul S. , Ammann Christian 
Published: December 2004

AbstractNovel cationic allylpalladium (II) comp, exes containing the alkaloid (−)sparteine (1) as a bidentate ligand have been prepared. Two of them, [η3(cyclohex‐2‐enyl)] (sparteine)palladium(II) hexafluorophosphate([Pd(η3‐C6 H9)(sparteine)][PF6] 3b) and (sparteine)[η3‐(1,1,3‐triphenylallyl)] palladium (II) trifluorophosphate ([Pd(η3‐Ph2CCHCHPh)(sparteine)][sparteine)] [CF3SO3]; (3c) were characterized by X‐ray diffraction. The application of 2D‐NMR methods (COSY and NOESY)affords a correlation between the solid‐state and solution structures for complex 3c.
New Spirostaphylotrichins from the Mutant Strain P 649 of Staphylotrichum coccosporum: The Biogenetic Interrelationship of the Known Spirostaphylotrichins
Authors: Sandmeier Peter , Tamm Christoph 
Published: December 2004

AbstractThe isolation and structure elucidation of the new Spirostaphylotrichins N (2), O (3), P (4), and T (7) from a mutant strain of S. coccosporum are described. The biogenetic relationship of the known spirostaphylotrichins is discussed.
The crystal structure of [1.1.1]propellane at 138 K
Authors: Seiler Paul 
Published: December 2004

AbstractThe molecular structure of [1.1.1]propellane has been determined from single‐crystal X‐ray diffraction measurements at 138 K. The crystals of this reactive compound were grown from the melt at ca. 263 K. The space group is C2, and the asymmetric unit contains four molecules. All have large thermal motion and two show orientational disorder as well. Because of these problems, the atomic positions cannot be determined with high accuracy. Within the experimental limits, the two ordered molecules have D3h symmetry, with corrected lengths of central and side bonds of ca. 1.60 Å and 1.53 Å, respectively. At lower temperature, the crystals undergo a phase transition. The transition temperature, in the range of 100 to 132 K, varied from one crystal sample to another. All crystals obtained of the low‐temperature phase were twinned, and its space group could not be established.
Rogiolol Acetate: A Novel β‐Chamigrene‐Type Sesquiterpene Isolated from a Marine Sponge
Authors: Guella Graziano , Mancini Ines , Chiasera Giuseppe , Pietra Francesco 
Published: December 2004

AbstractThe marine sponge Spongia zimocca SCHMIDT, 1862, collected in front of the torrent II Rogiolo, south of Livorno, contains the sesquiterpene rogiolol acetate (= (+)‐(2R,3S,6R,8R,9R)‐2,8‐dibromo‐9‐chloro‐1,1,9‐trimethyl‐5‐methylidenespiro[5.5]undec‐3‐yl acetate; (+)‐3a), which represents the first chamigrane isolated from a sponge. Although compounds of this class are common in red seaweeds of the genus Laurencia, and our sponge actually contains 9‐bromochamigrene and a variety of other metabolites of nearby growing Laurencia sp., (+)‐3a is unique to our sponge.
Reduktive Co‐Alkylierung von Heptamethyl‐cobyrinat mit dem Methylthiomalonat (S)‐Methyl‐3‐bromo‐2‐[(ethylthio) carbonyl]‐2‐methylpropanoat
Authors: Müller Susanna , Wolleb Annemarie , Walder Lorenz , Keese Reinhart 
Published: December 2004

Reductive Co Alkylation of Heptamethyl Cobyrinate with the Methylthiomalonate (S)‐Methyl 3‐Bromo‐2‐[(ethylthio)carbonyl]‐2‐methylpropanoateThe methylthiomalonate(−)‐(S)‐Methyl 3‐bromo‐2‐[(ethylthio)carbonyl]‐2‐methylpropanoate(5a)was prepared from dimethyl methylmalonate in five steps via the stereospecific cleavage of the (pro‐S)‐ester group of 1 with pig‐liver esterase in an overall yield of 26.5% (Scheme 4a). Reductive Co alkylation of heptamethyl Coβ‐perchlorato cob (II)yrinate (8) with 5a by electrosynthesis lead to the alkylcobalt complex 9a in 40% yield (Scheme 4b). The O2‐dependent reactions of the methyhnalonyl fragment produced by photolysis of 9a and its deuterated derivative 9c are reported (Scheme 5).
Azidinium‐Salze 24. Mitteilung Thermolyse heterocyclischer Azidinium‐tetrafluoroborate
Authors: Huys‐Francotte Martine , Balli Heinz 
Published: December 2004

Thermolysis of Heterocyclic Azidinium TetrafluoroboratesThe thermolysis of some azidinium salts was investigated. It led to a large variety of products which were isolated or identified by GC/MS. Reaction mechanisms are discussed to explain the product formation.
Azomalonate Syntheses Part II. Synthesis and Reactivity of Novel 1,2,4‐Triazin‐5‐one Derivatives
Authors: Heckendorn Roland 
Published: December 2004

AbstractBase treatment of azomalonates derived from N‐substituted dialkyl (2‐chloroacetamido)malonates results in the formation of 4‐substituted alkyl 5‐oxo‐1,4,5,6‐tetrahydro‐1,2,4‐triazine‐3‐carboxylates. The same malonates coupled with diazotized 2‐amino‐5‐chlorobenzophenone or methyl anthranilate afford triazinones which can be cyclized into novel triazino[1,6‐a]indoles. Two representative heterocycles are further characterized by typical reactions. Whereas oxidation gives the corresponding triazine‐5,6‐diones, the outcome of the reduction is strongly dependent on the nature of the substituent at C(4). Bromination followed by aqueous workup leads to the 6‐hydroxy derivatives. Some mechanistic aspects of this novel triazinone synthesis are discussed.
Luminescence Properties of Eu3+ Complexes of Tripode and Tetrapode Ligands Containing 2,2′‐Bipyridine Units
Authors: Balzani Vincenzo , Berghmans Erik , Lehn Jean‐Marie , Sabbatini Nanda , Terörde Robert , Ziessel Raymond 
Published: December 2004

AbstractThe Eu3+ complexes of the tripode and tetrapode ligands 1 and 2, respectively, containing 2,2′‐bipyridine coordinating units have been prepared. The UV absorption and luminescence spectra, lifetimes, and quantum yields have been measured under a variety of experimental conditions. The contributions of different paths to the decay of the luminescent excited state are evaluated, and the structures of the complexes are discussed on the basis of spectroscopic and photophysical data.
Separation of Enantiomeric Irones by Gas‐Liquid Chromatography on Modified Cyclodextrins
Authors: Marner Franz‐Josef , Runge Torsten , König Wilfried A. 
Published: December 2004

AbstractNatural irones found in the essential oil of Iris rhizomes often are mixtures of enantiomers. The separation of all optical isomers of the irones by GLC on modified cyclodextrins and the determination of their composition within different Iris oils is described. The significance for the biosynthesis of the cycloiridals, C31‐triterpenoids, which serve as precursors of the irones, is discussed.
Novel Hydroxyicosatetraenoic and Hydroxyicosapentaenoic Acids and a 13‐Oxo Analog. Isolation from a Mixture of the Calcareous Red Algae Lithothamnion corallioides and Lithothamnion calcareum of Brittany Waters
Authors: Guerriero Antonio , D'Ambrosio Michele , Pietra Francesco 
Published: December 2004

AbstractA mixture of the red calcareous algae Lithothamnion corallioides CROUAN and Lithothamnion calcareum (PALLAS) ARESCHOUGH, from Brittany waters, gives, on ethanolic extraction, the novel icosanoids ethyl 13‐hydroxy‐arachidonate (=(+)‐all‐Z‐ethyl 13‐hydroxyicosa‐5,8, 11,14,‐tetraenoate; (+)‐1)), ethyl 13‐hydroxytimnodonate (=(+)‐(all‐Z)‐ethyl 13‐hydroxyicosa‐5,8,11,14,17‐pentaenoate ((+)‐2), and (5Z,9E,11E,14E)‐ethyl 8‐hydroxy‐13‐oxoicosa‐5,9,11,14‐tetraenoate (3). Moreover, the ethyl esters of four known icosatetraenoic acids are contained in the above algae. Structural elucidations of these metabolites are based mainly on NMR data.
Carotinoide mit 7‐Oxabicyclo[2.2.1]heptyl‐Endgruppen. Teil II. Synthese von (2S,5R,6S,2′S,5′R,6′S)‐2,5:2′5′‐Diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐carotin
Authors: Gmünder Michael Roman , Eugster Conrad Hans 
Published: December 2004

Carotenoids mit 7‐Oxabicyclo[2.2.1]heptyl‐End Groups. Synthesis of (2S,5R,6S,2′S,5′R,6′S)‐2,5:2′5′‐Diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐caroteneMukayama's ester 6 (methyl (1S,2R,5S)‐2,5‐epoxy‐2,6,6‐trimethylcyclohexane‐1‐carboxylate) was transformed in a few conventional steps into the title compound 14. Its CD curve was found to be significantly different from that of the analogous 3,6‐epoxide, a fact we tentatively lake as an indication of a (weak) electronic interaction between the ring O‐atom and the π‐orbitals of the polyene chain.
Acyl Migration in d6 Iron Complexes
Authors: Kölbener Pius , Hund Hans‐Ulrich , Bosch H. William , Sontag Christoph , Berke Heinz 
Published: December 2004

AbstractThe η2‐acyl complex [Fe(η2‐EtCO)I (CO)(PEt3)2] (1a) reacts with phenylacetylene in refluxing Et2O to form a mixture of products including [Fe(C(Ph)CHC(O)Et}I(CO)(PEt3)2] (3), [Fe{C(Ph)CHC(O)Et}1(CO)2(PEt3)2] (4), and [Fe{C(CHPh)C(O)Et)I(CO)(PEt3)2] (5). Compound 3 contains a ‘metallafurane’ unit, while 5 consists of a 4‐member metallacycle. Compound 5 was characterized by X‐ray crystallography. In contrast to 1a, the η2‐acyl complex [Fe{η2‐(i‐Pr)CO}I(CO)(PEt3)2] (1b) reacts with phenylacetylene under similar conditions to produce [Fe{η2‐C(O)C(Ph)CH(i‐Pr)}I(CO)(PEt3)2 (7) which was characterized spectroscopically. Modified extended Hückel theory calculations were made on the model compounds [Fe(η2‐CHO)(CO)2(PH3)2]+ (14), [Fe(CHO)(HCCH)(CO)2(PH3)2]+ (15), [Fe(CCH2)(CHO)(CO)2(PH3)2]+ (16), [Fe{C(CH2)CHO}(CO)2(PH3)2]+ (17), and {Fe(CHCHCHO)(CO)2(PH3)2]+ (18). The calculations show that in the transformation 15→18, there exists a transition state lying 83.6 kJ/mol above the optimized geometry of 15 in which the formyl unit is rotated by 80° with respect to the Fe‐acetylene plane. Conversion of 15 to 17 involves a [1,2]‐H shift and an acyl‐acetylene coupling reaction which probably occur synchronously.
Reductive Radical Cyclisations of Bromo Acetals and (Bromomethyl)silyl Ethers of Terpenoid Alcohols
Authors: Lee Edward R. , Lakomy Ivo , Bigler Peter , Scheffold Rolf 
Published: December 2004

AbstractThe tin hydride promoted and the reductive vitamin B12 catalysed radical cyclisation of mixed 2‐bromo‐acetaldehyde acetals and of (2‐bromomethyl)dimethylsilyl ethers of allylic terpenoid alcohols has been investigated: 3‐oxadeca‐5,9‐dien‐l‐yl radicals undergo 5‐‘exo’ cyclisation to oxolanes (Scheme 4), 3‐oxa‐2‐siladeca‐5,9‐dien‐1‐yl radicals sequential 6‐‘endo’→5‐‘exo’ tandem cyclisation to cis‐3‐oxa‐4‐silabicyclo[4.3.0]nonanes (Scheme 5), and 3‐oxa‐2‐silatetradeca‐5,9,13‐trien‐l‐yl radicals sequential 6‐‘endo’→6‐‘endo’→5‐‘exo’ triple cyclisation to trans‐transoid‐trans‐ 12‐oxa‐11‐silatricyclo[7.4.0.02,6] tridecanes (Scheme 6).
Structure and Synthesis of Novel C12 Terpenoids from Quince Fruit (Cydonia oblonga MILL.)
Authors: Escher Sina , Niclass Yvan 
Published: December 2004

AbstractThe structure and synthesis of novel irregular C12 terpenoids isolated from quince fruit (Cydonia oblonga MILL.) are described: quince oxepine (= (E)‐2,3,6,7‐tetrahydro‐4‐methyl‐2‐(3‐methylbuta‐1,3 dienyl)oxepine; 3) and the quince oxepanes as a 1:1 mixture of cis‐ and trans‐isomers (= cis‐ and trans‐(E)‐4‐methyl‐2‐(3‐methylbuta‐1,3‐dienyl)oxepane; 4 and 5, resp.). The absolute configurations of the natural compounds have not been determined due to the minute amounts available, but both relative and absolute configurations of synthetic 4 and 5 were established by chemial correlation with (R)‐pulegone.
(Cycloheptatrienyl)hydridotungsten Complexes
Authors: Schwed Elke , Hund Hans‐Ulrich , Bosch H. William , Berke Heinz 
Published: December 2004

AbstractCarbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([WI(C7H7)(CO)L]; L = P(OMe)3, 1a; L = P[O(i‐Pr)]3, 1b; L = PPh3, 1c) were prepared from dicarbonyl(cycloheptatrienyl)iodotungsten ([WI(C7H7)(CO)2)] via a carbonyl‐substitution process. Similarly, bromocarbonyl(phosphorus donor)(1,2,4,6‐tetramethylcycloheptatrienyl)tungstens ([WBr(Me4C7H3)(CO)L]; L = P(OMe)3, 6a; L = P[O(i‐Pr)]3, 6b; L = PPh3, 6c) were obtained from the reaction of bromodicarbonyl(1,2,4,6)‐tetramethylcycloheptatrienyl)tungsten ([WBr(Me4C7H3)(CO)2]; 4) with L. The reduction of 1a‐c, 4, and 6a, b with sodiumdihydridobis(2‐methoxyethoxy)aluminium in toluene led to stable hydrido complexes [WH(R4C7H3)(CO)L] (R = H, L = P(OMe)3, 2a; R = H, L = P[O(i‐Pr)]3, 2b; R = H, L = PPh3, 2c; R = Me, L = P(OMe)3, 7a; R = Me, L = P[O(i‐Pr)]3, 7b; R = Me, L = CO, 7d). Complexes 2a and 7b were characterized by X‐ray structure analyses.
1H‐ and 13C‐NMR Investigations of Heptafulvenes
Authors: Bönzli Peter , Neuenschwander Markus 
Published: December 2004

Abstract1H‐ and 13C‐NMR spectra of a series of 8‐R1‐substituted as well as of 8,8‐R1, R2‐disubstituted heptafulvenes, varying from inversely polarized (3l) to unpolar (3h) and polar heptafulvenes with electron‐withdrawing groups (3d, e, f), have been analyzed and compared with those of methoxytropylium salt 5a. The results concerning 3J (H,H) values and 13C‐chemical shifts are shown in Figs. 5 and 6. It turns out that all the NMR parameters are strongly influenced by substituents R1, R2, but contrary to planar pentafulvenes, no linear correlations of the NMR parameter vs. Hammett substituent constant σ+ are obtained in the series 3l → 3d. 3J coupling constants J(2,3)/J(4,5) and J(3,4) are not much influenced by substituent changes in the series 3l → 3h, but are approaching in the row 3h → 3d. Similarly, signals of the 13C‐atoms undergo a moderate shift to higher frequencies in the row 3l → 3h, but are strongly influenced by M groups, whereby the sensitivity is decreasing in the series C(7) > C(2)/C(5) > C(3)/C(4) > C(1)/C(6). These results are essentially explained by a boat conformation of inversely polarized heptafulvenes of the type 3l and an increasing planarization of the ring on going to polar heptafulvenes of type 3d.
Novel Syntheses of Gabapentin via Addition of Hydrocyanic Acid to Cyclohexylidenemalonate or Cyano(cyclohexylidene)acetate
Authors: Griffiths Gareth , Mettler Hanspeter , Mills Lester S. , Previdoli Felix 
Published: December 2004

AbstractSeveral synthetic pathways to the anticonvulsivum gabapentin (1‐(aminomethyl)cyclohexaneacetic acid) have been investigated. Advantages and drawbacks of the different routes are discussed, and the most economical and technically most feasible synthesis is pointed out.
The Synthesis of Boronolide
Authors: Jefford Charles W. , Moulin Marie‐Claude 
Published: December 2004

AbstractRacemic boronolide (1) is prepared in six steps in 4.4% overall yield from acrolein dimer 6 and 1‐(trimethyl‐silyl)hex‐1‐yne (8). The latter, by hydromagnesiation, is condensed with 6 to give the corresponding threo‐allylic alcohol 13 (Scheme 2). Conversion of 13 to the erythro‐allylic alcohol 5 (Scheme 3), bis‐hydroxylation, and acetylation afford 1.
New Reactions of Amino‐Functionalized 3‐Vinyl‐1H‐indoles and Tetrahydropyridin‐4‐yl Analogues with Dienophiles
Authors: Medion‐Simon Mercedes , Pindur Ulf 
Published: December 2004

AbstractReactions of 3‐[2‐(morpholin‐4‐yl)vinyl]‐1H‐indole (1), the 1,2‐dihydro‐9H‐carbazole 2, as well as the 3‐(tetrahydropyridin‐4‐yl)‐1H‐indoles 3a and 3b with some carbo‐ and heterodienophiles are described. The scope and limitations of the synthetic utility of these amino‐ (or homoamino)‐functionalized 3‐vinyl‐1H‐indoles are reported and some MO calculations for the qualitative prediction of their reactivities are presented. The reactions gave rise to substitution products, redox products, Diels‐Alder adducts, ene adducts, and Michael‐type adducts (Schemes 2 and 3).
The 1,3‐Dipolar Cycloadditions of Nitrile Oxides and Nitrile Imines to Alkyl Dicyanoacetates
Authors: Neidlein Richard , Sui Zhihua 
Published: December 2004

AbstractThe readily available alkyl dicyanoacetates 1 reacted with the 1,3‐dipolar reagents arenecarbonitrile oxides 2′ and arenecarbonitrile imines 5′ to afford 1,2,4‐oxadiazol and 1,2,4‐triazol derivatives. The arenecarbonitrile oxides 2′ with electron‐donating groups on the arene ring gave products 3a–d resulting from addition on both CN groups of 1, and those with electron‐withdrawing groups provided mono‐adducts 4a–e (Scheme 1). Arylnitrile imines 5′ reacted with 1 to offer both bis‐ and mono‐addition products (Scheme 2); the bis‐adducts 8a,b possess an ester structure, whereas the mono‐adducts 6a–d present a ketene‐hemiacetal structure.
Stereoselective Conversion of Campholene‐ to Necrodane‐Type Monoterpenes. Novel Access to (−)‐(R,R)‐ and (R,S)‐α‐Necrodol and the Enantiomeric γ‐Necrodols
Authors: Pamingle Hervé , Snowden Roger L. , Schulte‐Elte Karl H. 
Published: December 2004

AbstractNaturally occurring (−)‐(R,R)‐α‐necrodol ((−)‐1) and its C(4)‐epimer (−)‐2 are obtained in 84 and 44% yields, respectively, by lithium ethylenediamide (LEDA) treatment of the corresponding β‐necrodols (−)‐3 and (−)‐4 (Scheme 1, Table), both readily available from (−)‐campholenyl acetate ((−)‐i) by an efficient stereoselective synthesis. The thermodynamically preferred (−)‐(R)‐γ‐necrodol ((−)‐5) becomes the major product (≥ 80% yield) after either prolonged treatment with LEDA or exposure of α‐ and β‐necrodols to BF3·Et2O. In an alternative route, (+)‐5 is prepared starting from (+)‐campholenal ((+)‐ii) via Pd‐catalysed decarbonylation to (−)‐(S)‐1,4,5,5‐tetramethylcyclopent‐l‐ene ((−)‐6) and subsequent application of an acid‐catalysed CH2O‐addition/rearrangement sequence (Scheme 2).
Synthesis of 1,2,3,4‐Tetrahydro‐4‐oxothieno[3,2‐d]pyrimidine and Perhydropyrimidine Derivates from Alkyl Dicyanoacetates
Authors: Neidlein Richard , Sui Zhihua 
Published: December 2004

AbstractNucleophilic addition of methyl 3‐aminothiophene‐2‐carboxylate (2) as well as of β‐alanine ethyl ester (11) to one CN group of the salts 1 of alkyl dicyanoacetates, followed by cyclization, yielded 1,2,3,4‐tetrahydro‐4‐oxothieno[3,2‐d]pyridimine derivatives 6–10 (Scheme 1) and perhydropyrimidine derivatives 17–19 (Scheme 2), respectively.
Glycosylidene Carbenes. Part 3. Synthesis of Spirocyclopropanes
Authors: Vasella Andrea , Waldraff Christian A. A. 
Published: December 2004

AbstractThermolysis of the glycosylidene‐derived O‐benzylated diazirine 1 in the presence of N‐phenylmaleimide (2), acrylonitrile (3), dimethyl fumarate (4), or dimethyl maleate (5) led in good yields to mixtures of the spirocyclopropanes 6/7, 8–11, 12/13, and 12/13/16/17. The diastereoselectivity depends upon the alkene. The cycloaddition of 1 to 5 is not diastereospecific, in keeping with previous results. Deprotection of 12, 13, 16, and 17 yielded the tetrols 14,15, 18, and 19, respectively.
Chiral Cooperativity: The Effect of Distant Chiral Centers in Ferrocenylamine Ligands upon Enantioselectivity in the Gold(I)‐Catalyzed Aldol Reaction
Authors: Pastor Stephen D. , Togni Antonio 
Published: December 2004

AbstractLong‐range chiral cooperativity in enantiomerically pure ferrocenylamine ligands containing both planar and multiple centers of chirality (multiple stereogenic C‐atoms) was demonstrated in the AuI‐catalyzed reaction of aldehydes and isocyanoesters. Synthetic methodology was developed for the synthesis of ferrocenylamine ligands with two and three chiral centers of known absolute configuration in the C‐side chain in addition to the planar chirality of the molecule. The diastereo‐ and enantioselectivity of the AuI‐catalyzed formation of the trans‐ and cis‐dihydrooxazoles 5 and 6, respectively, from benzaldehyde (1) and methyl isocyanoacetate (2) depend upon the sequence of chirality (absolute configuration of the chiral centers) in the side chain of the ferrocenylamine ligands. Particularly significant effects were observed upon the enantioselectivity for the minor cis‐dihydrooxazole 6, for which, in certain cases, resulted in a change in the enantiomeric dihydrooxazole 6 produced in excess with a change in the absolute configuration of a distant chiral center. Significant effects upon diastereo‐ and enantioselectivity were observed when chiral ferrocenylamine ligands containing free OH groups were utilized. Using ligands containing a free OH group gave 6 with an absolute configuration opposite to that produced by the corresponding ester and carbamate derivatives. The possible mechanisms for the transmission of chiral information in the proposed stereoselective transition state (TS) was discussed, including both the formation of a stereogenic N‐atom and steric effects based upon Newman's rule of six.
Nitroacetyl Group as a Peptide Synthon: Synthesis of Dipeptides with an α,α‐Bisallylglycine Residue at the N‐Terminus
Authors: Manjunatha Sulur G. , Chittari Pabba , Rajappa Srinivasachari 
Published: December 2004

AbstractN‐Nitroacetyl derivatives of L‐proline, L‐valine, and L‐phenylalanine esters were prepared in two steps under mild conditions (Scheme 2). Regiospecific mono‐ and bis‐allylation of these nitroacetyl derivatives were accomplished in presence of a Pd(0) catalyst. The bis‐allyl derivatives 7–9 were obtained in 40–75% yield. The tertiary NO2 group in these compounds could be transformed into an acetylamino group by Zn/AcOH/Ac2O. The final products 11–13 are dipeptides in which the N‐terminal glycine residue bears two α‐allyl substituents.
Zur Synthese von Derivaten des Pyrido[1,2‐a]azepins
Authors: Maicr Wolfram , Eberbach Wolfgang , Fritz Hans 
Published: December 2004

On the Synthesis of Derivatives of Pyrido[1,2‐a]lazepineThe conjugated pyridinium ylides of type 4 undergo 8π ‐electrocyclisation affording the heterobicyclic allenes 5 which, in the presence of H2O and H2O2, are subsequently transformed into the substituted pyrido[1,2‐a]‐azepinones 6, a novel heterocyclic system. The chemical behaviour of 6a,b is dominated by cleavage of the lactam bond and subsequent reaction to pyridinc and isoquinoline derivatives, respectively; e.g. reaction of 6a, b with 4,5‐dihydro‐4‐methyl‐3H‐1,2,4‐triazole‐3,5‐dione affords the cycloadducts 11 and 12 almost quantitatively. The successful transformation of 6b into 15 is described, the latter being the first representative of the presently unknown, potentially antiaromatic pyrido[1,2‐a]azepine (1).