bluuebunny/crossref_metadata_2025 huggingface dataset:
Röntgenstrukturanalyse von 2,4,6‐Tri(tert‐butyl)phenyl‐lithium · N,N,N′,N′‐Tetramethylpropan‐1,2‐diamin: Eine monomere Organolithium‐Verbindung
Authors: Maetzke Thomas , Seebach Dieter
Published: December 2004

X‐Ray Crystal‐Structure Analysis of 2,4,6‐Tri(tert‐butyl)phenyllithium · N,N,N′,N′‐Tetramethylpropane‐1,2‐diamine: a Monomeric Organolithium Compound

Tri(tert‐butyl)phenyllithium is an important reagent for the preparation of derivatives of main‐group elements with low coordination state as well as a highly hindered base for the generation of amine‐free Li‐enolates. Its monomeric nature in solution was previously deduced from NMR measurements. While Et2O, THF, and N,N,N′,N′‐tetramethylethylene‐1,2‐diamine (tmen) led to crystalline samples which were not suitable for structure analysis, the N,N,N′,N′‐tetramethylpropane‐1,2‐diamine (tmpn) gave good single crystals of the title compound from Et2O/hexane (disorder along the two‐fold crystallographic axis running through LiC(1) and C(4) of the Ph ring. The structure (Fig. 1, Table 1) has some remarkable features: (i) it is one of the very few monomeric organolithium compounds so far, (η1‐Li on aromatic ring); (ii) it has the rare trigonal‐planar coordination of the Li‐atom; iii) there are close contacts between the Li‐atom arid one of the Me groups in each ortho‐position (Fig. 3). The internal angle on the Ph‐ring ipso‐C‐atom is 114°. This angle as well as those of the other known phenyllithium (Table 2), ‐magnesium, and ‐aluminum structures are included in a plot of ipso‐angles against Pauling electronegativities (Fig. 2).
Thermal and Photochemical Reactions of 1,2‐Annelated Barrelenes and Hydrobarrelenes in the presence of transition‐metal carbonyls
Authors: Trifonov Latchezar S. , Orahovats Alexander S.
Published: December 2004

The [Co2(CO)8]‐mediated retro‐Diels‐Alder reaction of the annelated barrelenes 1 afforded the 1H‐indol‐2(3H)‐one derivatives 3 (Scheme 1), while the hydrobarrelene 4a, under the same conditions, was converted to the anilide 6 (Scheme 2); 4b remained unaffected. The direct irradiation of 1 led to the annelated cyclooctatetraenes 7 (Scheme 3). On irradiation in the presence of excess of [Fe(CO)5], 1a, 1b, and 4a gave the tricarbonyliron complexes 8, 9, and 11, respectively (Schemes 3 and 4); under these conditions, 4b was inert.
Synthesis of (+)‐(4S, 8R)hyphen;8hyphen;Epi‐ and (−)‐(4R, 8S)‐4‐Epi‐β‐bisabolol
Authors: Fráter Georg , Müller Urs
Published: December 2004

The first total enantioselective synthesis of (+)‐(4S, 8R)‐8‐epi‐β‐bisabolol(+)‐1 and of (−)‐(4R, 8S)‐4‐epi‐β‐bisabolol ((−))−1) is reported. The key step in the synthesis is the kinetic resolution of (±)−5 by means of the Sharpless epoxidation yielding (−)‐ and (+}−6, respectively. Reduction of the epoxides with LiAlH4 gave the diols (+)‐and(−)−7 which were transformed into (+)‐ and (−)−8, respectively, via the corresponding mesylate. Reaction of these epoxides with the Grignard reagent derived from homoprenylbromide, assisted by Li2CuCl4, finished the synthesis of the target compounds 1 with high diastereo‐ and enantioselectivity.
Studies on the Biosynthesis of Spirostaphylotrichin A
Authors: Sandmeier Peter , Tamm Christoph
Published: December 2004

Incorporation of 14C‐labelled acetate and amino acids as well as of [1‐13C]‐, [2‐13C]‐, and [1,2‐13C2] acetate, L‐[methyl13C] methionine, [2,3‐13C2] succinate, and L‐[2,3‐13C2] aspartate into spirostaphylotrichin A (1) by Staphylotrichum coccosporum demonstrates that the building blocks of 1 are 5 units of acetate/malonate, 1 unit of methionine, and a C4‐dicarboxylic acid. The latter is most likely aspartate and derived from the citric‐acid cycle. Using [2‐13C, 2‐2H3] acetate as a precursor, the starter unit of the polyketide chain was identified.
Struktur/wirkung‐Beziehungen bei Geruchsstoffen mit dem Bicyclo[2.2.2.]octan‐Gerüst
Authors: Spreitzer Helmut , Buchbauer Gerhard , Reisinger Sigrid
Published: December 2004

Structure‐Activity Relationships of Odorants with a Bicyclo[2.2.2]octane System

The synthesis of the olfactory interesting homonojigikualcohol 2 and of its epimer 10 leads to the keto alcohols 6a, b and 7a, b as intermediates. The latter have OH and CO groups (an AH/B system) fixed at the rigid bicyclic nucleus at different distances (2.8 and 4.7 Å) and confirm Ohloff's rule for odoriferous properties which is based on this distance.
Structure‐Activity Relationship in Ambergris‐Type Woody Odorants possessing a hydronaphthalene skeleton
Authors: Vial Christian , Thommen Walter , Näf Ferdinand
Published: December 2004

A series of methyl hydronaphthyl alcohols, formates, acetates, and ketones were prepared and their odour properties evaluated. Minor structural changes, even opposite to the osmophoric group, were found to have major effects on the odour. 13CNMR shift assignments of the hydronaphthyl derivatives are presented.
Complex formation equilibria of L‐Amino‐Acid amides with copper(II) in aqueous solution
Authors: Dallavalle Francesco , Fisicaro Emilia , Corradini Roberto , Marchelli Rosangela
Published: December 2004

Protonation and Cu(II) complexation equilibria of L‐phenyhilaninamide, N2‐methyl‐L‐phenylalaninamide, N2, N2‐dimethyl‐L‐phenylalaninamide, L‐valinamide, and L‐prolinamide have been studied by potentiometry in aqueous solution. The formation constants of the species observed, CuL2+, CuL, CuLH, CuL2H and CuL2H−2, are discussed in relation to the structures of the ligands. Possible structures of bisamidato complexes are proposed on the ground of VIS and CD spectra. Since Cu(II) complexes of the present ligands (pH range 6–8) perform chiral resolution of dansyl‐ and unmodified amino acids in HPLC (reversed phase), it is relevant for the investigation of the resolution mechanism to know which are the species potentially involved in the recognition process.
Synthesis of ethyl cis 2‐[(Diethoxyphosphoryl)methyl]‐7‐oxo‐3‐phenyl‐6‐phthalimido‐l‐azabicyclo[3.2.0]hept‐3‐ene‐2‐carboxylate and Methyl cis‐2‐Bromo‐3‐methyl‐8‐oxo‐7‐phthalimido‐4‐oxa‐1‐azabicyclo[4.2.0]octane‐2‐carboxylate
Authors: Hakimelahi Gholam H. , Jarrahpour Ali A.
Published: December 2004

The synthesis of a Δ1‐carbapenem and two β‐lactams possessing a Br‐atom at the N‐substituting center not involved in the lactam ring and bearing the carboxyl group is described. The β‐lactams having this kind of Br‐substitution are more susceptible to nucleophilic attack than those having a conjugated double bond with the N‐atom of the β‐lactam ring. DBU is found to be an excellent reagent for the elimination of the silyloxy function. Moreover, a simple method for the addition of diethyl phosphite to an α, β‐unsaturated double bond using a catalytic amount of NaH is described.
Synthese von (+)‐Aspicilin mit Bausteinen aus nachwachsenden Rohstoffen
Authors: Quinkert Gerhard , Fernholz Erhard , Eckes Peter , Neumann Doris , Dürner Gerd
Published: December 2004

Synthesis of (+)‐Aspicilin Using Building Blocks from Renewable Resources

The 18‐membered lichen macrolide (+)‐aspicilin (1) is easily built up from compounds 14, 16, 3, and 24 following the C3 + C7 + C6 + C2 = C18 pattern (see Schemes). The synthesis requires 15 steps and gives 1 in 13% overall yield from D‐mannose (2). The latter compound provides the stereogenic centers C(4), C(5), and C(6). The stereogenic center C(17) is supplied by building block 14 (from (−)‐(S)‐ethyl lactate).
Synthesis, Reactivity, and Application as Chiral Auxiliaries of the novel (3R)‐ and (3S)‐4,5‐dihydro‐3‐hydroxy‐4,4,5,5‐tetramethyl‐3‐phenylfuran‐2(3H)‐ones in the Paterno‐Büchi reaction
Authors: Oppenländer Thomas , Schönholzer Peter
Published: December 2004

Both enantiomers of the novel α‐hydroxy‐γ ‐lactone (±)‐3 (4,5‐dihydro‐3‐hydroxy‐4,4,5,5‐tetramethyl‐3‐phenylfuran‐2(3H)‐one) have been synthesized via hydrolysis of the oxetanes 2 derived from the photochemical [2 + 2] cycloaddition of the ketones 1 and 2,3‐dimethylbut‐2‐ene (Paterno‐Büchi reaction) involving conventional separation of diastereoisomers (Schemes 2 and 3). The absolute configuration of (R)‐ and (S)‐3 and of the corresponding oxetane precursors could be assigned on the basis of an X‐ray structural analysis of the (−)‐(1S, 4R)‐camphanoyl derivative (3′S)‐5 of (S)‐3. O‐Acylation of (S)‐and (±)‐3 to yield a variety of derivatives ((3′S)‐ and (3′RS)‐5, (S)‐ and (±)‐7, (±)‐8, (±)‐9) was accomplished by deprotonation with BuLi at room temperature and subsequent quenching of the Li alcoholate with acyl chlorides or acid anhydrides, demonstrating the extraordinary chemical stability of 3. Additionally, the course of the temperature‐dependent diastereoselective Paterno‐Büchi reaction of 2,3‐dimethylbut‐2‐ene to the benzoylformate (S)‐7 ( = (S)‐1d; obtained from (S)‐3) was shown to proceed with 58% de at 60°, leading to a decrease of enantiomeric purity in the hydrolysis product 3.
Photochemistry of ethyl 2,3‐dihydro‐2,2‐dimethyl‐3‐oxo‐1H‐pyrrole‐1‐carboxylate
Authors: Patjens Jan , Margaretha Paul
Published: December 2004

The title compound 7 is obtained by reductive dehalogenation from 4‐bromo‐2,3‐dihydro‐2,2. ‐dimethyl‐3‐oxo‐1H‐pyrrole‐1‐carboxylate (8) in 90% yield, Aza‐enone 7 undergoes [2 + 2] cycloaddition from the triplet state with both electron‐rich and electron‐deficient alkenes. The behaviour of 7 in light‐induced reactions is compared to those of 2,2‐dimethyl‐3(2H)‐furanone (1a) and of the corresponding thiophenone 1b. In the photodimerization and the cycloaddition to either 2,3‐dimethylbut‐2‐ene or to dimethyl maleate of these ketonic five‐membered heterocycles with one heteroatom, the overall efficiency increases in going from the furan 1a to the thiophene 1b and to the pyrrole 7.
New Cell Growth‐Inhibitory Cyclohexadienone Derivatives from Hypericum calycinum L.
Authors: Decosterd Laurent A. , Stoeckli‐Evans Helen , Chapuis Jean‐Charles , Sordat Bernard , Hostettmann Kurt
Published: December 2004

The crude petroleum‐ether extract of the aerial parts of Hypericum calycinum L. (Guttiferae) exhibited in vitro growth‐inhibitory activity against the Co‐115 human colon carcinoma cell line. Bioassay‐guided fractionation of this extract allowed the isolation of the cyclohexadienone derivatives 1–5, four of which are previously undescribed compounds. The structures of the known chinesin II (1) and of 2 (hypercalin A) were established by 1H‐ and 13C‐NMR spectroscopy and were confirmed by X‐ray analysis of their crystalline mixture which revealed the complete relative configuration of both compounds. The structure of 3 (hypercalin B) was elucidated by means of extensive 1D‐ and 2D‐NMR experiments, including DQ‐COSY, HETCOR and LR‐HETCOR. The structure of compound 4 (hypercalin C) was established by 1H‐ and 13C‐NMR spectroscopy and confirmed by X‐ray analysis to be the 3,5‐dihydroxy‐4‐{[(1R*,2S*, 5S*)‐2‐hydroxy‐2‐methyl‐5‐(1‐methylethenyl)cyclopentyl]methyl}‐6,6‐bis‐(3‐methylbut‐2‐enyl)‐2‐(2‐methylpropanoyl)cyclohexa‐2,4‐dien‐1‐one. The structures of the higher isomeric homologues 5a/5b were deduced by comparison of their UV, 1H‐, and 13C‐NMR spectra with those of 4. The isolated compounds appeared to be related to chinesin I and II previously isolated from Hypericum chinense L. and were responsible for the growth‐inhibitory activity of the extract against the Co‐115 human carcinoma cell line. Moreover, 1/2 and 3 showed molluscicidal activity against the schistosomiasis‐transmitting snail Biomphalaria glabrata.
Methyl‐jasmonat: Ein kurzer Weg zum Naturstoff und seinem unnatürlichen Enantiomer via Palladium(0)‐induzierte, enantiodivergente Alkylierung von Cyclopent‐2‐en‐1,3‐diol‐Derivaten
Authors: Montforts Franz‐Peter , Gesing‐Zibulak Ingrid , Grammenos Wassilios , Schneider Manfred , Laumen Kurt
Published: December 2004

Methyl Jasmonate: A Short Synthesis of Naturally Occurring Methyl Jasmonate and its Unnatural Enantiomer via Enantiodivergent Alkylation of Cyclopent‐2‐ene‐1,3‐diol Derivatives by Palladium(0)‐Induced Reactions

Palladium‐catalyzed alkylation of cyclopent‐2‐ene‐1,2‐diol derivatives like 2 is a useful method for enantiodivergent functionalization, resulting in both enantiomeric series of chiral building blocks. The chiral building blocks 3 and 13 can be transformed to methyl jasmonate (1)and its unnatural enantiomer ent‐1, recent statement [1b] that 1 has no odour at all and that ‘methyl jasmonate's’ fragrance is actually due to its cis‐isomer ent‐11 has been confirmed also for the enantiomeric series.
Tetrazinodiheteroarene: ‘Charge‐Transfer’‐Komplexbildung mit Akzeptorverbindungen
Authors: Hellrung Bruno , Balli Heinz
Published: December 2004

Charge‐Transfer Complexes of Tetrazinodiheteroarenes with Acceptor Compounds

The formation of charge‐transfer complexes and radical‐ion pairs of donor compounds 1–6 with acceptor compounds 7–12 has been investigated by means of VIS/NIR‐spectroscopic methods. The equilibrium constants KCT up to 1100M‐1 for the donor/acceptor couple dipyrido[1,2‐b:1,2′‐e][1,2,4,5]tetrazine (2)/ethylenetetracarbonitrile (11) and spectra of the CT complexes have been determined in 1,2‐dichloroethane solution at 25°. Results are discussed in relation to known CT‐complex properties and to voltammetric redox‐potentials E1/2.
Preparation, Characterisation, and Structure of N‐Methylated Derivatives of 1,3,5‐Triamino‐1,3,5‐trideoxy‐cis‐inositol: Polyalcohols with Unusual Acidity
Authors: Hegetschweiler Kaspar , Erni Isidor , Schneider Walter , Schmalle Helmut
Published: December 2004

1,3,5‐Trideoxy‐1,3,5‐tris(dimethylamino)‐cis‐inositol (TDCI) and 1,3,5‐trideoxy‐1,3,5‐tris(trimethylammonio)‐cis‐inositol (TTCI) were prepared by methylation of 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol (TACI). The ability of TDCI to form both intermolecular and intramolecular H‐bonds, as demonstrated by X‐ray diffraction, is probably responsible for the good solubility of TDCI in almost every common solvent. TTCI was found to be a polyol of unusual high acidity (pK1 = 8.14 ± 0.02, pK2 = 13.0 ± 0.2). This phenomenon could be explained by electrostatic interactions between the charged substituents of the cyclohexane residue.
Metal Complexes with Macrocyclic Ligands. Part XXXII. Reactivity studies of the pendant carboxylic group in a macrocyclic Cu2+ complex towards amide formation and its use as a protein‐labelling agent
Authors: Studer Martin , Kaden Thomas A. , Mäcke Helmut R.
Published: December 2004

The Cu2+ complex of 1, having a non‐coordinating carboxylic group, can be reacted under the typical conditions of peptide formation with amines such as 2‐methylpropylamine or (pyrid‐2‐yl)methylamine to give, after removal of Cu2+ with CN−, the amides 4 and 5. The Cu2+ ion is of paramount importance since it protects the four amino groups of the macrocycle so that the amide condensation can specifically be done with the exogenous amine It is also shown that the Cu2+ complex of 1 can be covalently attached to bovine serum albumin (BSA), thus opening the possibility to use this compound as a labelling agent for proteins and antibodies.
Synthesis, Reactivity Studies, and X‐ray Crystal Structure of (11R)‐25‐O‐Deacetyl‐11‐deoxo‐11‐hydroxy‐21,23‐O‐isopropylidenerifamycin S
Authors: Bartolucci Cecilia , Cellai Luciano , Cerrini Silvio , Lamba Doriano , Segre Anna Laura , Brizzi Vittorio , Brufani Mario
Published: December 2004

The protected intermediate (11R)‐25‐O‐deacetyl‐11‐deoxo‐11‐hydroxy‐21,23‐O‐isopropylidenerifamycin S (7) has been synthesized starting from rifamicin S (2; Scheme 2), the former being a potential substrate for the preparation of new types of rifamicin‐S derivatives modified at C(11) and/or C(25). The reactivity of 7 toward acylations has been studied under both base‐ and acid‐catalyzed conditions. The compound either did not react or nr underwent unexpected reactions, and no acylation products could be isolated. The X‐ray crystal structure of 7 reveals that both OH groups at C(11) and C(25) are hindered, and this is probably the reason, why other take place faster than acylation.
Catalysis of Ion Transfer by Tetraphenylborates in Neutral Carrier‐Based Ion‐Selective Electrodes
Authors: Gehrig Peter , Morf Werner E. , Welti Martin , Pretsch Ernö , Simon Wilhelm
Published: December 2004

For certain ionophores of extremely high lipophilicity, kinetic limitations of the carrier‐induced ion transfer between aqueous and membrane phase may heavily disturb the electromotive behaviour of the ion‐selective membrane electrode. These limitations may be overcome by adding tetraphenylborates to the membrane phase. Membranes prepared with different 3,6‐dioxaoctanediamide homologues and potassium tetrakis(P‐chlorophenyl)borate as phase‐transfer catalyst all exhibit the same ion selectivity as well as theoretical electrode response. This behaviour is corroborated by a theoretical description of the ion‐transfer process.
Dehydrosulfurization of Isothiocyanates by Gas‐Phase Fe(I) Cations
Authors: Eller Karsten , Akkök Semiha , Schwarz Helmut
Published: December 2004

Bare Fe(I) cations act in the gas phase as dehydrosulfurization catalysts for butyl isothiocyanate by specifically coupling the S‐atom with remote H‐atoms from the ω and (ω − l) position of the alkyl chain. Other losses induced by Fe(I) are due to ‘remote functionalization’, the formation of ion/dipole intermediates, and insertion/β‐hydrogen shift processes.
Isolation of the Cembranoid Preverecynarmin Alongside Some Briaranes, the Verecynarmins, from Both the Nudibranch Mollusc Armina maculata and the Octocoral Veretillum cynomorium of the East Pyrenean Mediterranean Sea
Authors: Guerriero Antonio , D'Ambrosio Michele , Pietra Francesco
Published: December 2004

It is shown that the nudibranch mollusc Armina maculata and its prey, the pennatulacean octocoral Veretillum cynomorium, of east Pyrenean waters contain a novel cembranoid, preverecynarmin ((+)‐8), besides the known cembranoid cembrene C (9) and three further briarane diterpenoids (verecynarmin E ((−)‐5), F ((−)‐6), and G ((−)‐7)). A biogenetic scheme is proposed.
Regiochemical Trends in Intramolecular [2 + 2] Photocycloadditions of 6‐(prop‐2‐enyl)cyclohex‐2‐enones and 5‐(prop‐2‐enyl)cyclopent‐2‐enones
Authors: Cruciani Giuliano , Margaretha Paul
Published: December 2004

The effect of substituents (X  H, Me, or F at C(6), R  H or Me at C(2′) of the allyl side chain) on the photoisomerization (λ = 350 nm) of 6‐allylcyclohex‐2‐enones 1 in MeCN is studied. Substituents X control the overall efficiency of intramolecular [2 + 2] photocycloadduct formation (Φ: Me > F > H) but do not exercise an influence on the orientation of addition of the exocyclic double bond to the enone CC bond. In contrast, replacement of the prop‐2‐enyl (R  H) by a 2‐methylprop‐2‐enyl (R  Me) side chain causes a change in the tricyclo[3.3.1.02,7]nonan‐6‐one 4 vs. tricyclo[4.2,1.03,8]nonan‐7‐one (5) product ratio from 100:0 (R  H) to roughly 2:1 (R  Me) but has almost no bearing on the relative rates of conversion of 1 to products. For C(6)‐unsubstituted enones 1aa and 1ba (X  H), the efficiency of cyclization becomes low enough so that lumiketone rearrangement to bicyclohexanones 6 and 3‐isopropylcyclopent‐2‐enones 9 becomes competitive. Enones 9 undergo consecutive intramolecular [2 + 2] photocycloaddition to tricyclo[3.2.1.03,6]octan‐2‐ones 7 and to tricyclo[3.2.1.03,6]octan‐7‐ones 8, compounds 8 only being formed when R  Me.
Halochrome Moleküle 9. Mitteilung[1]. Substituierte 6,11‐Dihydrospiro[[1]benzopyrano[4,3‐b]indol‐6,9′‐9′H‐xanthen]‐2′,6′‐diamine und ihre Aza‐analogen: Neue Chromogene für schwarze Farbbilder
Authors: Gunzenhauser Sigmund , Balli Heinz
Published: December 2004

Halochromic Molecules. Substituted 6,11‐Dihydrospiro[[1]benzopyrano[4,3‐b]indol‐6,9′‐9′H‐xanthene]‐2′,6′‐diamines and Their Aza Analogues: New Chromogenes for Black Images.

We have synthesized a series of substituted 6,11‐dihydrospiro[[1]benzopyrano[4,3‐b]indo1‐6,9′‐9′H‐xanthene]‐2′,6′‐diamines and their respective aza analogues. These compounds develop a black colour in acidic media. The assumed structures of the analytically pure starting and final products are consistant with the fragmentations in the MS and are also supported by FT 1H‐NMR. The UV/VIS spectra in buffered MeOH/H2O solutions were measured. From the ϵpH* curves, we determined the pK* values. The title compounds can be used in so‐called pressure‐sensitive copying systems.
Synthesis of the Enantiomerically Enriched Macrocyclic Lactones (+)‐(S)‐ and (−)‐(R)‐Phoracantholide I and (+)‐(S)‐Tetradecan‐13‐olide
Authors: Stanchev Stephan , Hesse Manfred
Published: December 2004

Synthesis of two naturally occurring macrocyclic lactones is described. (−)‐(R)‐Phoracantholide I ((−)‐1; Scheme 2) was synthesized by asymmetric and chemoselective reduction of the side‐chain CO group of (−)4‐(1‐nitro‐2‐oxocyclohexyl)butan‐2‐one ((−)‐6) with (R)‐Alpine‐Hydride (47% ee). It was shown that the formation of only one diastereoisomer of the hemiacetal 5, by methylation with (i‐PrO)2TiMe2 of ketoaldehyde (−)‐2 is thermodynamically controlled. (+)‐(S)‐Tetradecan‐13‐olide ((+)‐10) was obtained by reduction of diketone (±)‐11 with optically active borohydrides followed by denitration (Scheme 3).
Dipolare (1:1)‐Addukte aus der Reaktion von 3‐Amino‐2H‐azirinen mit 1,3,4‐Oxadiazol‐ und 1,3,4‐Thiadiazol‐2(3H)‐onen
Authors: Ametamey Simon M. , Vincent Beverly R. , Heimgartner Heinz
Published: December 2004

Dipolar 1:1 Adducts from the Reaction of 3‐Amino‐2H‐azirines with 1,3,4‐Oxadiazol‐ and 1,3,4‐Thiadiazol‐2(3H)‐ones

3‐Amino‐2H‐azirines 1 react with 5‐(trifluoromethyl)‐1,3,4‐oxadiazol‐2(3H)‐one (2) as well as with different 5‐substituted 1,3,4‐thiadiazol‐2(3H)‐ones (5a–e) in 2‐propanol at room temperature to give dipolar 1:1 adducts of type 3 and 6, respectively, in reasonable‐to‐good yields (Schemes 3 and 6, Tab. 1 and 2). The structure of two of these dipolar adducts, 6a and 6e, which are formally donor‐acceptor‐stabilized azomethin imines, have been elucidated by X‐ray crystallography (Figs. 1‐4). In the reaction of 2 and sterically crowded 3‐amino‐2H‐azirines 1c–e with a 2‐propyl and 2‐propenyl substituent, respectively, at C(2), a 4,5‐dihydro‐1,2,4‐triazin‐3(2H)‐one of type 4 is formed as minor product (Scheme 3 and Table 1). Independent syntheses of these products proved the structure of 4. Several reaction mechanisms for the formation of compounds 3 and 4 are discussed, the most likely ones are described in Scheme 4: reaction of 2 as an NH‐acidic compound leads, via a bicyclic zwitterion of type A, to 3 as well as to 4. In the latter reaction, a ring‐expanded intermediate B is most probable.
Boscialin and Boscialin 4′‐O‐Glucoside, Two New Compounds Isolated from the Leaves of Boscia salicifolia OLIV
Authors: Pauli Niklaus , Séquin Urs , Walter Angelika
Published: December 2004

Boscialin (1), a new compound structurally related to the ionones and abscisic acid, and its 4′‐O‐glucoside 2 were isolated from the MeOH extract of the leaves of the African medicinal plant Boscia salicifolia. The structures of the two compounds were determined mainly by NMR spectroscopy and by acid hydrolysis of the glycoside.
Conformation Analysis of the 8‐Membered Ring of 12H‐Dibenzo [d, g] [1, 3, 2] dioxathiocines: Symmetric and Asymmetric Conformations
Authors: Hug P. , Kolly Sandra , Meier Hansrudolf , Pitteloud Rita , Poppinger Dieter , Rihs Grety , Rist Günther
Published: December 2004

The 12H‐dibenzo [d, g] dioxathiocines 2 and 4 are prepared by condensation of the corresponding bis[phenols] 1 and 3 with SOCl2 and SCl2, respectively. X‐Ray analysis reveals the presence of the boat‐chair (BC) form as the only conformer in the solid state of the cyclic thiodioxy derivative 4a, whereas the sulfinyldioxy compound 2a exists in the asymmetric axial boat (B) form, i. e. with endo (axial) orientation of the exocyclic O‐atom. Conformational analysis using 1H‐NMR spectroscopy indicates the presence of a boat form for compounds 2, whereas compounds 4 again exist in the boat chair form. A comparison of 1H‐NMR and thermodynamic parameters with those of the cyclic sulfinyldioxy compound 5 with an equilibrium between e‐BC and a‐BC form (i.e. BC form with equatorial and axial orientation of the exocyclic O‐atom) is made.
Acid‐Promoted Rearrangements of N‐Substituted 8‐Oxa‐3‐azatricyclo[3.2.1.02′4] octane‐6,7‐dicarboxylates: Remote Substituent Effects on the Regioselectivity of the N‐Acylaziridine/Dihydrooxazone Rearrangement
Authors: Allemann Susy , Reymond Jean‐Louis , Vogel Pierre
Published: December 2004

Preparations of dimethyl (1RS,2SR,4RS,5SR,6SR,7RS)‐ and dimethyl (1 RS,2SR,4RS,5SR,6RS,7SR)‐8‐oxa‐3‐azatricyclo[3;2.1.024] octane‐6,7‐dicarboxylate 15 and18, resp.) and of their N‐(tert‐butyloxy)carbonyl (14, 17) and V‐benzoyl (16, 19) derivatives are described. While treatment with nucleophilic acids (HCl, HBr. AcOH) of the exo, exo‐diesters 14 and 16 gave the corresponding products 23–27 of aziridine trans ‐addition, the exo, endo ‐diesters 17 and 19 led to the corresponding amino‐lactones 63 (methyl (1RS,2RS,3SR,6RS,7SR,9RS)‐2‐{[(tert‐butyloxy)carbonyl] amino}‐5‐oxo‐4,8‐dioxatricyclo[4.2.1.0 37] nonane‐9‐carboxylate) and 64 (methyl (1RS,2RS,3SR,6RS,7SR,9SR)‐2‐(benzoylamino)‐5‐oxo‐4,8‐dioxatricyclo[4.2.1.0 3′7] (nonane‐9‐carboxylate). Under non‐nucleophilic acidic conditions, the N‐benzoylaziridine 16 was rearranged quantitatively into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)‐4‐phenyl‐5,10‐dioxa‐3‐azatricyclo[4.3.1.02′7] dec‐3‐ene‐8,9‐dicarboxylate(31), and 19 into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)‐4‐phenyl‐3,10‐dioxa‐5‐azatricyclo [5.2.1.02′6] dec‐4‐ene‐8,9‐di‐carboxylate (65). Possible mechanisms of these highly selective reactions and rearrangements are discussed.
Cationic Palladium(II), Platinum(II), and Rhodium(I) Complexes as Acetalisation Catalysts
Authors: Gorla Fabrizio , Venanzi Luigi M.
Published: December 2004

The 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 D8Si8O12

Deuterium 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

Alkylation 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

Novel 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

The 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

The 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

The 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‐methylpropanoate

The 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 Tetrafluoroborates

The 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

Base 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

The 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

Natural 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

A 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‐carotene

Mukayama'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

The 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

The 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

The 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

Carbonyl(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

1H‐ 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

Several 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

Racemic 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

Reactions 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

The 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

Naturally 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

Nucleophilic 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

Thermolysis 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

Long‐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

N‐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.