bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amide‐Bond Syntheses Catalyzed by Penicillin Acylase
Authors: Pessina Antonio , Lüthi Peter , Luisi Pier Luigi , Prenosil Jiri , Zhang You‐Shang 
Published: December 2004

AbstractThe enzymatic synthesis of amide bonds catalyzed by penicillin acylase is investigated both in H2O solution and in organic solvents containing reverse micelles. The specificity of the reaction is rather high on the side of the acyl component, practically only phenylacetic acid gives sizeable yields. On the contrary, a variety of amino‐acid esters, dipeptides, and tripeptides can be used as amino component, e.g., serine methyl ester, methionine ethyl ester, tyrosine ethyl ester, Gly–Asp, Ala–Tyr, Gly–Tyr–Gly etc. However, Many other amino‐acid residues do not react, and the possible reasons for this are discussed. Yields varyin rang the 10–80%. A. systematic study to optimize yields by varying the solvent composition is presented for one model reaction. The enzyme is also able to couple certain D‐amino‐acid residues (e.g. D‐methionine ethyl ester or Gly‐D‐Asp) though at lower rate. Reverse micelles formed by the cationic surfactant cetyltrimethylammonium bromide (CTAB) in CHCl3/isooctane are used to host penicillin acylase and to perform amide synthesis in which the product is perferentially soluble in the organic solvent mixture. The reaction is studied as a function of pH and certain micellar parameters, e. g. wo (wo = [H2O]/[CTAB]). A new membrane enzyme reactor is utilized to separate the product from the enzyme‐containing micelles. The adavantges and the limits of this approach are discussed.
Mécanisme de solvolyse des cis‐ et trans‐(p‐toluènesulfonates) d'aryl‐2‐cyclopentyle I. Etude de la première étape de la solvolyse: effets isotopiques de l' atone de deutérium en position 2, effets de sel basique et effet spécial de sel
Authors: Ronco G. , Petit J.‐P. , Guyon R. , Villa P. 
Published: December 2004

Solvolysis Mechanism of cis ‐ and trans‐2‐Arylcylopentyl p‐Toluenesulfonates. The Step: 1‐Deuterium Isotope Effects, Basic Salt Effects, and Special Salt EffectWe have studied the first step of the solvolysis of cis and trans‐2‐arylcyclopentyl p‐toluenesulfonates in HCOOH, AcOH, and EtOh. All substrates show a high kinetic 1‐deuterium isotope effect (kH/kD(1) >1.15). This fact indicates that first step leads to classical intimate ion‐pair Which dissociates to a solvet‐separated ion‐pair, without participation either of solvent, the 2‐aryl group, or a H‐atom at C(2). The slight influence of added basic ions on reaction rate allows us to exclude any direct solvent attack on the covalent substrate even in the most favorable case, i.e. ethanolysis of 2‐(p‐nitrophenyl)cylopentyl‐p‐toluenesulfonates. Furthermore, solvent‐separated ion pair formation is indicated by the special salt effect induced by LiClO4.
Mécanisme de solvolyse des cis‐ et trans‐(p‐toluénesulfonates) d' aryl‐2‐cyclopentyle III. Etude des étapes ultérieures à I'ionisation lors de lasolvolyse du trans‐ (p‐toluènesulfonate) de phényl‐2‐cyclopentyle
Authors: Ronco G. , Guyon R. , Villa P. 
Published: December 2004

Solvolysis Mechanism of cis‐and trans‐2‐Arylcycyclopentyl p‐ Toluenesulfonate. Subsequent Steps in trans‐2‐Phenylcyclopenthyl p‐Toluenesulfonate SolvolysisThe solvolysis of the 1‐deuteriated, 2‐deuteriated, and undeuteriated trans‐2‐phenylcyclopentyl p‐toluenesulfonate in HCOOH, AcOH, and EtOH has studied. We have shown that the classical secondary carbocation arising from substrate ionisation undergoes three concurent processes, namely kc (direct product formation),kip (hydrogenium bridged ion formation as tertiary carbocation or products precursor) and kΔph (phenonium‐ion formation as retained product precursor.) The kΔph process contribution increases with solvent ionising power. The kinetic iotope effect of DC(1) show, that the steps following ionisation have a preponderant effect on the total solvolysis rate.
Photophysical Properties and Photochemical Behaviour of Ruthenium(II) complexes containing the 2,2′‐bipyridine and 4,4′‐diphenyl‐2,2′‐bipyridine ligands
Authors: De Cola Luisa , Barigelletti Franceso , Cook Michael J. 
Published: December 2004

AbstractThe temperature dependence of the emission lifetime of the series of complexes Ru(bpy)n(4,4′‐dpb) (bpy = 2,2′bipyridine, 4,4′‐dpb = 4,4′‐diphenyl‐2,2′‐bipyridine) has been studied in propionitrile/butyronitrile (4:5 v/v) solutions in the range 90–293 K. The obtained photophysical parameters show that the energy separation between the metal‐to‐ligand charge tranfer (3MLCT) emitting level and the photoreactive metal‐centered (3MC) level changes across the series (ΔE = 3960, 4100, 4300, and 4700 cm−1 for Ru(bpy)), Ru(bpy)2(4,4′‐dpb)2+, Ru(bpy)(4,4′‐dpb), and Ru(4,4′‐dpb), respectively, where ΔE is the energy separation between the minimum of the 3MLCT potential curve and 3MLCT – 3MC crossing point. Comparison between spectral and electrochemical data indicated that the changes in ΔE are due to stabilization of the MLCT levels in complexes containing 4,4′‐dpb with respect to Ru(bpy)2+3. The photochemical data for the same complexes (as I− salts) have been obtained in CH2Cl2 in the presence of 0.01M Cl− upon irradiation at 462 nm. The complexes containing 4,4′‐dpb are more photostable than Ru(bpy). Comparison between the data for thermal population of the 3MC photoreactive state and those for photochemistry indicated that the overall photochemical process is governed by (i) a thermal redistribution between the emitting and photoreactive excited states, and (ii) mechanistic factors, likely related to the size of the detaching ligand.
8‐Aza‐7‐deaza‐2′,3′‐dideoxyguanosine: Deoxygenation of its 2′deoxy‐β‐D‐ribofuranoside
Authors: Seela Frank , Driller Hansjüegen 
Published: December 2004

AbstractThe synthesis of 6‐amino‐1‐(2′,3′‐dideoxy‐β‐D‐glycero‐pentofuranosyl)‐1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one ( =8‐aza‐7‐deaza‐2′,3′‐dideoxyguanosine; 1) from its 2′‐deoxyribofuranoside 5a by a five‐step deoxygenation route is described. The precursor of 5a, 3a, was prepared by solid‐liquid phase‐transfer glyscosylation which gave higher yields (57%) than the liquid‐liquid method. Ammonoloysis of 3b furnished the diamino nucleoside 3c. Compound 1 was less acid sensitive at the N‐glycosydic bond than 2′,3′‐dideoxyguanosine (2).
A novel rearrangement of 2(5H)‐furanones
Authors: Mack Robert A. , DeCory Thomas R. , Georgiev Vassil St. 
Published: December 2004

AbstractA novel rearrangement of 2(5H)‐furanones is described. When refluxed in aq. Ethanolic solution in the presence of excess KOH, the 2,5‐dihydro‐2‐oxofuran‐3‐carboxamides 6 underwent a novel rearrangement to the corresponding 4,5‐dihydro‐4‐oxo‐2‐(phenylamino)‐3‐furancarboxylic acids 1 in moderate‐to‐excellent yields.
Preparation of 3‐Oxo‐ and 3‐Ethylideneazetidine Derivatives
Authors: Bauman Hans , Duthaler Rudolf O. 
Published: December 2004

AbstractThe preparation of 3‐azetidinones with different N‐substituents and their transformation to 3‐ethylideneazetidines has been studied in relation with a projected synthesis of 3‐ethylideneazetidine‐2‐carboxylic acid (= polyoximic acid; 1). The stable crystalline 3‐azetidinone hydrochloride (18), obtained by hydrogenolysis of the known 1‐(diphenylmethyl)‐3‐azetidenone (4), is described for the first time, From this key intermediate, 3‐oxoazetidine‐derived amides, exemplified by benzamide 12,urethanes (e.g. 17), and ureas (e.g. 20) can be prepared in good yield (Scheme 3). The olefination of 3‐azetidinones with alkylidene(triphenyl)phosphoranes is a perparatively useful process only for derivatives with a pyramidal N‐atom, e.g. the diphenylmethyl derivative 4, and not for the amide 12 or the urethane 17 (Scheme 4). 3‐Alkylidene‐azetidines with an amide N‐atom should, therefore, be prepared by exchange of the N‐substituent after the introduction of the double bond.
4,10a‐(Epidithio)‐4,4a,10,10a‐tetrahydro‐1H‐5‐oxaanthracen‐1‐ones, tetracycles with a novel heterocyclic ring system
Authors: Kolly Sandra , Meier Hansrudolf , Rihs Grety , Winkler Tammo 
Published: December 2004

AbstractThe 4,4′,6,6′‐tetrasubstituted 2,2′‐alkylidene‐bisphenols 1 reacted with sulfur monochloride to give 4,10a‐(epidithio)‐4,4a,10,10a‐tetrahydro‐1H‐5‐oxaanthracen‐1‐ones (3 and 4). The structure of the products were elucidated by a combination of X‐ray crystal‐structure analysis and 1H‐ and 13C‐NMR spectroscopy.
The Reversible Proxibarbal‐Valofan Isomerisation. Part I. Kinetic and thermodynamic studies in aqueous solutions
Authors: Wittekind H. Harald , Testa Bernard , Estreicher Jurek 
Published: December 2004

AbstractThe tautomerisation between proxibarbal (I) and the two diastereoisomers of valofan, IIX and IIY, was investigated in aqueous solutions, and various rate and equilibrium caonstants were calculated by compartmental analysis. The proportion of I at equilibrium was found to increase with pH, and indeed, the two equilibrium constants are linear functions of pH. In contrast, the equilibrium‐concentratio ratio of IIY/IIX was close to 63:37 and remained constant in the pH range investigated. The rate constants were also determined as a function of temperature, allowing calculation of the tehrmolynamic parameters. Under physiological conditions, the difference in free energy favouring I vs. IIX and IIY is 6.7 and 5.4KJ · mol−1, respectively.
Syntheses and tandem Diels‐Alder reactivities of 7,7‐diphenyl‐[2.2.1]hericene (= 7‐(diphenylmethylidene)‐2,3,5,6‐ tetramethylidenebicyclo[2.2.1]heptane) and 7‐oxa[2.2.1]hericene ( = 2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptan‐7‐one)
Authors: Rubello Albino , Vogel Pierre 
Published: December 2004

AbstractSyntheses of 7,7‐diphenyl[2.2.1]hericene (4) and 7‐oxa[2.2.1]hericene (5) are presented. Rate constants k1 and k2 of the two successive Diels‐Alder additions of ethylenetetracarbonitrile (TCE) to 4 and to 5 have been evaluated. At 25° in toluene, the rate‐constant ratio k1/k2 = 260 and 21 for 4 and 5, respectively. These results are compared with those reported for the tandem Diels‐Alder reactivity of 2,3,5,6‐tetramethylidenebicyclo[2.2.1]heptane and other derivatives.
The Reaction of 3‐(Dimethylamino)‐2H‐azirines with 2,3‐Pyridinedicarboximide
Authors: Obrech Jean‐Pierre , Schönholzer Peter , Jenny Christain Johannes , Prewo Roland , Heimgartner Heinz 
Published: December 2004

AbstractReaction of 2,2‐dialkyl‐3‐(dimethylamino)‐2H‐azirines 1a and 1b with 2,3‐pyridinedicarboximide (4) in MeCN or DMF at room temperature yielded two regioisomeric tricyclic 1:1 adducts, the azacyclols 11/12 and 16/17, respectively (Schemes 3 and 4). The structure of 12 was established by X‐ray crystallography. Methanolysis of 11/12 and 16/17 led to mixtures of methyl [4, 4‐dialkyl‐5‐(dimethylamino)‐4H‐imidazol‐2‐yl] pyridine carboxylates 13/14 and 18/19, respectively. The structure of compound 14 is closely related to that of the powerful herbicide 9 (Scheme 9), i.e. the described reactions offer a new synthetic approach to this class of compounds. A mechanistic interpretation for the formation of regioisomeric 1:1 adducts as well as methyl (imidazol‐2‐yl) pyridine carboxylates is depicted in Scheme 5.
A Synthesis of 1D‐ and 1L‐myo‐Inositol 1,3,4,5,‐Tetraphosphate
Authors: Baudin Gisèle , Glänzer Brigitte I. , Swaminathan Kivalur S. , Vasella Andrea 
Published: December 2004

AbstractA synthesis of 1D‐ and 1L‐myo‐inositol 1,3,4,5,‐tetraphosphate (1a and 1b resp.) is described. The dibenzylated myo‐inositola 9a and 9b, which, by phosphorylation, gave 1a and 1b, respectively, were prepared via two routes. On the one hand, the racemate 3a/3b, obtained from myo‐inositol, was resolved by its transformation into the diastereoisomeric carbamates 5a and 5b. Benzylation and deprotecton of 5a and 5b gave the enantiomers 9a and 9b, respectively. On the other hand, treatment of the diester 18 with pig liver esterase gave the ester 21a with high enantiomeric excess. Benzylation and deprotection of 21a yielded 9b. The dibenzyl derivative 9a was obtained using the same enzymatic hydrolysis followed by a protection‐deprotection sequence.
Intramolecular Dynamics of Five‐coordinate iron Carbonyl Complexes with olefinic ligands as studied by variable‐pressure 1H‐NMR spectroscopy
Authors: Ioset Jacques , Helm Lothar , Merbach André , Roulet Raymond , Grepioni Fabrizia , Braga Dario 
Published: December 2004

AbstractVariable‐pressure 1H‐NMR Spectroscopy has been used to study the fluxionality of some five‐coordinated Fe complexes in solution. For [Fe(CO)2 1,3‐cyclooctadiene (PPh3)], the CO site exchange is known (by analogy with [Fe(CO)3(1,3‐cyclooctadiene)]) to be a non‐dissociative process, and an activation volume of ca. 0 cm3.mol−1 was indeed obtained. However, for [Fe(CO2){2,3‐η:O‐σ‐(7,7‐dimethoxybicyclo[2.2.1]hept‐2‐ene)}(PPh3)], the activation volume of +5 cm3 mol−1 suggests that an unprecedented dissociation process is responsible for the CO site exchange. The molecular structure of [Fe(CO)2(1,3‐cyclooctadiene)(PPh3)] was ascertained by single‐crystal X‐ray diffractometry. The crystals are triclinic, space group P1, a = 9.606(3), b = 16.795(2), c = 7.743(8) Å, α = 97.83(4), β = 109.63(4), γ = 83.37(2)°. The structure determination has shown that the complex possesses a tetragonal pyramidal coordination, with the endocyclic CC bond and PPh3 occupying basal sites.
Semicorrin Metal Complexes as Enantioselective Catalysts. Part 1. Synthesis of chiral semicorrin ligands and general concepts
Authors: Fritschi Hugo , Leutenegger Urs , Siegmann Konstantin , Pfaltz Andreas , Keller Walter , Kratky Christoph 
Published: December 2004

AbstractAn efficient synthesis of chiral semicorrin ligands is described (see 6–9, Schemes 2 and 3). Both enantiomers are readily obtained in enantiomerically pure form starting either from D‐or L‐pyroglutamic acid (1). Semicorrins of this type possess several features that make them attractive ligands for enantioselective control of metal‐catalyzed reactions. Their structure is characterized by C2 symmetry, a conformationally rigid ligand system, and two stereogenic centers adjacent to the coordination sphere. In a metal complex, the two substituents at the stereogenic centers shield the metal atom from two opposite directions and, therefore, are expected to have a pronounced effect on the stereochemical course of a reaction occurring in the coordination sphere. The structure of these two substituents can be easily modified in a variety of ways. A series of (semicorrinato)copper(II) complexes (see 10–14, Scheme 4) has been prepared, and in one case (14), the three‐dimensional structure has been determined by X‐ray analysis (Fig. 1).
Semicorrin metal complexes as enantioselective catalysts. Part 2. Enantioselective cyclopropane formation from olefins with diazo compounds catalyzed by chiral (semicorrinato)copper complexes
Authors: Fritschi Hugo , Leutenegger Urs , Pfaltz Andreas 
Published: December 2004

AbstractCopper complexes of chiral, C2‐symmetric semicorrin ligands were found to be efficient catalysts for the cyclopropane formation from olefins with diazo compounds. In the presence of 1 mode‐% of catalyst, alkyl diazoacetates reacted smoothly with terminal olefins such as styrene, butadiene, and 1‐heptene to give the corresponding optically active cyclopropanecarboxylic‐acid derivatives (Table 1 Scheme 2). With one of the catalysts, enantioselectivities up to 97% ee were obtained (Table 2). Usually, the reactions were carried out using bis(semicorrinato)copper(II) complexes as precatalysts. In order to produce active catalysts, these complexes had to be activated first by heating in the presence of diazoacetate or by treatment with phenylhydrazine. Experiments with (semicorrinato)copper(I) complexes, prepared in situ from copper(I) tert‐butoxide (Scheme 4), suggest that the actual catalyst is a [mono(semicorrinato)]copper(I).
Photoinduced Double Addition of Acetylene to 3‐Oxocyclopent‐1‐ene‐1‐carbonitrile or 3‐oxocyclopent‐1‐enyl acetate leading to 2,3‐dihydro‐1H‐inden‐1‐one and other rearranged products
Authors: Cavazza Marino , Guella Graziano , Pietra Francesco 
Published: December 2004

AbstractUV Irradiation of 3‐oxocyclopent‐1‐enyl acetate (17) and acetylene in MeCN at 0° gives, besides the product of normal enone‐alkyne [2 + 2] cycloaddition (cis‐4‐oxobicyclo[3.2.0] hept‐6‐en‐1‐yl acetate, 18) and its product of oxa‐di‐π‐methane rearrangement (5‐oxotricyclo[4.1.0.02,7]hept‐2‐yl acetate, 19), unexpected products of further addition of a molar equivalent of acetylene. These are indanone ( = 2,3‐dihydro‐1H‐inden‐1‐one, 16), in 21% yield, cis‐1‐cisoid‐1,2‐cis‐2‐ (20) and cis‐1‐transoid‐1,2‐cis‐2‐7‐oxotricyclo[4.3.0.02,5]non‐3‐en‐1‐yl acetate (21), 4‐oxo‐7‐‘exo’‐vinyltricyclo[3.2.0.02,6]hept‐2‐yl acetate (22), cis‐4‐oxo‐6‐‘endo’‐ (23) and cis‐4‐oxo‐6‐‘exo’‐vinylbicyclo[3.2.0]hept‐1‐yl acetate (24), and cis‐4‐oxo‐7‐‘exo’‐vinylbicyclo[3.2.0]hept‐1‐yl acetate (25). At least in part, indanone must be formed via intermediates 20 and 21. In fact, on heating a 9:1 mixture 20/21, indanone is obtained quantitatively. With 3‐oxocyclopent‐1‐ene‐1‐carbonitrile (15) in place of 17, indanone is formed in lower (8%) yield besides much tars.
Studies on Antifungal Agents. Part 25. 1‐[(3,5‐Bisaryl‐2‐methylisoxazolidin‐3‐yl)methyl]‐1H‐1,2,4‐triazoles
Authors: Bennett Grace A. , Swift Patricia A. , Mullen George B. , Mitchell Jeffrey T. , Allen Stanley D. , Jones Wendy E. , Kinsolving C. Richard , St. Georgiev Vassil 
Published: December 2004

AbstractThe synthesis and antifungal activity of a novel series of 1‐[(3,5‐bisaryl‐2‐methylisoxazolidin‐3‐yl)methyl]‐1H‐1,2,4‐triazoles 6 and 7 (i.e. 8–19) are discussed. The preparation of 8–19 was straightforward and highlighted by a regiospecific 1,3‐dipolar cycloaddition of α‐substituted (E)‐ketonitrones 4 with appropriate atyrene derivatives 5 that led to a cis/trans‐diastereoisomeric mixture of the corresponding triazoles (Scheme). The title compounds were evaluated for in vitro antifungal activity in solid agar cultures against a broad array of yeast and systemic mycoses and dermatophytes. The in vivo activity was determined in an immune‐compromised mouse model of systemic candidiasis. While the in vitro activity was evident throughout the series, it was moderate in potency. However, some of the triazole derivatives demonstrated a potent in vivo activity comparable to that of the standard drug ketoconazole. Analogue 12 (PR 988‐399) emerged as the best overall compound demonstrating potent antifungal activity in both in vitro and in vivo assays.
The Radical Anions of N,N′‐Dicyanoquinone Diimines, a New Class of Electron Acceptors
Authors: Gerson Fabian , Gescheidt Georg , Möckel Reinhart , Aumüller Alexander , Erk Peter , Hünig Siegfried 
Published: December 2004

AbstractThe radical anions of 12 N,N′‐dicyanoquinone diimines, a new class of electron acceptors, hace been characterized by their hyperfine data with the use of ESR and ENDOR spectroscopy. The largest coupling constant (0.30–0.45 mT), due to the two 14N nuclei in the exocyclic positions, gives rise to a conspicuous broadening of the peripheral ESR lines by an incomplete averaging of the hyperfine anisotropy. The most plausible interpretation of the experimental results for the radical anions of N,N′‐dicyano‐ 1,4‐benzoquinone diimine (1) and N,N′‐Dicyano‐9,10‐anthraquinone diimine (9) is in terms of both ‘syn’‐ and ‘anti’‐configurations contributing to the ESR and ENDOR spectra and having equal proton‐ and 14N‐coupling constants. The π‐spin distribution in the radical anions of N,N′‐dicyanoquinone diimines is compared with those in the analogous ions of tetracyanoquinodimethanes and quinones.
Eine neue Synthese von Muscon und Exalton®. Die Enamin‐Route der Ringerweiterungsreaktion
Authors: Bienz Stefan , Hesse Manfred 
Published: December 2004

A New Synthesis of Muscone and Exaltone®. The Enamine Approach of Ring‐Enlargement ReactionKey reaction in the synthesis of the title compounds is the treatment of the aldehydes 6 and 7 (obtained from 1) with a primary amine, e.g. pentylamine, in EtOH at room temperature. After stirring overnight, the products 8 and 9, respectively, are obtained in good yields. Both are enlargement by three ring members and can be transformed to Exalton® (12) and (±)‐muscone, (13), respectively.
Thioalkylation of Meldrum's Acid: Protected alkylidene derivatives of isopropylidene malonate
Authors: Eberle Martin , Lawton Richard G. 
Published: December 2004

AbstractThioalkylated Meldrum's acid is easily by treatment of Meldrum's acid with an aldehyde and thiophenol in the presence of catalytical amounts of piperidinium acetate (→1–6, Table 1). The adducts 1–6 are crystalline, stable compounds and they can be caused to react directly with nucleophiles and dienes (see 3→7–12, Scheme 1). The regeneration of the parent olefin is effected thereby by simply dissolving the adduct under neutral or basic conditions. Extension of this method to thiocarboxylic acids allowed the preparation of the corresponding formaldehyde derivatives 13 and 15 (Table 3).
Synthesen von enantiomerenreinen Apoviolaxanthin‐säuren, ‐olen und ‐alen (Persicaxanthin, Sinensiaxanthin und β‐Citraurin‐epoxid) und ihrer furanoiden Umlagerungsprodukte
Authors: Uebelhart Peter , Eugster Conrad Hans 
Published: December 2004

Synthesis of Enantiomerically Pure Apoviolaxanthinoic Acids, Apoviolaxanthinols, and Apoviolaxanthinals (Including Persicaxanthin, Sinensiaxanthin, and β‐Citraurin Epoxide) and of their Furanoid Rearrangement ProductsStarting from (1′S,2′R,4′S,2E,4E)‐5‐(1′,2′‐epoxy‐4′‐hydroxy‐2′,6′,6′‐trimethylcyclohexy1)‐3‐methy1‐2,4‐pentadienal (3), a recently described synthon [6], a full range of C20‐, C25‐, C27‐, and C30‐polyenic acids, alcohols, and aldehydes and their (8R)‐ and (8S)‐diastereoisomeric furanoid rearrangement products was prepared. The synthetic C25‐alcohols proved to be identical with persicaxanthin (= 12′‐apoviolaxanthin‐12′‐ol) and perisicachromes (= 12′‐apoauroxanthin‐12′‐ols) and the C27‐alcohols analogously with sinensiaxanthin and sinensiachromes. A correlation between the sign of the Cotton effects in the CD spectra of 5,6‐and 5,8‐epoxides and their configuration at C(6) and C(8), respectively, was established.
Anwendungsbreite der reduktiven Kupplung aromatischer Aldimin‐Derivate mit niedervalenten Titan‐Reagenzien zu 1,2‐Diarylethylendiaminen
Authors: Betschart Claudia , Schmidt Beat , Seebach Dieter 
Published: December 2004

Scope and Limitations of the Reductive Coupling of Aromatic Aldimine Derivatives with Formation of 1,2‐Diarylethylenediamine Units, Using Low‐Valent Titanium ReagentsBesides the adducts from lithium amides to aromatic aldehydes, iminium salts, animals, and N‐silylimines of aromatic aldehydes are coupled by the black suspension obtained from TiCL4 and Mg turnings in tetrahydrofuran (THF). The 1,2‐diarylethylenediamines with tertiary and primary amino groups thus obtained are formed with no or only moderate diastereoselectivity (products 4a–d (Scheme 2) and 5–e (Scheme 3), respectively); the amine component may contain a strained ring or additional heteroatoms as in azetidin, bis(2‐methoxyethyl)amine, piperazine, morpholine, and thiomorpholine (products 6a–e; Table 1). By an in‐situ procedure, ethylenediamines exclusively trans‐diaryl‐substituted piperazine and perhydro‐1,4‐diazepine derivatives (products 7a–f; Table 2). Enantiomerically pure monocyclic trans,cis‐5‐alkyl‐2,‐3‐diaryl‐piperazines and diazabicyclo[4.3.0]nonanes and ‐[4.4.0]decanes are obtained by employing suitable diamines prepared from the amino acids (S)‐alanine, (S)‐phenylalanine, (S)‐proline and from (S,S)‐ or (R,R)‐cyclohexane‐1,2‐diamine, respectively (products 11a–i, 7e; Table 4). The configuration of all products are derived from the high‐field NMR spectra, some of which are discussed in detail (Figs. 1 and 2, Tables 3 and 5); all new compounds are fully characterized by their physical data. Depending upon the structure of the components employed, the yields of purified products range from as low as 7% to essentially quantitative.