bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steroids and Sex Hormons. Part 263. [1]. On the Mechanism of the Reaction of 17‐Hydroxyimino‐steroids with Carbodiimide/Dimethylsulfoxide
Authors: Pfenninger Johannes , Graf Walter 
Published: December 2004

AbstractTreatment of the (Z)‐isomers 6 and 7 of the four isomeric 16‐acetoxy‐17‐hydroxyimino‐steroids 6–9 with DCC/DMSO/CF3COOH (Moffat fragmentation of oximes) yielded the seco‐α‐acetoxy‐nitriles 10 and 11, respectively, while similar treatment of both (E)‐isomers 8 and 9 gave the formyl‐carbonitrile 14. The mechanism of these fragmentations is discussed. 13C‐NMR. data of oximes are presented which show the γ‐gauche effect being associated with σ (CH)‐bond polarization.
A Norrish Type I cleavage in the photolysis of a steroidal α,β‐unsaturated δ‐lactone. Photochemical Reactions. XIV [1]
Authors: Cánovas Antonio , Bonet Juan‐Julio 
Published: December 2004

AbstractThe UV. irradiation of 17 β‐acetoxy‐4‐oxa‐5 α‐androst‐1‐en‐3‐one (1) yields A,B‐diseco‐steroids originating from a Norrish I process of the lactone function.
A structural investigation of the antibiotic rubiflavin. Preliminary communication
Authors: Nadig Heinz , Séquin Urs 
Published: December 2004

AbstractRubiflavin is shown to be a mixture of antibiotics. The main components have been named rubiflavin A (3) and rubiflavin B (2) and are identified by NMR. spectroscopy as desacetylpluramycin A and kidamycin, respectively.
Nucleoside und Nucleotide. Teil 15. Synthese von Desoxyribonucleosid‐monophosphaten und ‐triphosphaten mit 2(1H)‐Pyrimidinon, 2(1H)‐Pyridinon und 4‐Amino‐2(1H)‐pyridinon als Basen
Authors: Kohler Peter , Wachtl Michael , Tamm Christoph 
Published: December 2004

Nucleosides and Nucleotide. Part 15. Synthesis of Deoxyribonucleoside Monophosphates and Triphosphates with 2(1H)‐Pyrimidinone, 2(1H)‐Pyridinone and 4‐Amino‐2(1H)‐pyridinone as the BasesThe phosphorylation of the modified nucleosides 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐2(1 H)‐pyrimidinone (Md, 4), 4‐amino‐1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐2(1 H)‐pyridinone (Zd, 6) and the synthesis of 1–2′‐deoxy‐β‐D‐ribofuranosyl‐2(1 H)‐pyrimidinone‐5′‐O‐triphosphate (pppMd, 1), 1‐(2′‐deoxy‐β‐Dribofuranosyl)‐2(1 H)‐pyridinone‐5′‐O‐triphosphate (pppIId, 2), and 4‐amino‐1‐(2′‐deoxy‐βD‐ribofuranosyl)‐2(1 H)‐pyridinone‐5′‐O‐triphosphate (pppZd, 3) are described. The nucleoside‐5′‐monophosphates pMd (5) and pZd (7) were obtained by selective phosphorylation of Md (4) and Zd (6), respectively, using phosphorylchloride in triethyl phosphate or in acetonitril. The reaction of pMd (5) pII d (8) or pZd (7) with morpholine in the presence of DCC led to the phosphoric amides 9, 10 and 11, respectively, which were converted with tributylammonium pyrophosphate in dried dimethylsulfoxide to the nucleoside‐5′triphosphates 1, 2 and 3, respectively.
The Synthesis of an O‐2‐Isooxacephem
Authors: Hakimelahi Gholam Hosien , Just George , Ugolini Antonio 
Published: December 2004

AbstractThe synthesis of an iso‐oxacephem is described. Reaction of methanesulfonyl chloride with hydroxyaldylmalonates can form sulfones or sulfonates, their ratio varying with the basicity of the tertiary amine used in the sulfonation.
Structural Analysis of Eukovoside, A New Phenylpropanoid Glycoside from Euphrasia rostkoviana HAYNE
Authors: Sticher Otto , Salama Osama , Chaudhuri Ratan K. , Winkler Tammo 
Published: December 2004

AbstractThe isolation and structure determination of a phenylpropanoid glycoside from Euphrasia rostkoviana HAYNE, named eukovoside (1). are reported.
Chaetoglobosin L, a New Metabolite of Diplodia macrospora
Authors: Probst Alessandro , Tamm Christoph 
Published: December 2004

AbstractFrom cultures of Diplodia macrospora a new metabolite of the cytochalasan family, Chaetoglobosin L (3), has been isolated and its structure elucidated together with the known compounds diplosporin (1) and Chaetoglobosin K (2).
2′‐Deoxy‐β‐D‐ribofuranosides of N6‐Methylated 7‐Deazaadenine and 8‐Aza‐7‐deazaadenine: Solid‐phase synthesis of oligodeoxyribonucleotides and properties of self‐complementary duplexes
Authors: Seela Frank , Kaiser Klaus , Bindig Uwe 
Published: December 2004

AbstractThe syntheses of 7‐deaza‐N6‐methyladenine N9‐(2′‐deoxy‐β‐D‐ribofuranoside) (2) as well as of 8‐aza‐7‐deaza‐N6‐methyladenine N8− and N9−(2′‐deoxyribofuranosides) (3 and 4, resp.) are described. A 4,4′‐dimeth‐oxylritylation followed by phosphitylation yielded the methyl phosphoramidites 12–14. They were employed together with the phosphoramidite of 2′‐deoxy‐N6v‐methyladenosine (15) in automated solid‐phase oligonucleotide synthesis. Alternating or palindromic oligonucleotides derived from d(A‐T)6 or d(A‐T‐G‐C‐A‐G‐A*‐T‐C‐T‐G‐C‐A) but containing one methylated pyrrolo[2,3‐d]pyrimidine or pyrazolo[3,4‐d]pyrimidine moiety in place of a N6‐methylaminopurine (A*) were synthesized. Melting experiments showed that duplex destabilization induced by a N6‐Me group of 2′‐deoxy‐N6‐methyladenosine is reversed by incorporation of 8‐aza‐7‐deaza‐2′‐deoxy‐N6‐meihyladenosine, whereas 7‐deaza‐2′‐deoxy‐N6‐methyladenostne decreased the Tm value further. Regiospecific phosphodiester hydrolysis of d(A‐T‐G‐C‐A‐G‐m6A‐T‐C‐T‐G1‐C‐A) by the endodeoxyribonuclease Dpn I, yielding d(A‐T‐G‐C‐A‐G‐m6A) and d(pT‐C‐T‐G‐C‐A), was prevented when the residue c7m6Ad (2), c7m6z8Ad (3), or c7m6z8Ad′ (4) replaced m6Ad (1) indicating that N(7) of N6‐methyladenine is a proton‐acceptor site for the endodeoxyribonuclease.
Silicon‐Directed Regio‐ and Enantioselective Synthesis of α‐Hydroxy‐ketones Preliminary Communication
Authors: Lohray Braj B. , Enders Dieter 
Published: December 2004

Abstractα‐Silylated ketones (S)−2 (ee ≥ 98%), easily available through silylation or silylation/alkylation from ketones 1 using the (−)‐(S)‐1‐amino‐2‐(methoxymethyl)pyrrolidine (SAMP)−/(+)‐(R)‐1‐amino‐2‐(methoxymethyl)pyrrolidine (RAMP)‐hydrazone method, are oxidized to give α‐hydroxy‐ketones (R)−5 of high enantiomeric purity (ee ≥ 98%) and in good overall yields (51‐70%). The key step of the procedure is the silicon‐directed diastereoselective oxidation of the corresponding silyl enol ethers of (S)−2, with m‐chloroperbenzoic acid or 3‐phenyl‐2‐(phenylsulfonyl)oxaziridine, followed by flash chromatography and desilylation.
Synthèse du virensate de méthyle
Authors: Pulgarin César , Tabacchi Raffaele 
Published: December 2004

AbstractSynthesis of Methyl VirensateThe synthesis of methyl virensate (=methyl 4‐formyl‐3,8‐dihydroxy‐1,6,9‐trimethyl‐11‐oxo‐11H‐dibenzo‐[b, e][1,4]dioxepin‐7‐carboxylate; 18) by the condensation of the substituted β‐orcinol and orcinol units 9 and 10 followed by formylation and demethylation of the depsidone 13 is described.
The Infrared Multiphoton‐Dissociation Spectra of Bromopropene Isomeric Cations
Authors: Gäumann Tino , Riveros José M. , Zhu Zhiqing 
Published: December 2004

AbstractThe infrared quasi‐resonance stepwise‐multiphoton‐dissociation spectra of the molecular ions of 1‐bromo‐propene, 2‐bromopropene, 3‐bromopropene, and bromocyclopropane have been obtained at selected wavelengths between 9. 2 and 10. 7 μm in a Fourier ‐transform mass spectrometer. The resulting spectra and the photo fragmentation kinetics suggest that these molecular ions retain their identity upon ionization, and can, thus, provide fingerprint spectral identifications for the ions.
The chemistry of coumarin derivatives, part 2. Reaction of 4‐hydroxycoumarin with α,β‐unsaturated aldehydes
Authors: Appendino Giovanni , Cravotto Giancarlo , Tagliapietra Silvia , Nano Gian Mario , Palmisano Giovanni 
Published: December 2004

Abstract4‐Hydroxycoumarin (= 4‐hydroxy‐2H‐1‐benzopyran‐2‐one) reacts with enals to give 1,2‐ or 1,4‐addition products, depending on the nature and relative location of the substituents on the olefinic double bond (Scheme 2). The resulting adducts further react intra‐ or intermolecularly, affording dimeric coumarins or pyranocoumarins in the case of 1,2‐addition and acetalic pyranocoumarins in the case of 1,4‐addition. With enals bearing alkyl groups at C(β), 2H‐pyrano[3,2‐c]coumarins are the only products formed, and the reaction represents an easy and straightforward entry into this class of recently described biologically active natural products.
Configuration‐Odor Relationships in 5β‐Ambrox
Authors: Escher Sina , Giersch Wolfgang , Niclass Yvan , Bernardinelli Gérald , Ohloff Günther 
Published: December 2004

AbstractThe four possible A/B cis‐fused diastereoisomers of Ambrox® have been synthesized and their configurations and conformations established by X‐ray and NMR analysis. Only 5β‐ambrox (= 1,2,3a,4,5,5β,6,7,8,9,9a,9bα‐dodecahydro‐3aβ,6,6,9aβ‐tetramethylnaphtho[2,1‐b]furan; 5) has an odor quality comparable to Ambrox®. The 1,3‐synperiplanar/diaxial conformation of the substituents at C(8) ( = C(3a)) and C(10) (= C(9a)) has thus been confirmed to be a compulsory structure element for the particular odor.
Bicyclo[4.2.0]octa‐1,3,5‐triene: 2‐Mono‐ and 2,5‐Disubstituted Derivatives via Highly Regioselective Lithiation of Its Cr(CO)3 Complex and via Reductive Silylation/Oxidation
Authors: Kündig E. Peter , Ferret Celia , Rudolph Bruno 
Published: December 2004

AbstractTreatment of [η6‐(bicyclo[4.2.0]octa‐1,3–5 triene)]tricarbonylchromium(0) (2) with BuLi or lithium 2,2,6,6‐tetramethylpiperidinide (TMPLi) gives rise to a highly regioselective deprotonation at C(2). Subsequent reaction with electrophiles (6 examples) gives [η6‐(2‐R‐bicyclo[4.2.0]octa‐1,3,5‐triene)]tricarbonylchromiurn complexes 3 and 5–9 in moderate (RI, 50%; RCHO, 67%) to good (RMe, D, SiMe3, CO2Me, > 80%) yield (Scheme 1). Analogous reactions with tricarbonyl (η6‐indane)chromium (10) give mixtures of complexes substituted at C(4) and C(5) (Scheme 2). In 10, deprotonation β to the ring junction is strongly favoured with the bulky base TMPLi. Double lithiation/electrophile additions to 2 give access to [η6‐(2‐R′‐5‐R″‐bicyclo[4.2.0]octa‐1,3,5‐triene)]tri‐carbonylchromium complexes (e.g. 13 (R′R″Me3Si) and 14 (R′Me3Si, R″CHO)) as single products. The Cr(CO)3 group can be easily removed by oxidation (I2, Ce(IV), O2/light; 2 examples each) to give the free arenes. Base‐catalyzed (CsF, DMF/D2O) deuterodesilylation of 13 yields the [(2,5‐2H2)bicyclo[4.2.0]octa‐1,3,5‐triene]chromium complex 15, and treatment of 2,5‐bis(trimethylsilyl) compound 16 with CF3COOD gives the 2,4‐dideuterated 17. Compound 16 is also accessible more directly via reductive silylation/oxidation of bicyclo[4.2.0]octa‐1,3,5‐triene (1). Stereoselective base‐catalyzed (t‐BuOK.) H/D exchange of the benzylic H‐atoms. opposite to the Cr(CO)3 moiety in 2 takes place rapidly in (D6)DMSO, but benzylic functionalization via this route remains elusive.
Coenzyme F430 from Methanogenic Bacteria: Complete Assignment of Configuration Based on an X‐Ray Analysis of 12,13‐Diepi‐F430 Pentamethyl Ester and on NMR Spectroscopy
Authors: Färber Gerald , Keller Walter , Kratky Christoph , Jaun Berhard , Pfaltz Andreas , Spinner Christoh , Kobelt André , Eschenmoser Albert 
Published: December 2004

AbstractThe structure of a derivative of coenzyme F430 from methanogenic bacteria, the bromide salt of 12,13‐diepi‐F430 pentamethyl ester (5, X = Br), was determined by X‐ray structure analysis. It reveals a more pronounced saddle‐shaped out‐of‐plane deformation of the macrocycle than any hydroporphinoid Ni complex investigated so far. The crystal structure confirms the constitution proposed for coenzyme F430 (2) and shows that in the epimer 5, the three stereogenic centers in ring D, C(17), C(18), and C(19), have the (17S)‐, (18S)‐, and (19R)‐configuration, respectively. Deuteration and 2D‐NMR studies independently demonstrate that native coenzyme F430 (2) has the same configuration in ring D as the epimer 5. Therefore, our original tentative assignment of configuration at C(19) and C(18) [1] has to be reversed. This completes the assignment of configuration for all stereogenic centers in coenzyme F430, which has the structure shown in Formula 2.
Condensation of 2,3‐Di(methylidene)‐7‐oxabicyclo[2.2.1]heptane Derivatives into Dicarbonyl[η3:η3‐octa‐2,6‐diene‐1,8‐diyl]iron Complexes with Nonacarbonyldiiron. Crystal Structure of (1RS,2RS,3RS,4SR,5RS,6SR,1′RS,2′RS,3′RS,4′SR,5′RS,6′SR)‐Dicarbonyl‐{(2,3,C‐η:2′,3′,C‐η)‐2,2′‐ethylene‐5,5′,6,6′‐tetrakis[(methanesulfonyloxy)‐methyl]‐3,3′‐di(methylidene)‐bis[7‐oxabicyclo[2.2.1]hept‐2‐yl]}iron
Authors: Araki Shuki , Vogel Pierre , Blanc Eric , Chapuis Gervais , Schenk Kurt 
Published: December 2004

AbstractThe reactions of [Fe2(CO)9] with 2‐exo,3‐exo‐bis(chloromethyl)‐5,6‐di(methylidene)‐7‐oxabicycio[2.2.1]‐heptane (5) and with 5,6‐di(methylidene)‐7‐oxabicyclo[2.2.1]heptane‐2‐exo,3‐exo‐dimethyl bis(methanesulfonate) (6) afforded, together with the corresponding [exo‐Fe(CO)3(1,3‐diene)] complexes 7 and 8, the products of dimerization in the form of stable [Fe(CO)2{(1,2,3‐η:6,7,8‐η)‐octa‐2,6‐diene‐1,8‐diyl}] complexes 9 and 10, respectively, with high stereoselectivity. The structure of 10 was established by means of single‐crystal X‐ray diffraction.
Chiral Acylsilanes in Organic Synthesis. Diastereoselective 1,2‐Additions to Racemic Alkoxymethyl‐Substituted Acylsilanes
Authors: Bienz Stefan , Chapeaurouge Alexander 
Published: December 2004

AbstractThe synthesis of the three alkoxymethyl‐substituted acyisilanes 1–3 is described (Schemes 1 and 2). Their reactions with NaBH4 as well as PhLi gave the corresponding alcohols with moderate to good diastereoisomeric induction (up to 78% de; see Table), depending upon the solvent used (Scheme 3). The results indicate that in Et2O, the reactions with PhLi proceed via 6‐membered chelates (see C in Scheme 4) leading to the products with high de's (74–78%). In THF, these chelates are not formed, and as a consequence, the additions take place with reversed and lower stereoselectivities (34–50% de).
1,2‐Stereoinduction in Radical Reactions: Stereoselective Synthesis of 2‐Alkyl‐3‐hydroxybutanoates
Authors: Bulliard Michel , Zehnder Margareta , Giese Bernd 
Published: December 2004

AbstractRadical addition to 2‐cyclohexyl‐5‐methylidene‐6‐methyl‐1,3‐dioxan‐4‐one (2) affords stereoselectively 5,6‐trans‐products trans‐3. The size of the radical has no influence on the selectivity. These trans‐acetals are converted into threo‐3‐hydroxy‐butanoates 4. Methyl 2‐methylidene‐3‐[(tert‐butyl)diphenylsilyloxy]butanoate (5), treated under the same conditions, leads mainly to the erythro‐isomer of 4 after deprotection. An influence of the steric bulkyness of the radical is observed. The stereochemical course of the reactions is discussed.
Catalytic One‐Pot Osmylation of Cyclohexadienes: Stereochemical and conformational studies of the resulting polyols
Authors: Tschamber Théophile , Backenstrass Frédérique , Fritz Hans , Streith Jacques 
Published: December 2004

AbstractCatalytic double osmylation is described for a series of cyclohexadienes in acetone/H2O in the presence of the co‐oxidant N‐methylmorpholine N‐oxide (NMO). The formation of polyols occurred stereospecifically with cyclohexadienes 3,7, and 11a, leading thereby to tetrols 5a, and 9a and to allo‐inositol (14a), respectively. To the contrary, trans‐cyclohexadiene‐diol 15a gave a mixture of the stereoisomeric inositols 18a (epi), 19a (neo), and 20a (chiro). High‐field NMR let to clearcut conformational analyses of the polyhydroxylated derivatives.
Synthèse et propriétés photochromiques de 1, 3‐dihydrospiro[2H‐indole‐2,3′‐[3H]pyrimido[5,4‐f][1,4]benzoxazines] et de 1,3‐dihydrospiro[2H‐indole‐2,7′‐[7H]thiazolo[5,4‐f][1,4]benzoxazines]
Authors: Tardieu Pascale , Dubest Roger , Aubard Jean , Kellmann Arlette , Tfibel Francis , Samat André , Gugliemetti Robert 
Published: December 2004

Synthesis and Photochrmic Characteristics of 1,3‐Dihydrospiro[2H‐indole‐2,3′‐[3H‐]pyrimido[5,4‐f][1,4]benzoxazines] and 1,3‐Dihydrospiro[2H‐indole‐2,7′[7H]thiazolo[5,4‐f][1,4]benzoxazines]Two new series of 1,3‐dihydrospiro[2H‐indole‐ozazine] derivatives were synthesized, the 1,3‐dihydrospiro[2H‐indole‐2,3′‐[3H]pyrimido[5,4]pyrimido[5,4‐f][1,4]benzoxaines] 4‐10 and the 1,3‐dihydrospiro[2H‐indole2,7′‐[7H]thiazolo‐[5,4‐f][1,4]benzoxaines] 11–17. These series extend the available range of photochromic properties (rate constant of thermal bleaching, UV/VIS spectrum of the opened coloured form, and photocoloration yield), an interesting feature of variable‐transmission materials. The synthesis of these compounds (Scheme 1) required the preliminary synthesis of intermediate β‐hydroxy‐α‐nitrosotherocycles 18 and 19 (Scheme 2). Important amounts of a coloured, non‐photochromic, stable secondary product (See 20) were found in the condensation in the spiro[indole‐thiazolobenzoxazine] series. The photochromic characteristics of the new derivatives were determined using a flash‐photolysis apparatus coupled to a fast‐scanning spectrometer. The role of the heteroatoms in the oxazine moiety and the role of substitutents in the indole moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. The presence of an S‐atom gives rise to interesting properties which open up new prospects for synthesis and application.
Pterin Chemistry. Part 92.. Loading experiments with 6α,β‐tetrahydro‐L‐[3′‐2H1] biopterin
Authors: Adler Carmen , Curtius Hans‐Christoph , Wetzel Erich , Viscontini Max , Giudici Tullio A. , Blaskovics Milan , Rolland Marie O. , Guibaud Pierre 
Published: December 2004

Abstract6α,β‐Tetrahydro‐L‐[3′‐2H1]biopterin ([3′‐2H1]‐1) was administered orally to two primapterinuric patients in order to investigate the biosynthetic pathway of 7‐substituted pterins in humans. L‐Primapterin (2) and L‐biopterin were isolated from urine after loading and measured by GC/MS. L‐Biopterin and L‐primapterin were labelled with 2H to an equal extent. From this result, one can conclude that L‐primapterin is formed from tetrahydro‐L‐biopterin, very probably via an intramolecular rearrangement.
Nucleosides. Part L.. Structure of lumazine N1‐(2′‐deoxy‐D‐ribonucleosides) ( = 1‐(2′‐deoxy‐D‐ribofuranosyl)pteridine‐2,4(1H,3H)‐diones): A revision of the anomeric configuration
Authors: Cao Xiaodong , Pfleiderer Wolfgang , Rosemeyer Helmut , Seela Frank , Bannwarth Willi , Schönholzer Peter 
Published: December 2004

AbstractThe anomeric configuration of the glycosidic bond in lumazine N1‐(2′‐deoxy‐D‐ribonucleosides) 1–6 was investigated by NOE difference spectroscopy. The former configurational assignment of the α ‐ and β ‐D‐anomers 1 and 2, 3 and 4, and 5 and 6, respectively, has to be reversed to be in agreement with the physical data. Additional proof is presented by X‐ray analysis of 3 and 6. Chemical interconversions of 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐6,7‐diphenyllumazine (6) into 2,3′ ‐anhydrolumazine 2′‐deoxyribonucleosides 16 and 17 are also in agreement with the revised anomeric configuration.
Stereoselectivity in Reactions of Metal Complexes. Part XIV.. Use of circular dichroism to determine the stereoselective formation of [M(his)2] and [M(PhEt‐sal)2] (M = Ni2+, Cu2+, his = histidine, PhEt‐sal = N‐(1‐phenylethyl)salicylaldimine)
Authors: Bernauer Klaus , Bourqui Stephanie , Huti‐Cleary Deirdre , Warmuth Ruth 
Published: December 2004

AbstractThe stereoselective formation of the 1:2 complexes [M(his)2] and [M(PhEt‐sal)2] (M = Ni2+, Cu2+, PhEt‐sal = N‐(1‐phenylethyl)salicylaldimine) has been determined by circular dichroism (CD) measurements. Stereoselectivity, defined as S = Kmeso/2Krac' has been found to be 2.48 for [Ni(his)2], corresponding to a 21% excess of the mixed species relative to the statistical amount. This value is temperature‐independent between 15 and 35°. Whereas the absence of stereoselectivity in the formation of [Cu(prol)2] is confirmed, weak stereoselectivity is observed for [Cu(his)2] (2% excess of the mixed species). The CD intensity of the latter complex strongly depends on temperature and decreases by 12%, when the temperature is increased from 15 to 35°. Small but significant stereoselectivity is found for the formation of the Schiff‐base complexes [Ni(PhEt‐sal)2] and [Cu(PhEt‐sal)2] in acetone with 1.0% and 2.4% excess, respectively, of the mixed species over the statistical value.
Generation of ‘Bare’ FeF+ by CF Bond Activation in the Gas Phase and Evaluation of Thermochemical Data. Short communication
Authors: Schröder Detlef , Hrušák Jan , Schwarz Helmut 
Published: December 2004

AbstractThe title compound FeF+ has been generated in a Fourier‐transform ion‐cyclotron‐resonance mass spectrometer via CF bond activation by reacting hexafluorobenzene with bare FeO+. Bracketing experiments provide a bond‐dissociation energy (BDE) for FeF+ of 86 < BDE < 101 kcal/mol. High‐level CAS‐MCSCF pseudopotential ab initio calculation, including 501036 electronic configurations, predict a BDF(Fe+F) of 100.9 kcal/mol.
Ru‐Catalyzed Heptalene Formation from Azulenes and Dimethyl Acetylenedicarboxylate
Authors: Rippert Andreas Johannes , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that azulenes react with dimethyl acetylenedicarboxylate (ADM) in solvents such as toluene, dioxan, or MeCN in the presence of 2 mol‐% [RuH2(PPh3)4] already at temperatures as low as 100° and lead to the formation of the corresponding heptalene‐1,2‐dicarboxylates in excellent yields (Tables 1 and 2). The Ru‐catalyzed reaction of ADM with 1‐(tert‐butyl)‐4,6,8‐trimethylazulene (31) takes place even at room temperature, yielding the primary tricyclic addition product 32 and its thermal retro‐Diels‐Alder product dimethyl 4,6,8‐trimethylazulene‐1,2‐dicarboxylate (21; Scheme 4). At 100° in MeCN, 32 yields 90% of 21 and only 10% of the corresponding heptalene. These observations demonstrate that [RuH2(PPh3)4] catalyzes the first step of the thermal formation of heptalenes from azulenes and ADM which occurs in apolar solvents such as tetralin or decalin at temperatures > 180° (cf. Scheme 1).
Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate
Authors: Chen Yi , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that azulene (1) and dimethyl acetylenedicarboxylate (ADM) in a fourfold molar excess react at 200° in decalin to yield, beside the known heptalene‐ (5) and azulene‐1,2‐dicarboxylates (6), in an amount of 1.6% tetramethyl (1RS,2RS,5SR,8RS)‐tetracyclo[6.2.2.22,501,5]tetradeca‐3,6,9,11,13‐pentaene‐3,4,9,10‐tetracarboxylate(‘anti’‐7) as a result of a SHOMO (azulene)/LUMO(ADM)‐controlled addition of ADM to the seven‐membered ring of 1 followed by a Diels‐Alder reaction of the so formed tricyclic intermediate 16 (cf. Scheme 3) with a second molecule of ADM. The structure of ‘anti’‐7 was confirmed by an X‐ray diffraction analysis. Similarly, the thermal reaction of 5,7‐dimehtylazulene (3) with excess ADM in decalin at 120° led to the formation of ca. 1% of ‘anti’‐ 12, the 7,12‐dimethyl derivative of‘anti’‐7, beside of the corresponding heptalene‐ 10 and azulene‐1,2‐dicaboxylated (cf Scheme 2). The introduction of Me groups at C(1)and C(3)of azulene (1) and its 5,7‐dimethyl derivative 3 strongly enhance the thermal formation of the corresponding tetracyclic compound. Thus, 1,3‐dimethylazulene (2) in the presence of a sevenfold molar excess of ADM at 200° yielded 20% of ‘anti’‐9 beside an equal amount of dimethyl 3‐mehtylazulene‐1,2‐dicarboxylate (8;cf. Scheme 1), and 1,3,5,7‐tetramethylazulene (4) with a fourfold molar excess of ADM AT 200° gave a yield of 37% of‘anti’‐15 beside small amount of the corresponding heptalene‐ 13 and azulene‐1,2‐dicarboxylates 14 (cf.Scheme 2).