bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melt electrospinning from poly(L‐lactide) rods coated with poly(ethylene‐co‐vinyl alcohol)
Authors: Tian Sheng , Ogata Nobuo , Shimada Naoki , Nakane Koji , Ogihara Takashi , Yu Muhuo 
Published: April 2009

AbstractRodlike poly(L‐lactide) (PLLA) samples coated with poly(ethylene‐co‐vinyl alcohol) (EVOH) were made. Fibers were produced from these rodlike samples by using a melt electrospinning system equipped with a laser irradiating device, and the effects of EVOH content and the processing parameters of the melt electrospinning on fiber diameters were investigated. We also studied the fiber formation mechanism from the rods during the laser melt electrospinning process. The following conclusions were reached: (i) coating of EVOH on PLLA rods has a remarkable effect on decreasing fiber diameter from 3 μm to around 1 μm; (ii) increases in the electric field strength and temperature of spinning space decrease the average diameter of fibers produced from pure PLLA rods, and longer collector distance leads to lager PLLA fiber diameter; and (iii) the migration of PLLA component from the core to the surface of electrospun fibers takes place during the fiber formation process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Composition, thermal properties, and biodegradability of a new biodegradable aliphatic/aromatic copolyester
Authors: Han Ling , Zhu Guixiang , Zhang Wei , Chen Wei 
Published: April 2009

AbstractA series of new aliphatic/aromatic copolyesters [poly(hexylene terephthalate‐co‐hexylene adipate) (PHTA)] were synthesized on the bases of 1,6‐hexanediol, adipic acid, and dimethyl terephthalate and characterized by gel permeation chromatography, 1H‐NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and compost testing. 1H‐NMR results show that the compositions of the copolyesters were in accordance with the feed molar ratios. The WAXD patterns indicated that the crystal structures of the PHTA copolyesters were determined by the dominant crystal units, and the copolyesters became less crystallizable, even amorphous, with increasing comonomer content. The DSC curves showed that the glass‐transition temperatures (Tg′s) of the PHTA copolyesters decreased linearly, and both the melting temperature (Tm) and heat of fusion decreased first and then increased with increasing hexylene adipate unit content. Under compost conditions, PHTA copolyesters with less than 60 mol % aromatic units were biodegradable. Particularly, compared with the copolyester poly(butylene terephthalate‐co‐butylene adipate), the PHTA copolyester with the same aliphatic/aromatic composition possessed a lower Tg and Tm and better biodegradability. Additionally, the biodegradability of the copolyesters could be predicted by the number‐average sequence length of aromatic units, Tg, and the temperature difference between Tm and the temperature at which biodegradation took place. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Oxidative ortho CC Coupling of 4‐Ethylphenol by Dual Substrate Activation at a Bioinspired Dicopper Complex—Trapping of an Unusual Oligophenolic Cu6 Species
Authors: Prokofieva Angelina , Dechert Sebastian , Große Christian , Sheldrick George M. , Meyer Franc 
Published: April 2009

AbstractBioinspired dual activation: Dual activation within the bimetallic pocket of a bioinspired dicopper(II) complex suitably places two phenolato substrates for preferred ortho–ortho coupling. Spectroscopic data and the molecular structure of a unique Cu6 complex isolated from the reaction mixture reveal a novel terphenolato ligand and provide a clue about the activation mechanism (see picture).magnified image
Molecular Simulation Study of Hexane Diffusion in Dynamic Metal‐Organic Frameworks
Authors: XUE Chunyu , ZHONG Chongli 
Published: April 2009

AbstractThe modified MM3 force field for describing flexible IRMOF‐1 was extended to include other IRMOFs, and a molecular dynamics simulation study was performed on hexane diffusion in IRMOF‐1 and IRMOF‐16. The self‐diffusion coefficients and diffusion pathways of hexane, as well as the mobility of the frameworks were investigated, as a function of both temperature and loading. The results revealed that the diffusion pathway of hexane was largely influenced by loading, and the flexibility of IRMOF‐16 was much larger than that of IRMOF‐1. The microscopic information obtained is useful for understanding the diffusion mechanism of chain molecules in dynamic MOF.
Synthesis and Structural Characterization of a New 2D Coordination Polymer [Cu(pzta)2]n
Authors: HU Xin , LIU Cong , WANG Yongjiang , GUO Jixi 
Published: April 2009

AbstractA new copper(II) tetrazolate coordination polymer [Cu(pzta)2]n (1) (pzta=5‐pyrazinyltetrazolate) was prepared from the hydrothermal reaction of Cu(OAc)2·H2O with NaN3 and pyrazinecarbonitrile (pzCN) in the presence of ethanol, and characterized by elemental analysis, IR, TGA and X‐ray crystallography. The X‐ray diffraction analysis of 1 shows that the compound crystallizes in the monoclinic system with space group P2(1)/c and Cu(II) ion center is six‐coordinated by four different pzta ligands. The complex 1 features a 2D tetrazole coordination polymer. The thermal analysis of 1 shows that the decomposition of the complex occurs in two regions.
Homology Model Adjustment and Ligand Screening with a Pseudoreceptor of the Human Histamine H4 Receptor
Authors: Tanrikulu Yusuf , Proschak Ewgenij , Werner Tim , Geppert Tim , Todoroff Nickolay , Klenner Alexander , Kottke Tim , Sander Kerstin , Schneider Erich , Seifert Roland , Stark Holger , Clark Timothy , Schneider Gisbert 
Published: April 2009

AbstractA new pseudoreceptor modeling method (PRPS) was applied to the refinement of a homology model of the human histamine H4 receptor (H4R), the prediction of a ligand binding site, and virtual screening. Retrieval of two new H4R ligands demonstrates the biological relevance of the pseudoreceptor model and provides a means for finding new hits and leads in the early phases of drug discovery.magnified imageA computer‐assisted method for the generation of pseudoreceptor models is presented together with two practical applications. From a three‐dimensional alignment of known histamine H4 receptor ligands, a pseudoreceptor model of the putative ligand binding site was constructed and used for virtual screening of a large collection of commercially available compounds. Two bioactive chemotypes were retrieved, demonstrating the general applicability of the approach. The pseudoreceptor model was also used to find the putative ligand binding pocket within the transmembrane receptor domain. For each frame of a molecular dynamics simulation of a homology‐based H4 receptor model, we automatically extracted potential ligand binding pockets and used their compatibility with the pseudoreceptor as a selection criterion. The best‐matching pocket fits perfectly with existing mutation data and previously published hypotheses suggesting Glu1825.46 as the preferred binding partner of a positively charged moiety of H4 receptor ligands. This new pseudoreceptor approach has demonstrated its suitability for both structure‐based prioritization of protein receptor models, and ligand‐based virtual screening with the aim to perform scaffold hopping.
Ultrafast Dynamics of o‐Bromofluorobenzene Studied by Time‐Resolved Photoelectron Imaging
Authors: Cao Zhen‐Zhou , Wei Zheng‐Rong , Hua Lin‐Qiang , Hu Chang‐Jin , Zhang Song , Zhang Bing 
Published: April 2009

AbstractPhotodissociation dynamics and rotational wave packet coherences of o‐bromofluorobenzene are studied by femtosecond time‐resolved photoelectron imaging (see figure). The decay of different photoelectron rings shows the population decay of states from which the lifetimes of different states are determined. The variation of photoelectron angular distributions reflects the evolution of rotational coherences.magnified imagePhotodissociation dynamics and rotational wave packet coherences of o‐bromofluorobenzene are studied by femtosecond time‐resolved photoelectron imaging (TR‐PEI) spectroscopy combined with the (1+2′) resonance‐enhanced multiphoton ionization (REMPI). Photoelectron kinetic energy and angular distributions indicate ionization dynamics from some Rydberg states at the (1+1′) photon energy. The lifetimes of the S1 (A′) and T2 (A′) states are determined from the decay of the photoelectron signals to be 38 ps and 27 ps. The electron population decay of the two states is attributed to predissociation and tunneling dissociation. The variation of time‐dependent anisotropy parameters in the first 5 ps shows the rotational wave coherences of molecule.
Heat shock factor 1 deficiency via its downstream target gene αB‐crystallin (Hspb5) impairs p53 degradation
Authors: Jin Xiongjie , Moskophidis Demetrius , Hu Yanzhong , Phillips Andrew , Mivechi Nahid F. 
Published: April 2009

AbstractHeat shock factor Hsf1 regulates the stress‐inducibility of heat shock proteins (Hsps) or molecular chaperones. One of the functions attributed to Hsps is their participation in folding and degradation of proteins. We recently showed that hsf1−/− cells accumulate ubiquitinated proteins. However, a direct role for Hsf1 in stability of specific proteins such as p53 has not been elucidated. We present evidence that cells deficient in hsf1 accumulate wild‐type p53 protein. We further show that hsf1−/− cells express lower levels of αB‐crystallin and cells deficient in αB‐crystallin also accumulate p53 protein. Reports indicate that αB‐crystallin binds to Fbx4 ubiquitin ligase, and they target cyclin D1 for degradation through a pathway involving the SCF (Skp1‐Cul1‐F‐box) complex. Towards determining a mechanism for p53 degradation involving αB‐crystallin and Hsf1, we have found that ectopic expression of Fbx4 in wild‐type mouse embryo fibroblasts (MEFs) expressing mutant p53 (p53R175H) leads to increase in its degradation, while MEFs deficient in hsf1 or αBcry are defective in degradation of this p53 protein. In addition, immunoprecipitated p53R175H from wild‐type MEFs is able to pull‐down both αB‐crystallin and Fbx4. Finally, immunoprecipitated wild‐type p53 from doxorubicin treated U2OS cells can pull‐down endogenous αB‐crystallin and Fbx4. These results indicate that hsf1‐ and αBcry‐deficient cells accumulate p53 due to reduced levels of αB‐crystallin in these cells. Elevated levels of p53 in hsf1‐ and αBcry‐deficient cells lead to their increased sensitivity to DNA damaging agents. These data reveal a novel mechanism for protein degradation through Hsf1 and αB‐crystallin. J. Cell. Biochem. 107: 504–515, 2009. © 2009 Wiley‐Liss, Inc.
Synthesis and properties of 1,4‐dimethylpyridazino[4,5‐d] pyridazines
Authors: Adembri G. , De Sio F. , Nasi R. , Scotton M. 
Published: April 2009

AbstractThe synthesis and properties of several 1,4‐dimethylpyridazino[4,5‐d]pyridazines are described. Treatment of diethyl 3,6‐dimethylpyridazine‐4,5‐dicarboxylate (1a) with lithium aluminium hydride and hydrazine did not afford the expected 1,4‐dimethylpyridazino[4,5‐d]pyridazine (21b) but a mixture of compounds 13, 18, 19, and 20, whose structures were deduced from spectroscopic data.
Etudes en série indolique: VII Synthèse de nouveaux pyridocarbazoles obtenus par photocyclisation de (β‐indolyl)‐1 (pyridyl)‐2 acrylonitriles
Authors: Dieng C. , Thal C. , Husson H.‐P. , Potier P. 
Published: April 2009

AbstractLa photochime des (β‐indolyl)‐1 (α‐, β‐ and γ‐ pyridyl)‐2 acrylonitriles a permis de réaliser la synthèse de différents pyrido[a]carbazoles isomères. Des différences de réactivité ont été observées selon la place qu'occupe l'atome d'azote Nb du cycle pyridinique. La diversité des résultats obtenus montre, de plus, que le processus photochimique ne peut se ramener à celui connu dans le cas des stilbènes.
Solvent shifts in the NMR spectra of monomethoxyflavones a comparison of four solvent systems
Authors: Looker James H. , Mader J. Woodson , Kingsbury Charles A. 
Published: April 2009

AbstractNmr chemical shifts of methoxyl protons are reported for the eight monomethoxyflavones in four solvents: deuteriochloroform, benzene, dimethylsulfoxide, and pyridine. Benzene shift data are presented, and Δ values interpreted on the basis of a preferential approach of benzene molecules near the positive end (hetero oxygen atom) of a large pyrone dipole. Pyridine shifts, relative to deuteriochloroform and dimethylsulfoxide, are reported. The Δ values for monomethoxyflavones indicate that only in 2′‐methoxyflavone is the shift value positive.
A novel synthesis of 2‐(disubstituted amino)‐5(4)phenylimidazoles
Authors: Nishimura Tamio , Nakano Katsuo , Shibamoto Shinji , Kitajima Koji 
Published: April 2009

AbstractThe reaction of 1‐phenyl‐1,2‐propanedione with 1,1‐disubstituted guanidines in methanol yielded 2‐(disubstituted amino)‐4‐hydroxy‐4‐methyl‐4H‐imidazoles (III). Compound III produced 5(4)methylimidazoles by catalytic hydrogenation and 5(4)chloromethylimidazoles (IV) by concentrated hydrochloric acid treatment. Solvolysis of IV in water and alcohols gave 5(4)hydroxymethyl‐ and 5(4)alkoxymethylimidazoles, respectively.
New routes to the v‐triazolo[1,5‐a]pyridine and pyrazolo[1,5‐a]pyridine ring systems
Authors: Tamura Yasumitsu , Kim Joong‐Hyup , Miki Yasuyoshi , Hayashi Hironori , Ikeda Masazumi 
Published: April 2009

AbstractNew routes to the v‐triazolo[1,5‐a]pyridine and pyrazolo[1,5‐a]pyridine ring systems are described. Treatment of the N‐amine salts of 2‐picolinealdehyde oxime or 2‐pyridyl ketone oximes with polyphosphoric acid gave v‐triazolo[1,5‐a]pyridines in fair yields. Treatment of 2‐picolyl ketones or their oximes with O‐mesitylenesulfonylhydroxylamine produced directly pyrazolo‐[1,5‐a]pyridines. These reactions were extended to the quinoline cases.
Additions radicalaires du tétrahydrothiophène à des dérivés éthyléniques: Préparation de tétrahydrothiophènes substitués en 2
Authors: Lalande Robert , Bourgeois Marie‐Josèphe , Maillard Bernard 
Published: April 2009

AbstractL'addition radicalaire du tétrahydrothiophène à des dérivés éthyléniques, sous amorçage peroxydique conduit à des tétrahydrothiophènes substitués en 2. Cette réaction semble être une voie synthétique intéressante de ces hétérocycles.
Studies of thieno[2,3‐b]pyrazines in preparation of pyrazino[2′,3′:4,5]thieno[3,2‐d]pyrimidines and related molecules
Authors: Schneller S. W. , Clough F. W. 
Published: April 2009

AbstractA variety of 2,3‐disubstituted derivatives of the previously unknown thieno[2,3‐b]pyrazine ring system have been employed as a synthetic foundation for pyrazino[2′,3′:4,5]thieno[3,2‐d]‐pyrimidine and several of its derivatives.
Chemistry of thienopyridines. XX. The relation of dipole moment to molecular structure
Authors: Klemm L. H. , Jacquot R. D. 
Published: April 2009

AbstractDipole moments were measured for three bicyclic thienopyridines and three tetracyclic diben‐zothienopyridines in benzene solution at 25°. Results agreed closely with predicted values based on vector addition of dipole moments for reference constituent compounds.
Massenspektrometrische untersuchung organischer stickstoffverbindungen ‐ XVI: Elektronenstossinduzierte fragmentierungen von α‐pyridiyl‐ω‐phenylalkanonen und α‐phenyl‐ω‐pyridylalkanen
Authors: Schwarz Helmut , Herrmann Rupert , Wolfschütz Roland 
Published: April 2009

AbstractThe electron impact induced fragmentations of twelve pyridine derivatives are discussed. The fragmentation pattern of these compounds is strongly influenced by the number of methylene groups as well as the position of substitution in the pyridine nucleus. By means of mass spectrometry a differentiation between the 2‐pyridyl and the 4‐pyridyl derivatives is possible and this fact could be important with respect to an analytical identification of the compounds.
Electrophilic substitution of furo[3,2‐c] pyridine
Authors: Mcfarland John W. , Essary William A. , Cilenti Lale , Cozart William , Mcfarland Philip E. 
Published: April 2009

AbstractFuro[3,2‐c] pyridine (I) was nitrated to give 2‐nitrofuro[3,2‐c]pyridine (II). Bromination and chlorination of I gave, respectively, 2,3‐dibromo‐2,3‐dihydrofuro[3,2‐c]pyridine (III) and 2,3‐dichloro‐2,3‐dihydrofuro[3,2‐c]pyridine (IV). Oxidation of I with hydrogen peroxide afforded furo[3,2‐c]pyridine 5‐oxide (V) which was converted to I by phosphorus trichloride and to 4‐chlorofuro[3,2‐c]pyridine (VI) by phosphorus oxychloride.
Synthèse de 2H ‐furo[3,4‐b] (3H, 5H, 7H) pyrannediones‐4,5. Acylation de (2H, 5H) furannediones‐2,4 (acides tétroniques) par les chlorures d'acides α‐éthyléniques
Authors: Celin Suzanne , Pollet Patrick 
Published: April 2009

AbstractDirect acylation of tetronic acids by α,β‐ethylenic acid chlorides with tin tetrachloride gave a new type of fused heterocyclic compounds: 2H‐furo[3,4‐b] pyran‐4,5‐diones. Acylation in alkaline medium gave enol esters which could be transposed in furopyrandiones. However, the first route was more satisfactory.
Heterocyclic compounds from 3,3‐dimercapto‐1‐aryl‐2‐propen‐1‐ones. Note 3. Condensation with N‐methyl‐o‐phenylenediamine and N‐benzyl‐o‐phenylenediamine
Authors: Nardi D. , Pennini R. , Tajana A. 
Published: April 2009

AbstractTwo seven‐membered ring compounds and three five‐membered ring compounds were obtained by reaction in hot xylene of 3,3‐dimercapto‐l‐phenyl‐2‐propen‐1‐one (1) with N‐alkyl‐o‐phenylenediamines (2). Compounds isolated were the 4‐phenyl‐5‐alkyl‐1,5‐dihydro‐2H‐1,5‐benzodiazepine‐2‐thiones (3) the 1‐alkyl‐4‐phenyl‐1,3‐dihydro‐2H‐1,5‐benzodiazepine‐2‐thiones (4), the 1‐alkyl‐2‐phenacylbenzimidazoles (5), the 1‐alkyl‐2‐phenylbenzimidazoles (6) and the 1‐alkyl‐2‐methylbenzimidazoles (7). The structures of these compounds were elucidated from their chemical reactivity and their nmr and ir spectra.
The use of amino acids in the mannich reaction
Authors: Short James H. , Ours C. Wayne 
Published: April 2009

AbstractAmino acids have been found to participate as the amine component in the Mannich reaction with both ketones and phenols. The phenolic Mannich bases may be cyclized with sulfuric acid to 1,2‐dihydro‐4(3/H)isoquinolones. In the presence of thionyl chloride the same Mannich bases undergo lactonization to benz[f]‐1,4‐oxazepin‐4(3H)ones.
Synthesis of pyrazolo[1′,5′:1,2]‐1,3,5‐triazino[5,6‐a]benzimidazoles
Authors: Senga Keitaro , Robins Roland K. , O'Brien Darrell E. 
Published: April 2009

AbstractThe synthesis of a new class of tetracyclic bridgehead heterocycle pyrazolo[1′,5′:1,2]‐1,3,5‐triazino[5,6‐a] benzimidazoles is reported. The key intermediate 2‐(3‐aminopyrazol‐2‐yl)benzimidazoles were prepared by the reaction of 2‐hydrazinobenzimidazole with an appropriate reagent such as ethyl ethoxymethylenecyanoacetate, ethoxymethylenemalononitrile, β‐cyanoacetophenone or α‐formylphenylacetonitrile. The treatment of these key intermediates with triethylorthoesters afforded the corresponding pyrazolo[1′,5′:1,2]‐1,3,5‐triazino[5,6‐a]benzimidazoles.
Studies on quinoline derivatives and related compounds. III. A novel pyridine synthesis to give substituted 1,4‐dihydro‐4‐oxonicotinic acids
Authors: Agui Hideo , Tobiki Hisao , Nakagome Takenari 
Published: April 2009

AbstractA variety of 5‐mono‐ and 5,6‐disubstituted 1,4‐dihydro‐4‐oxonicotinates were prepared by a novel pyridine synthesis which involves thermal cyclisation of enaminomethylenemalonates 9. The intermediates 9 were readily prepared through a few steps from commercially available starting materials.
Mass spectra of substituted pyrazolo[1,5‐a]‐1,3,5‐triazines
Authors: El Khadem Hassan S. , Foltz Rodger L. , Novinson Thomas , Senga Keitaro 
Published: April 2009

AbstractHigh resolution electron impact mass spectrometric measurements have been made on twelve pyrazolo[1,5‐a]‐1,3,5‐triazines. Substituents attached to carbon atoms 2, 4, 7, and 8 were used to label the various fragments. Three major ions were observed (a) the molecular ion, (b) an ion corresponding to M‐RCN where R is the substituent attached to C‐4 and (c) an aryl cyclopropenyl cation which was observed in 7‐aryl derivatives. Intensities and accurate mass‐measurements are given for all ions having intensities exceeding 2% of the base peak. Nine of the twelve pyrazolo‐[1,5‐a]‐1,3,5‐triazines included in this study are described here for the first time.
The stobbe condensation with substituted succinic esters. II A synthesis of benzothiophene derivatives
Authors: El‐Rayyes N. R. , Al‐Salman (Mrs.) N. A. 
Published: April 2009

AbstractThe condensation of some thienyl carbonyl compounds with dimethyl phenylsuccinate using either sodium hydride or potassium t‐butoxide as condensing agents, gave a stereoisomeric mixture of (E)‐ and (Z)‐half‐esters (3). The (E)‐half‐esters la‐c were either cyclised to the corresponding benzothiophene derivatives or hydrolysed to the (E)‐dibasic acids VIa‐e, which were cyclised to the corresponding anhydrides VIIa‐c. Methylation of VIIa,c gave the isomeric half‐esters VIIIa,c. The (Z)‐half‐ester Id can cyclise easily to the lactone IX.
Synthesis of 1,2,3‐thiadiazolo[4,5‐d] pyridazines, A new heterocyclic ring system
Authors: Shafiee Abbas 
Published: April 2009

AbstractA method was developed for the synthesis of 5‐carbethoxy‐4‐formyl‐1,2,3‐thiadiazole (I), its isomer (II); 5‐benzoyl‐4‐formyl‐1,2,3‐thiadiazole (III), and its isomer (IV). It was demonstrated that although compounds I, III and IV with hydrazine gave 7H‐1,2,3‐thiadiazolo[4,5‐d]‐pyridazin‐7‐one (XXII), 7‐phenyl‐1,2,3‐thiadiazolo[4,5‐d]pyridazine (XXIII) and 4‐phenyl‐1,2,3‐thiadiazolo[4,5‐d]pyridazine (XXV), respectively; however, compound I gave its corresponding hydrazone (XXIV).
Intramolecular diels‐alder reactions. XI. Modal selectivity in the syntheses of some parent cyclolignan lactones
Authors: Klemm L. H. , Tran Vinh Tan , Olson D. R. 
Published: April 2009

AbstractPh(C2)CH2Cl and Ph(C2)'CO2Na [where (C2) = ‐C=C‐ or trans‐CH=CH‐, (C2)' = ‐C=C‐ or cis‐CH=CH‐] reacted in refluxing dimethylformamide to yield unsaturated esters Ph(C2)'CO2‐CH2(C2)Ph and/or their intramolecular Diels‐Alder cyclization products (cyclolignan lactones). It was found that modal selectivity for cyclization in DMF sometimes varies from that found previously with acetic anhydride as solvent. Two new parent tetrahydrocyclolignan lactones were synthesized.
Tetrahydro‐ and octahydropyrido[1,2‐a]pyrimidin‐4‐ones
Authors: Yale Harry L. , Spitzmiller Ervin R. 
Published: April 2009

AbstractThe catalytic hydrogenation of 2‐methyl‐, 1 2,8‐dimethyl‐, 2, 2,9‐dimethyl‐, 3, 9‐methyl‐2‐propyl‐, 4, 2,3,9‐trimethyl‐, 5, 9‐methyl‐2‐phenyl‐, 6, 9‐hydroxy‐2‐methyl‐, 7, 9‐acetoxy‐2‐methyl, 8, 9‐carboxy‐2‐methyl‐, 16, 9‐carboethoxy‐2‐methyl‐, 17, 9‐carbomethoxy‐2‐methyl‐, 18, and several 9‐carboxamido‐2‐methyl‐, 19, 20, and 21, derivatives of the pyrido[1,2‐a]pyrimidin‐4‐one heterocycle has led to a series of novel 6,7,8,9‐tetrahydro‐ and fully saturated, octahydro analogs. In deuteriochloroform or DMSO‐d6 solution, the pmr spectra of the tetrahydro derivatives derived from 1‐7 revealed only the 6,7,8,9‐tetrahydro structures. In the pmr spectra of 16‐21, there was evidence of a facile 1,3‐prototropic shift of the proton from position‐9 to position‐1, resulting in equilibria between tautomeric species, i.e., magnified image. The ratio of tautomers present at equilibrium, with the esters, favored the enamine conformation, whereas, with both the carboxylic acid and the amides, the imine structure predominated. Supportive evidence for the enamine structure with the esters was derived also from the ir spectra. Alkylation of the anion derived from the tetrahydro 9‐carbomethoxy derivative with sodium hydride led exclusively to derivatives of 6,7,8,9‐tetrahydro system.
The reaction of 1‐azirines with 2‐pyridyl isothiocyanate: Possible approaches to benzodiazepine and benzodiazepine derivatives
Authors: Nair V. , Kim K. H. 
Published: April 2009

AbstractThe structure of the dimer (5) from 2‐pyridyl isothiocyanate (1) has been confirmed by 13C nmr spectral studies. The cycloaddition of 2‐pyridyl isothiocyanate with 1‐azirines results in the formation of thiazoles (10). Thermal decomposition of the vinyl azide (14) gives the pyrrole (15) and the pyridazine (16) instead of 2‐(2‐pyridyl)‐1‐azirine (12).