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A variety of computational methods, including the semiempirical techniques AM1, PM3, and MNDO, and the thermochemical basis sets of Benson and Stine, was used to calculate and compare heats of formation (ΔHf°) data for optimized geometries of a variety of aromatic and nonaromatic heterocycles. Detailed analyses, including 6-31G* and MP2/6-31G* ab initio calculations, were performed for the oxazole and thiazole heterocycles. The results indicate a scatter among the methods sensitive to the nature of the heterocycle. This was in particular evident in the oxazole molecule, where AM1 gave a singularly high value of ΔHf° consistent with longer calculated bond lengths, particularly about the oxygen atom. Aromatic stabilization energy appears to be addressed differently among the employed methods. Implications of this contrast applied to calculation of macromolecular systems containing heterocyclic units are discussed. 相似文献
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Thomas Trimaille Michael Mller Robert Gurny 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4379-4391
New monoalkyl‐substituted lactides were synthesized by reaction of α‐hydroxy acids with 2‐bromopropionyl bromide, and polymerized with various catalysts in the presence of benzyl alcohol by ring‐opening polymerization (ROP). The classic tin(II) 2‐ethylhexanoate (Sn(Oct)2) catalyst was leading to polymers with narrow distribution and predictable molecular weights, in polymerizations in bulk or toluene at 100 °C. The polymerization rate was corresponding to the steric hindrance of the alkyl substituents, such as butyl, hexyl, benzyl, isopropyl, and dimethyl groups. A yield of 83% was obtained with the hexyl‐substituted lactide after 1 h of polymerization. Excellent conversions (97%) could be achieved by using the alternative catalyst 4‐(dimethylamino)pyridine (DMAP). This latter organic catalyst was most efficient in polymerizing the more steric‐hindered lactides with good molecular weight and polydispersity control, in comparison to the tin(II) 2‐ethylhexanoate and tin(II) trifluoromethane sulfonate [Sn(OTf)2] catalysts. The efficiency of the DMAP catalyst and the variability of the monomer synthesis route for new alkyl‐substituted lactides allow to prepare and to envision a wide range of new functionalized polylactides for the elaboration of tailored materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4379–4391, 2004 相似文献
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Three new thiosemicarbazones have been synthesized by condensation reaction of 2‐bromo‐1‐arylethanones with thiosemicarbazide, which reacted with various 2‐bromo‐1‐arylethanones in ethanol under refluxing to give a series of substituted ethanone hydrazone derivatives. Their structures were confirmed by elemental analysis, IR, 1H NMR, and MS spectra. 相似文献
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Ana Dunja Mance Branko Borovi
ka KreImir Jakop
i Gordana Pavlovi Ivan Leban 《Journal of heterocyclic chemistry》2002,39(2):277-285
Methoxy or nitro group present in the furan ring of tertiary alkenylfurfurylamine changes the expected results of both, the intramolecular [4+2]cycloaddition and the acid catalyzed ring‐opening reaction of the derived oxatricycloadduct. With a 5‐methoxy group, in addition to the expected 5‐methoxyisoindoline 3 , the corresponding hydroxy derivative 5 was obtained. On the other hand a 5‐nitro group changes the outcome of the reaction even more profoundly. Instead of the expected 5‐nitroisoindoline 12 , 5‐nitro‐substituted epoxy‐isoindoline 6 submitted to ring‐opening reaction with the mixture of hydrobromic and acetic acid, yielded the mixture of bromo‐substituted epoxy compounds 7,8, 9 and/or bromo‐substituted isoindolines 10 and 11 . 相似文献
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Zhan‐Hui Zhang Jian‐Jiong Li Yuan‐Zhe Gao Yu‐Heng Liu 《Journal of heterocyclic chemistry》2007,44(6):1509-1512
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Muscarine, imidazole, oxazole and thiazole alkaloids 总被引:1,自引:0,他引:1
Jin Z 《Natural product reports》2005,22(2):196-229
Novel and structurally diverse natural products containing imidazol-, oxazole-, or thiazole-unit(s) display a wide variety of biological activities. The isolation, biological activity and total synthesis of naturally occurring muscarine, imidazole, oxazole and thiazole alkaloids have been reviewed. The literature covers from January 2003 to June 2004. 相似文献
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Jin Z 《Natural product reports》2003,20(6):584-605
The occurrence, structure determination, biological activities, as well as total syntheses of muscarine, imidazole, oxazole and thiazole alkaloids have been reviewed. The literature covers from the middle of 2001 to the end of 2002, and 149 references are cited. 相似文献
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Jin Z 《Natural product reports》2011,28(6):1143-1191
A great number of structurally diverse natural products containing five-membered heterocyclic subunits, such as imidazole, oxazole, thiazole, and their saturated congeners, are abundant in nature. These naturally occurring metabolites often exhibit extensive and pharmacologically important biological activities. The latest progress in the isolation, biological activities, chemical synthetic studies, and biosynthetic pathways on these natural products is summarized in this review. 相似文献
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1,2‐Diazepinone derivatives 6a–d, 8a,b, and 10a–c were synthesized from the reaction of olefines carrying EWG as ethoxymethylene malononitrile, ethoxymethylene cyanoacetate, and tetracyanoethylene with 1a–f respectively. Also, 5‐alkyl‐6‐oxotetrahydropyridazine‐4,4‐dicarboxylate derivatives 12a–c were afforded via the reaction of 1d–f with diethyl ethoxymethylene malonate. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:259–264, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20294 相似文献
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Andrey A. Kirilchuk Aleksandr A. Yurchenko Aleksandr N. Kostyuk Alexander B. Rozhenko 《Journal of computational chemistry》2015,36(1):42-48
1,2‐Migration of the phosphano‐group to the carbene center in N‐phosphano functionalized N‐heterocyclic carbenes has been studied by density functional theory (DFT) calculations. An intramolecular mechanism with a three‐center transition state structure seems to be most plausible for the isolated carbenes, while an intermolecular pathway catalyzed by azolium salts may be preferable for a migration proceeding in the course of generating the carbenes in situ. Our calculations show that amino‐substitution at the phosphorus atom and an enhanced nucleophilicity of the heterocycle scaffold facilitate the phosphorus shift. Calculated singlet‐triplet energy gaps do not correlate with thermodynamic stability of the studied carbenes and their disposition toward the 1,2‐rearrangement. © 2014 Wiley Periodicals, Inc. 相似文献
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Hideki Misaka Eisuke Tamura Kosuke Makiguchi Kensuke Kamoshida Ryosuke Sakai Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(10):1941-1952
For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ5,4Λ5‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4), was confirmed. Among these superbases, only t‐Bu‐P4 showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P4‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P4 system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P4‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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Uday C. Mashelkar Deepak M. Rane Rajesh S. Kenny 《Journal of heterocyclic chemistry》2008,45(3):865-872
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Several 1‐(1‐aryl‐1,4‐dihydro‐3‐carboxy‐6‐methylpyridazin‐4‐one)‐4‐aryl thio‐semicarbazides and their corresponding oxadiazole, thiadiazole and triazole derivatives were prepared and characterized by their spectral data. The preliminary biological tests showed that some new compounds exhibit good anti‐fungal activity. 相似文献
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Davis MR Singh EK Wahyudi H Alexander LD Kunicki JB Nazarova LA Fairweather KA Giltrap AM Jolliffe KA McAlpine SR 《Tetrahedron》2012,68(4):1029-1051
Peptidomimetic-based macrocycles typically have improved pharmacokinetic properties over those observed with peptide analogs. Described are the syntheses of 13 peptidomimetic derivatives that are based on active Sansalvamide A structures, where these analogs incorporate heterocycles (triazoles, oxazoles, thiazoles, or pseudoprolines) along the macrocyclic backbone. The syntheses of these derivatives employ several approaches that can be applied to convert a macrocyclic peptide into its peptidomimetic counterpart. These approaches include peptide modifications to generate the alkyne and azide for click chemistry, a serine conversion into an oxazole, a Hantzsch reaction to generate the thiazole, and protected threonine to generate the pseudoproline derivatives. Furthermore, we show that two different peptidomimetic moieties, triazoles and thiazoles, can be incorporated into the macrocyclic backbone without reducing cytotoxicity: triazole and thiazole. 相似文献
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New 6‐chloro‐ and 6,7‐dichloro‐4‐(4‐aminophenyl)‐2‐(N‐alkylcarbamoyl)‐1,2‐dihydrophthalazines ( 12,18 ) were synthesized starting from 6‐chloro‐ and 6,7‐dichloro‐4‐(4‐nitrophenyl)phthalazine ( 8 ). Routes to 1‐unsubstituted ( 12 ) and 1‐methyl ( 18 ) derivatives are different. Key intermediates 8 were prepared from 4‐chloro‐ and 3,4‐dichlorotoluene via ortho‐formylbenzophenone derivatives 7 . 相似文献