- A near-infrared and lysosomal targeting thiophene-BODIPY photosensitizer: Synthesis and its imaging guided photodynamic therapy of cancer cells
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In this study, a novel NIR and lysosomal targeting thiophene-BODIPY photosensitizer SBOP-Lyso was synthesized to explore its potential applications in photodynamic therapy of A549 cells. In the strategy of designing SBOP-Lyso, S atom in thiophene as well as heavy atom I were introduced to promote ISC efficiency to ensure high singlet oxygen yield. A common lysosome targeted group (M1: 1-(2-morpholinoethyl)-1H-indole-3-carbaldehyde) was linked to SBOP to extend its wavelength to the NIR region. Its absorption peak was at 660 nm (εmax = 5.2 × 104 cm?1 M?1) and its corresponding emission peak was located at 705 nm. Singlet oxygen could be quickly generated by SBOP-Lyso in the presence of 660 nm LED irradiation and the singlet oxygen yield was up to 44.1%. In addition, it also had good biocompatibility and could enter cells or zebrafish in a short time. SBOP-Lyso had negligible dark cytotoxicity (cell survival rate > 80%) and excellent phototoxicity (IC50 = 0.2 μM). DCFH-DA (ROS indicator) proved that SBOP-Lyso could generate singlet oxygen with 660 nm LED irradiation. Singlet oxygen produced by SBOP-Lyso could kill cancer cells in PDT process and it had the ability to effectively inhibit A549 cells migration. Besides that, lysosomal colocalization assay showed that it had good lysosomal localization ability (Pearson colocation coefficient, R = 0.93). Considering the above results, SBOP-Lyso as a unique lysosome-targeted photosensitizer with excellent properties would exhibit positive results in PDT process of cancer cells.
- Bai, Jin,Zhang, Lei,Qian, Ying
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supporting information
(2021/02/16)
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- Low-cost clean method for preparing 2,4-dimethyl pyrrole-3,5-dicarboxylate
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The invention discloses a low-cost clean method for preparing 2,4-dimethyl pyrrole-3,5-dicarboxylate. The method comprises the following steps: mixing ethyl acetoacetate or tert-butyl acetoacetate with glacial acetic acid, slowly introducing inert gas into the mixed solution for 30 minutes, then introducing a nitrosation reagent nitric oxide gas at the flow rate of 0.5-1mL/min, conducting reacting at room temperature for 10 hours, controlling the temperature of the reaction solution to be 40 DEG C or lower, adding zinc powder in batches, dropwise adding ethyl acetoacetate at the same time, conducting reacting at 95 DEG C for 4 hours, conducting cooling, adding a reaction solution into ice water, conducting filtering, recrystallizing a filter cake with ethanol to obtain white ethyl 2,4-dimethyl pyrrole-3,5-dicarboxylate, and concentrating a filtrate to recover zinc acetate and acetic acid so as to realize the cleanness of the preparation process.
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- Novel indole-BODIPY photosensitizers based on iodine promoted intersystem crossing enhancement for lysosome-targeted imaging and photodynamic therapy
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In this work, we report the new lysosome-targeting indole-BODIPY derivatives BDP-Lys, IBDP-Lys, and I2BDP-Lys. BDP-Lys dye was designed for fluorescence imaging through introduction of an indole-containing morpholine moiety to a BODIPY core. Monoiodine and diiodine were incorporated into BDP-Lys dye to develop the photosensitizers IBDP-Lys and I2BDP-Lys. The maximum absorption (λabs) for IBDP-Lys and I2BDP-Lys displayed a redshift at approximately 11 nm and 27 nm, respectively, compared with the BDP-Lys dye (λabs= 504 nm). Similarly, the maximum emission also exhibited a redshift. The fluorescence quantum yield (ΦF) of IBDP-Lys (ΦF= 0.37%) and I2BDP-Lys (ΦF= 0.71%) was much lower than that of BDP-Lys dye (ΦF= 7.48%). The singlet oxygen quantum yields were measured as 43.10% for IBDP-Lys and 71.00% for I2BDP-Lys, which were higher than the iodine-free dye BDP-Lys. The theoretical calculation reasonably explains that iodine atoms promoted the intersystem crossing (ISC) process, and di-iodine further enhanced the ISC in indole-BODIPY dyes. Moreover, monoiodine photosensitizer IBDP-Lys was able to balance the generation of singlet oxygen and biocompatibility in cancer treatment. IBDP-Lys exhibited low dark toxicity (cell viability >90%), satisfactory biocompatibility, and precise lysosome targeting, with a Pearson coefficient of 0.93. The IBDP-Lys photosensitizer also was able to kill tumour cells. Considering the above results, the novel structure of indole-BODIPY photosensitizers could serve as a potential platform for lysosome-targeted imaging and photodynamic therapy.
- Liu, Miao,Qian, Ying,Wang, Chengjun
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supporting information
p. 18082 - 18089
(2021/10/12)
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- Design and synthesis of perfluoroalkyl decorated BODIPY dye for random laser action in a microfluidic device
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New and highly emissive 2,6-diacetynyl and 2,6-bis-(phenylacetynyl) functionalized pentamethyldifluoroboron-dipyrromethane (BODIPY) derivatives (FBDP1-2) with perfluorinated pendant groups at the boron center have been synthesized successfully by the combination of two strategies: extending the π-conjugation and functionalization at the boron centre. The newly synthesized dyes have been characterized unambiguously by using various analytical tools such as multinuclear NMR, MALDI-TOF, and single crystal XRD analysis. The dyes (FBDP1-2) exhibit excellent photophysical properties in the yellow to red spectral region (λabs = 530 nm and 555 nm, and λem = 555 nm and 596 nm, respectively) with relatively good Stokes shifts (849 cm-1 and 1240 cm-1), high quantum efficiency (?F = 0.72 and 0.61) and excellent brightness (2.95 × 104 and 2.38 × 104 M-1 cm-1). Most importantly, under a transverse pumping condition at 532 nm, the dyes show efficient and stable laser action, having a good tunable range (20 nm and 13 nm) with a maximum lasing efficiency of 45% and 38% for FBDP1 and FBDP2, respectively. Moreover, the random lasing behavior of FBDP1 has been investigated in a dye-circulated polydimethylsiloxane (PDMS) based disordered microfluidic device. The appearance of randomly positioned sharp spikes with a full width at half maximum (FWHM) of less than 0.3 nm around 555 nm indicates the random laser (RL) emission. The relationship between input pump energy and output random lasing intensity has also been demonstrated, with the random lasing threshold of 0.5 mJ.
- Maity, Apurba,Sarkar, Anirban,Bhaktha B.n, Shivakiran,Patra, Sanjib K.
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supporting information
p. 14650 - 14661
(2020/10/02)
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- A water-soluble BODIPY based ‘OFF/ON' fluorescent probe for the detection of Cd2+ ions with high selectivity and sensitivity
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A water-soluble dilithium salt BODIPY derivative (LiBDP) with appended dicarboxylate pseudo-crown ether [NO4] coordinating sites has been designed, synthesized and characterized successfully for the selective and sensitive recognition of Cd2+ in aqueous media. The chemosensor exhibits a remarkable increase in fluorescence intensity as well as a distinct color change upon the addition of Cd2+ over other environmentally and biologically relevant metal ions in H2O. The fluorometric response of LiBDP is attributed to the metal chelation-enhanced fluorescence (MCHEF) effect which has been confirmed by a strong association constant of 2.57 ± 1.06 × 105 M?1 and Job's plot, indicating 1?:?1 binding stoichiometry between LiBDP and Cd2+. Frontier molecular orbital analysis (obtained from DFT studies) also illustrates the turn-on fluorescence of the probe by blocking photoinduced electron transfer (PET) after coordination to Cd2+. The probe can detect Cd2+ in a competitive environment up to a submicromolar level in a biologically significant pH range. The sensor is proved to be reversible and reusable by the alternative addition of Cd2+ followed by S2?. The OFF/ON/OFF sensing behavior is utilized to construct an INHIBIT molecular logic gate based on the two inputs of Cd2+ and S2? and a fluorescence intensity at 512 nm as an output. The test paper experiment demonstrates the practical utility of LiBDP to monitor Cd2+ in an aqueous sample. Finally, the sensing probe was utilized to monitor Cd2+ in living cells.
- Maity, Apurba,Ghosh, Utsav,Giri, Dipanjan,Mukherjee, Devdeep,Maiti, Tapas Kumar,Patra, Sanjib K.
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supporting information
p. 2108 - 2117
(2019/02/12)
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- Preparation method of sunitinib intermediate
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The invention discloses a preparation method of a sunitinib intermediate. The method includes the following steps of 1, synthesis of 2, 4-dimethylpyrrole-3, 5-diethyl dicarboxylate, 2, synthesis of 4-ethoxycarbonyl-3, 5-dimethylpyrrole-2-carboxylic acid, 3, synthesis of 2, 4-dimethyl-3-ethyl pyrrole-2-carboxylate, 4, synthesis of 2, 4-dimethyl-5-aldehyde-1H-pyrrole-3-ethyl formate, and 5, synthesis of 2,4-dimethyl-5-aldehyde-1H-pyrrole-3-carboxylic acid. The method has the advantages that the raw materials are cheap, the environmental pollution is small, the industrial production is easy to achieve, the processing steps are fewer, the operation is simple, the reaction yield is very high, the mass production of enterprise is facilitated, and application and popularization are facilitated.
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Paragraph 0016-0017; 0022; 0027; 0028; 0033; 0038-0039; 0044
(2019/05/04)
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- Divergent Synthesis of Multisubstituted Unsymmetric Pyrroles and Pyrrolin-4-ones from Enamino Esters via Copper-Catalyzed Aerobic Dimerization
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A facile synthetic method to access multisubstituted unsymmetric pyrrole and pyrrolin-4-one derivatives is disclosed. In the presence of Cu(OAc)2 and KOAc, substituted pyrrole derivatives are produced in good yields (up to 93 %) through oxidative cyclization of enamino esters. Meanwhile, using CuCl2 and TFA (trifluoroacetic acid), pyrrolin-4-one derivatives are obtained in excellent yields (up to 94 %) through 1,2-aryl migration. A wide range of functional groups have been tolerated, and a reliable method for the synthesis of valuable multisubstituted pyrroles and pyrrolin-4-ones has been developed.
- Chen, Zhi-Wei,Zheng, Lei,Liu, Jin
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p. 3051 - 3060
(2019/05/24)
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- Synthesis and evaluation of a [18F]BODIPY-labeled caspase-inhibitor
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BODIPYs (boron dipyrromethenes) are fluorescent dyes which show high stability and quantum yields. They feature the possibility of selective 18F-fluorination at the boron-core. Attached to a bioactive molecule and labeled with [18F]fluorine, the resulting compounds are promising tracers for multimodal imaging in vivo and can be used for PET and fluorescence imaging. A BODIPY containing a phenyl and a hydroxy substituent on boron was synthesized and characterized. Fluorinated and hydroxy substituted dyes were coupled to an isatin-based caspase inhibitor via cycloaddition and the resulting compounds were evaluated in vitro in caspase inhibition assays. The metabolic stability and the formed metabolites were investigated by incubation with mouse liver microsomes and LC-MS analysis. Subsequently the fluorophores were labeled with [18F]fluorine and an in vivo biodistribution study using dynamic PET was performed.
- Ortmeyer, Christian Paul,Haufe, Günter,Schwegmann, Katrin,Hermann, Sven,Sch?fers, Michael,B?rgel, Frederik,Wünsch, Bernhard,Wagner, Stefan,Hugenberg, Verena
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supporting information
p. 2167 - 2176
(2017/03/23)
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- Synthesis, photophysical and concentration-dependent tunable lasing behavior of 2,6-diacetylenyl-functionalized BODIPY dyes
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2,6-Diacetylenyl- and 2,6-bis(arylacetylenyl)-functionalized pentamethyl-difluoroborondipyrromethene (BODIPY) derivatives, namely, PBDP1 and PBDP2-4 (aryl = phenyl, 4-methoxyphenyl, or 4-cyanophenyl), respectively, which exhibit extended π-conjugation, were synthesized and characterized by various spectroscopic methods. Significant bathochromic shifts in both absorption and emission were observed upon modifying the structure of the BODIPY core via the strategy of extending its π-conjugation. The derivatives displayed efficient emission in the yellow-to-red spectral region, with a high fluorescence quantum yield and a relatively large Stokes shift. Under conditions of transverse pumping in a cuvette, PBDP1 and PBDP2 exhibited highly efficient and stable laser activity for up to 180 and 110 minutes of continuous irradiation, respectively. Amplified spontaneous emission (FWHM of ca. 2.5 nm) with an efficiency of 41% and 36% was achieved for PBDP1 and PBDP2, respectively, in toluene, which had tunable ranges of 561 to 580 nm and 602 to 617 nm, respectively, on irradiation with a Q-switched Nd:YAG laser at 532 nm. The lasing properties of PBDP3 and PBDP4, which contain electron-donating (-OMe) and electron-withdrawing (-CN) arylacetylenyl moieties, respectively, were also investigated. A corresponding digold(i) diacetylide organometallic complex, namely, (PPh3)Au-C≡C-BODIPY-C≡C-Au(PPh3) (PBDP5) was also synthesized and characterized to study the effect of Au(i). PBDP5 exhibited phosphorescence in the vis-NIR region centered at 751 nm at 77 K owing to heavy-atom-induced intersystem crossing.
- Maity, Apurba,Sarkar, Anirban,Sil, Amit,B. N., Shivakiran Bhaktha,Patra, Sanjib K.
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supporting information
p. 2296 - 2308
(2017/03/22)
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- A process for the preparation of nun
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The invention relates to a method for preparing sunitinib. The method comprises the steps of dissolving 5-fluoro-1,3-indoline-2-ketone and N-(2-diethylin ethyl)-2,4-dimethyl-5-formyl group-1H-pyrrole-3-formamide into methylbenzene, then carrying out backflow reaction for 2.5-3.5 hours with piperidine as a catalyst, cooling to room temperature, carrying out suction filtering, and washing and drying filter cakes obtained by suction filtration through petroleum ether, so as to obtain the sunitinib, wherein the N-(2-diethylin ethyl)-2,4-dimethyl-5-formyl group-1H-pyrrole-3-formamide is prepared through hot melting and decarboxylation of 3,5-dimethyl-1H-pyrrole-4-carbethoxy-2-carboxylic acid, Vilsmeier-Haack formylation, hydrolysis reaction and amidation. According to the method, an intermediate of the sunitinib is prepared and synthesized through a solvent-free method, so that the overall yield of the sunitinib is greatly increased; in addition, the technology for elementary reaction is optimized; furthermore, the raw materials are easy to obtain, and by optimizing all reaction steps in the synthetic process, the elementary reaction yield of each step is increased, the total yield of the sunitinib is increased, and thus the synthetic cost of the sunitinib is lowered.
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Paragraph 0045; 0051-0058
(2020/02/07)
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- A Benzisoelenazolone modified pyrrole methyl ester substituted indole ketone compound and use thereof
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The invention discloses a benzisoselenazolone-modified pyrrolyl formate-substituted indolone compound and a use thereof. The invention depends on and claims the priority of a Chinese patent application 201110105248.0 submitted on April 26, 2011. Through reference, all contents of the Chinese patent application 201110105248.0 are incorporated into the invention. The benzisoselenazolone-modified pyrrolyl formate-substituted indolone compound is shown in the general formula I. The 2-indolone compound provided by the invention has excellent antitumor activity and can be widely used for preparation of antitumor drugs.
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Paragraph 0291-0293
(2016/10/08)
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- Design and synthesis of new potent PTP1B inhibitors with the skeleton of 2-substituted imino-3-substituted-5-heteroarylidene-1,3-thiazolidine-4-one: Part I
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A new series of 2-substituted imino-3-substituted-5- heteroarylidene-1,3-thiazolidine-4-ones as the potent bidentate PTP1B inhibitors were designed and synthesized in this paper. All of the new compounds were characterized and identified by spectra analysis. The biological screening test against PTP1B showed that some of these compounds have the positive inhibitory activity against PTP1B. The activity of the compounds with 5-substituted pyrrole on 5-postion of 1,3-thiazolidine-4-one are more potent than that of those compounds with 5-substituted pyridine group. Compound 14b, 14h and 14i showed IC50values of 8.66?μM, 6.83?μM and 6.09?μM against PTP1B, respectively. Docking analysis of these active compounds with PTP1B showed the possible interaction modes of these biheterocyclic compounds with the active sites of PTP1B. The inhibition tests against oncogenetic CDC25B were also conducted on this set of compounds to evaluate the selectivity and possible anti-neoplastic activity. Compound 14b also showed the lowest IC50of 1.66?μM against CDC25B among all the possible inhibitors, including 14g, 14h, 14i and 15c. Some pharmacological parameters including VolSurf, steric and electric descriptors of all the compounds were calculated to give some hints about the relative relationship with the biological activity. The result of this study might give some light on designing the possible anti-cancer drugs targeting at phosphatases. The most active compound 14i might be used as the lead compound for further structure modification of the new low molecular weight PTP1B inhibitors with the N-containing heterocyclic skeleton.
- Meng, Ge,Zheng, Meilin,Wang, Mei,Tong, Jing,Ge, Weijuan,Zhang, Jiehe,Zheng, Aqun,Li, Jingya,Gao, Lixin,Li, Jia
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p. 756 - 769
(2016/08/18)
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- An improved synthesis of sunitinib malate via a solvent-free decarboxylation process
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To search for an economical and convenient synthesis of sunitinib and its malate salt, optimization of a scalable synthetic route was explored by designing a standard experimental protocol on laboratory scale using commercially available materials including acetyl ethyl acetate, 4-fluoroaniline, and N 1,N 1-diethylethane-1,2-diamine. The optimal conditions were established based on investigating the main reaction steps, including cyclization, hydrolysis, decarboxylation, formylation, and condensation, giving optimized yields for each step of 94.4, 97.6, 98.5, 97.1, 91.0, 86.3, 85.5, 88.2, 99.1, 97.3, and 58.7 %, respectively. The synthesis process of 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid as the important intermediate was significantly improved by using solvent-free decarboxylation instead of the traditional process in a high-boiling-point solvent. The subsequent formylation was conducted directly using the dichloromethane solution of the crude product from decarboxylation, leading to an almost quantitative combined yield of these two steps. The overall yields of sunitinib and its salt using the optimal synthesis process were 67.3 and 40.0 % based on acetyl ethyl acetate. The obtained data could be used as reference for future industrialization, especially for avoiding expensive solvents and reducing reaction time.
- Meng, Ge,Liu, Chunyan,Qin, Shidong,Dong, Mengshu,Wei, Xiaomi,Zheng, Meilin,Qin, Liwen,Wang, Huihui,He, Xiaoshuang,Zhang, Zhiguo
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p. 8941 - 8954
(2015/10/28)
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- Vinyl azides derived from allenes: Thermolysis leading to multisubstituted 1,4-pyrazines and Mn(III)-catalyzed photochemical reaction leading to pyrroles
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Thermolysis of phosphorus-based vinyl azides under solvent- and catalyst-free conditions furnished a new route for 1,4-pyrazines. A simple one-pot, Mn(III)-catalyzed photochemical route has been developed for multisubstituted pyrroles starting from allenes and 1,3-dicarbonyls via in situ-generated vinyl azides. The utility of new phosphorus-based pyrroles is also demonstrated in the Horner reaction. The structures of key products are unequivocally confirmed by X-ray crystallography.
- Sajna, K. V.,Swamy, K. C. Kumara
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p. 8712 - 8722,11
(2020/09/15)
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- Direct synthesis of chiral 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines via a catalytic asymmetric intramolecular aza-Friedel-Crafts reaction
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The direct asymmetric intramolecular aza-Friedel-Crafts reaction of N-aminoethylpyrroles with aldehydes catalyzed by a chiral phosphoric acid represents the first efficient method for the preparation of medicinally interesting chiral 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines with high yields and high enantioselectivities. This strategy has been shown to be quite general toward various aldehydes and pyrrole derivatives.
- He, Yuwei,Lin, Maohui,Li, Zhongmin,Liang, Xinting,Li, Guilong,Antilla, Jon C.
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supporting information; scheme or table
p. 4490 - 4493
(2011/10/09)
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- Synthesis and spectral properties of new 3,3'-bis(dipyrrolylmethene) with acetylene spacer
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Bis(2,4,7,9-tetramethyl-8-ethyldipyrrolylmethen-3-yl)acetylene dihydrobromide (H2L·2HBr), new bis(dipyrrolylmethene), in whose molecule dipyrrolylmethene domains were connected through 3,3'-carbon atoms of internal pyrrole nuclei by acetylene spacer, were synthesized by original procedure. The compound was characterized by element analysis, IR, 1H NMR, and electronic spectroscopy. The comparative analysis of spectral properties shows the reduction of the basicity of H2L ligand in comparison with the structural analogs, which contain internal methylene spacer. The quantum-chemical simulation showed that the rigid acetylene spacer gives linear structure to the H2L molecule in contrast to the spiral-shaped geometry of structural analogs with-CH2-spacer. Pleiades Publishing, Ltd., 2010.
- Antina,Guseva,Loginova,Semeikin,V'Yugin
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p. 2374 - 2381
(2011/04/14)
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- Chemoselective radical cleavage of Cbz-protected nitrogen compounds
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(Matrix presented) Tributylstannyl radicals promote the deprotection of N-Cbz derivatives of amides and nitrogen-containing heteroaromatic rings. These radical conditions do not affect N-Cbz derivatives of basic amines.
- Bennasar, M.-Lluisa,Roca, Tomas,Padulles, Ariadna
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p. 569 - 572
(2007/10/03)
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- Selective cleavage of Cbz-protected amines
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(MatrixPresented) Under conditions of catalytic Ni(0) and in most cases just over 1 equiv of Me2NH·Br3/K2CO3 or Cs2CO3, a Cbz-protected nitrogen, which is part of a heteroaromatic ring, can
- Lipshutz, Bruce H.,Pfeiffer, Steven S.,Reed, Anthony B.
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p. 4145 - 4148
(2007/10/03)
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- Deprotection of N-sulfonyl nitrogen-heteroaromatics with tetrabutylammonium fluoride
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The deprotection of N-methylsulfonyl, N-(p-toluenesufonyl), and N-phenylsulfonyl nitrogen-heteroaromatic compounds proceeds easily in excellent yields by refluxing with tetrabutylammonium fluoride (TBAF) in THF.
- Yasuhara, Akito,Sakamoto, Takao
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p. 595 - 596
(2007/10/03)
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- Electrochemical Version of the Knorr Reaction
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Electrochemical reduction of ethyl 2-hydroxyimino-3-oxobutanoate in acetic acid in the presence of sodium acetate requires four electrons per molecule and yields an intermediate amino derivative, whose condensation with ethyl acetoacetate affords diethyl 2,4-dimethylpyrrol-3,5-dicarboxylate. The substance-based yields of the pyrrol are 74% at a steel cathode, 72% at a nickel cathode, 68% at a platinum cathode, 67% at a lead cathode, and 63% at a copper cathode. Electrolysis conditions: current density 120 mA/cm2; amount of electricity 161 A h per mol of the initial compound; 95°C. With an amount of electricity of 107 A h per mol of the initial compound, the yield of diethyl 2,4-dimethylpyrrole-3,5-dicarboxylate at a steel cathode increases from 37 to 73% in the temperature range from 40 to 105°C. The process can be regarded as an electrochemical version of the Knorr synthesis.
- Zakharov,Panenko,Kargin
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p. 1281 - 1283
(2007/10/03)
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- Thermochemistry of substituted pyrroles
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The heats of solution of a series of substituted pyrroles in benzene, carbon tetrachloride, chloroform, DMF, and pyridine were measured by a calorimetric method at 298.15 K.The influence of substituents in the pyrrole molecule on the energy parameters of solvation by organic solvents is discussed.
- Berezin, M. V.,Semeikin, A. S.,V'yugin, A. I.,Krestov, G. A.
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p. 449 - 453
(2007/10/02)
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- On the Mechanism of Pyrrole Formation in the Knorr Pyrrole Synthesis and by Porphobilinogen Synthase
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Attempts to synthesise a derivative of N-vinylaminoethanal either by oxidation of the corresponding alcohol or by hydrolysis of the corresponding dithioacetal were unsuccessful, but such derivatives were characterised by 1H and 13C NMR spectroscopy of reactions between ethyl 2-aminoacetoacetate and an excess of ethyl acetoacetate, leading to diethyl 2,4-dimethylpyrrole-3,5-dicarboxylate.
- Fabiano, Emmanuel,Golding, Bernard T.
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p. 3371 - 3376
(2007/10/02)
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- The total synthesis of chlorophyll a
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The total synthesis of chlorophyll a starting from Knorr's pyrrole (1) is described with full experimental detail. Forty six stages are involved to reach the target molecule, chlorin e6 trimethyl ester (46), from which the preparation of chlorophyll a has already been described. The four pyrroles which are required for rings A, B, C and D are elaborated largely by known reactions, although with considerable improvements. These pyrroles are manipulated to give two dipyrrin derivatives: a left-hand component (26, comprising rings A and D) and a right-hand component (the thioaldehyde 31, comprising rings B and C). These are brought together in a carefully controlled, stepwise, condensation to give a single porphyrin product (35) in 50% yield. This synthesis of an unsymmetrically-substituted porphyrin bearing an electron-withdrawing substituent and a meso-substituent is seen as a very considerable advance, both in conceptual and practical terms, over earlier approaches. During the course of the closure of the macrocycle, intermediates which exemplify a new group of dihydroporphyrins, the phlorins (e.g. 34), are recognised. Eleven steps remain. The porphyrin (35) is shown to undergo dehydrogenation (again via a phlorin intermediate) on brief treatment with acetic acid in air to give the meso-crylic acid derivative (36), which in acetic acid under nitrogen at 110° slowly reaches equilibrium with the purpurin (37). The introduction of the reactive vinyl group at C-3 has been delayed until this point in the synthesis. Photo-oxygenation of the product, the vinylpurpurin (38), cleaves the cyclopenteno-ring giving the methoxalylpurpurin (39). A reverse Claisen reaction now generates the methoxylactone, rac-isopurpurin 5 methyl ester (40), the first substance in this synthetic series which can be compared with a sample (albeit optically active) derived from natural chlorophyll a. rac-Isopurpurin 5 methyl ester (40) is hydrolysed to the lactol, chlorin 5 (41), which is resolved (diastereoisomeric salts with quinine). The less soluble salt gives synthetic act-chlorin 5, identical with a sample of natural provenance. Diazomethane treatment of the free acid (42) yields purpurin 5 dimethyl ester (43), again identical with the naturally-derived compound. Treatment with hydrogen cyanide in triethylamine leads to the cyanolactone (44), reductive cleavage and methylation of which give the chlorin e6 nitrile (45). Methanolysis of this furnishes synthetic crystalline chlorin e6 trimethyl ester (46), identical (mp, mixed mp, electronic spectrum, infra red spectrum) with a naturally-derived sample, so completing the total synthesis.
- Woodward, Robert Burns,Ayer, William A.,Beaton, John M.,Bickelhaupt, Friedrich,Bonnett, Raymond,Buchschacher, Paul,Closs, Gerhard L.,Dutler, Hans,Hannah, John,Hauck, Fred P.,Ito, Sho,Langemann, Albert,Le Goff, Eugene,Leimgruber, Willy,Lwowski, Walter,Sauer, Juergen,Valenta, Zdenek,Volz, Heinrich
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p. 7599 - 7659
(2007/10/02)
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- A CRITICAL EVALUATION OF THE KNORR SYNTHESIS OF TRIFLUOROMETHYLPYRROLES AND THE REACTIVITY OF DIETHYL 4-TRIFLUOROMETHYL-2-METHYLPYRROLE-3,5-DICARBOXYLATE
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β-Trifluoromethylpyrroles are readily obtained by the Knorr synthesis, but the procedure fails for the preparation of the α-isomers.The β-trifluoromethyl group reacts with alkoxide anions and is reduced with lithium aluminium hydride.
- Jones, R. Alan,Rustidge, David C.,Cushman, Susan M.
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p. 575 - 584
(2007/10/02)
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- Alkylation process
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Substituted pyrrole compounds, such as 3-ethyl-4-methyl-5-carbethoxy pyrrole, 2,4-dimethyl-3-acetyl pyrrole and 2-methyl-5-carboxy pyrrole-4-propionic acid diethyl ester, are alkylated in a single step by reaction with an aldehyde or ketone in the presence of both an acid condensing agent such as hydriodic acid and a compatible reducing agent such as metallic zinc or stannous chloride. Suitable carbonyl reactants include formaldehyde, paraldehyde, isobutyraldehyde, acetone, cyclohexanone and methyl-isobutyl ketone. This application is a continuation application of U.S. application Ser. No. 281,624 filed Aug. 18, 1972, now abandoned, which is a continuation-in-part application of U.S. application Ser. No. 832,001, filed June 10, 1969, now abandoned.
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