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71.
Rhodium/Silver‐Cocatalyzed Transannulation of N‐Sulfonyl‐1,2,3‐triazoles with Vinyl Azides: Divergent Synthesis of Pyrroles and 2 H‐Pyrazines 下载免费PDF全文
The first cyclization reaction between vinyl azides and N‐sulfonyl‐1,2,3‐triazoles is reported. A Rh/Ag binary metal catalyst system proved to be necessary for the successful cyclization. By varying the structure of vinyl azides, such reaction allows the divergent synthesis of pyrroles and 2H‐pyrazines. The cyclization reactions feature a broad substrate scope, good functional group tolerance, high reaction efficiency, and good to high product yields. 相似文献
72.
A Ru (II) complex bearing pyridyl-based benzimidazole-phosphine tridentate NNP ligand was synthesized and structurally characterized by NMR, IR. The complex can efficiently and selectively catalyze the acceptorless dehydrogenation of primary alcohols to esters under relatively mild conditions and the synthesis of pyrroles by means of the reactions of secondary alcohols and β-amino alcohols through acceptorless deoxygenation condensation. 相似文献
73.
Condensed N‐heterocycles were prepared by using C? H activation reactions catalyzed by Pd(OAc)2 (5 mol %) and (p‐tolyl)3P (10 mol %). The key step of these ring closures is chemoselective intramolecular C? H activation of the methyl group at position 2 of the pyrrole ring. Functionalized 9H‐pyrrolo[1,2‐a]indoles and pyrrolo[1,2‐f]phenanthridine derivatives were prepared in good yields. The preparation of some complex N‐heterocycles by using successive reactions is also described. 相似文献
74.
75.
According to the density functional theory calculations, the X···H···N (X?N, O) intramolecular bifurcated (three‐centered) hydrogen bond with one hydrogen donor and two hydrogen acceptors causes a significant decrease of the 1hJ(N,H) and 2hJ(N,N) coupling constants across the N? H···N hydrogen bond and an increase of the 1J(N,H) coupling constant across the N? H covalent bond in the 2,5‐disubsituted pyrroles. This occurs due to a weakening of the N? H···N hydrogen bridge resulting in a lengthening of the N···H distance and a decrease of the hydrogen bond angle at the bifurcated hydrogen bond formation. The gauge‐independent atomic orbital calculations of the shielding constants suggest that a weakening of the N? H···N hydrogen bridge in case of the three‐centered hydrogen bond yields a shielding of the bridge proton and deshielding of the acceptor nitrogen atom. The atoms‐in‐molecules analysis shows that an attenuation of the 1hJ(N,H) and 2hJ(N,N) couplings in the compounds with bifurcated hydrogen bond is connected with a decrease of the electron density ρH···N at the hydrogen bond critical point and Laplacian of this electron density ?2ρH···N. The natural bond orbital analysis suggests that the additional N? H···X interaction partly inhibits the charge transfer from the nitrogen lone pair to the σ*N? H antibonding orbital across hydrogen bond weakening of the 1hJ(N,H) and 2hJ(N,N) trans‐hydrogen bond couplings through Fermi‐contact mechanism. An increase of the nitrogen s‐character percentage of the N? H bond in consequence of the bifurcated hydrogen bonding leads to an increase of the 1J(N,H) coupling constant across the N? H covalent bond and deshielding of the hydrogen donor nitrogen atom. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
76.
A kinetic and product study of the dichloroacetic acid catalyzed chlorination of 1-methylpyrrole with 3- and 4-substituted N-chlorobenzamides was carried out. Protonated N-chlorobenzamides served as carriers of CI+. A Hammett correlation was obtained with ρ=−0.68 (r=0.98, n=8). General acid catalysis was observed with α=0.48 (r=0.99 and n=7). The yields of 2-chlorination (84±0.7%) and 3-chlorination (2.6±0.4%) were essentially constant (constant intramolecular selectivity) as the substituent on the N-chlorobenzamide was varied. Observation of constant intramolecular selectivity indicated that two intermediates were formed during the acid catalyzed chlorination of 1-methylpyrrole with N-chlorobenzamides. The carrier method is applicable to all types of aromatic systems and limited only by the availability of suitable carrier molecules. 相似文献
77.
Glushkov V. A. Ausheva O. G. Shurov S. N. Shklyaev Yu. V. 《Russian Chemical Bulletin》2002,51(5):894-896
1-R-3,3-Dimethyl-2-azaspiro[4.5]deca-1,6,9-trien-8-ones were synthesized through three-component condensation of anisole, isobutyraldehyde, and a corresponding nitrile in dichloromethane in the presence of concentrated sulfuric acid. 相似文献
78.
N,N,N-Trialkyl-2,5-bis(1-aminoethyl)pyrroles, prepared by the heterocyclization of 1,8-dibromooctan-3,6-dione with aliphatic amines, underwent the Pictet-Spengler reaction with formaldehyde and aromatic aldehydes to give substituted 5H-1,2,3,4,6,7,8,9-octahydrodipyrido[4,3-b;3,4-d]pyrroles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 617–622, May, 2000. 相似文献
79.
Andrei V. Afonin Igor A. Ushakov Alexander V. Vashchenko Dmitry E. Simonenko Andrei V. Ivanov Alexander M. Vasil'tsov Al'bina I. Mikhaleva Boris A. Trofimov 《Magnetic resonance in chemistry : MRC》2009,47(2):105-112
According to the 1H, 13C and 15N NMR spectroscopic data and DFT calculations, the E‐isomer of 1‐vinylpyrrole‐2‐carbaldehyde adopts preferable conformation with the anti‐orientation of the vinyl group relative to the carbaldehyde oxime group and with the syn‐arrangement of the carbaldehyde oxime group with reference to the pyrrole ring. This conformation is stabilized by the C? H···N intramolecular hydrogen bond between the α‐hydrogen of the vinyl group and the oxime group nitrogen, which causes a pronounced high‐frequency shift of the α‐hydrogen signal in 1H NMR (~0.5 ppm) and an increase in the corresponding one‐bond 13C–1H coupling constant (ca 4 Hz). In the Z‐isomer, the carbaldehyde oxime group turns to the anti‐position with respect to the pyrrole ring. The C? H···O intramolecular hydrogen bond between the H‐3 hydrogen of the pyrrole ring and the oxime group oxygen is realized in this case. Due to such hydrogen bonding, the H‐3 hydrogen resonance is shifted to a higher frequency by about 1 ppm and the one‐bond 13C–1H coupling constant for this proton increases by ~5 Hz. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
80.
Dariusz Cal Piotr Zagórski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2295-2302
Abstract New trifluoromethyl-functionalized 2-phosphonopyrroles were obtained by 5-exotrig cyclization of trifluoromethyl and phosphonyl functionalized enaminoketones. GRAPHICAL ABSTRACT 相似文献