共查询到20条相似文献,搜索用时 31 毫秒
1.
Nicolas Dietl Marianne Engeser Dr. Helmut Schwarz Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(26):4861-4863
No need for a metal : A combination of mass spectrometry and computational studies (density functional theory and coupled‐cluster methods) shows that [P4O10].+ is the first polynuclear nonmetal oxide cation that is capable of activating the C? H bond of methane at room temperature (see picture). This process represents a further example in the reactivity of oxygen‐centered radicals.
2.
3.
Martiskainen O Sztanke K Matosiuk D Pihlaja K 《Rapid communications in mass spectrometry : RCM》2006,20(17):2548-2552
The electron ionization mass spectra of the title compounds (1: a R = H, b 2-CH(3), c 4-CH(3), d 2,3-diMe, e 2-OCH(3), f 4-OCH(3), g 2-Cl, h 3-Cl, i 4-Cl, j 3,4-diCl) were recorded at 70 eV to determine the effects of substituents and the possible keto-enol tautomerism. The compounds showed several common fragment ions but also fragment ions which divided them into three classes, namely 1a-1d (parent compound and Me-substituted derivatives), 1e and 1f (MeO-substituted derivatives), and 1g-1j (Cl-substituted derivatives). The presence of the HOCN(+.) ion as well as the exponential dependence of its total ion current in the case of p- and also 3-Cl-substituted compounds (1a, c, f, h-j) on the Hammett sigma constants and the loss of CHO or one or two HOCN moieties can be somewhat easier explained by the presence of the enol form but as a whole the results support the predominance of the keto form, in parallel to the situation in solution. 相似文献
4.
A series of tetraoxane? triazine hybrids and spiro[piperidine‐4,3′‐tetraoxanes] have been synthesized, and all the compounds were screened for in vitro antimalarial activity against chloroquine‐sensitive (D6) and chloroquine‐resistant (W2) strains of Plasmodium falciparum. Most of the spiro[piperidine‐4,3′‐tetraoxanes] exhibited moderate to good antimalarial activities, and two compounds have shown good antimalarial activity with IC50 values in the range of 0.30 to 0.70 μM against both the strains with high selectivity index and no cytotoxicity towards mammalian kidney cell line. 相似文献
5.
Niloofar Tavakoli‐Hoseini Raheleh Moloudi Abolghasem Davoodnia Mohammad Shaker 《中国化学》2011,29(11):2421-2426
A convenient and efficient method for the synthesis of pyrazolo[3,4‐d]pyrimidin‐4‐ones via heterocyclization reaction of 5‐amino‐1H‐pyrazole‐4‐carboxamides with triethyl orthoesters using two Br?nsted‐acidic ionic liquids, 3‐methyl‐1‐(4‐sulfonic acid)butylimidazolium hydrogen sulfate [MIM+(CH2)4SO3H][HSO4?] or N‐(4‐sulfonic acid)butyl triethylammonium hydrogen sulfate [Et3N+(CH2)4SO3H][HSO4?], as efficient homogeneous catalysts under solvent‐free conditions is described. 相似文献
6.
7.
A new and efficient synthesis of 2‐[1‐alkyl‐5,6‐bis(alkoxycarbonyl)‐1,2,3,4‐tetrahydro‐2‐oxopyridin‐3‐yl]acetic acid derivatives by a one‐pot three‐component reaction between primary amine, dialkyl acetylenedicarboxylate, and itaconic anhydride (=3,4‐dihydro‐3‐methylidenefuran‐2,5‐dione) is reported. The reaction was performed without catalyst and under solvent‐free conditions with excellent yields. Notably, the ready availability of the starting materials, and the high level of practicability of the reaction and workup make this approach an attractive complementary method to access to unknown 2‐[1‐alkyl‐5,6‐bis(alkoxycarbonyl)‐1,2,3,4‐tetrahydro‐2‐oxopyridin‐3‐yl]acetic acid derivatives. The structures were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of domino Michael addition? cyclization reaction is proposed (Scheme 2). 相似文献
8.
Malihe Javan Khoshkholgh Mohammad Reza Hosseindokht Saeed Balalaie Mohammad Reza Bozorgmehr Hamid Reza Bijanzadeh 《Helvetica chimica acta》2012,95(1):52-60
The CuI‐catalyzed intramolecular oxa‐Diels? Alder reaction of 2‐(prop‐2‐yn‐1‐yloxy)benzaldehydes as unactivated terminal alkynes with 4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one is described. The reaction proceeds with remarkable chemoselectivity to yield pyranones 3 (Scheme 1). A theoretical investigation of the reaction in terms of HOMO? LUMO interactions in the gas phase is also reported. The reaction could be regarded as an inverse‐electron‐demand Diels? Alder cycloaddition. The theoretical results are in high agreement with the experimental evidences. 相似文献
9.
10.
Ming‐Bo Zhou Rui Pi Ming Hu Yuan Yang Ren‐Jie Song Yuanzhi Xia Jin‐Heng Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(42):11520-11523
This study describes a new rhodium(III)‐catalyzed [3+2] annulation of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp2) H bond and addition/protonolysis of an alkene CC bond. This method is applicable to a wide range of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles and internal alkynes, and results in the assembly of the spiro[indene‐1,2′‐pyrrolidine] architectures in good yields with excellent regioselectivities. 相似文献
11.
Gunar Hadiprono 《Nachrichten aus der Chemie》2001,49(6):768-769
12.
13.
Starting from perfluoroheptane, saturated aqueous potassium carbonate solution, methanol, toluene and suitable dyes, a three‐phasic mixture is prepared initially. After shaking – not only stirring – four layers develop. Addition of pentane changes the sequence of two layers. The layers are added in a new sequence and the way of mixing demonstrates the complexity of multi‐phasic systems. 相似文献
14.
15.
16.
David J. Burns Daniel Best Martin D. Wieczysty Hon Wai Lam 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(34):10096-10100
1,3‐Enynes containing allylic hydrogens cis to the alkyne function as three‐carbon components in rhodium(III)‐catalyzed, all‐carbon [3+3] oxidative annulations to produce spirodialins. The proposed mechanism of these reactions involves the alkenyl‐to‐allyl 1,4‐rhodium(III) migration. 相似文献
17.
18.
19.
Venkateshwarlu Gurram Dr. Narender Pottabathini Ramesh Garlapati Dr. Avinash B. Chaudhary Dr. Balaram Patro Prof. Mahesh K. Lakshman 《化学:亚洲杂志》2012,7(8):1853-1861
Reaction conditions for the C? C cross‐coupling of O6‐alkyl‐2‐bromo‐ and 2‐chloroinosine derivatives with aryl‐, hetaryl‐, and alkylboronic acids were studied. Optimization experiments with silyl‐protected 2‐bromo‐O6‐methylinosine led to the identification of [PdCl2(dcpf)]/K3PO4 in 1,4‐dioxane as the best conditions for these reactions (dcpf=1,1′‐bis(dicyclohexylphosphino)ferrocene). Attempted O6‐demethylation, as well as the replacement of the C‐6 methoxy group by amines, was unsuccessful, which led to the consideration of Pd‐cleavable groups such that C? C cross‐coupling and O6‐deprotection could be accomplished in a single step. Thus, inosine 2‐chloro‐O6‐allylinosine was chosen as the substrate and, after re‐evaluation of the cross‐coupling conditions with 2‐chloro‐O6‐methylinosine as a model substrate, one‐step C? C cross‐coupling/deprotection reactions were performed with the O6‐allyl analogue. These reactions are the first such examples of a one‐pot procedure for the modification and deprotection of purine nucleosides under C? C cross‐coupling conditions. 相似文献
20.
Dense or Porous Packing? Two‐Dimensional Self‐Assembly of Star‐Shaped Mono‐, Bi‐, and Terpyridine Derivatives 下载免费PDF全文
Dr. Daniel Trawny Philomena Schlexer Krista Steenbergen Prof. Dr. Jürgen P. Rabe Prof. Dr. Beate Paulus Prof. Dr. Hans‐Ulrich Reissig 《Chemphyschem》2015,16(5):949-953
The self‐assembly behavior of five star‐shaped pyridyl‐functionalized 1,3,5‐triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono‐ and bipyridine derivatives self‐assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers. 相似文献