- Chemo- And regioselective ring-opening of donor-acceptor oxiranes with: N -heteroaromatics
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The first ring-opening of D-A oxiranes with N-heteroaromatics in a chemoselective C-C bond cleavage manner was achieved. In the presence of 5 mol% of Y(OTf)3 as the catalyst, diverse N-heteroaromatics, including benzotriazoles, purines, substituted benzim
- Sang, Ji-Wei,Xie, Ming-Sheng,Wang, Man-Man,Qu, Gui-Rong,Guo, Hai-Ming
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supporting information
p. 4552 - 4555
(2021/05/17)
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- The Employment of Sodium Hydride as a Michael Donor in Palladium-catalyzed Reductions of α, β-Unsaturated Carbonyl Compounds
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Sodium hydride was employed as a Michael donor under the catalysis of PdCl2 for 1,4-conjugate reductions of α, β-unsaturated carbonyl compounds, which features operational simplicity, mild conditions and high atom-economy. The merits of NaH as a reductant were demonstrated by the one-pot or cascade reactions for the syntheses of complex molecules. (Figure presented.).
- Liu, Ye,Mao, Yujian,Hu, Yanwei,Gui, Jingjing,Wang, Liang,Wang, Wei,Zhang, Shilei
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supporting information
p. 1554 - 1558
(2019/02/16)
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- Synthesis of chiral tetrahydrofurans via catalytic asymmetric [3 + 2] cycloaddition of heterosubstituted alkenes with oxiranes
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An efficient diastereo- and enantioselective [3 + 2] cycloaddition of heterosubstituted alkenes with oxiranes via selective C-C bond cleavage of epoxides has been developed. The reaction was catalyzed by a chiral N,N′-dioxide/Ni(II) catalyst, and a variety of chiral highly substituted tetrahydrofurans were obtained in up to 99% yield, 92/8 dr, and 99% ee.
- Yuan, Xiao,Lin, Lili,Chen, Weiliang,Wu, Wangbin,Liu, Xiaohua,Feng, Xiaoming
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p. 1237 - 1243
(2016/02/19)
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- The Regiospecific Preparation of 2-Substituted Tribenzotriquinacenes
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Several substituted tribenzotriquinacene derivatives (TBTQ) carrying functional groups exclusively in the 2-position (OMe, OH, Br, CHO, CN, styryl, etc.) have been prepared by our new synthesis of the tribenzotriquinacene framework. The route has been ext
- Saravanakumar, Rajendran,Markopoulos, Georgios,Bahrin, LucianGabriel,Jones, PeterG.,Hopf, Henning
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p. 453 - 456
(2013/04/10)
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- Tribenzotriquinacene: A versatile synthesis and C3-chiral platforms
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Fusing rings: A new synthesis of the bowl-shaped hydrocarbon tribenzotriquinacene is presented (see scheme). The synthesis allows easy access to ortho-functionalized and C3-chiral derivatives that are attractive for supramolecular chemistry and
- Markopoulos, Georgios,Henneicke, Lars,Shen, Jun,Okamoto, Yoshio,Jones, Peter G.,Hopf, Henning
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supporting information
p. 12884 - 12887
(2013/02/23)
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- An efficient iodine-catalysed Knoevenagel condensation reaction in the presence of acetic anhydride
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A mild, simple and efficient iodine catalysed system has been developed for the Knoevenagel condensation of 1,3-dicarbonyl compounds with various aromatic aldehydes in the presence of acetic anhydride. The reaction gave good to excellent yields for a broad range of substrates.
- Li, Zhong-Xian,Liu, Xiao-Pei,Qiu, Zhen,Xu, Dan,Yu, Xue-Jun
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experimental part
p. 35 - 36
(2011/04/24)
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- Solvent-free NbCl5 catalyzed condensation of 1,3-dicarbonyl compounds and aldehydes: a facile synthesis of trisubstituted alkenes
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A simple preparation of trisubstituted alkenes by condensation of β-diketones or β-ketoesters with aldehydes in presence of NbCl5 as a Lewis acid catalyst in solvent-free conditions is described.
- Yadav,Bhunia, Dinesh C.,Singh, Vinay K.,Srihari
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experimental part
p. 2470 - 2473
(2009/08/09)
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- A new route to 2-alkenyl-1,3-dicarbonyl compounds, intermediates in the synthesis of dihydrofurans
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A two step synthetic strategy for obtaining 2-alkenyl-1,3-dicarbonyl compounds from the corresponding 1,3-dicarbonyl compounds is reported. The method is based on a Knoevenagel condensation and a Michael addition using a high order organocuprate procedure, and proves to be of general value. Obtained compounds are useful starting materials for the synthesis of furan derivatives.
- Antonioletti, Roberto,Bovicelli, Paolo,Malancona, Savina
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p. 589 - 596
(2007/10/03)
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- A synthetic entry into fused pyran derivatives through carbon transfer reactions of 1,3-oxazinanes and oxazolidines with carbon nucleophiles
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Acid catalysed condensations of various 2 substituted 1,3-oxazinanes 3 and 1,3-oxazolidines 4 with cyclic carbon nucleophiles viz. 5,5-dimethyl-1,3-cyclohexanedione and 1,3-cyclohexanedione furnish xanthene derivatives, whereas a Knoevenagel reaction proceeds with acyclic nucleophiles. In case of 4b and 4c, a unique synthesis of functionalised α-tetralones has emerged. Reactions of mixtures of cyclic and acyclic carbon nucleophiles with 3 provide some functionalised and partially reduced benzopyran derivatives.
- Singh, Kamaljit,Singh, Jasbir,Singh, Harjit
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p. 14273 - 14280
(2007/10/03)
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- (Hexaphenyltrimethylene)methane dication and related carbocations
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By ionization of the respective alkenediol (8a), the (hexaphenyltrimethylene)methane dication (2) has been prepared and found stable in solution under superacidic stable ion conditions (FSO3H/SO2CIF) up to at least -20 °C. The spectroscopic data and AMI theoretical modeling indicate that although the entire π-system is twisted, phenyl groups stabilize the positive charges in 2 to a similar degree as those in the trityl cation. The hexa-p-CF3 derivative of 2 was also observable but only at very low temperatures (-90 °C). Disruption of the 3-fold symmetry and reduction of the number of stabilizing phenyl rings even to five resulted in intramolecular allylation and subsequent formation of the corresponding indenyl cations. In all the cases studied no evidence for "Y-aromatic" stabilization was found.
- Head, Nicholas J.,Olah, George A.,Prakash, G. K. Surya
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p. 11205 - 11210
(2007/10/03)
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- Minute synthesis of electrophilic alkenes under microwave irradiation
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Condensation of carbonyl derivatives 2 with active methylene compounds 1 is efficiently achieved, within 3 to 15 minutes under microwave irradiation by a solvent free reaction in the presence of carefully adjusted amounts of piperidine leading to Knocvenagel products 3 in good to excellent yields.
- Ayoubi,Texier-Boullet,Hamelin
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p. 258 - 260
(2007/10/02)
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- Kinetics of Amine Addition to Benzylidene-1,3-indandione and Other Vinylic β-Diketones. Effect of Cyclic Structure and Steric Strain on Intrinsic Rate Constants
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The kinetics of the reactions of benzylidene-1,3-indandione (4) with piperidine, morpholine, n-butylamine, 2-methoxyethylamine, glycinamide, and cyanomethylamine and the reactions of benzylidene-3,5-heptanedione (5), benzylidene-2,6-dimethyl-3,5-heptanedione (6), and benzylidenedibenzoylmethane (7) with piperidine and morpholine have been measured in 50% Me2SO-50% water (v/v) at 20 °C and 0.5 M ionic strength. The reactions lead, in all cases, to the reversible formation of the zwitterionic adduct PhCH(RR′NH+)C(COX)2- (TA±) that is in fast equilibrium with its anion PhCH(RR′N)C-(COX)2-(TA-). Rate constants for nucleophilic addition (k1) and its reverse (k-1) as well as the pKa, of TA± were determined for all reactions. The intrinsic rate constant (k0 = k1 = k-1 when K1 = 1) for amine addition to 4 is abnormally high, whereas k0 for the reactions of 5-7 are abnormally low and similar to k0 in magnitude for amine addition to benzylideneacetylacetone reported previously. The terms "abnormally high" and "abnormally low" refer to positive and negative deviations, respectively, from a plot of log k0 for amine addition to a series of electrophilic olefins of the type PhCH=CYY′ vs log k0 for deprotonation of carbon acids of the type CH2YY′. The high k0 for the reaction of 4 is attributed to its cyclic structure, which assures that the π-overlap required for the stabilization of the adduct is strongly developed in the transition state. The low k0 values for the reactions of 5-7 arise from intramolecular hydrogen bonding, which is strong in TA± but poorly developed in the transition state, and from steric strain in the adduct, which is strongly developed in the transition state. All these effects can be viewed as manifestations of the principle of nonperfect synchronization (PNS).
- Bernasconi, Claude F.,Stronach, Michael W.
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p. 2222 - 2227
(2007/10/02)
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- The Complex Reaction of Acetohydrazides with Unsaturated Diketones: Alternative Cyclizations to 1,2-Diazepin-3-ones and Pyrazolopyridines
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The reaction of 2-cyanoacetohydrazide (1) and 2-(ethoxycarbonyl)acetohydrazide (26) with unsaturated 1,3-diketones leading with moderate yields to 1,2-diazepinones (3, 23, 24) and pyrazolopyridines (5, 15, 20, 25) together with the corresponding acetohydrazones have been studied.The reaction course depends on the temperature and the relative reactivity of the carbonyl groups of the starting materials.When one of these carbonyl groups is less reactive (benzoyl or ethoxycarbonyl groups), the reaction does not yield diazepinones but only pyrazolopyridines and/or acetohydrazones.
- Alonso, Paloma,Martin-Leon, Nazario,Quinteiro, Margarita,Seoane, Carlos,Soto, Jose L.
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p. 841 - 846
(2007/10/02)
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- Stereochemical Behavior of Intermediary Compounds in the Amine-Catalyzed Knoevenagel Reaction
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Treatment of the active methylene compounds and aldehydes with a catalytic amount of a secondary amine produces thermodynamically stable alkenes, and the intermediary amino compounds are isolated.The reaction involves many reversible steps, and the stereochemistry of products is determined in the elimination step from the intermediary compounds via stable planar carbanions, in which the small difference in the steric requirements of two electron-withdrawing groups is effective.Steric and electronic effects in the intermediates sometimes bring about the carbon-carbon bond fission with recovery of active methylene compounds, and these effects prevent the Knoevenagel reaction from occuring.
- Tanikaga, Rikuhei,Konya, Naoto,Hamamura, Kazumasa,Kaji, Aritsune
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p. 3211 - 3216
(2007/10/02)
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