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1.
Helio G. Bonacorso Liliane M.F. Porte Gisele R. Paim Fabio M. Luz Marcos A.P. Martins Nilo Zanatta 《Tetrahedron letters》2010,51(29):3759-3761
In this study, the versatile diethylaminosulfur trifluoride (DAST), a well-known fluorinating agent, was applied in the dehydration, intramolecular cyclization, and mono- and difluorination reactions of some 5-trifluoromethyl-1H-pyrazoles and 2-pyrazolines employing a general, mild, and efficient methodology. The azole precursors were synthesized from the reactions of acyclic and cyclic trifluoroacetylated enol ethers with hydrazines [NH2NHR, where R = C6H5, C6F5, 2-Furanoyl] and showed a differentiated chemical behavior in the presence of DAST. 相似文献
2.
Helio G. Bonacorso Liliane M.F. Porte Cleber A. Cechinel Gisele R. Paim Everton D. Deon Nilo Zanatta Marcos A.P. Martins 《Tetrahedron letters》2009,50(13):1392-3335
This study describes, firstly, the synthesis of a new precursor, 4,6,6-trimethoxy-1,1,1-trifluorohex-3-en-2-one (1), from the trifluoroacetylation reaction of 1,1,3,3-tetramethoxybutane, in 65% yields. Afterwards, the reaction of 1 with two hydrazines (NH2NHR, where R = 2-furanoyl, C6F5) led to a new series of 4,5-dihydro-1H-pyrazoles, containing an acetal-protected aldehyde function as substituent, in 90-97% yields. In a subsequent step, the dehydration reactions of these 4,5-dihydro-1H-pyrazoles gave the respective aromatic 1H-pyrazoles. Finally, we report the results of the deprotection reactions of the acetals to obtain the respective aldehyde function, as well as, the subsequent fluorination reaction using DAST, leading to new difluorinated derivatives in 55-60% yields. 相似文献
3.
Kalawati Meena Sudesh Kumari Jitender M. Khurana Amita Malik 《Tetrahedron letters》2018,59(15):1493-1496
Efficient syntheses of novel 10-aryl-5a-(arylamino)-9-hydroxy-5a,6,7,8-tetrahydroindeno[1,2-b]chromen-11(10H)-one derivatives has been reported by [4+2] cycloaddition reactions of electron-deficient 2-(arylmethylene)-1H-indene-1,3(2H)-dione heterodienes with electron-rich enaminones in [bmim]BF4 at 80?°C and in acetic acid at 80?°C. Dimedone/cyclohexane-1,3-dione enaminones have been used as dienophiles in Inverse Electron Demand hetero-Diels-Alder reactions. The products were obtained in high yields by a simple work up. 相似文献
4.
Graham Pattison Dmitry S. Yufit Judith A.K. Howard John A. Christopher 《Tetrahedron》2009,65(43):8844-5866
Pyridazin-3(2H)-one systems have very useful biological properties and have found many applications within the pharmaceutical and agrochemical industries but, in general, synthesis of polysubstituted analogues can be very difficult to achieve. An approach to the syntheses of polyfunctional pyridazinone systems involving sequential nucleophilic substitution reactions of N-aryl and N-THP protected 4,5,6-trifluoropyridazin-3(2H)-ones as the core scaffolds is described. 相似文献
5.
An efficient ionic liquid system was developed for the preparation of various heterocycle-fused pyrimidine-2, 4(1H,3H)-diones in moderate to excellent yields (52–95%). It was found that [HDBN+][TFE?], a simple and easily prepared ionic liquid, could act as both the solvent and reaction promoter, and that the reactions could be efficiently carried out at atmospheric pressures of CO2. 相似文献
6.
Wenjuan Li 《Tetrahedron letters》2010,51(41):5448-5450
Phthalazin-1(2H)-ones and 3-hydroxyisobenzofuran-1(3H)-ones were synthesized by the reactions of tropones with hydrazines and alcohols, respectively, via the ring contraction. 相似文献
7.
Rainer Streubel 《Coordination chemistry reviews》2002,227(2):175-192
In this review, important aspects of λ3-2H-azaphosphirene metal complexes are discussed in relation to synthesis, physical properties and synthetic applications; ab-initio calculations on relative energies of CH2NP isomers and of λ3-2H-azaphosphirene metal complexes (Cr, Mo, W) are also presented. Currently, there are three routes to this unsaturated three-membered ring system, which are discussed in detail: two of them use a rearrangement of metal carbene complexes, whereas the other relies on [2+1] cycloaddition reactions of electrophilic terminal phosphanediyl complexes and carbonitriles. The structural data show characteristics of a very strained heterocyclic ring system, which partially helps to understand the reactivity of this heterocycle complex in solution. The synthetic potential of λ3-2H-azaphosphirene metal complexes is illustrated by selected examples, which demonstrate their ability to serve, under very mild conditions as precursor for various new building blocks, i.e. nitrilium phosphanylide complexes, electrophilic terminal phosphanediyl complexes and phosphavinyl-nitrene complexes. 相似文献
8.
Dmitry S. Ryabukhin Anna D. Lisakova Anna S. Zalivatskaya Irina A. Boyarskaya Galina L. Starova Rostislav E. Trifonov Vladimir A. Ostrovskii Aleksander V. Vasilyev 《Tetrahedron》2018,74(15):1838-1849
Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the action of Brønsted superacid CF3SO3H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles, as products of hydroarylation of acetylene bond, in yields up to 98% with predominant formation of E-isomers. Cationic intermediates of these reactions have been studied theoretically by DFT calculations. Addition of CF3SO3H to the triple bond of acetylene tetrazoles leads to the corresponding E-/Z-vinyl triflates in high yields. Hydration of triple bond in these tetrazoles in H2SO4 results in the formation of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-tetrazoles. Tandem hydroarylation-ionic hydrogenation of acetylene tetrazoles in the systems acid(CF3SO3H or AlCl3)-arene-cyclohexane affords 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles. 相似文献
9.
Ruonan ZhangGeorge Iskander Paulo da SilvaDaniel Chan Valentina VignevichVi Nguyen Mohan M. BhadbhadeDavid StC Black Naresh Kumar 《Tetrahedron》2011,67(16):3010-3016
A series of novel 5-arylidenefuran-2(5H)-ones and 5-arylidene-4-arylfuran-2(5H)-ones were synthesized via the Suzuki-Miyaura reactions of fimbrolide derivatives 5-(bromomethylene)furan-2(5H)-one and 4-bromo-5-(bromomethylene)furan-2(5H)-one, respectively. A regioselective Suzuki-Miyaura reaction on 4-bromo-5-(bromomethylene)furan-2(5H)-one allowed the synthesis of unsymmetrically substituted 5-arylidene-4-arylfuran-2(5H)-ones. The crystal structure of the intermediate 5-arylidene-4-bromofuran-2(5H)-one revealed interesting Br?O halogen bonding. 相似文献
10.
Ren Li Fengyan Jin Xian-Rong Song Tao Yang Haixin Ding Ruchun Yang Qiang Xiao Yong-Min Liang 《Tetrahedron letters》2019,60(4):331-334
A novel and efficient p-TsOH-promoted cascade cyclization of 2-propynolphenols is developed to give 4-tosyloxy-2H-chromenes in moderate to efficient yields. It is noted that p-TsOH acts not only as a promoter in this reaction, and also as the sulfonate source. Importantly, the obtained 4-tosyloxy-2H-chromenes can be used as versatile intermediates for the synthesis of various functionalized compounds through diverse metal-catalyzed cross-coupling reactions. Moreover, this method can be enlarged to gram scale. 相似文献
11.
6-Chloro-2(2H)-pyranone, which can be prepared in high yield from commercially available trans-glutaconic acid, undergoes facile Pd/Cu-catalyzed reaction with various 1-alkynes to give rise to the corresponding 6-(1-alkynyl)-2(2H)-pyranones in moderate to good yields. These last hitherto unknown compounds have been used as direct precursors to 6-alkyl- and 6-[(Z)-1-alkenyl]-2(2H)-pyranones. 相似文献
12.
Lewis acid promoted anomeric substitution reactions of a stereoselectively prepared hexahydro-2H,5H-pyrano[2,3-b]pyran-2-one derivative was studied as a model for diarylheptanoid synthesis. Aromatic nucleophiles consistently provided the expected thermodynamic C-aryl pyranoside product. 相似文献
13.
Teresa M.V.D Pinho e Melo Ana L CardosoAntónio M.d'A Rocha Gonsalves 《Tetrahedron》2003,59(13):2345-2351
The dehalogenation of 2-halo-3-phenyl-2H-azirine-2-carboxylates is described. Using sodium borohydride and tributyltin hydride 3-phenyl-2H-azirine-2-carboxylates were obtained in moderate yields. The synthesis of a new 2-bromo-2H-azirines with a chiral auxiliary, 10-phenylsulfonylisobornyl 2-bromo-3-phenyl-2H-azirine-2-carboxylate, is reported. Its dehalogenation led to 10-phenylsulfonylisobornyl 2H-azirine-2-carboxylate as single stereoisomer together with the formation of 10-phenylsulfonylisobornyl acetate. 相似文献
14.
For the synthesis of 2-substituted 4H-4-chromenones, 2-methylsulfonyl-4H-4-chromenones as common intermediate were reacted with nucleophiles such as amines and thiophenol to afford the corresponding 2-substituted adducts in very high yields. 相似文献
15.
Karel Pomeisl Jaroslav Kví?ala Antonín Klásek Vladislav Kubelka Jan ?ejka 《Tetrahedron》2007,63(42):10549-10561
3-(Fluoroacyloxy)quinoline-2,4(1H,3H)-diones react with triethyl phosphite to afford either the product of the Perkow reaction or the corresponding 4-ethoxyquinolin-2(1H)-one. In both reactions, the fluorocarboxylate anion acts as the leaving group. For the corresponding 3-(fluoroiodoacetoxy) derivative this observation precludes the application of the intramolecular Wittig-Horner synthesis to modify quinoline-2,4(1H,3H)-diones by the annulation of a fluorinated but-2-enolide moiety. 相似文献
16.
Teresa M.V.D. Pinho e Melo Ana L. CardosoClara S.B. Gomes António M.d'A. Rocha Gonsalves 《Tetrahedron letters》2003,44(33):6313-6315
2H-Azirine-3-carboxylates unsubstituted at C-2 act as dipolarophiles in the reaction with diazomethane giving new 4,5-dihydro-3H-pyrazole derivatives. The synthesis of a pyrimidine was also achieved via 1,3-dipolar cycloaddition of methyl 2-bromo-3-phenyl-2H-azirine-2-carboxylate with an azomethine ylide. 相似文献
17.
Air stable benzodiazepine containing palladacycles were synthesized by a C-H activation reaction and studied by mass spectrometry and X-ray crystallography. Catalytic C-H functionalizations of 1-methyl-5-phenyl-1H-1,4-benzodiazepin-2(3H)-one with diphenyliodonium hexafluorophosphate led to a mixture, which included the starting material and the expected product 1-methyl-5-(2′-biphenyl)-1H-1,4-benzodiazepin-2(3H)-one. 相似文献
18.
A series of dibenzo-18-crown-6 lariat ethers containing two C7H15 (11), (CH2)2C6F13 (14), (CH2)2C8F17 (15), NHC7H15 (18) and NHCH2C6F13 (19) sidearms were prepared and the single crystal X-ray structure of cis-4,4′-di(1H,1H,2H,2H-perfluorodecyl)-dibenzo-18-crown-6 (15a) is reported. The “light fluorous” dibenzo-18-crown-6 ether (14) has emerged as a stable and robust PTC catalyst, which can be recycled efficiently by fluorous solid-phase extraction, and gives better PTC catalytic activity compared to the parent, non-fluorinated PTC catalyst, dibenzo-18-crown-6, and the alkylated derivative (11) in aliphatic and aromatic nucleophilic substitutions. 相似文献
19.
Double asymmetric induction in Michael reactions has been studied. Enantioselective alkylation of a cyclic ketone (1-indanone) with α-phenyl-nor-gramine was carried out. The relative configuration of (2S∗)-2-[(R∗)-1H-indol-3-yl(phenyl)methyl]-2,3-dihydro-1H-inden-1-one was established by X-ray diffraction. The relative configuration of (R∗,R∗,S∗)- and (S∗,R∗,S∗)-2-1H-indol-3-yl(phenyl)methyl]-2,3-dihydro-1H-inden-1-ols was established by 1H NMR studies. 相似文献
20.
Willem A.L. van Otterlo E. Lindani Ngidi Samuel Kuzvidza Garreth L. Morgans Simon S. Moleele Charles B. de Koning 《Tetrahedron》2005,61(42):9996-10006
Six 4H-chromenes were synthesized from substituted phenols using vinylstannylation and ring-closing metathesis (RCM) as key steps. In addition, a different approach involving amongst other steps, an aryl allyl isomerization and RCM afforded a set of seven 2H-chromenes from phenolic precursors. 相似文献