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1.
The action of enamines on tosylated isonitrosomalonic derivatives leads through substitution of the tosyloxy group to substituted 4-amino-2-aza-1,3-dienes. The structure and the configurational (respectively conformational) stability of the 4-amino-2-aza-1,3-dienes suggest a restricted rotation about the C4N bond, a fast rotation about the C3C4 bond and the configurational stability of the azomethinic bond. 相似文献
2.
In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl2 complexes {Cl2Co[P ∼ P]} and Me3Al or methylaluminoxane, acyclic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydrovinylation products. The regioselectivity (1,4- or 1,2-addition) and the alkene configuration (E- or Z-) of the resulting product depend on the nature of the ligand and temperature at which the reaction is carried out. Cobalt(ii)-complexes of 1,1-diphenylphosphinomethane and similar ligands with narrow bite angles give mostly 1,2-addition, retaining the E-geometry of the original diene. Complexes of most other ligands at low temperature (–40 °C) give almost exclusively a single branched product, (Z)-3-alkylhexa-1,4-diene, which arises from a 1,4-hydrovinylation reaction. A minor product is the linear adduct, a 6-alkyl-hexa-1,4-diene, also arising from a 1,4-addition of ethylene. As the temperature is increased, a higher proportion of the major branched-1,4-adduct appears as the (E)-isomer. The unexpectedly high selectivity seen in the Co-catalysed reaction as compared to the corresponding Ni-catalysed reaction can be rationalized by invoking the intermediacy of an η4-[(diene)[P ∼ P]CoH]+-complex and its subsequent reactions. The enhanced reactivity of terminal E-1,3-dienes over the corresponding Z-dienes can also be explained on the basis of the ease of formation of this η4-complex in the former case. The lack of reactivity of the X2Co(dppb) (X = Cl, Br) complexes in the presence of Zn/ZnI2 makes the Me3Al-mediated reaction different from the previously reported hydroalkenylation of dienes. Electron-rich phospholanes, bis-oxazolines and N-heterocyclic carbenes appear to be poor ligands for the Co(ii)-catalysed hydrovinylation of 1,3-dienes. An extensive survey of chiral ligands reveals that complexes of DIOP, BDPP and Josiphos ligands are quite effective for these reactions even at –45 °C and enantioselectivities in the range of 90–99% ee can be realized for a variety of 1,3-dienes. Cobalt(ii)-complex of an electron-deficient Josiphos ligand is especially active, requiring only <1 mol% catalyst to effect the reactions. 相似文献
3.
Prof. Steven T. Diver Elise Glickert Laurence N. Rohde Jr. Thérèse Wild 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202635
A variety of 1-aryl-1,3-dienes were isomerized from E to Z isomers by photocatalysis using Ru(bpy)3[PF6]2 and blue LED light. Enrichment of the Z-isomer is thought to occur by selective triplet energy transfer from the photocatalyst to the stereoisomeric mixture. The 1,3-diene starting materials are easily made by catalytic ene-yne metathesis (EYM). To access 1,3-diene Z-stereoisomers directly, a one pot procedure was developed. Additional 1,3-dienes were investigated for both isomerization and Z-enrichment. The combination of cross EYM with photocatalysis allows for the stereoconvergent synthesis of Z-1,3-dienes. 相似文献
4.
Pieter P.J. MortierFrederik E.A. Van Waes Kurt G.R. MasscheleinThomas S.A. Heugebaert Christian V. Stevens 《Tetrahedron letters》2011,52(33):4273-4276
N-Vinyl 2,2-bisphosphonoaziridines are formed by treatment of 1,1-bisphosphono-2-aza-1,3-dienes with diazomethane. Depending on the substituents at the 4-position of the 1,1-bisphosphono-2-aza-1,3-dienes, exclusively 1-(ethenylamino)-2-phosphonoethenylphosphonates or mixtures of 1-(ethenylamino)-2-phosphonoethenylphosphonates and 2-imino-2-phosphonoethylphosphonates are obtained as side products. 相似文献
5.
Srinivas Reddy Dubbaka 《Tetrahedron》2005,61(6):1523-1530
2-Methylprop-2-ene-1-sulfonyl fluorides can be easily prepared via the ene reaction of methallylsilanes and SO2. In the presence of a base, aldehydes and 2-methylprop-2-ene-1-sulfonyl fluorides give 1,3-(E) and (Z)-dienes. Their (Z)→(E) isomerization by classical means fails or leads to their polymerization. It is shown that SO2 can isomerize 1-aryl-3-methyl-1,3-dienes at low temperature, without formation of sulfolenes (cheletropic addition/elimination). Preliminary mechanistic studies suggest that SO2 adds to 1,3-dienes forming 1,4-diradical intermediates that are responsible for the (Z)→(E) isomerizations. 相似文献
6.
S Jayakumar 《Tetrahedron》2004,60(19):4315-4324
The reactions of 1,3-diazabuta-1,3-dienes 1 with 2-aminothiophenol have been shown to result in excellent yields of N-benzothiazol-2-yl-N′-aryl benzamidines 2. Their regioselective [4+2] cycloadditions with various ketenes are shown to yield novel benzothiazolo pyrimidinones 4. A similar and convenient protocol for the synthesis of bisthiosubstituted 1,3-diazabuta-1,3-dienes 8 and 9 and interesting rearrangements accompanying their [4+2] cycloadditions with a number of ketenes are described. 相似文献
7.
Mirza Arfan Yawer Stefanie Reim Ehsan Ullah Inam Iqbal Helmut Reinke Peter Langer 《Tetrahedron》2007,63(51):12562-12575
A variety of 4-chlorophenols, 10-chloro-7-hydroxy-6H-benzo[c]chromen-6-ones, and 4-chloro-1-hydroxy-9H-fluoren-9-ones were prepared by formal [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-dienes with 2-chloro-3-(silyloxy)alk-2-en-1-ones. 相似文献
8.
The [4+3] cycloaddition of ethyl cyclopropylideneacetate (1) with 1,3-dienes proceeded in the presence of Ni(cod)2-TOPP (tri-o-biphenylyl phosphite). The reaction provided a new method for the synthesis of cycloheptene derivatives. The mechanism of the reaction was proposed. 相似文献
9.
The Cr(CO)3(CH3CN)3 complex is found to catalyze the 1,4-addition of hydrogen to 1,3-dienes such as 2-methyl-1,3-butadiene, trans-1,3-pentadiene, and trans, trans-2,4-hexadiene at low temperature (40°) and low H2 pressure (20 psi). For trans, trans-2,4-hexadiene the only product obtained when D2 is used is 2,5-dideuterio-cis-3-hexene. The catalytic 1,4-hydrogenation can be carried out in neat dienes, and turnover numbers for the catalyst of greater than 3000 have been observed. 相似文献
10.
B. A. Demidchuk V. S. Brovarets A. N. Chernega J. A. K. Howard A. N. Vasilenko A. V. Turov B. S. Drach 《Russian Journal of General Chemistry》2007,77(3):474-481
Reactions of polychlorinated 2-aza-1,3-dienes of the general formuls ArCCl=NCCl=CCl2 with 3(5)-aminopyrazoles, 3(5)-amino-1,2,4-triazoles, and 5-aminotetrazole led to the formation of substituted pyrazolo[1,5-a][1,3,5]triazines, [1,2,4]triazolo[1,5-a][1,3,5]triazines, and 2-azido-1,3,5-triazine derivatives whose structure was reliably established by spectral methods and X-ray analysis. 相似文献
11.
Jianjun Xu 《Journal of fluorine chemistry》2007,128(1):71-77
A straightforward method to prepare symmetrical (1Z, 3Z)- and (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes is described. High E/Z ratio 1-bromo-1-fluoroalkenes, prepared by isomerization from the E/Z ≈ 1:1 isomeric mixtures, reacted with Bu3SnSnBu3 and Pd(PPh3)4 to afford (1Z, 3Z)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in good yield. (Z)-1-Bromo-1-fluoroalkenes, which were prepared by kinetic reduction from 1-bromo-1-fluoroalkenes (E/Z ≈ 1:1), can undergo similar reaction with Bu3SnSnBu3 and Pd(PPh3)4/CuI to prepare (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes. 相似文献
12.
Hetro-Diels-Alder Reaction with 1,3-Thiazol-5(4H)-thiones On heating in toluene to 180° and on treatment with BF3·Et2O in CH2Cl2 room temperature, 1,3-dienes react with the C?S group of 1,3-thiazol-5(4H)-thiones 1 in a reversible Diels-Alder reaction to give spiro[4.5]-heterocycles of type 6. A 1:1 mixture of two regioisomeric cycloadducts is formed in the thermal reaction with 2-methylbuta-1,3-diene (isoprene, 5b ). In contrast, the formation of one regioisomer is strongly preferred in the BF3-catalyzed reaction. Frontier-orbital control as well as steric factors seem to be responsible for the observed regioselectivity. BF3-Catalyzed, cyclic 1,3-dienes and 1 also undergo a smooth Diels-Alder reaction. Whereas cyclohexa-1,3-diene ( 5c ) reacts with 1a and 1b to give a single isomer (presumably the ‘exo’-adduct), cyclopenta-1,3-diene ( 5d ) leads to a ca. 3:1 mixture of ‘exo’-and ‘endo’-isomer. 相似文献
13.
The cross-coupling reaction of (Z) 1-bromo-1-fluoroalkenes catalyzed by PdCl2(PPh3)2-2PPh3 (3%) and CsF in Tetrahydrofuran (THF) in presence of bis(pinacolato)diboron led to (1E,3E) 2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in high yields. 相似文献
14.
Qun Zhao Jianjun Wang Tatiana Besset Xavier Pannecoucke Jean-Philippe Bouillon Thomas Poisson 《Tetrahedron》2018,74(41):6033-6040
Here we reported a Pd-catalyzed coupling reaction between acrylate derivatives and BTP (2-bromo-3,3,3-trifluoropropene) to access 3-trifluoromethylated 1,3-dienes. The reaction allows the formation of the corresponding products in good to excellent yields and moderate Z/E diastereoisomeric ratios. This method broadens the current toolbox to access 3-trifluoromethylated 1,3-dienes. 相似文献
15.
A gas-phase pyrolysis of methyl-substituted gem-difluorocyclopropanes in a flow-tube reactor in the presence of Al2O3 at 185—250 °C gives 2-fluorobuta-1,3-dienes and vinylacetylenes. 相似文献
16.
Alan H. Cowley Nicholas C. Norman Constantine A. Stewart Bruce R. Whittlesey 《Tetrahedron letters》1984,25(33):3519-3520
The stabilized radical, [(Me3Si)2CH]2P·, reacts with 1,3-dienes to afford 1,4-diphosphino-2-butenes. 相似文献
17.
Herein we report that LiAlH4/AlCl3 is a very efficient reagent for the reductive dehydration of aryl propargylic alcohols in tetrahydrofuran solvent at reflux to give 1,3-dienes with good yields and high E selection. The reaction conditions are mild and easy to operate, and a variety of aryl functional groups, such as bromo, fluoro, butyl, and methoxyl groups, are tolerated. With our protocol, useful (E,E)-1,3-dienes can be synthesized. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
18.
CeCl3·7H2O-NaI effectively catalyzed intramolecular cyclization of cyclic 7-hydroxy-1,3-dienes, yielding hexahydrobenzofurans in diastereoselective fashion. This cyclization has been applied to synthesize tetrahydrofurans from acyclic 7-hydroxy-1,3-dienes. 相似文献
19.
Hetero-Diels–Alder reactions of perfluoroalkyl thioamides with electron-rich 1,3-dienes such as 2,3-dimethylbutadiene, isoprene or penta-1,3-diene gave a simple and efficient access to new 2-aminosubstituted-3,6-dihydro-2H-thiopyrans. Three different procedures were used depending on the nature of the polyfluoroalkyl chains (RF=CF3, (CF2)nCF3, (CF2)4H) and on the nitrogen substituents of the thioamides (R1, R2=H, p-Tol, morpholino, Ac). Moreover, cycloadditions of silyloxydienes (1- or 2-trimethylsilyloxy-1,3-butadiene and Danishefsky's diene) with N-acyl,N-tolyl trifluoromethylthioamides afforded in almost all cases the corresponding 3,6-dihydro-2H-thiopyrans or 3-oxo-tetrahydrothiopyrans. For non-symmetrical 1,3-dienes, the regio- and stereochemistry of the reactions were studied (especially using X-ray diffraction analysis) indicating a strong similarity with those reported for fluorinated thiocarboxyl derivatives. Finally, two silylated 3,6-dihydro-2H-thiopyrans underwent an unexpected base-induced ring contraction to give new 1,3-thiazolidin-4-ones. 相似文献
20.
Haizhen Jiang Lan Sun Shijie Yuan Wenjun Lu Wen Wan Shizheng Zhu Jian Hao 《Tetrahedron》2012,68(13):2858-2863
A facile one-pot procedure has been developed for the synthesis of 1,3-imidazolines and 1,3-oxazolines bearing fluorinated alkyl groups at the 2-position. The reaction involves the condensation of N-monosubstituted ethane-1,2-diamines or 2-aminoethanols with a fluorinated carboxylic acid in the presence of PPh3/CX4. The proposed mechanism is that the amide intermediates were initially formed, and then converted to the imidoyl halide intermediates in the presence of PPh3/CX4, followed by rapid intramolecular cyclization to 1,3-diazoline products. This protocol allows for the synthesis of 2-bromodifluoromethyl-1,3-imidazoline, a useful CF2Br-heterocyclic building block, which can be used for the synthesis of gem-difluoromethylene linked compounds. 相似文献