共查询到20条相似文献,搜索用时 15 毫秒
1.
Yasser M.A. MohamedTrond Vidar Hansen 《Tetrahedron letters》2011,52(10):1057-1059
The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product. 相似文献
2.
Qibo Liu 《Journal of fluorine chemistry》2011,132(2):128-130
Palladium(0) catalyzed coupling of β-bromostyrene (E/Z = 89/11) with (E)-(1,2-difluoro-1,2-ethenediyl)bis[tributylstannane], 1, in DMF at room temperature stereospecifically gave only (1E,3E,5E)-3,4-difluoro-1,6-diphenylhexatriene. Similarly, palladium(0) catalyzed coupling of (E)-ethyl 3-bromoacrylate as the vinyl halide precursor stereospecifically gave (2E,4E,6E)-diethyl-4,5-difluoroocta-2,4,6-trienedioate. This work demonstrates that a non-fluorine-containing vinyl bromide will selectively undergo coupling with 1 and enable the stereospecific preparation of a mixed polyene system. The (E)-ethyl 3-bromoacrylate coupling with 1 illustrates that mixed functionalized hexatriene systems can be easily accessed via this methodology. The X-ray structure of (2E,4E,6E)-diethyl-4,5-difluoroocta-2,4,6-trienedioate confirmed its structure. 相似文献
3.
An efficient synthetic method for the preparation of (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles has been developed. The reaction of (E)- and (Z)-3-styrylchromones with hydrazine hydrate afforded the corresponding (E)- and (Z)-4-styrylpyrazoles, respectively, saved 4′-nitro-derivatives where both (E)- and (Z)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations was discussed and the stereochemistry of all products was assigned by NMR experiments. 相似文献
4.
Jin Liu Kelly J. Boarman Natalie L. Wendt Lina M. Cardenas 《Tetrahedron letters》2005,46(30):4953-4956
Photoisomerization of five fluorinated E,E-1-(R-phenyl)-4-phenyl-1,3-butadienes in solution (R = 1: p-monofluoro, 2: m,m′-difluoro, 3: m,m′,p-trifluoro, 4: o,o′,m,m′-tetrafluoro, 5: o,o′,m,m′,p-pentafluoro) was investigated via direct irradiation. Our results indicated that cis-trans photoisomerization of the fluorinated 1,4-diphenyl-1,3-butadienes in the excited singlet state took place exclusively at the CC bonds closer to the fluorine substituents. 相似文献
5.
Ethyl (Z)-3-fluoropropenoate (Z-5) has been prepared in a pure state in 68% yield by a Wittig procedure developed by Burton. Ethyl (E)-3-fluoropropenoate (E-6) was prepared in 38% yield following the synthetic method of Purrington. The Z isomer gives cycloaddition with 1,3-diphenylisobenzofuran and cyclopentadiene to give a product with completely endo configurations. The E isomer also gives cycloadducts with same dienes to give mixtures of endo and exo products. 相似文献
6.
Pieter Van der VekenIstván Kertèsz Kristel SentenAchiel Haemers Koen Augustyns 《Tetrahedron letters》2003,44(33):6231-6234
(E)- and (Z)-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors were synthesized. A Wadsworth-Horner-Emmons reaction, followed by amide formation and reduction of the amide were used for the construction of the α-fluoro-α,β-unsaturated amine functionality. 相似文献
7.
Qibo Liu 《Journal of fluorine chemistry》2009,130(10):922-925
(E)-(1,2-Difluoro-1,2-ethenediyl)bis[tributylstannane], 3, readily undergoes a Pd(PPh3)4/CuI-catalyzed cross-coupling reaction with iodotrifluoroethene to yield (E)-octafluoro-1,3,5-hexatriene, 4, in high isomeric purity. (1Z,3E,5Z)-(1,2,3,4,5,6-Hexafluoro-1,3,5-hexenetriyl)bis[tributylstannane], 7, was sequentially prepared from (1Z,3E,5Z)-(1,2,3,4,5,6-hexafluoro-1,3,5-hexenetriyl)bis[triethylsilane], 5, which was prepared via a Pd(PPh3)4/CuI-catalyzed cross-coupling reaction of 3 with (E)-1,2-difluoro-1-iodo-2-triethylsilylethene, 6. Pd(PPh3)4/CuI cross-coupling of 7 with iodotrifluoroethene gave (3E,5E,7E)-dodecafluoro-1,3,5,7,9-decapentaene, 8. 相似文献
8.
Direct irradiation of the 1E,3E isomers of six cisoid fluorinated butadienes in an organic solvent at room temperature showed a predominant formation of the 1Z,3E isomers. 相似文献
9.
Reaction of (E)-2-(benzylidene-amino)ethanol 2 with nitric oxide afforded an (E)-rotamer dominant mixture of (E)- and (Z)-N-nitroso-2-aryl-1,3-oxazolidine 3 at room temperature in good overall yields. 相似文献
10.
Fabrice Lacombe 《Tetrahedron》2004,60(34):7315-7324
A concise, practical and stereoselective entry into macrocyclic (E)-alkenes is outlined comprising a sequence of ring closing alkyne metathesis (RCAM), trans-selective hydrosilylation of the resulting cycloalkynes catalyzed by [Cp∗Ru(MeCN)3]PF6, and a protodesilylation of the ensuing vinylsilanes with AgF in aq. THF/MeOH. Moreover, the first examples of intramolecular enyne-yne metathesis reactions catalyzed by the Schrock alkylidyne complex (tBuO)3WCCMe3 are reported; the resulting cyclic enynes can be converted along similar lines into the corresponding (E,E)-configured 1,3-dienes in good overall yields. Cycloalkyne 4 and the (E)-configured cyclic olefins 6 and 21 were characterized by X-ray crystallography. 相似文献
11.
Rhodium-catalyzed carbonylative cyclization without carbon monoxide was investigated. Cyclization of various formamides having alkynyl groups proceeded smoothly in the presence of Rh4(CO)12 to provide α-alkylidene-γ-lactams or 3-alkylideneoxindoles in moderate to good yields with high (E)-selectivity. 相似文献
12.
Bárbara Menéndez Pérez 《Tetrahedron letters》2009,50(8):960-11295
Stereoselectivity for (5-phenyltetrahydrofur-2-yl)alkan-1-ol formation (cis:trans < 1:99) from 5-methyl- and 5-phenyl-substituted 1-phenylpent-4-en-1-ols via cobalt-catalyzed aerobic oxidation was independent of the olefinic π-bond configuration of the substrates. 相似文献
13.
Acyclic conjugated (E,Z,E,E)-tetraenes, upon thermolysis, undergo a domino pericyclic process involving 6π electrocyclisation of the (E,Z,E)-triene moiety to give the corresponding cis-disubstituted 5-vinyl-1,3-cyclohexadienes, followed by an intramolecular Diels-Alder reaction with the vinyl side chain to give tricyclo[3.2.1.02,7]oct-3-enes. 相似文献
14.
Direct oximation of 2-oxo-2-phenylacetate (3) gave the (Z)-methyl 2-(methoxyimino)-2-phenylacetate (1) in 71% yield, while the E oxime 2 was prepared from 3 in 65% yield via oxime isomerization of 2-(methoxyimino)-2-phenylacetic acid (5). Computational studies suggest that the isomerization of 5 is thermodynamically driven, while the direct oximation of ketoester 3 is kinetically controlled. 相似文献
15.
The homocoupling reaction between the conjugated n-(2-chloroethenyl)pyridine; n, 2-, 3- and 4- (or quinoline; n, 2- and 4-) mediated by zero-valent nickel complexes at room temperature affords to the corresponding 1,4-diaryl-1,3-butadiene, always as the 1E,3E stereoisomer. The yield in 1,4-diaryl-1,3-butadiene increases with the nickel catalyst and hence, the active zero-valent nickel catalyst is not regenerated during the homocoupling reaction.The stereospecific synthesis of (1Z,3Z)-1,4-di(4′-pyridyl)-1,3-butadiene stereoisomer was efficiently carried out by partial hydrogenation of the appropriate 1,4-di(4′-pyridyl)-1,3-butadiyne. 相似文献
16.
Chongzhao Ran 《Tetrahedron letters》2004,45(42):7851-7853
An efficient approach for synthesis of the food odorant 2E,4E,6E-dodecatrienal (DTE) by extension of 2E,4E-decadienal (DDE) is reported. DTE shows higher protein crosslinking ability than the lipid peroxidation products DDE and 4-hydroxy-2E-nonenal. 相似文献
17.
Reaction of 1,1-dimethoxy-2-butyne (II) with sodium methoxide in dimethyl sulfoxide at 100° yields (1E)-1,3-dimethoxybutadiene (III) (20–30%). The diene III undergoes ready Diels-Alder reaction with maleic anhydride, N-phenyltriazolinedione and dimethyl acetylenedicarboxylate. 相似文献
18.
N. A. Anisimova A. A. Kuzhaeva G. A. Berkova V. M. Berestovitskaya 《Russian Journal of General Chemistry》2009,79(7):1458-1460
Synthesis of a new representative of β-aminophosphonic acids and related esters, namely, 11-amino-9,10-dihydro-9,10-(ethano)anthracen-12-ylphosphonic
acid and the respective bis(2-chloroethyl)-phosphonate was carried out. 相似文献
19.
Gildas PriéSébastien Richard Jean-Luc ParrainAlain Duchêne Mohamed Abarbri 《Journal of fluorine chemistry》2002,117(1):35-41
(E)- or (Z)-perfluorinated β-enaminoesters were prepared by direct addition of primary or secondary amines to ethyl perfluoroalkynoates without any catalyst. 相似文献
20.
A simple, novel diastereoselective synthesis of both (E)- and (Z)-allylsilanes via organoboranes is developed. (E)-1-Alkenylboronate esters easily prepared from the corresponding terminal alkynes via hydroboration with dibromoborane-methyl sulfide complex followed by treatment with 1,3-propane diol readily react with trimethylsilylmethyllithium at −78 °C in methanol followed by reaction with iodine in methanol to produce the corresponding (Z)-allylsilanes in high yields (72-80%) and in high stereochemical purities (98% as evidenced by CMR spectral data). Similarly, the (Z)-1-alkenylboronate esters react with trimethylsilylmethyllithium at −78 °C in methanol followed by treatment with iodine in methanol to produce the corresponding (E)-allylsilanes in moderate yields (57-65%) in high stereochemical purities (>98% as revealed by CMR spectral data). 相似文献