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1.
Isoxazolines 2 from the cycloaddition of imidazoline 3-oxides 1 with DMAD rearrange in the presence of methoxide to give cis-3-methoxy-7-(methoxycarbonyl)-2,7a-diaryl-5-oxo-2,3,5,7a-tetrahydro-1H-pyrrolo[1,2-e]imidazol-6-olates 3 with 100% de. The acidic hydrolysis of 3 led to kinetically controlled formation of methyl 1-formyl-4-hydroxy-5-oxo-2-phenyl-2-((arylamino)methyl)-2,5-dihydro-1H-pyrrole-3-carboxylates 6a-e. The intramolecular transformylations of the latter to the corresponding (E)- and (Z)-methyl 4-hydroxy-2-((N-(aryl)formamido)methyl)-5-oxo-2-phenyl-2,5-dihydro-1H-pyrrole-3-carboxylates 7a-e were shown to be substituent dependent (correlate with σ) and characterized by Hammett type equations. The effect of temperature was investigated and the ρ constants determined for the same reaction series at 50, 60 and 70 °C. The amide diastereomeric ratio [(E)-7]/[(Z)-7] is substituent dependent and can be described by the equation log[(E)]/[(Z)]x=−ρσI+log[(E)]/[(Z)]x=H. 相似文献
2.
Ahmed El-GokhaGerhard Maas 《Tetrahedron》2011,67(16):2849-2857
A diastereomeric mixture of dimethyl (2-formyl-2-methyl-1-phenylcyclopropyl)phosphonate ((Z)-6, (E)-6) was obtained by thermally induced cyclopropanation of α-methylacrolein with α-diazobenzylphosphonate 5. Application of proline or proline-derived organocatalysts accelerated the reaction, but had a minor effect on the Z/E ratio of 6. By reaction with benzylamine or methyl esters of glycine, (S)-alanine, and (S)-phenylalanine, the Z/E-mixture of 6 was converted into cyclopropylaldimines, which after reduction gave the corresponding N-substituted (2-aminomethyl-cyclopropyl)phosphonates. 相似文献
3.
4.
A new method for the synthesis of fluoromethylenecyclopropane nucleosides by alkylation-elimination procedure is described. Fluorination of methylenecyclopropane carboxylate 6 gave fluoroester 7. Treatment of 7 with phenylselenenyl bromide afforded the desired ethyl (E)-2-bromomethyl-1-fluoro-2-phenylselenenylcyclopropane-1-carboxylate 11 in 85% yield. DIBALH reduction of 11 gave 13, which after acetylation to 14 was reacted with 2-amino-6-chloropurine to give the 9-alkylated product 15 in 87% yield. Se-oxidation of 15 with hydrogen peroxide afforded 16, which underwent smooth elimination in a mixture of THF-DMF at 60 °C giving rise to a Z,E mixture of protected nucleosides 17. Deacetylation gave Z-1a and E-1a which were separated on a silica gel column. Both Z-1a and E-1a were converted into the respective guanine analogues Z-1b and E-1b. 相似文献
5.
Palladium-catalyzed methoxycarbonylation of (−)-(2R,3S)-1-tert-butyldimethylsiloxy-3-methyl-2-methoxypenta-4-yne 9 derived from (2R,3S)-epoxy butanoate 5 gave the acetylenic ester 10, which was treated with MeOH in the presence of Bu3P to afford selectively (Z)-β-methoxy acrylate congener 11 in 86% yield. Treatment of (Z)-11 with 99.8% enrichment of CDCl3 followed by consecutive desilylation and oxidation afforded the left-half aldehyde (+)-2. The overall yield (10 steps from 5; 23%) of (+)-2 via the present route was improved in comparison to that (10 steps from 5; 10%) of the previously reported route. By applying the modified Julia's coupling method, selectivity (E/Z=14:1) of the (E)-form (cystothiazole A 1) against the (Z)-form was improved in comparison to the Wittig method (E/Z=4:1 to 6.9:1). 相似文献
6.
(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-phenyl-2-thioxothiazolidin-4-one (7a-q) derivatives have been synthesized by the condensation reaction of 3-phenyl-2-thioxothiazolidin-4-ones (3a-h) with suitably substituted 2-(1H-indol-3-yl)-2-oxoacetaldehyde (6a-d) under microwave condition. The thioxothiazolidine-4-ones were prepared from the corresponding aromatic amines (1a-e) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a-h) were synthesized from the corresponding acid chlorides (5a-d) using HSnBu3. 相似文献
7.
(1Z,3Z)-Butyltelluro-4-methoxy-1,3-butadiene 2 was obtained by the hydrotelluration of (Z)-1-methoxy-but-1-en-3-ynes 1. The butadienyllithium 3 obtained by the Te/Li exchange reaction in the (1Z,3Z)-1-butyltelluro-4-methoxy-1,3-butadiene 2 reacted with aldehydes to form the corresponding alcohols 4a-d with total retention of configuration. The alcohols formed undergo hydrolysis, resulting in the α,β,γ,δ-unsaturated aldehydes of (E,E) configuration, which are precursors of trienes obtained from natural sources. The products of this reaction were employed in the synthesis of methyl-(2E,4E)-decadienoate 7, which is a component of the flavor principles of ripe Bartlett pears. Performing the Wittig reaction of the methyl triphenylphosphorane with the deca-(2E,4E)-dienal 5a, we were able to synthesize the undeca-(1,3E,5E)-triene 6a. This compound is a sex-pheromone component of the marine brown algae Fucus serratus, Dictyopteris plagiograma, and Dictyopteris australis. Performing the Wittig reaction of methyl triphenylphosphorane with the octa-(2E,4E)-dienal 5c, the nona-(1,3E,5E)-triene 6b was synthesized. The compound obtained is a sex-pheromone component of the marine brown alga Sargassum horneri. The octa-(1,3E,5E)-triene 6c was easily obtained from hepta-(2E,4E)-dienal 5d by the Wittig reaction with methyl triphenylphophorane. This compound is a sex-pheromone component of the marine brown alga Fucus serratus. 相似文献
8.
《Tetrahedron》2003,59(7):1021-1032
The conjugate (E)- and (Z)-(4′-pyridylethenyl)-4-phenylethyne (E-4 and Z-4) has been satisfactorily prepared by two different routes: (a) by dehydrohalogenation of 4′-pyridylethenyl-4-phenyl-β-chloroethene; (b) by the Wittig reaction between p-(iodobenzyl)(triphenyl)phosphine ylide and 4-pyridinecarboxaldehyde, E/Z isomer separation, and cross-coupling with 2-methyl-but-3-yn-2-ol followed the propanone elimination. The Glaser oxidative dimerization of (Z)-4 yields (Z,Z)-1,4-di[(4′-pyridylethenyl)-4-phenyl]-buta-1,3-diyne in good yield, (Z,Z)-5. (E,E)-5 was obtained by phase transfer oxidative dimerisation of (E)-4 in presence of their N-methyl salt (E)-10. Mono- and di-N-methylated salts of conjugate (E,E)-5 and (Z,Z)-5, were obtained by quaternation with iodomethane. The (Z,Z)-5 di-N-methylated salt forms charge-transfer complexes with TCNE, TCNQ and TMPD. 相似文献
9.
Karel Pomeisl 《Journal of fluorine chemistry》2006,127(10):1390-1397
Mixtures of ethyl (E)- and (Z)-4-alkoxy-2-fluoro-3,4-diphenylbut-2-enoates (6-8) prepared from benzoin ethers and ethyl 2-(diethoxyphosphoryl)-2-fluoroacetate were transformed in high yields to the target 3-fluoro-4,5-diphenylfuran-2(5H)-one (14) using bromine in tetrachloromethane at room temperature. The non-cyclisable Z-isomers 6b-8b were gradually isomerised to the cyclisable E-isomers 6a-8a during the process. The reaction of the (E)-butenoates 6a-8a with boron trifluoride led to furanone 14, while in Z-isomers 6b-8b both alkoxy group and vinylic fluorine were substituted with bromine during the reaction. Mechanisms for both complex reactions have been proposed. Furanone 14 was transformed to 2-[tert-butyl(dimethyl)silyloxy]-3-fluoro-4,5-diphenylfuran (18) as a novel building block. 相似文献
10.
Zhichao Ma 《Tetrahedron》2008,64(27):6500-6509
A Na2S2O4-promoted radical addition reaction of perfluoroalkyl iodides with allenes has been studied in which a Z/E mixture of 2-iodo-1-perfluoroalkyl-2-alkenes 3 were afforded in 52-69% yields. A kinetic resolution using Sonogashira coupling reaction in MeCN using Et2NH as the base was developed to synthesize the 2-iodo-1-perfluoroalkyl-2(Z)-alkenes (Z-3) and E-4-perfluoroalkylmethylalk-4-en-2-ynols (E-5) stereoselectively. A complete Sonogashira coupling procedure in Et2NH at 40 °C was also developed affording a mixture of E and Z-4-perfluoroalkylmethyl-4-en-2-ynols (E-5 and Z-5), which may be easily separated by chromatography on silica gel. 相似文献
11.
Sarah HelbigKirill V. Axenov Stefan TussetschlägerWolfgang Frey Sabine Laschat 《Tetrahedron letters》2012,53(27):3506-3509
Chiral tetrahydropentalenes (3aR,6aR)-1 have been prepared and used as ligands in the Rh-catalyzed 1,4-addition of 1-alkenylboronic acids to cyclic enones 5. It has been discovered that the stereochemistry of the reaction was controlled by the steric properties of the aryl groups in 1 rather than their electronic nature. In the vinylation with (E)-2-phenylethenylboronic acid 5, ligands (3aR,6aR)-1 provided enantioselectivity up to 87% ee and gave high yields of ethenylketones 6 in the presence of 1 (6.6 mol %). The configuration of all ketone products obtained with (3aR,6aR)-1 is (S). Rh-catalyzed reaction of cyclopentenone 4a and (Z)-propenylboronic acid 7 in the presence of ligands (3aR,6aR)-1 yielded at 50 °C an inseparable mixture of (Z)- and (E)-ketones 8 with (Z)-8 as the major product and both in only moderate enantiomeric excess. 相似文献
12.
Pentacarbonyl(η2-cis-cyclooctene)chromium(0) (1) catalyzes efficiently reactions of diazo compounds with electron-rich furans. The reaction of 2-methoxyfuran (2) with alkyl α-diazoarylacetate (3a-g) furnishes the (2E,4Z)-2-aryl-hexadienedioic acid diesters (4a-g) in excellent yields. These reactions are highly regioselective. The cyclopropanation intermediates formed from 1 and diazo compounds 3a-g always arise from a carbene addition to the less substituted CC bond of 2. The resulting cyclopropanation product undergoes a ring opening reaction to form the corresponding (2E,4Z)-2-aryl-hexadienedioic acid diesters (4a-g). The pentacarbonylchromium(0)-catalyzed reactions of 2-alkylfuran (5a-b) with ethyl α-diazophenylacetate (3a) and 9-diazo-9H-fluorene (3h) produce the 1(E),3(E)-butadienes (6a-d) in very good yields. 相似文献
13.
Three new unstable metabolites, (6E,10Z)-2′-O-methylmyxalamide D (1), 2′-O-methylmyxalamide D (2) and (6E)-2′-O-methylmyxalamide D (3) were isolated from the myxobacterium Cystobacter fuscus. The planar structures were elucidated by spectroscopic analyses to be geometrical isomers of a polyene amide related to a myxobacterial metabolite, myxalamide D (4). Their absolute stereochemistry was determined by synthesis of degradation products. Antifungal activities of 1-3 as well as their acetates were evaluated against the phythopathogenic fungus Phythopthora capsici. 相似文献
14.
We designed two aromatic analogues 1a and 1b of macrolactin A with expectation of enhancing biological activity and metabolical stability. As a result of retrosynthetic analysis of these compounds 1a-b, two synthetic strategies have been examined. The first strategy includes the enantioselective addition of nonadienyl anion, derived from 3, to aldehyde 4 as a key step. The second one includes epimerization of ynone 7 to (E,E)-conjugated dienone 31 and subsequent diastereoselective hydride-reduction of 31. Although the former route furnished no desired target, the latter one was revealed to work well for the synthesis of 1. Unfortunately, the aimed (2Z,4E)-analogue 1a could not be synthesized due to an epimerization of the (2Z)-olefin into the (2E)-olefin. However, these methods could be applied to the total asymmetric synthesis of the (2E,4E)-analogue 1b. Overall, control of all of the four stereocenters was achieved by means of asymmetric and diastereoselective reactions without using any chiral natural sources. 相似文献
15.
Interest in the synthesis of the C(23)-C(40) fragment 2 of tetrafibricin prompted us to develop a new method for the synthesis of 1,5-syn-(E)-diols. Toward this end, the kinetically controlled hydroboration of allenes 6, 33, ent-39, 42, and 45 with the Soderquist borane 25R were studied. Tetrabutylammonium allenyltrifluoroborate 45 gave superior results and was utilized in a double allylboration sequence with two different aldehydes to provide the targeted 1,5-syn-(E)-diols in generally high yields (72-98%), and with high enantioselectivity (>95% ee), diastereoselectivity (dr >20:1), and (E)/(Z) selectivity (>20:1). This new method was applied to the synthesis of the C(23)-C(40) fragment 2 of tetrafibricin. 相似文献
16.
Highly functionalized (E)-stilbenes 3a-m and 4-aryl-6-styryl-pyran-2-ylidineacetonitriles 4a-b have been prepared and delineated through the ring transformation of 6-aryl-3,4-disubstituted-2H-pyran-2-ones 1 with commercially available (E/Z)-4-phenyl-3-buten-2-one 2 without the use of any catalyst. 相似文献
17.
Thorsten Lifka 《Tetrahedron》2008,64(27):6551-6560
(E,E)-3,6-Bis(styryl)pyridazines (3a-t) bearing 2, 4 or 6 alkoxy chains were prepared by applying the Siegrist reaction of 3,6-dimethylpyridazine (13) and the corresponding azomethines 10a-t. The transversal dipole moment of these calamitic compounds effects an extremely high tendency for self-organization in thermotropic LC phases (N, SA, SB, SC, SE, SI/F, and Cub). The conjugated core structure represents moreover a chromophore with a high photosensitivity for (E,E)?(E,Z) isomerization reactions: this property makes the compounds interesting for optical imaging and switching techniques. 相似文献
18.
Shigeki Sano Yoko Kuroda Katsuyuki Saito Yukiko Ose Yoshimitsu Nagao 《Tetrahedron》2006,62(51):11881-11890
(Z)-α-Fluoro-α,β-unsaturated esters (Z)-7a-f were stereoselectively prepared by a tandem reduction-olefination of triethyl 2-acyl-2-fluoro-2-phosphonoacetates 6a-f with NaBH4 in EtOH. A concise synthesis of Cbz-Gly-Ψ[(Z)-CFC]-Gly (26) as a dipeptide isostere was achieved via the tandem reduction-olefination of the corresponding 2-acyl-2-fluoro-2-phosphonoacetate 20. 相似文献
19.
Herbert Meier Thorsten Lifka Peter Seus Annette Oehlhof Sabine Hillmann 《Tetrahedron》2008,64(47):10754-10760
3,6-Bis(styryl)pyridazines 1a-f with 2-6 alkoxy groups show on irradiation in solution a stereoisomerization which leads to a photostationary state of (E,E)- and (E,Z)-isomer. Sensitizing and quenching experiments reveal that the (E,E)→(E,Z) route is a pure triplet process, whereas the (E,Z)→(E,E) route can have a minor singlet by-reaction.Hexyloxy or dodecyloxy chains on the terminal benzene rings convey the (E,E)-isomers of compounds 1a,b,d-f thermotropic liquid crystalline properties. In particular SA, SC, and SF/I phases were studied with regard to their photochemical behavior. Depending on the system, photodegradation of the smectic phase to the isotropic melt (S→I) or photoinduction of the smectic phase (I→S) can be achieved by alteration of the (E,E)/(E,Z) ratio. These processes represent the basis for imaging techniques (writing and erasing of information). 相似文献
20.
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