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1.
Reaction of mucochloric and mucobromic acid with (ethoxycarbonylmethylene) triphenyl-phosphorane affords the ethyl ester of (2, 4 -4,5-dichloro- and (2, 4) -4, 5-dibromo-2,4-pentadienoic acid respectively; in the latter case ethyl (2 -5-bromo-2-penten-4-ynoate is formed concomittantly. 相似文献
2.
E.G. Frandsen 《Tetrahedron》1977,33(8):869-873
The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2,5-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2-benzo [b]-pyran-2,4-diones. 相似文献
3.
Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones () and () were prepared by treataent of the salts () and () with carbonate anion on polymeric support. The hydrolysis under basic conditions of () and () afforded the erythro-3-amino-1,2-diols () and () which were fully acetylated: the 2-amino-2-deoxyerythritol derivative () was obtained in 91% yield. 相似文献
4.
The cycloaddition of α,β-epoxyaldehydes or ketones () with the ketene acetal MeHC=C(OMe)2 () gives epoxyoxetanes () in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones () via the epoxy esters and trihydroxy esters (). The lactones appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones () and 3-methyl-5-ylidene-2-5H-furanones () 相似文献
5.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Akihiko Tomoto 《Tetrahedron letters》1981,22(37):3629-3632
1-Benzoyl-2-methy1-3,4-dihydro-2-thianaphthalene () underwent novel intermolecular 1,4-rearrangement in refluxing toluene to give an enol ether , while rearrangement of 2-phenyl derivative proceeded intramolecularly in refluxing xylene to afford a 1,4-rearranged enol ether . On the other hand, ylides were refluxed in alcohols to afford some ring-opened products . 相似文献
6.
Ignacio H. Sánchez María Isabel Larraza Fernande Basurto Ricardo Yaf?ez Salvador Avila Ricardo Tovar Pedro Joseph-Nathan 《Tetrahedron》1985,41(12):2355-2359
(±)--methylperezone () was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether (). Compound () was prepared by condensation of 2,3,5-trimethoxytoluene () with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor was prepared in four steps from 2,3-dimethoxytoluene () and, alternatively, in three steps from 5-bromoveratraldehyde (). Racemic and were directly compared with the optically active molecules prepared from natural R(-)-perezone (). 相似文献
7.
Condensation of 3-fluoro-2-butanone () with alkyl diethylphosphonoacetates () gave alkyl 4-fluoro-3-methyl-2-pentenoates (). Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates () which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2- pentenoates (). Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (), another route was taken. The esters were hydrogenated to alkyl 4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine (). 相似文献
8.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
9.
4,4-Dimethyl-2-phenyl-2-thiazolin-5-thione () reacts with 2,3-diphenylcyclopropenone () at 145°C and with benzonitrilio-2-propanide () at room temperature to yield the 1,6-dithia-spiro[4.4]nonadienes and , respectively. 相似文献
10.
Janina Karolak-Wojciechowska Marian Mikołajczyk Andrzej Zatorski Katarzyna Kiec-Kononowicz Alfred Zejc 《Tetrahedron》1985,41(20):4593-4602
The crystal and molecular structures of the title isomeric compounds and , obtained by intramolecular N,S--dialkylation of 5,5-diphenyl-2-thiohydantoin with 1,2-dibro-moethane, have been determined from X-ray diffractometer data. 2,3-Dihydro-6,6-diphenylimidazo-[2,1-b]-thiazol-5(6H)-one crystallizes in space group P212121 with a=11.376(3), b=12,255(5), c=8.434(3) Å and Z=4. Crystals of , containing one molecule of benzene, are monoclinic,space group P21/c with a=11.539(6), b=10.242(3), c=16.353(5) Å, β=95.45(5)° and Z=4. In both cases a planar geometry of the two fused five-membered heterocyclic rings was found. The selected bond lengths in and , as well as those analogous imidazothiazinones and , were used to calculate EHOSE (Harmonic Oscillation Stabilization Energy). The problem of stability and chemical reactivity of compounds to is also discussed. 相似文献
11.
Haruhisa Shirahama Kiyoharu Hayano Yoshiro Kanemoto Shunjiro Misumi Toshikazu Ohtsuka Nobuhiro Hashiba Akio Furusaki Shizuaki Murata Ryoji Noyori Takeshi Matsumoto 《Tetrahedron letters》1980,21(50):4835-4838
Two cyclohumulanoids, dl-bicyclohumulenone () and dl-africanol ( were synthesized through newly developed conformationally selective transannular cyclization of humulene 9,10-epoxide (). The epoxide was converted to a bicyclohumulenediol diacetate in 70% yield by treatment with BF3·OEt2-Ac2O, while treatment of with trimethylsilyl trifluoromethansulfonate gave an africen-10-ol (a and b) in 80% yield. The two intermediates and furnished the natural products and in 30 and 8 % yield from respectively. 相似文献
12.
4-(N-Alkylimino)methyl-2,6-di--butylphenols (), Schiff bases of 3,5-di--butyl-4-hydroxybenzaldehyde can be oxygenated in the presence of Co(Salpr), a five coordinate Co(II)-Schiff base complex to give N-alkyl-3--butyl-5-formyl-2-hydroxy-2-pivaloyl-1,2-dihydropyridines ( as the main product together with 3-formyl-2,5-di--butyl-2,4-cyclopentadienone () and 2,6-di--butyl-4-formyl-6-hydroxy-4,5-epoxy-2-cyclohexenone (). These products result from dioxygen incorporation into the ortho position of . 相似文献
13.
The protection of the 6-oxo group of deoxyguanosine with the 2-trimethylsilylethyl (), phenylthioethyl (), 4-nitrophenylthioethyl (), 4-nintrophenethyl (), and cyanoethyl () groups is described. Each protecting group is introduced in good yield and is cleaved under mild conditions. Compatibility with the various approaches to oligonucleotide synthesis is discussed. 相似文献
14.
Organolithium react with 5-ethoxy 2,5 dihydro-furan-2-one , easily obtained by photoxidation of furfural, leading selectively to 5-hydroxy-2,5-dihydro-furans or to 5-ethoxy-2,5 dihydro-furans disubstituted on carbon 4 ; the odcydation of the hemi-acetals transforms them with good yields in 3-2 butenolides disubstituted on carbon 4. 相似文献
15.
Two minor lipid components of the brown seaweed were characterized as (all Z) - 5′,7′-dihydroxy-2′-nonadeca-4,7,10,13,16-pentenyl-chrome chromone () and 5′,7′-dihydroxy-2′-pentadecylchrome (). 相似文献
16.
Tsutomu Kumagai Akihiko Tokida Kazuo Kidoura Osamu Seshimoto Toshio Mukai 《Tetrahedron letters》1982,23(8):873-876
The reactions of 1H-azepine derivatives ( and ) with singlet oxygen gave the [6+2] cycloadducts () and the [4+2] cycloadducts ( and ). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated. 相似文献
17.
Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′, 2, 2″, 5, 6)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′, 2, 5, 6)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran. 相似文献
18.
Tetsuji Kametani Hiroo Matsumoto Toshio Honda Mitsuo Nagai Keiichiro Fukumoto 《Tetrahedron》1981,37(15):2555-2560
A stereoselective synthesis of des-A-ring steroids and has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2-one-2-ethylene ketal and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol , respectively. 相似文献
19.
2-Alkoxy-5-furan-4-ones (7,8) and 4-alkoxy-5-furan-2-ones (4,5) were prepared regiospecifically and in high yields from tetronic acids (4-hydroxy-5-furan-2-ones) (2) in the first case by acetylating the 4-OH group and then reacting with trialkyloxonium tetrafluoroborate, and in the second case by alkylating tetrabutylammonium tetronates with dialkyl sulfate, respectively. Direct alkylation of tetronic acids with trialkyloxonium tetrafluoroborate gave in four cases regiospecific 2-O-alkylation, in one case 4-O-alkylation and in two other cases mixtures of 2- and 4-alkoxy derivatives. 相似文献
20.
In the presence of 1-methylimidazole, 2--acyl guanine (as in ), thymine (as in ) and uracil (as in ) residues react readily with the phosphorylating agent derived from 2-chlorophenyl phosphorodichloridate () and 1-hydroxybenzotriazole. 相似文献