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1.
The 6-hydroperoxy-1,4-cyclooctadiene (), which is formed in the photosensitized oxygenation of 1,5-cyclooctadiene (), affords on further singlet oxygenation 5,8-dihydroperoxy-1,3-cyclooctadiene (), which via triphenylphosphine reduction leads to -5,8-dihydroxy-1,3-cyclooctadiene () and subsequent pyridinium chlorochromate oxidation to 1,3-cyclooctadien-5,8-dione (). 相似文献
2.
Intramolecular Diels-Alder reactions of all- ethyl 10-diethylamino-2,7,9-decatrienoate and 11-diethylamino-2,8,10-trienoate occur readily to produce and -fused products in ratios of 85:15 and 55:45, respectively. 相似文献
3.
The photochemical addition of CF3I to buta-1,3-diene and vinylacetylene in the gas phase gave 1,4-adducts as the main products. In gas phase reactions only products derived from hydrogen abstraction were detected in the CF3I/penta-1,3-diene system, but the 1,4-adducts again predominated in the liquid phase. CCl3Br similarly gave a mixture of 1,2- and 1,4-adducts, the latter predominating, on photochemical reaction with penta-1,3-diene. The 1,2-adduct was the main product from the CCl3Br/pent-1-en-4-yn reaction, but some hydrogen abstraction was observed. The preference shown by conjugated dienes to give 1,4-adducts in the - configuration is interpreted in terms of steric factors and the propensity of dienes to adopt the - conformation. 相似文献
4.
The reaction of both - and -2-amino-1-(1-phenylvinyl)- cyclopentanols with aldehydes affords -2-alkyl--3a-aryl-4-oxo-octahydro indoles stereoselectively. 相似文献
5.
Structure of an alkaline hydrolysis product of heavenly blue anthocyanin was determined to be -4-0-(6-0-(-3-0-(β-D-glucopyranosyl)caffeyl)-β-D- glucopyranosyl)caffeic acid (). 相似文献
6.
Joseph J. Gajewski Charles W. Benner Bruce N. Stahlly Ralph F. Hall Ronald I. Sato 《Tetrahedron》1982,38(6):853-862
cis- and trans - 2,3 - Dimethylenemethylenecyclopropane ( and ) interconvert at 160.0° with a small normal kinetic isotope effect (KIE) when the exo-methylene is deuterated, but the 1,3-shift products, 2-methylethylidenecyclopropane, show a large normal KIE, 1.35 and 1.31, when formed from and , respectively. This data can be interpreted in terms of either parallel reactions or a common trimethylenemethane diradical intermediate formed with a normal KIE of 1.11 and closing to 1,3-shift product with a normal KIE of 1.29 due to the effect of deuterium in the required 90° rotation of the exo-methylene carbon.The kinetics of the thermal 1,3- and 3,3-shifts of cis- and rans-3,4-dimethyl-1,2-dimethylenecyclobutane ( and ) were determined in a flow reactor. The first order rate constants are log kCB (sec?1) = 13.7 ? 42,200/2.3 RT and log kTB (sec?1) = 13.6 ? 41,900/2.3 RT (Ea in kcal/m) which compare favorably to that from the parent hydrocarbon. 1,2-dimethylenecyclobutane, after reasonable correction for dimethyl substitution.Rearrangement of and its bis(dideuteriomethylene) derivative at 230.0° revealed a normal KIE of 1.08. This KIE could be interpreted in terms of either a methylene rotational isotope effect in a concerted reaction or formation of a bisallyl diradical with the expected normal rotational IE on closure to the 1,3-shift product of 1.12 with no IE in the ring opening when the result is corrected for return of the biradical to starting material.The kinetics of intramolecular 2 + 2 cycloaddition of 1,2,8,9-decatetraene were determined in a flow reactor. The first order rate constant is log k(sec?1) = 9.4 ? 30,800/2.3 RT (Ea in kcal/m). These energetics are compared with those of other 2 + 2 cycloadditions. The major product is 3,4-dimethylenecyclooctene () which is also found from the minor product, cis-7,8-dimethylenebicvyclo[4.2.0]octane (), at higher temperatures. The trans isomer, , also gives at about the same rate as . 相似文献
7.
The temperature dependent CD spectra of two chiral Schiff bases of all--retinal reveal a three-band absorption pattern for the retinal chromophor. A preliminary analysis suggests that the band at 260 nm corresponds to the -peak. 相似文献
8.
The formation of a thermally unstable (4+2)-cycloadduct, a 4H-1,2-oxazine 2-oxide derivative (), from the reaction of 1-nitrocyclopentene with 1-phenyl-2-(1-pyrrolidinyl)acetylene has been proven by the structure elucidation of isoxazole derivative which results from thermal rearrangement and by the structure determination of the 1,3-dipolar adducts of with electron-deficient acetylenes. 相似文献
9.
In the paper a highly stereoselestive route to -1,4-di-tert-butylbutatriene --BuCu induced 1,3-substitution in ()--BuCHC(Br)CCH is described. 相似文献
10.
In an attempt to prepare short-bridged hydroxymetacyclophanes , the spirocyclohexadienones were pyrolyzed by flash vacuum thermolysis (FVT). Instead of , variable amounts of 4-(5-hexenyl)phenol (), β-hydroxybenzocycloalkenes () and 4-(trans-1-alkenyl) phenols () were obtained. The formation of these products is explained by invoking cleavage of a spiro bond in under formation of the intermediate diradical which, depending on the length of the aliphatic chain and on the temperature, has several pathways open for isomerization to spin-paired products. 相似文献
11.
The conformation of several -2,3-diaryloxy-1,4-dioxanes has been studied using 1H NMR techniques. -2,3-bis(4-nitrophenoxy)-1,4-dioxane and -2,3-bis(4-methoxyphenoxy)-1,4-dioxane have been found to be predominantly ( ≈98%) in diaxial conformation in CDCl3). On the other hand, -2,3-bis(2,6-dimethylphenoxy)-1,4-dioxane exists in the same conditions as a 66:33 mixture of diaxial and diequatorial conformers. An explanation based on the fulfilment of the exo-anomeric effect is provided. 相似文献
12.
Youichiro Naito Yoshihisa Inoue Taizo Ono Yoshio Arakawa Chikara Fukaya Kazumasa Yokoyama Yoshiro Kobayashi Kouichi Yamanouchi 《Journal of fluorine chemistry》1984,26(4):485-497
Electrochemical fluorination of N-methyldecahydroquinoline afforded mainly a mixture of and N-(F-methyl)-F-decahydroquinoline, their rearranged isomers and F-propyl-F-cyclohexane arising from the cleavage at carbon-nitrogen bonds, in a ratio of approximately 2:4:6:3. N-Methyldecahydroisoquinoline was also fluorinated electrochemically to give a mixture of and N-(F-methyl)-F-decahydroisoquinoline, their rearranged isomers and 1-(F-ethyl)-2-(F-methyl)-F-cyclohexane in a ratio of approximately 4:4:6:1. No correlation was found between the and ratio of starting materials and that of the corresponding perfluorinated amines. Fluorination of N-methyl-1,2,3,4-tetrahydroquinoline gave much lower yields. 相似文献
13.
Gábor Bernáth Perenc Fülöp Gyula Argay Alajos Kálmán Pál Sohár 《Tetrahedron letters》1981,22(38):3797-3800
8-Aza-12-oxasteroids have been synthesized in a simple three-step process. As a consequence of two stareocontrolled reactions, the product is a stereospecifically homogeneous isomer with all- ring junctions; its structure has been determined by 1H and 13C NMR spectroscopy and X-ray diffraction. 相似文献
14.
The action of either cyanate or acetate ions on -3-mesyloxyflavanones led to the formation of flavones and aurones while the reaction with the respective S-nucleophiles (thiocyanate and thioacetate ions) resulted in -and -3-thiocyanato- and 3-acetylthioflavanones ( and ). The participation of the concurrent nucleophilic substitution, β-elimination and elimination with ring-contraction is dependent on the “hard-soft” character of the nucleophile and the increase of the “soft” character favours the displacement. 相似文献
15.
Françoise Barrière Jean-Claude Barrière Derek H.R. Barton Jeanine Cleophax Alice Gateau-Olesker Stephan D. Géro Fatemeh Tadj 《Tetrahedron letters》1985,26(26):3119-3120
The 1-cyano-1-thiophenylcyclopentone derivative , obtained from (R,R)-(+)-tartaric acid, has been converted into a number of derivatives including the important -(3S,4S)-dibenzyloxycyclopentanone in 45% overall yield. 相似文献
16.
The - and -2-amino-4-cyclohexene-1-carboxylic acids and react with imidates to give the condensed-skeleton, bicyclic - and -pyrimidin-4-ones and . The amino acids and were reduced to the -and -1, 3-aminoalcohoIs and , which were cyclized by means of imidates to the bicyclic tetrahydro-4-3,1-benzoxazines and , or were converted, the corresponding carbamates and into the tetrahydro-4-3,1-benzoxazin-2(1)-ones and . The 2-thioxo analogues and were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols and by treatment with carbon disulphide. The -aminoalcohol and its saturated analogue reacted with -chlorobenzaldehyde to furnish the hexahydro and octahydro-4-3,1-benzoxazine , respectively. 1H and 13C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized isomrs , , and occurred as the preferred conformer in the heterocyclic twist inverse form of -inside type ( C6-N bond) (B). In the isomers containing a saturated C-2 atom ( and ), H-2 and H-6 are in relative positions. 相似文献
17.
Gunda I. Georg 《Tetrahedron letters》1984,25(35):3779-3782
Addition of dianions of 3-hydroxybutyrates to benzylideneaniline results in direct formation of -3-(l-hydroxyethyl)-1,4-diphenyl-2-azetidinone with 95% diastereoselectivity. Inversion of the configuration at Cα, gives the desired -2-azetidinone in high yield. 相似文献
18.
The diborane-mediated reduction of labile β-diketones 4, 5 and 6 has been employed as the key step in the synthesis of the three polyquinanes, all--tetracyclo-[6.6.0.01,5.08,12]tetradecane 1, all--tricyclo[6.3.0.01,5]undecane 2 and all--tetracyclo-[5.5.1.04,13.O10,13]tridecane, staurane 3, respectively. 相似文献
19.
20.
Richard D. Chambers Colin G.P. Jones Michael J. Silvester David B. Speight 《Journal of fluorine chemistry》1984,25(1):47-56
Base-catalysed additions of alcohols to F-2-butyne (1) give mainly products of -addition while -addition predominates in uncatalysed additions of alcohols carried out in a diluent. The stereochemistry of addition of diethylamine is very dependent on the solvent used and - or -addition may predominate. Stepwise and concerted mechanisms are advanced to account for these observations. Nucleophilic addition of sulphur to (1) gives F-tetramethylthiophene (68%) and hydration gives CF3CH2COCF3 (91%). 相似文献