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1.
Three new electron donors, acenaphtho[5,6-]-1,2-dithiole (), acenaphtho[5,6-]-1,2-diselenole (), and acenaphtho[5,6-]-1,2-ditellurole (), can be prepared in 28%, 22%, and 14% yields respectively by reaction of the elemental chalcogens (S, Se, Te) with 5,6-dilithioacenaphthylene (). Compound is generated by treatment of 5,6-dibromoacenaphthylen (), for which a convenient preparation is described, with -butyllithium (2 equiv.) in THF at ?78°C. 相似文献
2.
Two cleavage products, -dimethylmuconate () and -dimethyl-muconate (), are inefficiently produced in the 9,10-dicyanoanthracene (DCA) sensitized photooxidation of -dimethoxybenzene (-DMB) in polar solvents. An electron transfer mechanism is proposed in which superoxide ion (O?20 combines with ortho-dimethoxybenzene to form a dioxetane (3), which cleaves to form (). The initial products is , which is rapidly converted to and other products under the conditions; cis-trans isomer is formed. 相似文献
3.
Yasuo Sakai Shingo Toyotani Yoshito Tobe Yoshinobu Odaira 《Tetrahedron letters》1979,20(40):3855-3856
Oxidative decarboxylation of [n.2.2]propellane carboxylic acids (-) with lead tetraacetate gave the bicyclic acetates (, ) having a bridgehead double bond and/or the tricyclic acetates (, ) in good yields. Vapor phase thermolysis of or afforded the bridgehead olefin or quantatively. 相似文献
4.
Regioselective opening of trans epoxide gave and tetramethylated carveols and respectively, which were oxidized to tetramethylcarvone () and its unstable exocylic isomer ; reduction of with DIBAH gave tetramethylated carveol exclusively, whilst analogus reduction of produced an epimeric mixture of :=85:15. 相似文献
5.
Eleven homoerythrina-type alkaloids (-, , ) have been isolated from A. cupressoides (Taxodiaceae), of which six (-, ,) had not previously been reported. 相似文献
6.
Treatment of , , and with methyllithium affords , ; , ; and respectively in serviceable yields carbenoid cyclization. 相似文献
7.
Herbert Muffler Guenter Siegemund Werner Schwertfeger 《Journal of fluorine chemistry》1982,21(2):107-132
4.5-Perfluoro-1.3-dioxolanes are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides or -ketone with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes are formed by reaction with triethylamine- hydrofluoride. 相似文献
8.
2-heptafluoro--dioxan has been lithiated using methyl lithium in ether and thence converted to heptafluoro-p-dioxan-2-carboxylic acid (characterised as its anilinium and S-benzylthiouronium salts and methyl ester), 2-(heptafluoro--dioxanyl)propan-2-ol [dehydrated to 2-(heptafluoro--dioxanyl)propene], heptafluoro--dioxanyltrimethylsilane, and heptafluoro-2-iodo--dioxan. This last was converted to its Grignard reagent, and to bis(heptafluoro--dioxanyl)mercury, and was copper-coupled to trans-1-chloro-2-iodoethylene.Decomposition of heptafluoro--dioxanyl-lithium gave hexafluoro--dioxene. 2-heptafluoro--dioxan, with KOH and formaldehyde, afforded hexafluoro--dioxanylmethanol. 相似文献
9.
13C-NMR analysis of the Reformatsky intermediates from t-btyl-α-bromo acetate, t-btyl-α-bromo isobutyrate and t-btyl-α-bromo prpionate have evidenced C-metallated species. Their ability to act as ncleophilic reagents under mild conditions and their selectivity towards hlogen-and oxygen containing electrophiles is reported. 相似文献
10.
Aminomalonates, e.g., and , smoothly reacted with difluoro- and chlorofluorocarbene to produce the adducts (, , and ) in good yields. These products were successfully converted to various versatile β-fluorinated alanine derivatives, i.e., β,β-difluoroalanine (), N-acyl-β-fluorodehydroalaninate (), and fluoropyruvic acid (). 相似文献
11.
The reaction of tigogenin () with amalgamated zinc yields tetrahydrotigogenin () and the furostan . While undergoes acid catalyzed elimination to give the rearranged product , spontaneously decomposes to a mixture of and . 相似文献
12.
John F. Blount Glenna D. Gray Karnail S. Atwal Thomas Y.R. Tsai Karel Wiesner 《Tetrahedron letters》1980,21(46):4413-4416
The α,β-unsaturated ketone yields with allene the photocycloadduct predicted by our empirical photoaddition rule and the byproduct 7. The formation of this material may be rationalized by the sequence → → → → . The isomeric ketone is unreactive under the same conditions, since α addition is prohibited by the rule and β addition is severely blocked. 相似文献
13.
Wojciech Dmowski 《Journal of fluorine chemistry》1984,26(3):379-394
1-Phenylpentafluoropropenes readily react with lithium dialkylamides to give, in most cases, mixtures of 1-aminosubstituted alkenes and 2-amino-substituted alkenes , with the latter being the favoured products. The reactions with bulky lithium diethylamide and lithium 2-methylpiperidinoamide gave exclusively 1-amino-substituted products . The effect of the increased bulk of N-nucleophiles is opposite to that observed for the reactions of alkenes with C-nucleophiles Increasing electronegativity of the phenyl ring substituents in alkenes shifts the regioselectivity of the attack of lithium amides towards the C2 carbon atom. The E to Z isomer ratios of enamines were found to be time dependent and the slow isomerisation of the kinetic isomers E to the thermodynamic isomers Z was observed, while the ratio of isomers of enamines did not change with time.A concerted, single-step process is suggested for the reactions of alkenes with lithium dialkylamides, and a tentative explanation of the different stereochemistry of enamines and is given. 相似文献
14.
Hiroshi Onoue Masayuki Narisada Shoichiro Uyeo Hiromu Matsumura Kyo Okada Toshisada Yano Wataru Nagata 《Tetrahedron letters》1979,20(40):3867-3870
Allylazetidinones , , prepared by coupling of allylcoppers with chloroazetidinones , , were converted into carbapenem esters , – using an Emmons-Horner reaction to introduce the 6-side chain and an intramolecular Wittig reaction to form the carbapenem ring system. 相似文献
15.
A short route to the 2-azabicyclo[3.3.1]nonan-7-one system is described. Condensation of 4-piperidones with diethyl 2-oxopropylphosphonate, followed by catalytic hydrogenation furnished the corresponding piperidylpropanones which were cyclized with mercuric acetate in acetic acid to the target target bicyclic ketones . The Fischer indole synthesis from afforded regioselectively the indole [3,2-f]morphan , a new heteromorphan type. 相似文献
16.
Alkylation of the distal double bond of pseudoionone has been carried out with isoprene epoxide (ZnCl2 /MeNO2 ) leading directly to α-, α- and γ hydroxyprenylionones. The α- and γ-isomers have been converted in few steps into the C50 carotenoids decaprenoxanthin and C.p. 450 respectively. 相似文献
17.
β-Lactam reacts with hetero nucleophiles under ring cleavage to give 2,2-dimethyl-3-oximinobutanoic esters and . -hydroxyazetidine , the precursor of β-lactam 1, is prepared by a new method. 相似文献
18.
Malvina Farcasiu Edward W. Hagaman Ernest Wenkert Paul von Ragué Schleyer 《Tetrahedron letters》1981,22(16):1501-1504
Unexpected differences in the aluminium bromide-catalyzed rearrangement behaviour of 1,2--trimethylenenorbornane () and its 1,2--isomer () are interpreted. Isotopic labelling studies indicate that reversible abstraction of the tertiary 2- hydride in does not occur. Instead, rearrangement to is favored. The label scrambling in the final product, adamantane (), is attributed to degenerate isomerization in the proto-adamantyl precursor, . 相似文献
19.
Paul von Ragué Schleyer Peter Grubmüller Wilhelm F. Maier Otto Vostrowsky Lars Skattebøl Kjetil H. Holm 《Tetrahedron letters》1980,21(10):921-924
Tricyclo(4.2.2.o1,5)decane () in the presence of AlBr3 rearranges partly “forwards” to adamantane () and partly “backwards” to tetrahydrodicyclopentadiene (, largely the oxo isomer). Intermediate , characterizing the →exo-→→→ forward pathway, is found only in small amounts. The detection of a new intermediate, , also shows that a second major rearrangement route from to is being utilized (see dashed lines in Figure 1). 相似文献
20.
-() and -1,3-Butadienylcyclobutane (), all--1-(1 ,3-butadieny1 )-2- vinylcyclobutane (), and all--1,2-bis(1,3-butadienyl)cyclobutane () have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes. 相似文献