- Synthesis of substituted benzenes and phenols by ring-closing olefin metathesis
-
New synthetic approaches to substituted aromatic compounds are reported. Ring-closing olefin metathesis (RCM)/dehydration and RCM/tautomerization are the key processes in the synthesis of substituted benzenes 3 and phenols 6, respectively. Readily accessible 1,5,7-trien-4-ols 7, which are the precursors of benzenes, were prepared from β-halo-α, β-unsaturated aldehydes 11 or β-halo-α,β-unsaturated esters 19 by utilizing reliable transformations in which cross-coupling with vinylic metal reagents 12 and allylation with allylic metal reagents 13 were employed as carbon-carbon bond forming reactions. RCM of 7, followed by dehydration, afforded a wide variety of substituted benzenes 3. In addition, RCM of 1,5,7trien-4-ones 9, which were prepared by oxidation of 7, furnished various substituted phenols 6 by automatic tautomerization.
- Yoshida, Kazuhiro,Takahashi, Hidetoshi,Imamoto, Tsuneo
-
experimental part
p. 8246 - 8261
(2009/09/29)
-
- Gold(I)-catalyzed benzannulation of 3-hydroxy-1,5-enynes: an efficient synthesis of substituted tetrahydronaphthalenes and related compounds
-
We report a novel gold(I)-catalyzed benzannulation of 3-hydroxy-1,5-enynes to prepare tetrahydronaphthalenes. The reaction is catalyzed by 2.5 mol % Ph3PAuCl and 2.5 mol % AgOTf in dichloromethane. We discovered that this process can be also catalyzed by 1 mol % Ph3PAuCl and 1 mol % TfOH. To the best of our knowledge, this constitutes the first report of an active gold catalyst generated from Au(PPh3)Cl and triflic acid. This mild process is compatible with a variety of functional groups and proves to be an effective method to synthesize various meta-substituted aromatic rings in good yields.
- Grisé, Christiane M.,Rodrigue, Eric M.,Barriault, Louis
-
p. 797 - 808
(2008/04/12)
-
- Gold-catalyzed synthesis of substituted tetrahydronaphthalenes
-
(Diagram presented) We report a gold-catalyzed benzannulation of 3-hydroxy-1,5-enynes to generate tetrahydronaphthalenes. This mild process proves to be an effective method to synthesize various metasubstituted aromatic rings in good yields.
- Grise, Christiane M.,Barriault, Louis
-
p. 5905 - 5908
(2007/10/03)
-
- Intermediate Formation ofMetacyclophane on Flash Vacuum Thermolysis
-
Pyrolysis of 2,6-tetramethylene Dewar benzene (2a) under flash vacuum thermolysis (FVT) conditions at 400 deg C gave 6- and 5-methylindan (8a (2.5percent) and 10a (2.5percent), respectively) as well tetralin (5a) (45percent).These products indicate that metacyclophane (1a) was formed in the gas phase, but it decomposed under the reaction conditions either via homolytic cleavage of one of the benzylic bonds to yield a diradical (6a) leading to 8a and 10a or it gave 5a via benzvalene intermediate (4a).Deuterium labeling supports the proposed mechanism.A very similar course of events was observed on FVT of metacyclophane at 600 deg C; it yielded methyl-substituted tetralins (8c, 10c) as the sole products.The analogies and differences in the behavior of the two metacyclophanes are discussed.
- Kostermans, Gerardus, B. M.,Dansik, Paul van,Wolf, Willem H. de,Bickelhaupt, Friedrich
-
p. 4531 - 4534
(2007/10/02)
-
- Synthesis of Biological Markers in Fossil Fuels. 2. Synthesis and 13C NMR Studies of Substituted Indans and Tetralins
-
Unambiguous syntheses of all possible methyl, ethyl, n-propyl, and n-butyl derivatives of indan and tetralin were developed using the Kumada coupling procedure involving the reaction of aryl or vinyl halides with Grignard reagents in the presence of nickel(II) chloride.An analysis of the 13C NMR spectra of these compounds was also completed.
- Adamczyk, Maciej,Watt, David S.,Netzel, Daniel A.
-
p. 4226 - 4237
(2007/10/02)
-
- IDENTIFICATION OF LOW-BOILING FRACTION OF PYROLYSIS OIL
-
Composition of the low-boiling fraction of the pyrolysis oil obtained from continuous rectification has been determined by combination of capillary gas-liquid chromatography with other identification methods (catalytic hydrogenation, polymerization).In this way components have been identified which form overall 86.0 per cent (m/m) of the low-boiling fraction.The said pyrolysis oil fraction has been found to contain almost 50 per cent (m/m) of unsaturated components able of polymerization, especially methylindenes, methyl-, ethyl- and dimethylvinylbenzenes, divinylbenzenes and 1,2-dihydronaphthalene.Elution behaviour of all the identified isomeric methylindenes, divinylbenzenes and 1,2-dihydronaphthalene has been evaluated by determination of parameters of the equation Ist.phase(2) = k.Ist.phase(1) + q. The Kovats elution indices of all the identified aromatic hydrocarbons have been determined with the use of a glass capilary column wetted with Carbowax 20M at 80o C.
- Novrocik, Jan,Novrocikova, Marta
-
-
- Dehydration of 1-Substituted Secondary and Tertiary Bicyclononan-9-ols. A Substituent-Driven Rearrangement to 4-Substituted and/or Angularly Substituted Hexahydroindenes
-
The acid-catalyzed dehydration of substituted bicyclononan-9-ols (1-9) has been studied as a route to substituted hexahydroindenes via skeletal rearrangement.The nature of the substituent at C1 strongly affects the rearrangement.Thus 1-substituted secondary alcohols 1-3 (R = Ph, CH3, H) afford 4-substituted 2,3,4,5,6,7-hexahydroindenes 1b-3b, while a mixture of 3a-carbethoxyhexahydroindenes (4a,b) is produced from 4 (R = CO2Et).Tertiary alcohols 5-9 afford cis-3a-substituted 2,3,3a,6,7,7a-hexahydroindenes 1a-9a.These processes are discussed in terms of relative stabilities of the intermediate carbonium ions.
- Balata, Fabrizio,Jacono, Anna R. Dello,Gambacorta, Augusto
-
p. 566 - 570
(2007/10/02)
-
- Preparation of 4 and 5-methylindanes
-
Indane is reacted with an α,α-dichloromethyl lower alkyl ether, the reaction mixture is treated with water to produce a mixture of 4-formylindane and 5-formylindane, the aldehyde isomers are separated and the aldehydes are catalytically hydrogenated to produce 4-methylindane and 5-methylindane.
- -
-
-