19656-98-5Relevant academic research and scientific papers
Synthesis of 4-hydroxy-5-methyl- and 4-hydroxy-6-methylcyclohexenones by PdII-catalyzed oxidation and lipase-catalyzed hydrolysis
Meister, Anne C.,Nieger, Martin,Braese, Stefan
, p. 5373 - 5380 (2012/11/06)
A short route for the syntheses of methyl-substituted hydroxycyclohexenones, which are building blocks for various natural products, is presented. Both oxygen atoms were introduced as acetates by a palladium(II)-catalyzed 1,4-addition to a 1,3-diene. The
Isomer differentiation by tri-osmium cluster complexation of substituted 1,3-cyclohexadienes
Ingham,Johnson,Sadler,Nairn
, p. 237 - 242 (2007/10/03)
A series of methyl- and dimethyl-substituted 1,3-cyclohexadienes have been prepared from their aromatic analogues via Birch reduction and subsequent isomerisation with Fe(CO)3 fragments. These ligands were reacted with [Os3(CO)10(CH3CN)2] to form tri-osmium decacarbonyl cluster compounds containing the η4-coordinated substituted 1,3-cyclohexadienes. The various isomers of the substituted dienes show a dramatic difference in their reactivity towards the tri-osmium cluster and it is likely that this is due to the steric interactions between the methyl substituents and the cluster framework, with this effect being more marked for the di-substituted ligands.
Thermal Decomposition of 2,3-Dihydro-1,4-benzodioxin and 1,2-Dimethoxybenzene
Schraa, Gerrit-Jan,Arends, Isabel W. C. E.,Mulder, Peter
, p. 189 - 198 (2007/10/02)
Rates and mechanisms of decomposition of 2,3-dihydro-1,4-benzodioxin (1) and 1,2-dimethoxybenzene (27) have been investigated in the gas phase near atmospheric pressure between 750 and 900 K in a tubular flow reactor in a large excess of radical trapping agents.The following rate expressions for decomposition have been determined: log kt/s-1 (1) = 15.7 - (271 kJ mol-1/2.303 RT); log kt/s-1 (27) = 15.7 - (251 kJ mol-1/2.303 RT).The main decomposition routes for 1 are the formation of o-benzoquinone (2) and 2-methyl-1,3-benzodioxole (7) through a biradical intermediate.The measured activation energy is 20 kJ mol-1 above the required C-O bond dissociation energy.Compound 2 rapidly loses CO to form cyclopenta-2,4-dien-1-one (6) which after dimerisation decomposes mainly into 3-phenylprop-2-enal (12) and indenols (14).The main product of the thermolysis of 27 is o-hydroxybenzaldehyde (33).The O-methyl bond is weakened by 16 kJ mol-1 compared to methoxybenzene as a result of the o-methoxy-substitution.
Hydrogen Transfer Reactions, 19. - The Catalysis of Hydrogen Transfer and 1,5-H Shift by Rhodium(III) Chloride in Homogeneous Organic Systems
Wehage, Hubert,Heesing, Albert
, p. 209 - 215 (2007/10/02)
In homogeneous solution, partly in the presence of a phase-transfer catalyst, rhodium(III) chloride catalyzes the disproportionation of 1,3-cyclohexadiene and to a lesser extent 1,5-H shifts.In the start phase the catalyst is reduced to the active monovalent state.In these catalytic systems the dehydrogenation proceeds stereoselectively. - This was shown by tracer experiments and isotopes effects using deuterated 1,3-cyclohexadienes 1a-d, which were synthesized with high isotopomeric purity.Key Words: Rhodium chloride / Hydrogen transfer / Deuterated 1,3-cyclohexadienes / Isotope effects
Rotational Barriers of Vinyl-Substituted Olefines
Doering, William von E.,Roth, Wolfgang R.,Bauer, Frank,Boenke, Martin,Breuckmann, Rolf,et al.
, p. 1461 - 1470 (2007/10/02)
For the vinyl-substituted olefines 1-14 activation parameters for the geometrical isomerisation have been determined in the gas-phase.By comparison of these barriers with the corresponding ones of the isolated double bonds, each corrected by the contribution of the steric energy to the ground and transition state, a value of 13.5 +/- 1.1 kcal mol-1 for the allyl stabilisation energy (ASE), defined as replacement of alkyl by vinyl, has been derived.
Stereo-and Regioselective Palladium-Catalyzed 1,4-Diacetoxylation of 1,3-Dienes
Baeckvall, Jan-E.,Bystroem, Styrbjoern E.,Nordberg, Ruth E.
, p. 4619 - 4631 (2007/10/02)
Palladium-catalyzed oxidation of 1,3-dienes in acetic acid using an oxidation system of MnO2 and catalytic amounts of p-benzoquinone selectively gives 1,4-diacetoxy-2-alkenes.The reaction proceeds with high stereo-and regioselectivity, and by ligand control the reaction can be made to take place with either cis or trans 1,4-diacetoxylation across the diene in cyclic systems.Also in an acyclic system the 1,4-relative stereochemistry can be controlled as shown by the stereoselective oxidation of (E,E)- and (E,Z)-2,4-hexadiene to their corresponding dl (>88percent dl) and meso (>95percent meso) diacetates 15 and 18, respectively.Evidence is provided that supports a mechanism involving a trans acetoxypalladation of the conjugated diene to give an intermediate (?-allyl)palladium complex, followed by either a cis or trans attack by acetate on the allyl group.The cis attack is best explained by a cis migration from a (?-allyl)palladium intermediate.The diacetoxylation reaction was applied to the preparation of a key intermediate for the synthesis of dl-shikimic acid.
Conversion of conjugated diolefins to diacyloxy olefins
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, (2008/06/13)
A catalyst comprising a uranium compound, an alkali metal ion, and a halide, is effective to convert conjugated dienes in carboxylic acid media to diacyloxy olefins.
