- ORGANIC COMPOUNDS WITH A WOODY-PEPPERY ODOUR
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(Z)-Configured 5-substituted 5,6-dimethylhepta-3,6-dien-2-one possessing very characteristic dark woody odour with typical agarwood-like spicy peppery connotation.
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Page/Page column 8; 9
(2016/04/20)
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- Tuning the selectivity in the hydrogenation of aromatic ketones catalyzed by similar ruthenium and rhodium nanoparticles
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Ru and Rh nanoparticles (NPs) RuI, RuII, RhI and RhII, stabilised by triphenylphosphine (PPh3) and diphenylphosphinobutane (dppb) were synthesised, characterised and applied as catalysts in the hydrogenation of several aromatic ketones. The effects of the nature of the metal and of the stabilising agent on the aryl versus ketone hydrogenation were studied. For RhNPs, the coordination of arene dominates the interaction of the substrate with the NP, whereas the coordination of the ketone group was not evidenced. For RuNPs, however, the results show that both arene and ketone coordinate to the NPs surface in a competitive manner. The properties of the stabilising ligands have a clear influence on the outcome of the reaction, and for the Rh-catalysed reactions, products of hydrogenolysis were only formed if PPh3 was used as the stabiliser. The structure of the substrate was also a key factor for the selectivity.
- Castelbou, Jessica Llop,Bres-Femenia, Emma,Blondeau, Pascal,Chaudret, Bruno,Castilln, Sergio,Claver, Carmen,Godard, Cyril
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p. 3160 - 3168
(2015/02/19)
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- Practical one-pot preparation of ketones from aryl and alkyl bromides with aldehydes and DIH via Grignard reagents
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Various diaryl ketones, alkyl aryl ketones, and dialkyl ketones were efficiently prepared in good yields by the reactions of the Grignard reagents derived from aryl or alkyl bromides, followed by the reactions with aromatic or aliphatic aldehydes and the subsequent treatment with 1,3-diiodo-5,5- dimethylhydantoin and K2CO3, in a one-pot method. The same treatment of aromatic bromides bearing electron-withdrawing groups, such as ester, nitrile, ketone, and nitro groups with i-PrMgCl·LiCl or PhMgCl instead of Mg, also provided the corresponding diaryl and alkyl aryl ketones in good yields. The above methods are simple and practical transition-metal-free methods for the preparation of various diaryl ketones and alkyl aryl ketones bearing electron-rich aromatic groups and electron-deficient aromatic groups, as well as dialkyl ketones.
- Dohi, Souya,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 6557 - 6564
(2012/08/27)
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- Mechanistic studies on PET-oxidative cyclization of unsaturated silyl enol ethers: Dependence of the regioselectivity on alcohol addition and pressure effects
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Unsaturated silyl enol ethers are irradiated in the presence of electron transfer sensitizers. The efficiency of the cyclization reaction using different sensitizers is investigated. The endo/exo regiochemistry of the ring closure reaction can either be controlled by variation of the silyl group or by addition of alcohol. Furthermore, a dependence of the regiochemistry on pressure is revealed and it seems that it can be related to acetonitrile acting as a nucleophile at 1500 bar. As key intermediates radical cations and radicals are involved.
- Ackermann, Lutz,Heidbreder, Andreas,Wurche, Frank,Klaerner, Frank-Gerrit,Mattay, Jochen
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p. 863 - 869
(2007/10/03)
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- Synthesis of α-Diketones by Direct, Low-temperature, in Situ Nucleophilic Acylation of Esters by Acyllithium Reagents
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Addition of n-, sec-, or tert-butyllithium to a CO-saturated solution of an ester, R'CO2R'' in a solvent system of 4:4:1 (by volume) THF/Et2O/pentane at -110 deg C (or at -135 deg C in 3:1 (by volume) Me2O/THF), followed by hydrolysis with saturated aqueous NH4Cl, results in the formation of α-diketones, BuC(O)C(O)R', yellow liquids, in good yield.Similar reactions with diethyl succinate gave in one instance both t-BuC(O)C(O)CH2CH2CO2Et and t-BuC(O)C(O)CH2CH2C(O)C(O)Bu-t.The monoacylation product of dimethyl oxalate, t-BuC(O)C(O)CO2Me, readily formed a crystalline hydrate, t-BuC(O)C(OH)2CO2Me.
- Seyferth, Dietmar,Weinstein, Robert M.,Hui, Richard C.,Wang, Wei-Liang,Archer, Colin M.
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p. 5768 - 5773
(2007/10/02)
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- Copper (I)-Activated Addition of Grignard Reagents to Nitriles. Synthesis of Ketimines, Ketones, and Amines
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The nucleophilic addition of Grignard reagents to nitriles, especially when using sterically demanding components, is effectively catalyzed by copper(I) salts.Alkyl and aromatic nitriles and a selection of Grignard reagents were employed to prepare sterically hindered ketimines after addition, ketones after a tandem addition-hydrolysis procedure, and branched primary amines after a tandem addition-reduction sequence.
- Weiberth, Franz J.,Hall, Stan S.
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p. 3901 - 3904
(2007/10/02)
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- Application of Force Field Calculations, 7. - Synthesis and Thermolysis of 1,1'-Disubstitueted trans-Azoneopentanes. - Steric and Resonance Effects of the Substituents on the Thermal Stability of Secondary Azoalkanes
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A number of secondary azoalkanes 1, R1R2CH-N=N-CHR1R2, R1 = t-C4H9, R2 = aryl (meso- and D,L-1a-i) and R2 = cyclo-C6H11 (D,L-1k), have been synthesized by partial catalytic hydrogenation of the corresponding ketazines.The configuration of 1 was elucidated by photolysis of crystalline samples of 1, which yielded the dimers 6 with retention of configuration.The kinetics of thermal fragmentation of 1a-k and of 1n (R1 = CH3, R2 = C6H5) into the radicals 7 was followed by DSC.The activation parameters were determined by fitting theoretical curves to the experimental data with the help of a computer program. - The rate of decomposition of 1 with R1, R2 = alkyl is sterically accelarated by increasing size of the substituents (back strain), but the fragmentation of 1a-i (R2 = aryl) is sterically inhibited, e.g. k 2 = C6H5, R1 = t-C4H9)>/k 2 = C6H5, R1 = CH3)> = 10-2.The strain enthalpies Hs of 1 and 7 were calculated by the force field method.The results show that both steric effects are a result of the change in strain during the reaction s = 2Hs(7) - Hs(1)>.A fraction of 0.5 - 0.6 of Ds contributes to ΔG excit. (150 deg C), thus effecting the rate of the reaction.The large positiv value of Ds for R2 = aryl e.g.Ds (1a) = 7.8 kcal/mol, results from a strong repulsion between R1 and R2 in 7 due to the coplanar arrangement of the aryl ring with the radical center. - The resonance effect on the rate of thermolysis has a similar magnitude for R2 = phenyl, p-X-C6H4 (X = Cl, OCH3, t-C4H9, C6H5) and 2-naphthyl, but is considerable stronger for R2 = 1-naphthyl.The measured effect corresponds to a resonance stabilisation of 1-naphthylmethyl radicals by additional 4.5 kcal/mol, compared to benzyl radicals.
- Peyman, Anuschirwan,Hickl, Ernst,Beckhaus, Hans-Dieter
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p. 713 - 726
(2007/10/02)
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