2808-80-2Relevant academic research and scientific papers
Effect of ketene additive and Si/Al ratio on the reaction of methanol over HZSM-5 catalysts
Hassanpour, Javad,Zamani, Mehdi,Dabbagh, Hossein A.
, (2018/03/01)
The influence of ketene as possible intermediate for the reaction of methanol to aromatics was investigated over HZSM-5 catalysts (Si/Al ratio of 15 and 9) using diketene-acetone (2,2,6-trimethyl-4H-1,3-dioxin-4-one) as ketene precursor under atmospheric
Construction of Distant Stereocenters by Enantioselective Desymmetrizing Carbonyl-Ene Reaction
Luo, Weiwei,Lin, Lili,Zhang, Yu,Liu, Xiaohua,Feng, Xiaoming
supporting information, p. 3374 - 3377 (2017/07/15)
An efficient desymmetrizing carbonyl-ene reaction of 1-substituted 4-methylenecyclohexanes with glyoxal derivatives was thus executed by a chiral N,N′-dioxide/NiII catalyst, providing facile access to cyclohexene derivatives bearing two remote 1,6-related stereocenters. This distal stereocontrol methodology originates from the efficient interaction between the catalyst with enophiles, discrimination of the two chair conformations of olefinic components, and the intrinsic six-membered transition-state structure of ene process.
Halogenated Terpenoids. XXIX the 1-Bromo 1-Bromomethyl Cyclohexyl System
Brecknell, Douglas J.,Carman, Raymond M.,Edwards, Ross A.,Hansford, Karl A.,Karoli, Tomislav,Robinson, Ward T.
, p. 689 - 700 (2007/10/03)
Bromination of methylene groups exocyclic to cyclohexyl systems normally affords two isomeric products; the axial 1-bromo equatorial 1-bromomethyl compound and the axial 1-bromomethyl equatorial 1-bromo derivative. Free energy differences between these two isomers, and the conformations adopted by the axial 1-bromomethyl group, have been explored by n.m.r. spectroscopy, by X-ray crystallography and by MM3 calculations. Evidence is presented to show that the ax-bromomethyl group exists primarily as those rotamers which site the bromine atom synclinal to the vicinal bromine. The A value for a bromomethyl group in this system is then similar to that of an unsubstituted methyl group.
Synthesis of Bridgehead-Substituted Bicycloheptanes by Radical Cyclization
Della, Ernest W.,Knill, Andrew M.,Pigou, Paul E.
, p. 2110 - 2114 (2007/10/02)
A kinetic investigation shows that the rate of cyclization (kC) of the (4-methylenecyclohexyl)methyl radical 3 at 25 deg C is 4.4 x 102 s-1, which is considerably slower than that (2.3 x 105 s-1) of the parent 5-hexenyl radical.The energy of activation for the process 3 -> 4 is 12.8 kcal mol-1, which is in excellent agreement with theoretical values derived from force-field calculations.Ring-closure of appropriately substituted (4-methylenecyclohexyl)methyl radical precursors allows the synthesis of bicycloheptyl systems with useful functionality at the bridgehead to be achieved readily and in high yield.An interesting example is given of the application of an iodine-atom-transfer cyclization to the synthesis of a bicycloheptane functionalized at C7 and C1.
Reaction of Azoalkanes with Isolable Cation Radical Salts
Engel, Paul S.,Robertson, Donald M.,Scholz, John N.,Shine, Henry J.
, p. 6178 - 6187 (2007/10/02)
Three tertiary azoalkanes related in the sense acyclic, cyclic, and bicyclic are shown to evolve nitrogen upon oxidation with stable cation radical salts.Thus azo-tert-octane (ATO), 3,3,6,6-tetramethyl-1,2-diazacyclohexene (TMDAC), and 1,4-dimethyl-2,3-diazabicyclooct-2-ene (Me2DBO) react rapidly with thianthrenium perchlorate (Th(.1+)ClO4(1-)), tris(p-bromophenyl)aminium hexachloroantimonate (TBPA(.1+)SbCl6(1-)), and TBPA(.1+)SbF6(1-).The ether and olefin products, which are formed in high yield in CH2Cl2/MeOH solvent, are not those expected from the usual free-radical decomposition of azoalkanes but instead implicate carbocations.Althrough the reaction stoichiometry clearly requires 2 equiv of cation radical salt to one of azoalkane, the mechanism is not yet clearly defined.A complication in these studies is found in the ability of certain cation radical salts to oxidize more azoalkane than expected based on the 2:1 stoichiometry.
