19381-80-7Relevant academic research and scientific papers
Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels-Alder Reaction of Propargyl Aldehyde
Hatano, Manabu,Sakamoto, Tatsuhiro,Mizuno, Tomokazu,Goto, Yuta,Ishihara, Kazuaki
supporting information, p. 16253 - 16263 (2018/11/27)
The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewis acid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate control, enantio-, endo/exo-, π-facial-, regio-, site-, and substrate-selectivities could be controlled by the present U-shaped catalysts. The obtained reaction products could access the concise synthesis of chiral diene ligands and a key intermediate of (+)-sarkomycin. The results presented here might partially contribute to the development of artificial enzyme-like supramolecular catalysts for multiselective reactions, which will be able to target organic compounds that have thus far eluded synthesis.
Relative Thermodynamic Stabilities of 3-Ethylidenecyclohexenes and Isomeric Ethylcyclohexadienes
Taskinen, Esko,Nummelin, Kari
, p. 11693 - 11698 (2007/10/02)
The relative thermodynamic stabilities of the E and Z forms of 3-ethylidenecyclohexene, 1-ethyl-1,3-cyclohexadiene, 2-ethyl-1,3-cyclohexadiene and 1-ethyl-1,4-cyclohexadiene were determined by t-BuOK catalyzed chemical equilibration in DMSO solution.From the variation of the equilibrium composition with temperature the enthalpy, entropy and Gibbs energy differences between the isomeric species were evaluated.The ethylidenecyclohexenes were found to be the most abundant species at thermodynamic equilibrium, owing to their 9-12 kJ mol-1 lower enthalpy values.The entropy term, however, favors the cyclohexadienes by 7-11 J K-1 mol-1.
Organic Photochemistry with 6.7-eV Photons. The Divergent Photobehavior of exo- and endo-7-Methyl-2-norcarene
Leigh, William J.,Srinivasan, R.
, p. 3970 - 3979 (2007/10/02)
The photochemistry of exo- and endo-7-methylbicyclohept-2-ene (7-methyl-2-norcarene) upon direct and toluene-sensitized photolysis has been investigated.Direct photolysis of the two isomers in hydrocarbon solution with monochromatic 214-nm light leads to widely divergent photobehavior.Ring opening, yielding cis-5-methyl-1,3,6-heptatriene (via a formal process), and exo-endo isomerization are major decomposition pathways in both cases, accounting for 30-45percent of the observed products.The formation of 7-methylnorbornene and 4-methylbicyclohept-2-ene is observed to proceed stereospecifically in each case, while the formation of cyclopropyl ring opening/hydrogen migration products appears to depend strongly on the orientation of the methyl group in the starting isomer.Common biradical intermediates are thus believed not to be involved in the direct photolyses of 2 and 3.Toluene-sensitized photolysis of the two isomers leads to formation of exo-4-methylbicyclohept-2-ene (the photochemical vinylcyclopropane rearrangement) and exo-endo isomerization.These results are rationalized in terms of the expected behavior of two common biradical intermediates, which are formed with different efficiencies from the isomeric 2 and 3 upon triplet sensitization.
Synthesis and Catalytic Activity of Some Neutral (η-Cycloenyl)(η-1,5-cyclooctadiene)rhodium(I) Complexes
Stuehler, Hans-Otto
, p. 340 - 342 (2007/10/02)
2 (COD = 1,5-cyclooctadiene) reacts with i-C3H7MgBr in the presence of 4-vinylcyclohexene and 1-methyl-1,4-cyclohexadiene to give the neutral, diamagnetic ?-complexes in which the central metal achieves a 16-electron valence shell.The catalytic activity of these complexes is described. - Keywords: (1,5-Cyclooctadiene)(ethylcyclohexenyl)rhodium(I), (1,5-Cyclooctadiene)(methylcyclohexenyl)rhodium(I), Catalytic Activity
