87012-30-4Relevant articles and documents
NbCl3-catalyzed [2+2+2] intermolecular cycloaddition of alkynes and alkenes to 1,3-cyclohexadiene derivatives
Obora, Yasushi,Takeshita, Keisuke,Ishii, Yasutaka
experimental part, p. 428 - 431 (2009/06/28)
NbCl3(DME)-catalyzed [2+2+2] intermolecular cycloaddition of alkynes and alkenes was successfully achieved to give 1,4,5-trisubstituted-1,3- cyclohexadiene derivatives in good yields. The Royal Society of Chemistry 2009.
Regio- and stereoselective synthesis of the 1,3-cyclohexadiene nucleus by [2 + 2 + 2] cycloaddition reactions catalyzed by titanium aryloxide compounds
Johnson, Eric S.,Balaich, Gary J.,Rothwell, Ian P.
, p. 7685 - 7693 (2007/10/03)
A variety of titanium aryloxide reagents catalyze the cross coupling of two alkyne units with 1 equiv of olefin to produce the 1,3-cyclohexadiene nucleus. Catalysts include isolated titanacyclopentadiene or titanacyclopentane complexes. The reaction proceeds via attack of the olefin upon a titanacyclopentadiene compound initially formed by coupling of two alkyne units. The reaction is limited to bulky alkyne substrates that undergo slow catalytic cyclotrimerization via competing attack of a third alkyne upon the titanacyclopentadiene ring. The organic products isolated are typically the result of an isomerization within the initially produced 1,3-cyclohexadiene nucleus. Mechanistic studies show that these isomerization processes occur via sequential, metal-mediated 1,5-hydrogen shifts upon a single face of the six-membered ring, exclusively leading to a cis-stereochemistry within the final products. In the reactions of the diynes R-C≡C(CH2)4C≡C-R (R = Et, SiMe3), coupling with ethylene and α-olefins produces a variety of substituted hexalins. A combination of NMR spectroscopy, photochemistry, and molecular mechanics calculations has been applied to determine the stereochemistry and ground state conformations adopted by the product 1,3-cyclohexadienes and hexalins. The primary and secondary photoproducts obtained from some of these 1,3-cyclohexadiene compounds have been characterized.
Isomerization and Aromatization of the 1,3-Di-tert-butylcyclohexadienes in Strongly Basic Media
Venkatasubramanian, N.,Hawkins, Adrian,Siegel, Samuel
, p. 1222 - 1226 (2007/10/02)
The five isomeric 1,3-di-tert-butylcyclohexadienes are equilibrated in t-BuOK/Me2SO at 30-55 deg C.In lithium ethylamide in ethylamine at 0 deg C, equilibration is accomplished within the set of three dienes which possess a tertiary hydrogen or between the other two dienes; however, one set is not transformed to the other.Aromatization accompanies the equilibration of the set of three but not the set of two.With a large excess of KAPA, the diene is transformed rapidly to the salt which aromatizes.With an excess of diene, the interconversion of all of the dienes accompanies aromatization (intraset isomerization being faster than interset interchange).In KAPA at 0 deg C, the introduction of dicyclohexyl-18-crown-6 inhibits aromatization; however, after a time reaction slows although the basicity of the solution remains strong enough to abstract a proton from a tertiary carbon.The effect of the base system upon the competitive reactions of cyclohexadienyl carbanions is understood in terms of the differing interactions of the carbanionic salts with the medium.
Dienes as Possible Intermediates in the Catalytic Hydrogenation of Aromatic Hydrocarbons. 2. Dienes Derived from 1,3-Di-tert-butylbenzene and a Rhodium Catalyst
Cozort, James Ray,Outlaw, James F.,Hawkins, Adrian,Siegel, Samuel
, p. 4190 - 4197 (2007/10/02)
The evolution of the products from the catalytic hydrogenation (Rh/Al2O3) of the five isomeric diene derivatives of 1,3-di-tert-butylbenzene (9) is compared with the formation of the observable cyclohexene intermediates and the saturated products from the
