15971-76-3Relevant academic research and scientific papers
Photorearrangements of Epoxy Ketones. Epoxides of Hexamethylbicyclohepta-2,5-dienone, a Valence Tautomer of Hexamethyltropone
Hart, Harold,Chen, Sun-Mao,Lee, Shin,Ward, Donald L.,Kung, Wei-Jen Hu
, p. 2091 - 2096 (1980)
The double bond in the four-membered ring of hexamethylbicyclohepta-3,6-dien-2-one (1) is selectively oxidized by m-chloroperbenzoic acid, whereas the enone double bond is selectively epoxidized by alkaline hydrogen peroxide to give 2 and 3, respectively.In each case, a single stereoisomer is formed.The exo stereochemistry of the epoxides was deduced from X-ray structures on diepoxides 4 and 5 obtained by further epoxidation of 2 and 3.Irradiation of 2 gives pentamethylphenol (6) and ketene; if 2 is labeled at the C4 methyl with deuterium, the resulting 6 is labeled para to the hydroxyl group.A novel rearrangement of the four-membered ring to give a 7-norbornenyl-type intermediate is suggested to rationalize the labeling result.Irradiation of 3 gives, in addition to minor amounts of pentamethylphenol and its acetate, a tetracyclic product formulated as 10, which rearranges thermally to 1-acetylpentamethylcyclopentadiene (12).A mechanism involving photochemical C-C bond cleavage of the epoxide ring in 3 is suggested to account for the results.
The Photoisomerization of 1,2,3,4,5-Pentamethyl-5-vinyl-1,3-cyclopentadiene
Burger, Ulrich,Etienne, Robert
, p. 2057 - 2062 (1984)
The title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone-sensitized photolysis at 300 nm, the syn-vinyl-pentamethylhousene 5, which spontaneously rearranges in a -sigmatropic process to give the bicycloheptadiene skeleton 2.Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di-?-methane rearrangement.The bicycloheptadiene derivative 2 gives pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.
SYNTHESIS OF HIGHLY ALKYLATED FUNCTIONALIZED CYCLOPENTADIENES
Koschinsky, Rainer,Koehli, Thies-Peter,Mayr, Herbert
, p. 5641 - 5644 (1988)
Tetra- and pentaalkylated cyclopentadienyl ketones and carboxylic acids are prepared by electrophilic allylation of enolizible 1,3-dicarbonyl compounds and successive acid catalyzed cyclisation.
Photolysis of the Carbon-Hydrogen Bond in Pentamethylcyclopentadiene. Properties of the Pentamethylcyclopentadienyl Radical
Davies, Alwyn G.,Lusztyk, Janusz
, p. 692 - 696 (2007/10/02)
Irradiation of pentamethylcyclopentadiene (A) in liquid solution with u.v. light results in homolysis of the ring C-H bond to give the pentamethylcyclopentadienyl radical (B) , and atomic hydrogen which abstracts hydrogen from a second molecule of (A) to give molecular hydrogen and a second radical (B).The radicals (B) self-react at a diffusion-controlled rate (2kt 2 x 1E9 l mol-1 s-1 in hexane at 25 degC) by two different routes.The first, which is thermally and photolytically reversible, is the combination to give the dehydrodimer (C), and the second, which is irreversible, is the disproportionation to give the parent cyclopentadiene (A) and the tetramethylfulvene (D).
A Contribution to the Mechanism of Light-induced Isomerizations of the 4-Methylenebicyclohex-2-ene
Brune, Hans Albert,Jobst, Helmuth,Lach, Peter
, p. 511 - 519 (2007/10/02)
Deuterium-labelling of 1,2,3,5,6-exo-pentamethyl-4-methylenebicyclohex-2-ene (exo-1) and 1,2,3,5,6-endo-pentamethyl-4-methylenebicyclohex-2-ene (endo-1) was used to get insight into the mechanisms of the reversible photo-isomerization exo-1 endo-1 and of their light-induced rearrangements to 1,2,3,4,6-pentamethyl-5-methylene-1,3-cyclohexadiene (2).
