Thermal and UV-induced isomerization of fluorinated hexatrienes
作者:R. Hrabal、Z. Chvátal、V. Dědek
DOI:10.1016/s0022-1139(00)80562-x
日期:1993.8
0]hex- 2-ene (V). The analogous photolysis of hexatriene I in the liquid phase led to an equilibrium mixture of the starting compound I (cis-isomer) and the trans-isomer II, respectively. Photolysis of 2,3,4,5-tetrafluoro-1,3,5-hexatriene (VI) gave a mixture of cis- and trans- isomers, both in the vapour and liquid phases. Thermal reaction of hexatriene I gave octafluoro-1,3-cyclohexadiene (IV) as the
Valence isomerization of fluorodienes and fluorotrienes
作者:Richard Hrabal、Zdeněk Chvátal、Václav Dědek
DOI:10.1016/s0022-1139(00)83396-5
日期:1985.8
The perfluoro-1,3,5-hexatrienes
作者:Naiyong Jing、David M. Lemal
DOI:10.1021/jo00086a040
日期:1994.4
trans-Perfluoro-1,3,5-hexatriene was obtained by catalytic isomerization of the cis isomer, and their configurations were confirmed by a photochemical method. Equilibration of these isomers with iodine and light at 13 degrees C revealed that the cis isomer is slightly more stable than the trans (K-c-->t = 0.83). The trienes undergo reactions under the influence of heat and light which contrast with those of their hydrocarbon counterparts. Cis triene cyclizes reversibly to perfluoro-3-vinylcyclobutene at 160 degrees C (K-eq = 12.2), and at higher temperatures perfluoro-1,3-cyclohexadiene is formed irreversibly. Cyclization of trans triene to the vinylcyclobutene is much slower than that of the cis isomer, as required by the finding that thermal ring opening of the vinylcyclobutene gives cis triene cleanly. Ultraviolet irradiation of the trienes with and without mercury sensitization yields the same two cyclization products, but the cyclohexadiene undergoes a further rapid photocyclization to give perfluorobicyclo[2.2.0]hex-2-ene, as reported recently by Dedek's group. Mercury photosensitization of the vinylcyclobutene proceeds smoothly to yield this same bicyclic olefin.
Novel Keto−Enol Systems: Cyclobutane Derivatives
作者:Patrick E. Lindner、Ricardo A. Correa、James Gino、David M. Lemal
DOI:10.1021/ja952998h
日期:1996.1.1
of its strength as a hydrogen bond donor. In the monocyclic counterpart of this keto−enol system, 2H-perfluorocyclobutanone (1) and perfluorocyclobut-1-enol (2), the enol is more stable yet. Here ketone is undetectable under equilibrating conditions in all media examined, including carbon tetrachloride. Among unhindered and unconjugated enols, 2 and 4 are more stable relative to their ketones than any