1,3-cyclooctadiene, 1,3,6-cyclooctatriene and bicyclo-[4.2.0]-2,4-octadiene give normal Diels-Alder-adducts with nitrosobenzenes. In the reaction of 1,3,5-cyclooctatriene with nitro-substituted nitrosobenzenes, too, [2+4]-cycloadducts are formed which, however, rearrange by heating in solution to [2+6]-cycloadducts. These isomers are the only products isolated in the addition of nitrosobenzene and
[4 + 2] Cycloaddition reactions of hexachlorotropone
作者:M. Akhtar、D.M. Bratby、J.C. Chadwick、G.I. Fray
DOI:10.1016/0040-4020(76)85144-7
日期:1976.1
The cycloaddition of hexachlorotropone to selected olefins, including 1,3-dienes, has been examined. Unlike tropone, which undergoes [6 + 4] cycloadditions with 1,3-dienes, only [4 + 2] processes were observed with hexachlorotropone. Its apparent preference for exo-addition (contrast tetrachlorocyclopentadienone) probably results from thermodynamic control of the endo : exo product ratios.
Reduction of semibullvalene (5) with potassium more closely resembles deprotonation of tetrahydropentalenes by n-butyl-lithium-potassium t-pentoxide than it does the reduction of (5) with lithium; the former prccesses both provide the cyelo-octatetraenyl dianion (4), plausibly via the intermediate bicyclo[3.3.0]octadienediyl dianion (3).