4469-33-4Relevant academic research and scientific papers
Cyclisation of 2-Substituted 2-Bromomethyl-1,3-dioxacyclohept-5-enes; Hydrogen Transfer Reactions of 1,3-Dioxacyclohept-5-enes and 1,3-Dithiacyclohept-5-enes
Hindson, Andrew C.,MacCorquodale, Finlay,Walton, John C.
, p. 871 - 877 (2007/10/02)
2-Bromomethyl-1,3-dioxacyclohept-5-enes (2-bromomethyl-4,7-dihydro-1,3-dioxepins), containing an additional substituent at the 2-position, cyclise to afford 1-substituted 2,7-dioxabicyclooctanes on treatment with tributyltin hydride.The rate constants for cyclisation of the 2-methyl- and 2-phenyl-4,7-dihydro-1,3-dioxepin-2-ylmethyl radicals are 8.4 * 105 and 4.9 * 105 s-1 respectively at 298 K.Hydrogen is readily abstracted from the 4- and 7-positions of 4,7-dihydro-1,3-dioxepins by tert-butoxyl radicals to give 4,7-dihydro-1,3-dioxepin-4-yl radicals which have been characterised by EPR spectroscopy.The Arrhenius parameters for inversion of the 'flap' conformers have been determined from the exchange-broadened spectra of the 2,2-dimethyl and 2,2-diethyl radicals.The analogous radicals, expected on hydrogen abstraction from 1,3-dithiacyclohept-5-enes (4,7-dihydro-1,3-dithiepins), cannot be spectroscopically observed.Instead, the same spectrum, which we attribute to a degradation intermediate, is obtained from a series of 2,2-dialkyl-4,7-dihydro-1,3-dithiepins.
Fragmentation of Cyclic Carboxonium Ions, III. 1,3-Dioxepan-4-ylium Ions, a Key for the Synthesis of Tetrahydrofuran-3-carbaldehydes
Scharf, Hans-Dieter,Frauenrath, Herbert
, p. 1472 - 1479 (2007/10/02)
The formation of 1,3-dioxepane-4-ylium ions (3) is achieved by protonation of 4,5-dihydro-1,3-dioxepines (2).These are prepared by ?-bond isomerization of 4,7-dihydro-1,3-dioxepines (1) under basic conditions.Thermal fragmentation of 3 and subsequent recy
