- Synthesis and pyrolytic and kinetic behaviour of β,δ′-dioxo-stabilised phosphorus ylides: Convenient preparation of γ,δ-alkynyl ketones and 2,3-functionalised butadienes
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Both ketone- and ester-stabilised phosphorus ylides undergo Michael addition to vinyl ketones to give the β,δ′-dioxo ylides 3 and 5, respectively, although in the latter case careful temperature control is required to avoid an undesired side-reaction. Under conditions of flash vacuum pyrolysis at 650 °C the ylides 3 generally undergo Ph3PO extrusion to afford the γ,δ-alkynyl ketones 14, although these are found to partly undergo a secondary fragmentation. In contrast, the ylides 5 react under the same conditions to give the synthetically useful 1,3-dienes 20 by way of cyclobutenes. Rate constants for the reaction of selected ylides 3 and 5 are reported. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
- Aitken, R. Alan,Al-Awadi, Nouria A.,Balkovich, Mark E.,Bestmann, Hans Juergen,Clem, Oliver,Gibson, Scott,Gross, Andreas,Kumar, Ajith,Roeder, Thomas
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p. 840 - 847
(2007/10/03)
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- Organic Photochemistry with 6.7-ev Photons: γ,δ-Unsaturated Ketones
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The photochemistry of a series of acyclic, aliphatic γ,δ-unsaturated ketones in pentane solution with 185-nm light has been investigated.The variety of products formed can be rationalized as arising from discrete reactions of the individually excited chromophores.Neither intramolecular energy transfer nor internal conversion leading to population of the lowest (n,?*) singlet state are competitive with product formation at 185 nm.The mechanism of alkyne formation in the solution-phase photolysis of these and terminal alkenes at 185 nm is elucidated by using a deuterated derivative, and the reaction is postulated to proceed from the olefinic ?,?* singlet state.
- Leigh, William J.,Srinivasan, R.
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p. 4424 - 4429
(2007/10/02)
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