The Reaction of Stable Phosphoranes with Acid Anhydrides. A New Synthesis of Acetylenic Ketones

Chopard, P. A.; Searle, R. J. G.; Devitt, F. H.

doi:10.1021/jo01015a015

Cited by 98 publications

(29 citation statements)

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“…In previous such cases there has been little selectivity with almost equal proportions of the two possible products being formed. 34,35 This also proved to be the case here, with compound 9 undergoing complete extrusion of Ph 3 PO at 500°C to afford a mixture of 37 (26%) and 39 (58%), while the benzoyl compound 10 gave a mixture of 38 (29%) and 40 (30%) under the same conditions (Scheme 9). All these alkynyl ketone products are previously unknown.…”

Section: Resultssupporting

confidence: 67%

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

et al. 2016

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A range of twelve stabilised phosphonium ylides containing tetrahydrofuran, tetrahydropyran or 2,2-dimethyl-1,3-dioxolane rings have been prepared and fully characterised, including one X-ray structure determination of each type. The X-ray structures confirm the PvC and CvO functions to be syn and all the compounds undergo thermal extrusion of Ph 3 PO to give the corresponding alkynes. In some cases there is also competing loss of Ph 3 P to give different carbene-derived products and evidence has been obtained for the generation of 2-phenyloxete in this way. Raising the pyrolysis temperature leads in several cases to new secondary reactions of the alkyne products involving a sequence of alkyne to vinylidene isomerisation, intramolecular CH insertion, and retro Diels Alder reaction.

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Section: Resultssupporting

confidence: 67%

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

et al. 2016

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“…However compound 8 seems much more promising since extrusion of Ph 3 PO can only occur in the desired sense, whereas unsymmetrical β,β'-dioxo ylides such as 9 are known to eliminate Ph 3 PO in both possible directions to give a mixture of isomeric alkynes. 12 The only previous FVP study of β,γ-dioxo ylides involved compounds of the type Ph 3 P=CH-COCOR and did give the alkynes HC≡CCOR for R = OMe and OEt but not for R = Ph. 13 We therefore decided to start by preparing the parent compound 8 (R 1 = R 2 = H) as a precursor to flavone.…”

Section: Resultsmentioning

confidence: 99%

New Gas-Phase Domino Processes Leading to Benzopyranones and Benzofurans

Aitken

Chang²

2016

HETEROCYCLES

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-A new domino approach to flavones by gas phase pyrolysis of -dioxophosphonium ylides containing a 2-methoxyphenyl group is frustrated by unexpected and novel decarbonylation of the intermediate flavon-3-yl radical leading to 2-phenylbenzofuran. Alternative approaches based on dioxolane protection of one carbonyl, or selective elimination in '-dioxo or -oxo-'-thioxo ylides were not successful, but pyrolysis of a -oxo-'-phenylimino ylide did give the required domino reaction leading to a protected benzopyranone in moderate yield.

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“…As one of us has noted previously, [6] ylides of this type may exhibit restricted rotation of the ester group at room temperature leading to separate signals for the (E) and (Z) isomers in the 31 P and 13 C NMR spectra of 5a,b and 5d. Scheme 2 Previous studies on the pyrolysis of ylides where there is a choice of different carbonyl oxygen atoms available for elimination have shown that while the β,βЈ-dioxo ylides 10 undergo non-selective elimination to give a mixture of alkynes, [7] the β,γ,βЈ-trioxo ylides 11 undergo selective elimination across the ''central'' position to give diacylalkynes in most cases. [8] On the other hand, ylides such as 12 and 13 lose Ph 3 PO exclusively between the ylide function and the more remote carbonyl group to give cyclopentenones and cyclohexenones as shown, with no trace of the acetylenic ketones expected from 1,2-elimination.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2003

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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)

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The Reaction of Stable Phosphoranes with Acid Anhydrides. A New Synthesis of Acetylenic Ketones

Cited by 98 publications

References 0 publications

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

New Gas-Phase Domino Processes Leading to Benzopyranones and Benzofurans

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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