Pyrolyses of pentafluorophenyl prop-2-enyl and [2,3,3-2H3]prop-2-enyl ethers. Formation of 1-fluorovinyl 2,3,4-trifluorophenyl ketones via internal Diels–Alder reactions
- 1 January 1976
- journal article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 1
- No. 13,p. 1463-1465
- https://doi.org/10.1039/p19760001463
Abstract
The formation of 1-fluorovinyl 2,3,4-trifluorophenyl ketone (XIV) by pyrolysis of pentafluorophenyl prop-2-enyl ether (I) at 440 °C in the vapour phase is rationalised in terms of a reaction involving one of two possible internal Diels–Alder adducts (V) of the intermediate 2,3,4,5,6-pentafluoro-2-(prop-2-enyl)cyclohexa-3,5-dienone (II). The same adduct is an intermediate in a reaction which enables an ortho–ortho rearrangement of the allyl group in (II) to take place before conversion of (II) into (XIV), a reaction which has been observed by using pentafluorophenyl [2,3,3-2H3]prop-2-enyl ether (VI). This gives not only 1-fluoro[2,2-2H2]vinyl 2,3,4-trifluoro[5-2H1]-phenyl ketone (XVIII)(1 part), the product expected from 2-([1,1,2-2H3]prop-2-enyl)cyclohexa-3,5-dienone (IX), but also 1-fluorovinyl 2,3,4-trifluoro[5,6-2H2]phenyl ketone (XIX)(1 part), from 2-([2,3,3-2H3]prop-2-enyl)cyclohexa-3,5-dienone (X), the relative proportions of the products indicating complete equilibration of (IX) and (X) before further reaction.Keywords
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