Flash vacuum pyrolysis of oxo-stabilised phosphonium ylides containing methoxythiophene and methylthiophene groups
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Ten new oxo-stabilised phosphonium ylides containing substituted thiophene groups, as well as two deuterium-labelled analogues, are prepared and fully characterised. Upon flash vacuum pyrolysis at 800 °C, the simpler examples undergo extrusion of Ph3PO coupled with domino cyclisation to give thieno[3,2-b]furan and thieno[3,4-b]furan products but the corresponding approach to a thieno[2,3-b]furan fails. One ylide designed to give a thieno[3,4-b]furan instead gives phenylbutadiyne and 2-phenyl-3-vinylthiophene at 725 °C and the mechanism of this unusual process is elucidated by deuterium labelling. Attempts to access more complex heterocyclic products from extended methoxythienyl ylides failed. Two ylides bearing a 3-methyl-2-thienylacryloyl group gave 5-benzylbenzothiophene, 5-(α-methylbenzyl)benzothiophene and fluoreno[3,4-b]thiophene upon FVP at 800 °C and the mechanism was again elucidated by deuterium labelling.
Aitken , R A & Garnett , A N 2018 , ' Flash vacuum pyrolysis of oxo-stabilised phosphonium ylides containing methoxythiophene and methylthiophene groups ' , Journal of analytical and applied pyrolysis , vol. 135 , pp. 369-378 . https://doi.org/10.1016/j.jaap.2018.08.013
Journal of analytical and applied pyrolysis
© 2018 Elsevier B.V. All rights reserved. This work has been made available online in accordance with the publisher’s policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1016/j.jaap.2018.08.013
DescriptionWe thank EPSRC (UK) for a studentship to ANG.
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