Flash vacuum pyrolysis of oxo-stabilised phosphonium ylides containing methoxythiophene and methylthiophene groups
Abstract
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.
Citation
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
Publication
Journal of analytical and applied pyrolysis
Status
Peer reviewed
ISSN
0165-2370Type
Journal article
Description
We thank EPSRC (UK) for a studentship to ANG.Collections
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