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Understanding anionic Chugaev elimination in pericyclic tetracene formation

Burroughs, Laurence; Ritchie, John; Woodward, Simon

Authors

Laurence Burroughs

John Ritchie

SIMON WOODWARD simon.woodward@nottingham.ac.uk
Professor of Synthetic Organic Chemistry



Abstract

The reaction pathway for the formation of tetracenes from the diols 1,2-C6H4(CHOHC‚Č°CAr)2 , LiHDMS, CS2 and MeI has been modelled by computational methods at the CBS-QB3 level of theory. Comparison of PhCHOC(=S)YCCPh (Y = S- or SMe) indicates a slight kinetic advantage for the anionic system towards [3,3]-sigmatropic rearrangement [Eact(calc.) 19.7 vs 21.8 kcal mol-1]. Using anthracene-based models, 10-{SC(=O)Y}-4a,10-dihydroanthracene (Y = S- or SMe), allows direct comparison of both syn and anti-manifolds in the neutral vs. anionic Chugaev elimination. Syn elimination of [HSC(=O)S]- is distinctly favoured [Eact(calc.) 11.4 kcal mol-1] vs. syn elimination of neutral methylated HSC(=O)SMe [Eact(calc.) 27.5 kcal mol-1]. The smaller barrier to syn elimination of the anionic leaving group is in accord with the low temperature conditions required for this Chugaev reaction (60 oC) and suggests a general advantage in carrying out Chugaev eliminations in anionic manifolds.

Citation

Burroughs, L., Ritchie, J., & Woodward, S. (2016). Understanding anionic Chugaev elimination in pericyclic tetracene formation. Tetrahedron, 72(13), https://doi.org/10.1016/j.tet.2016.02.025

Journal Article Type Article
Acceptance Date Feb 8, 2016
Online Publication Date Feb 10, 2016
Publication Date Mar 31, 2016
Deposit Date Feb 10, 2016
Publicly Available Date Feb 10, 2016
Journal Tetrahedron
Print ISSN 0040-4020
Electronic ISSN 0040-4020
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 72
Issue 13
DOI https://doi.org/10.1016/j.tet.2016.02.025
Public URL http://eprints.nottingham.ac.uk/id/eprint/31578
Publisher URL http://www.sciencedirect.com/science/article/pii/S0040402016300886
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0





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