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RESEARCH FRONT
Contents Vol 63(12)

Demethylation of an Allene Bearing Two Dimethoxythioxanthene Groups by Oxidation via a Vinyl Cation Intermediate

Torahiko Yamaguchi A , Shin-ichi Fuku-en A , Shun Sugawara A , Satoshi Kojima A and Yohsuke Yamamoto A B
+ Author Affiliations
- Author Affiliations

A Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.

B Corresponding author. Email: yyama@sci.hiroshima-u.ac.jp

Australian Journal of Chemistry 63(12) 1638-1644 https://doi.org/10.1071/CH10297
Submitted: 10 August 2010  Accepted: 31 October 2010   Published: 6 December 2010

Abstract

With the objective of preparing an isolable triplet carbene, we have carried out the oxidation of an allenic compound bearing two thioxanthene moieties (5). Relatively weak oxidants such as Ph3C+BF4 – gave 8, which is the conjugate acid of 5, as a result of a one-electron oxidation followed by hydrogen abstraction, whereas relatively strong oxidants such as SbCl5 furnished a dicationic ketal (9) as a consequence of oxidation and demethylation. Computations on the supposed dicationic intermediate suggest that the singlet state is more stable than the triplet state by 6.7 kcal mol–1 and that the reason for this peculiarity is because the singlet state is essentially a vinyl cation stabilized by a coordinating methoxy group.


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