Thermal and microwave assisted reactions of 2,5-disubstituted thienosultines with [60]fullerene: Non-Kekulé biradicals and self-sensitized oxygenation of the cycloadduct

Chih Chin Chi, I. Feng Pai, Wen-Sheng Chung*

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Refluxing an o-dichlorobenzene solution of 2,5-disubstituted thienosultines 10a-f with [60]fullerene for 2-24 h gave both 1:1 and 2:1 cycloadducts in 37-79% isolated yields. The reaction was highly accelerated by microwave irradiation giving comparable yields of cycloadducts. Sultines 10a-f underwent cheletropic extrusion of SO 2 to form the corresponding non-Kekulé biradical intermediates 11a-f, which were subsequently trapped by [60]fullerene to form corresponding cycloadducts. The activation energy barriers (ΔG c ) determined for the boat-to-boat inversion of these 4′,5′,6′,7′-tetrahydrobenzo[c]thieno- [5′,6′:1,2][60]fullerene adducts 12a-f were found to be in the range of 13.5-14.8 kcal/mol. Unexpectedly, one of the monoadduct 12a was found to be labile when kept in air under ambient light. Two new products 15 (a sulfine-enone) and 16 (an endione) were isolated from the decomposed 12a and were found to derive from self-sensitized singlet oxygen reaction on the 2,5-dimethylthieno moiety of 12a.

Original languageEnglish
Pages (from-to)10869-10876
Number of pages8
JournalTetrahedron
Volume60
Issue number48
DOIs
StatePublished - 22 Nov 2004

Keywords

  • Cycloaddition
  • Microwave
  • Non-Kekulé biradical
  • Singlet oxygen reaction
  • TME biradical
  • [60]Fullerene

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