Studies on Flash Vacuum Thermolysis of Thiones of Selected N-, O-, and S-heterocycles

Tomasz Drewnowski 1,2Anna Chrostowska 1Said Khayar 1Alain Dargelos 1Stanisław Leśniak 2Grzegorz Mlostoń 2

1. Laboratoire de Chimie Théorique et Physico-Chimie Moléculaire, UMR 5624, Pau 64013, France
2. University of Łódź, Department of Organic and Applied Chemistry, Narutowicza 68, Łódź 90136, Poland

Abstract

α-Oxo-ketenes have been shown to be very useful intermediates in organic synthesis and their physico-chemical properties were studied from theoretical as well as experimental points of view [1]. In contrast, relatively little is known about their sulfur analogous [2], which should be interesting in the thio-heterocyclic synthesis. We focused our attention on the thermal decomposition of thiones of selected N-, O-, and S- heterocycles under FVP-conditions. In the case of six-membered 4H-3,1-benzoxatthiin-4-thione 1 the course of the reaction depends mainly on the substitution pattern at C(2). For the non-substituted derivative 1a, the reaction led to the unstable product, which upon treatment with MeOH was converted quantitatively into methyl ortho-mercaptobenzoate.

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An analogous reaction with the 2,2-dimethyl derivative 1b yielded 2-methylthiochromen-4-thione as an exclusive product. A mixture of three different compounds was identified as a result of benzo[e][1,3]thiazine-4-thione 2 thermolysis. Two of them are supposed to be formed by dimerization of initially generated 6-(thioxomethylene)cyclohexsa-2,4-dienthione. UV-Photoelectron Spectroscopy (PES) in conjunction with quantum calculations were applied to provide fundamental information about the structures and bonding of highly reactive intermediates formed during these transformations and to elucidate the reaction pathways in the gas phase.

[1] a) C. Wentrup, W. Heilmayer, G. Kollenz, Synthesis 1994, 1219. b) G. I. Yranzo, J. Elguero, R. Flammang, C. Wentrup, Eur. J. Org. Chem. 2001, 2209.

[2] T. Drewnowski, S. Leśniak, G. Mlostoń, R. Siedlecka, J. Skarżewski, Helvetica Chim. Acta in press.

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Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 2, by Tomasz Drewnowski
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-12 16:15
Revised:   2009-06-07 00:44
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