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COMPOSES SULFURES HETEROCYCLIQUES. XCII (1). SYNTHESE ET REARRANGEMENT D'IODURES DE -3 DITHIOLE-1,2 YLIUM
Sauve, Jean-Pierre,Lozac'H, Noel
, p. 577 - 581 (2007/10/02)
In the presence of pyridine, 3-(1,2-dithiol-3-ylidenemethyl)-1,2-dithiolium cations 1 are deprotonated, with rearrangement, sometimes in two ways, whereas 2-(thiopyrane-2-ylidenemethyl)-thiopyrylium cations 3 are stable. Cations 7 possess both a dithiole and a thiopyran ring and have been synthetized by condensation of 2-methylthio-thiopyrilium iodides with 3-methyl-1,2-dithiolium iodides in 1-butanol.In acetic acid, the intermediates 6 can be isolated: they lose methanethiol, yielding 7, by heating in 1-butanol. By analogy with cations 1, deprotonation (with rearrangement) of 7 could be expected to give two different structures 9 and/or 11.When treated with triethylamine, the salts 7 lead to unstable neutral compounds.If the reaction is followed by oxidation with benzonitrile oxide, compounds 11 are obtained.Their formation arises from a rearrangement analogous to that observed only in some cases with the dithiolic compounds.Starting from 7, the main rearrangement observed in the dithiole series would give the 2-(thiopyran-2-ylidene)-thiophen-3-one 9 which has been synthetized by condensation of 2-methylthio-4,6-diphenylthiopyrylium iodide with 5-phenylthiophen-3-one.The structure of α-(1,4 dithiainden-2-ylidene)-ketones 11 is consistent with UV,IR and NMR spectra.Progressive complexation with tris (dipivaloylmethanato) europium permits the attribution of all the 1H NMR signals of the molecule.
