- Does diatomic sulfur (S2) react as a free species?
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A detailed study into the design and synthesis of stable 1,2-dithietane derivatives for the generation of diatomic sulfur (S2) was undertaken. Computer-aided evaluation of enthalpic differences was used to direct the synthesis of target compounds and, although all of the compounds calculated to afford S2 that were prepared did yield diatomic sulfur, an isolable 1,2-dithietane other than dithiatopazine failed to materialize. The results of this study provide convincing evidence that the computational procedure outlined can be successfully used to predict the course of S2 extrusion pathways from potential dithionocarbonylated derivatives. To determine if the disulfide moiety found in the Diels-Alder adduct derived from the addition of diatomic sulfur to conjugated 1,3-dienes is due to a transference mechanism involving the transient 1,2-dithietane intermediate, a chiral nonracemic binaphthyl source of S2 was prepared. Reactions of S2 from this source with chiral nonracemic and prochiral conjugated 1,3-dienes indicate that the added disulfide moiety would be inconsistent with a transference mechanism and that a "free" acting S2 unit is more likely to be involved.
- Steliou, Kosta,Salama, Paul,Yu, Xiaoping
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p. 1456 - 1462
(2007/10/02)
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- SYNTHESE DE DILACTONES MACROCYCLIQUES ASSISTEE PAR LES ORGANOSTANNIQUES APPLICATION AUX MACROCYCLES SOUFRES (SULFURES, SULFOXYDES, DISULFURES) COMPLEXATION SELECTIVE DE L'ION Ca(2+)
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Tin "template driven" condensation of diacid fluorides with triphenyltin derivatives of diols affords macrocyclic dilactones in good yields.The reaction proceeds at moderate dilution conditions from diacids and diols without isolation of the intermediate activated species.The dilution, temperature and ring-size effects on this reaction are detailed.This method is applied to the praparation of sulfur-, disulfide- and sulfoxide-containing macrocyclic dilactones, as well as to the preparation of chiral macrocycles derived from α-aminoacids.The binding abilities of these twelve new ligands (12- to 21-membered rings) are estimated by picra te extraction from water to chloroform.Selective complexation for calcium is found in some cases.
- Picard, C.,Cazaux, L.,Tisnes, P.
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p. 3503 - 3520
(2007/10/02)
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