O-Dithiols

When a,o -dithiols are reacted with dibutyltin oxide, stannathianes are formed and used as templates for the preparation of thialactones <2004JOC8550> (Scheme 3). The example template shown in Scheme 3 is easily obtained, when dibutyltin oxide 9 is suspended in toluene and heated to reflux. Then 3-thiapentane-l,5-dithiol 10 dissolved in toluene is added dropwise and the resulting mixture is refluxed for 24 h. After cooling to 25 °C the product is concentrated by vacuum and the residue is purified by chromatography to give 2,2-dibutyl-2-stannatrithia-cyclooctane 11 in 83% yield. When 11 is treated with pimeloyl dichloride 12, two thialactones are obtained 13 (1 1 ratio product, 63%), and 14 (2 2 ratio product, 20%). 

Macrocyclic sulfides.1 Macrocyclic sulfides are prepared conveniently by reaction of the cesium salts of l,o>-dithiols, prepared in situ from Cs2C03 in DMF, with 1,gd-dibromoalkanes. 

The oxidative dimerization of a,o -dithiols carried out by a large number of oxidizing reagents is a well-known and widely used method for the synthesis of cyclic disulfides. An alternative one-step conversion of the acyclic bisthio-cyanates 297 using TBAF in dry THF at room temperature to form cyclic disulfides in moderate yields, including a limited number of 1,2-dithiolanes 298 (Scheme 54), has been developed <1999TL6489>. The available mechanistic information indicates that the process, induced by so-far-unreported nucleophilic attack by fluoride, tolerates ester and ketal groups, while silyl ethers are cleaved. 

A new type of approach to thiocrown ether synthesis involving a [2 + 2] coupling of boron aluminium alkoxide couple has been described [27]. 

More recently Hahn and coworkers reported the synthesis of several homochiral triple-stranded helicates of Ti(IV) using bis bidentate (benzene-o-dithiolate) ligands which are the thiol version of Raymond tetradentate ligands. 

Small pieces of Na added during 1.5 hrs. to a vigourously stirred refluxing suspension of 1,3-benzodithiolium fluoroborate in liq. NHg until a blue color persists for 10 min. 1,2-benzenedithiol. Y 80-85%. - This is the second step of a two-stage prepn. of o-dithiols from o-aminocarboxylic acids. 1. Degani and R. Fochi, Synthesis 1976, 471. 

The stability of a cyclic disulfide is dependent on its structure and purity, Lipoic acid is relatively stable in the solid state [120]. If, however, the disulfide is heated above its melting point, polymerization readily occurs [123]. For the disulfides of C5-C12 M-alkyl cx,(o-dithiols, both the six- and seven-membered ring compounds are reported to be stable in pure forms [124], Conversely, another study on the same series of disulfides reports that only seven-, nine- and eleven-membered rings are stable in the pure form [119]. Another study reports only... 

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