2 -1 -thio-1 -alkene

The same ketene acetal, as well as telluro(thio)ketene acetals has been obtained with retention of configuration by subsequent treatment of ( )-l-bromo-l-seleno(or thio) alkenes with n-BuLi and diphenyl ditelluride, resulting from the preferential Br/Li exchange over chalcogeno exchange. ... 

Anionic Reactions The use of cesium alkynides in bisthiolation of alkynes has been described to give (Z)-isomers 31, whereas Hthinm alkynides are known to nndergo further reaction to give tri-thio-alkenes... 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

In addition, Suehiro et al. (1987) were able to accurately determine the rates of dediazoniation of twenty substituted aryldiazenyl radicals formed from aryl(aryl-thio)diazenes (Scheme 8-36), in cyclopropane and in alkenic solvents at -48 to — 117°C, using a time-resolved ESR method. 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

Bis [(trifluoromethyl)thio] acetaldehyde (83a) has been prepared from an enam-ine precursor (84), although refluxing in aqueous ethanolic HCl is required to effect this reaction.The aldehyde is less stable than its enol tautomer (83b), and many reactions typical of aldehydes fail. For example, addition of aqueous silver nitrate immediately yields the silver salt of (83b), rather than giving precipitation of (elemental) silver. The (trifluoromethyl)thio substituent has pseudohalogenic character and, together with the hydroxy group, stabilizes the alkene tautomer in the manner of a push-pull alkene. The enol-aldehyde equilibrium mixture in acetonitrile shows an apparent of 2.6 when titrated with aqueous hydroxide. 

A number of 3,5-dihalogenoalkenyl-l,2,4-thiadiazoles (346) have been obtained204 by treatment of the dimercapto compound with dichloro-alkenes (e.g. 2,3-dichloropropene) in aqueous sodium hydroxide. The reaction with chloroacetic acid yields l,2,4-thiadiazolyl-3,5-di(thio-glycollie) acid,144 which forms salts and may be esterified in the usual way. 

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