2-(3,5-Diaryl-Δ4-1,3,4-thiadiazolin-2-yliden)-1,3-dithiole eine neue klasse elektronenreicher olefine

The dithiolium perchlorates 3a and b were smoothly converted into the phosphonium perchlorates 4a and b by reaction with tributylphosphin. Their deprotonation with butyllithium generates the methylen-phosphoranes 7 (not isolates), from which the electron-rich olefines 9a-d are obtained by successive treatment with the Δ⁴-1,3,4-thiadiazolium perchlorates 5d and e such as triethylamine. The olefine synthesis can be performed too by the reverse way, that is by the reaction of the phosphonium salts 6a-c with the dithiolium salts 3a and b under authentic conditions. In this way the electron-rich olefines 9e-h are obtained.