Mechanism and stereochemistry of domino reaction of 2,3-dichloroprop-1-ene with diphenyl dichalcogenides in the system hydrazine hydrate—KOH

A new scheme of the domino reactions of diphenyl dichalcogenides with 2,3-dichloroprop-1-ene in the system hydrazine hydrate—KOH was suggested, which included nucleophilic substitution of the allylic chlorine atom in dichloropropene, dehydrochlorination of the product obtained with the formation of an allene derivative, addition of a nucleophile to the allene system, allene-acetylene rearrangement, addition of a nucleophile to the triple bond with the formation of a Z -adduct, isomerization of a 2,3-dichalcogenide product to Z -1,2-dichalcogenylprop-1-enes, and isomerization of Z -adducts to E -isomers. The most plausible mechanisms of individual steps, involving carbanions stabilized by the α-chalcogen atom, were considered.