Synthesis of previously unknown 3,3′-linearly linked sulfur- and selenium-containing bispyrazoles by reactions of 3-alkenyl-5-chloropyrazoles with bischalcogenols

By reactions of 3-alkenyl-5-chloropyrazoles with appropriate dichalcogenols the fi rst specimens were obtained of previously unknown 3,3’-linearly linked bispyrazoles containing in the alkyl chain of the linker two heteroatoms, sulfur or selenium. 3-Vinyl-5-chloropyrazoles react with 1,3-propanedithiol, 2-hydroxy-1,3-propanedithiol, and 2-hydroxy-1,3-propanediselenol under UV irradiation and heating at 60°C over 8 h affording products of the addition against Markovnikoff rule. The radical addition of 1,3-propanedithiol to 3-isopropenyl-5-chloropyrazole required a longer time, 15 h.