ALKATRIENYL SULFOXIDES AND SULFONES. PART IV. SYNTHESIS AND ELECTROPHILEINDUCED CYCLIZATION REACTIONS OF 3-METHYL-1-METHYLSULFONYLPENTA-1,2,4-TRIENE

A method for synthesis of 3-methyl-1-methylsulfonylpenta-1,2,4-triene (3) by [2,3] sigmatropic rearrangement of 3-methylpent-1-en-4-yn-3-yl methanesulfinate (2), formed in the reaction of 3-methylpent-1-en-4-yn-3-ol (1) with methylsulfinyl chloride has been found. Electrophile-induced reactions of the vinylallenyl sulfone (3) occur in different pathways depending on the used electrophiles. The halogenation leads to the formation of (1E)-2-halo-3-methylene-1-methylsulfonylpenta-1,4-dienes (4) and (5). Reactions with phenylsulfenyl and phenylselenenyl chlorides afford only heterocyclic products, 3-methyl-2-[methylsulfonylmethyl]thiophene (6) in the case of sulfenyl chloride, and a mixture of 2,5-dihydroselenophene (7) and selenophene (8) in the case of selenenyl chloride.