Formation and Electrophilic Reactions of Benzeneselenenyl p-Toluenesulfonate. Perparation and Properties of Addition Products with Acetylenes

Article abstract of DOI:10.1021/jo00008a039

Benzeneselenenyl p-toluenesulfonate (1) was generated in situ by the reaction of silver p-toluenesulfonate with benzeneselenenyl chloride in acetonitrile.The reagent reacted with acetylenes by electrophilic 1,2-addition to afford the β-(phenylseleno)vinyl p-toluenesulfonates 2-12, generally in high yield.The latter were formed preferentially by anti addition, but with poor regioselectivity, unless a strongly orienting group (e.g., phenyl) was present.Selenenyl sulfonate 1 was also unexpectedly produced via radical pathways by heating p-toluenesulfonic acid with AIBN in the presence of diphenyl diselenide, or from the pyrolysis of sulfinyl sulfone 15 with the diselenide.The regioisomeric adducts 3 and 4 were prepared from 1 and 1-decyne, and both underwent elimination with potassium tert-butoxide to afford the acetylenic selenide 19 initially, which isomerized to a 6:1 mixture of the propargylic and allenic selenides 20 and 21 upon further equilibration.A Fritsch-Buttenberg-Wiechell rearrangement is proposed for the elimination of 4.The syn elimination of the selenoxide of 4 required forcing conditions and afforded only ca. 20percent of the corresponding allenic sulfonate 22.The electrophile 1 induced the efficient cyclization of 5-hexen-1-ol and 4-pentenoic acid to the corresponding pyran 24 and lactone 25, respectively.It failed to cyclize alkynols, but afforded the lactones 28 and 29 from 4-pentynoic acid in low yield.