Preparation of Allenic Sulfones and Allenes from the Selenosulfonation of Acetylenes

Article abstract of DOI:10.1021/jo00278a030

β-(Phenylseleno)vinyl sulfones 2 are readily obtained from the free-radical selenosulfonation of acetylenes.Compounds 2 isomerize to allyl sulfones 4 under base-catalyzed conditions in nearly quantitative yield, with high stereoselectivity favoring the Z configuration.Allyl sulfones 4 afford generally high yields of allenic sulfones 1 when subjected to oxidation with m-chloroperbenzoic acid or tert-butyl hydroperoxide, followed by selenoxide syn-elimination.The sulfone-stabilized anion intermediates in the isomerizations of 2 to 4 can be alkylated, deuterated,or silylated in the α-position prior to oxidation, providing allenic sulfones with an additional α-substituent.In some cases, spontaneous elimination of the phenylseleno group occurred, producing the allenic sulfone without the need for an oxidation step.Desulfonylation of allyl sulfones 4f, 4c, and 25 with sodium amalgam afforded vinyl selenides that were converted to allenes in moderate to good yields by oxidation-elimination.The copper catalyzed coupling of allyl sulfones 4 with Grignard reagents comprises an alternative route to vinyl selenide precursors of allenes.These procedures permit the synthesis of various α- and γ-substituted allenic sulfones and allenes from acetylenes.