SELENOSULFONATION OF CONJUGATED ENYNES AND THE ENYNE EQUIVALENT 1,4-DICHLORO-2-BUTYNE - PREPARATION OF SULFONYL-SUBSTITUTED ALLENIC ALCOHOLS AND DIENES USING [2,3] SIGMATROPIC REARRANGEMENTS AND ORGANOCUPRATE ADDITIONS

Conjugated enynes undergo free-radical selenosulfonation under either photochemical or thermal conditions with Se-phenyl p-tolueneselenosulfonate (1). Addition to the triple bond occurred preferentially with enynes having an acetylenic terminus (6–8) affording 1,2-adducts 10–12, respectively, as well as the 1,4-adduct 13 from 8. Enyne 9, which has a terminal olefin and a disubstituted acetylene moiety, afforded 1,2- and 1,4-addition products to the double bond (14 and 15, respectively). [2,3] sigmatropic rearrangement of the selenoxides of the 1,2-adducts 10–12 produced the sulfonyl-substituted allenic alcohols 18–20, respectively. The rearrangement was stereospecific, providing that excess oxidant was employed and the reaction promptly worked up. Otherwise, equilibration occurred and the products were obtained as mixtures of diastereomers. l,4-Dichloro-2-butyne was converted to the sulfonyl-substituted allenic alcohol 23 by selenosulfonation, reductive dehalogenation, oxidation, and [2,3] sigmatropic rearrangement of the resulting selenoxide. The addition of organocuprates to 23, followed by dehydration, afforded a series of 3-alkyl- or propenyl-substituted 2-sulfonyl-l,3-dienes 5a-e. Alternatively, the treatment of 23 with acetic anhydride-triethylamine or thionyl chloride produced the 3-acetoxy- and 3-chloro-2-sulfonyl-1,3-dienes 5f and 5g, respectively. These methods therefore provide convenient access to a variety of synthetically useful sulfonyl-substituted allenic alcohols and dienes. © 1990, American Chemical Society. All rights reserved.