Addition of Heteroaromartic Thiols to Electron-Rich Alkenes: A Reversed Hetero Ene Reaction

Article abstract of DOI:10.1021/jo00125a036

Benzothiophenethiol 1a reacted with styrene to give thiol 2a, which resulted from a ''reversed hetero ene reaction''.When the reaction was carried out in the presence of radical precursors, products deriving from radical addition to the styrene double bond of both thiols 1a and 2a formed.The reaction of 1a with butyl vinyl ether (BVE) gave the α,β-unsaturated dithioester 23a, deriving from the ''ene reaction product'' 22a through elimination of butanol.Similar behavior was exhibited by benzofuranthiol 1b, which reacted with styrene to give thiol 2b and with BVE to give the thionoester 23b.Both dithio- and thionoesters 23a,b were trapped as Diels-Alder adducts.In contrast, thiophenethiol 1c did not react with styrene and reacted with BVE to give an electrophilic 1:1 adduct.Ene reaction of thiols 1a,b occurred only with electron-rich olefins.In agreement, 1a did not react with hex-1-ene and methyl acrylate and reacted with dimethyl maleate to give a nucleophilic adduct.