Selective Thiolative Lactonization of Internal Alkynes Bearing a Hydroxyl Group with Carbon Monoxide and Organic Disulfides Catalyzed by Transition-Metal Complexes

Although many transition-metal catalysts
are ineffective for the
addition and carbonylative addition of organic disulfides to internal
alkynes, dicobalt octacarbonyl and palladium complexes such as Pd­(PPh3)4 and Pd­(OAc)2 were found to exhibit
excellent catalytic activity for the thiolative lactonization of internal
alkynes bearing a hydroxyl group. In the presence of the cobalt or
palladium catalyst, internal alkynes bearing a hydroxy group, such
as homopropargyl alcohol derivatives, successfully undergo thiolative
carbonylation with carbon monoxide and an organic disulfide regio-
and stereoselectively to afford the corresponding thio group bearing-lactones
in good yields. In the Co-catalyzed reaction, the cobalt–alkyne
complex from dicobalt octacarbonyl and internal alkyne acts as a key
species, making it possible to attain thiolative lactonization of
internal alkynes with a hydroxyl group. In the Pd-catalyzed reaction,
the coordination of the hydroxy group to the palladium catalyst plays
an important role for the thiolative lactonization.