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

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journal contribution
posted on 17.07.2015, 00:00 by Shinya Higashimae, Taichi Tamai, Akihiro Nomoto, Akiya Ogawa
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.