Platinum- and gold-catalyzed hydroalkoxylation and tetramerization of propiolate esters

• PtCl2-catalyzed hydroalkoxylation of propiolate esters affords (E)-vinyl ethers.
• PtCl2-catalyzed bis(hydroalkoxylation) of propiolate esters affords acetals.
• AuCl3-catalyzed tetramerization of propiolate esters affords cyclooctatetraenes.

PtCl2 was found to efficiently catalyze intermolecular additions of propiolate esters with alcohols. The reaction of propiolate esters and alcohols in the presence of PtCl2 gave (E)-vinyl ethers as the major products at 60 °C, whereas alkyl 3,3-dialkoxypropanoates were predominantly obtained when the reaction temperature was set to 80 °C. On the other hand, a novel regioselective tetramerization of propiolate esters catalyzed by AuCl3 under mild conditions afforded 1,2,5,6-tetrasubstituted-cyclooctatetraene (1,2,5,6-COT) in moderate yields.

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