Mercuric chloride readily adds to the carbon-carbon triple bond of certain 4-hydroxy-2-alkyn-l-ones (3a, 3b, and 3e) to give vinylmercurials which appear to be the first syn addition compounds of mercuric chloride. These vinylmercurials readily dehydrate to 3-furylmercurials. Palladium-promoted carbonylation of these compounds affords 3-furyl carbonyl compounds.Mercury(II) salts are known to readily add to a variety of acetylenes to afford vinylmercurials (eq 1). Thus, Cl, OAc, SON mercuric halides are reported to add to acetylene (anti),2"7 propyne (anti),8 cyclooctyne,® vinylacetylene (anti?),8•10 11"12