Synthesis of heterocycles via organopalladium intermediates

A number of oxygen- and nitrogen-containing heterocycles have been prepared by employing organopalladium intermediates. First, mercuric chloride readily adds to the carbon-carbon triple bond of certain 4-hydroxy-2-alkyn-1-ones 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. Second, the mercuration of allenic acids and esters has been examined. Low yields of (beta)-substituted (DELTA)(\u27(alpha),(beta))-butenolides could be obtained from mercuration and palladium-assisted carbonylation or acetoxylation of the allenic acid. Third, a new approach to the synthesis of tetracyclic sequiterpenes via vinylation-carbonylation of 2,3-dimethylnorbornadiene-palladium dichloride and 2-methylnorbornadiene-palladium dichloride was explored. Finally, palladium-assisted olefination-cyclization of thallated p-tolylacetic acid, N-methylbenzamide, benzamide, and acetanilide have been studied. N-Methylisoquinolones, isocarbostyrils, and indoles have been prepared by this new route in moderate to good yields. Our method, which employs organometallic intermediates, is often shorter and more efficient than older methods for obtaining many of the compounds studied