New Approaches to Bicylic Vinyl Heterocycles from Propargylic Acetals

The paper describes further studies on the intramolecular carbolithiation of propargylic acetals with aryllithiums leading to 2-vinylbenzofurans and 3-vinylfuropyridines. Attempts to extend the cascade to [4.4.0] binuclear heterocycles met with limited success. An alternative, two-step entry to such ring systems has been developed using the palladium-induced cyclization/hydride capture methodology. A new route to isoquinilinones from simple benzamides is also disclosed.