Stereoselective inter- and intramolecular Pauson-Khand reactions of N-(2-alkynoyl) derivatives of chiral oxazolidin-2-ones

A complete account of the intermolecular and intramolecular Pauson-Khand re actions of N-(2-alkynoyl) derivatives of chiral 2-oxazolidinones is present ed. The intermolecular Pauson-Khand reactions with norbornene or norbornadi ene take place under mild conditions and in high yields. Phenyl- or trimeth ylsilylpropiolate derivatives lead to the exclusive formation of 1,4-dicarb onyl regioisomers, while mixtures of 1,3- and 1,4-regioisomers are obtained with derivatives. The diastereoselectivity of the determined by the substi tution pattern of the oxazolidinone moieties, can be very high (up to 17.5: 1 dr) for the formation of 1,4-dicarbonyl regioisomers, and the diastereome ric products can often be separated by column chromatography. Under the app ropriate conditions, the intramolecular Pauson-Khand reactions of oxazolidi none-derived enynes can also take place with very good yields, but with low diastereoselectivities. The absolute configurations of several adducts hav e been determined, and the stereochemical outcome of the reaction has been rationalized.