Abstract Sequential insertion of carbon monoxide and alkynes into alkylmanganese pentacarbonyl complexes at pressures of 6 kbar provides unsaturated manganacycles in a regioselective manner. The manganacycles can be transformed under acidic conditions into a mixture of enone and furanone. Alternatively, themanganacycle can be reduced with DIBAL-ate complex to furnish the butenolide.
