Synthesis of enones and butenolides using organomanganese pentacarbonyl complexes.

✍ Scribed by Philip DeShong; Daniel R. Sidler; Greg A. Slough

• Publisher: Elsevier Science
• Year: 1987
• Tongue: French
• Weight: 213 KB
• Volume: 28
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)96088-x

✦ Synopsis

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.

In the preceding Communication, we demonstrated that alkylmanganese pentacarbonyl complexes (1) reacted with selected alkenes at pressures of 6 kbar to produce manganacycles arising from the sequential insertion of carbon monoxide and the alkene into the carbon-manganese bond. These manganacycles were demetalated by photolysis in the presence of molecular oxygen to produce highly functionalized carbonyl compounds.2 The overall transformation resulted in the formation of two carbon-carbon bonds, incorporation of one molecule of carbon monoxide, and the regioand stereoselective attachment of an acyl residue to the alkene. In this Communication, we report that alkynes also participate in the sequential insertion process with alkylmanganese pentacarbonyl complexes (1) to yield manganacycle 2. Subsequent treatment of 2 with acid yields a mixture of enone 3 and furanone 4; whereas, reduction of the manganacycle with DIBAL-ate complex gives the corresponding butenolide 5 (Scheme 1).