Manganese-catalyzed carbonylation of alkyl iodides

Abstract

The palladium-catalyzed cross-coupling of aryl bromides with zirconocene-benzyne complexes has been investigated by S.L. Buchwald and coworkers. This method allows the formation of substituted biphenyls and terphenyls, however only two ortho-substituents are tolerated in this transformation. The studies reportd herein aimed at the synthesis of tri- and tetra substituted biaryls, since they are important precursors to biaryl phosphine ligands. The project did not succeed due to stability problems of the formed substituted zirconium biaryl. A general method for the manganese-catalyzed carbonylation of alkyl iodides while using a variety of nucleophiles was developed. The method concerns the alkoxy and amino carbonylation as well as the use of more unconventional nucleophiles such as thiols, azide and hydride. The method employs alkyl iodides although bromides are also feasible substrates through in situ Finkelstein reaction with catalytic to substoichiometric amounts of sodium iodide. The functional group tolerance is high and the conditions for the transformation are mild using only 40 psi of carbon monoxide pressure and temperatures between r.t. and 90°C for more difficult cases.