The Binomial Copper‐Catalysis and Asymmetric Ring Opening of Strained Heterocycles: Past and Future Challenges

Abstract

This minireview is focused on the use of chiral copper‐catalysts for the asymmetric ring opening of unsaturated strained heterocycles. Starting from the activity of my research group in Pisa over the years a report of the recent literature in this field is provided. From a mechanistic point of view the ring‐opening reactions of unsaturated strained heterocycles with organometallic reagents are a sort of allylic alkylation in which the leaving group remains at the end of the reaction. Therefore, chiral ligands useful for copper‐catalyzed asymmetric allylic alkylation and conjugate addition such as phosphoramidites and ferrocenyl phosphines have shown to be effective for ring‐opening reactions as well. As consistently shown in the article, the regio‐ and stereoselectivities obtained with copper are in most cases complimentary to the selectivities attainable by other common metal catalysts such as palladium, nickel and rhodium. In recent years, the introduction of versatile boron atoms by the use of nucleophilic (chiral) copper‐boryl complexes has enlarged considerably the synthetic potential of ring‐opening reactions.