Enantioselective Main Group Catalysis: Modern Catalysts for Organic Transformations

• An overview of emerging main group catalysts used in chiral induction is outlined.
• Mechanistic aspects of various enantioselective catalytic cycles are described.
• Solutions to common limitations of main group systems are offered.
• Main group alternatives to traditional transition metal complexes are presented.

This review highlights a number of recent developments in the field of main group enantioselective catalysis. Many essential transformations can be effected catalytically such as hydrosilylation, hydroamination and hydrogenation reactions, amongst others, in an asymmetric fashion using earth abundant s- and p-block elements such as calcium, strontium, boron and aluminum. Recent work in this area has shown that these systems are not only active in catalysis but may also have the potential to compete with transition metal based systems with the reduced cost and toxicity sometimes associated with main group chemistry.

The current field of synthetic enantioselective catalysis is dominated by transition metals such as ruthenium, palladium and copper, launched through the success of pioneering work by Knowles, Noyori and Sharpless, however, there are inherent problems with using heavy rare earth transition metals, namely their prohibitive costs and potential toxicity. To combat this an alternative has been found in the form of main group centered catalysts. Indeed the recent application of main group elements in catalysis has expanded to encompass enantioselective transformations. As main group elements, for example calcium, magnesium, boron and aluminum have become more preeminent as active catalysts, their applications in enantioselective catalysis has also made great strides in recent years. In this review we highlight the importance of earth abundant main group s- and p-block catalysts as candidates for effective asymmetric induction in a range of organic transformations such as 1,4-additions, hydrosilylation, hydrogenation and phosphonylation as well as dispelling common myths surrounding early s- and p-block elements with regard to their catalytic applications.Figure optionsDownload high-quality image (199 K)Download as PowerPoint slide