Directed C—H Activation Reactions of Synthetically Versatile Substrates: A Journey to Practicality

摘要

The recent emergence of diverse catalytic transformations that allow conversion of inert C—H bonds into various functional groups has greatly enriched our approach towards synthetic disconnections. Multi-faceted influences on organic synthesis can be envisaged: shortening the synthetic route by either skipping prefunctionalization steps or achieving optimal convergency; bestowing synthetically useful reactivity to abundant but less functionalized chemicals; allowing for rapid diversification of advanced synthetic intermediates or complex target molecules; and providing new approaches for asymmetric catalysis through chiral recognition of sp3 carbon centers. While the potential for synthetic applications of C—H activation reactions are undisputably vast, the challenges encountered in this endeavor are equally overwhelming. First, the reactivity of C—H bonds in commonly used synthetic substrates is usually poor. Second, the catalytic cycles often involve uphill redox chemistry and suitable oxidants are required to close the catalytic cycle. Third, control of the site selectivity is extraordinarily challenging due to the presence of multiple C—H bonds in substrates.