Radical addition to the CC bond meets (1,n)-HAT: recent advances in the remote C(sp³)–H or C(sp²)–H functionalization of alkenes

Abstract

In recent years, remarkable advances on remote C(sp3)-H bond or aldehydic C(sp2)-H functionalizations enabled by intermolecular radical addition to C=C bond/(1,n)-HAT tandem sequences have been witnessed, which provided an efficient...

Remote Radical 1,3-, 1,4-, 1,5-, 1,6- and 1,7-Difunctionalization Reactions

“…Radical 1,6- and 1,7-difunctionalization reactions require special alkene substrates which can undergo 1,5- or 1,6-HAT reactions ( Figure 4 ). Since a couple of recent reviews covered the progress on this topic [ 88 , 89 ], only selective examples and most recent examples are presented herein.…”

Asymmetric, Remote C(sp3)−H Arylation via Sulfinyl‐Smiles Rearrangement

“…Inspired by these studies, we hypothesized that a radical-mediated tandem 1,n-hydrogen-1,4-aryl migration [19] could provide a de novo entry to the remote arylation of C(sp 3 )À H bonds with high levels of absolute stereocontrol. Under photoredox neutral conditions, unactivated olefins [20] are envisaged as viable radical acceptors to produce reactive C-centered radicals prone to 1,n-HAT followed by subsequent sulfinyl-Smiles rearrangement. Herein, we present a photoredox-catalyzed asymmetric remote arylation of sulfinyl amides combining a sequential 1,n-HAT and a sulfinyl-Smiles rearrangement (Scheme 1B).…”

Direct C(sp2)–H activation of allenes via hydrogen-atom transfer (HAT) in organic synthesis

“…The direct functionalization of unactivated C–H bonds has been recognized as a reliable approach for constructing complex compounds due to its high atom- and step-economy as well as ubiquitous starting materials. 1,2 In recent years, intensive research efforts have been undertaken toward the development of new strategies for C–H bond functionalization, among which radical-induced hydrogen-atom transfer (HAT) reactions arguably constitute thus far the most valuable tool. 2…”

“…1,2 In recent years, intensive research efforts have been undertaken toward the development of new strategies for C–H bond functionalization, among which radical-induced hydrogen-atom transfer (HAT) reactions arguably constitute thus far the most valuable tool. 2…”

“…HAT is defined as the transfer of a hydrogen atom between two functional groups in a single step, which represents a key elementary reaction step in free-radical chemistry. 2 The selectivities and rates of hydrogen-atom abstraction reactions from the corresponding C–H bonds depend not only on C–H bond dissociation enthalpies but also on polar effects in the respective transition states. 3 Generally, an electrophilic radical, such as the chlorine radical (Cl˙), preferentially abstracts hydrogen from an electron-rich C–H bond, 4 whereas a nucleophilic radical selectively cleaves an electron-deficient C–H bond (Scheme 1a).…”