Resurgence and advancement of photochemical hydrogen atom transfer processes in selective alkane functionalizations

Abstract

By drawing inspiration from photoredox catalysis, the field of radical-mediated alkane functionalization has made remarkable advancements recently to address the challenges of today and future.

A survey of the iron ligand-to-metal charge transfer chemistry in water

“…14,15 For a successful transition, the empty d * orbital of the metal has to be low in energy and this is the case for highly electrophilic high-valent metals such as Ce 4+ , Fe 3+ , or Bi 3+ among many other candidates. 16–18 Suitable ligands for the light-induced bond homolysis are nucleophilic σ- or σ + π – donors such as halides, alcohols, carboxylic acids or azides (Scheme 2). 17,19–24 In this review we discuss water ligands, that, located in the middle region of the spectrochemical row, also favour LMCT transitions.…”

Electrochemical C(sp3)−H Functionalization Using Acetic Acid as a Hydrogen Atom Transfer Reagent

“…Methyl radical can function as a new class of hydrogen atom abstractor suitable for C(sp 3 )À H functionalization because of its exceptionally high bond dissociation energy (BDE = 105 kcal/mol) [31] and unique nucleophilic nature. [32] Despite attractive properties, the generation of methyl radical, an sp 3 -hybridized carbon-centered radical, [33][34][35] is quite challenging; therefore, there have been very few reports on the use of methyl radical for the functionalization of C(sp 3 )À H bonds. In 2002, the Tomioka group was the first to demonstrate the use of methyl radical as a hydrogen atom abstractor for C(sp 3 )À H functionalization.…”

Asymmetric Three-Component Radical Alkene Carboazidation by Direct Activation of Aliphatic C–H Bonds

“…The direct and selective functionalization of C­(sp 3 )–H bonds has been an outstanding goal in the field of synthetic organic chemistry, which would offer great potential to simplify synthetic routes and modify complex molecules via late-stage derivatization. − Unactivated hydrocarbons, such as alkanes, are abundant chemical feedstocks and readily available on a large scale from petrochemicals. The selective conversion of unactivated alkanes into value-added chiral molecules has received intensive attention due to its advantages in atom and step economy and sustainability. − Nevertheless, the intrinsic inertness of C­(sp 3 )–H bonds and the lack of functional groups in unactivated hydrocarbons have presented formidable challenges in the development of stereoselective transformations. − Despite notable progress achieved in recent years, the enantioselective functionalization of C­(sp 3 )–H bonds in hydrocarbons remains underdeveloped and provides potential opportunities for chemical research.…”