Visible-Light-Induced Nickel-Catalyzed Radical Cross-Couplings to Access α-Aryl-α-trifluoromethyl Alcohols

Visible light induced hydroxyfluoroalkylation of quinoxalin-2(1H)-ones with N-trifluoroethoxyphthalimide under catalyst-free conditions

For the first time, we achieved visible light-induced direct C3-hydroxyfluoroalkylation of quinoxalin-2(1H)-ones using N-trifluoroethoxyphthalimide as the trifluoroethanol radical precursor, without the need for a photocatalyst. The metal-free and catalyst-free nature of this method makes it an efficient and environmentally friendly approach for synthesizing C3-hydroxyfluoroalkylated quinoxalin-2(1H)-ones.

Direct Synthesis of 2-Hydroxytrifluoroethylacetophenones via Organophotoredox-Mediated Net-Neutral Radical/Polar Crossover

Alkene difunctionalization is a very attractive tool in synthetic organic chemistry. Herein, we disclose an operationally and practically simple method to access 2-hydroxytrifluoroethylacetophenones from styrene derivatives via photoredox catalysis. This light-mediated transformation promotes the generation of the 1-hydroxy-2,2,2-trifluoroethyl carbon-centered radical as key synthon, which undergoes Giese addition with styrenes followed by a Kornblum oxidation process. The presented method is not only mild and cost-effective, but also utilizes an organic photocatalyst and DMSO as oxidant. Experimental investigations support the operative mechanism via net-neutral radical/polar crossover.

Photoredox-Catalysis Fluorosulfonyldifluoromethylation of Unactivated Alkenes and (Hetero)arenes with ICF2SO2F

The fluorosulfonyldifluoromethylation of unactivated alkenes and (hetero)arenes with iododifluoromethanesulfonyl fluoride (ICF2SO2F) under visible light photoredox catalysis was successfully developed. Key to the successful fluorosulfonyldifluoromethylation of aromatic compounds was the usage of AgOTf as an additive to promote the formation of the CF2SO2F radical. The protocol provided a straightforward way to introduce the interesting and useful CF2SO2F group on sp3 and sp2 carbons.

Synthesis of Hexafluoroisopropyl Aryl Ethers via Dual Photoredox/Nickel-Catalyzed C-O Coupling

Herein we report a photoredox/nickel-catalyzed cross-coupling of aryl bromides with 1,1,1,3,3,3-hexafluoroisopropanol for the construction of hexafluoroisopropyl aryl ethers. The mild reaction conditions employed allow for the applicability of a wide range of aryl and heteroaryl bromides. Late-stage functionalization and preliminary mechanistic studies have been demonstrated.

A Dual Ni/Photoredox Cross-Coupling Approach toward Mandelic Acids

Mandelic acid derivatives represent a valuable class of compounds due to their wide use in synthetic organic chemistry and the pharmaceutical sector. Herein, we report a novel reductive Ni/photoredox cross-coupling of readily accessible, bench stable N-alkoxyphthalimides and aryl halides to prepare unprotected mandelic acid ester derivatives. Mechanistic experiments suggest that this cross-coupling likely proceeds via a pathway that is distinct from previous reports using similar redox-active alkoxy radical precursors.

Hydroxytrifluoroethylation and Trifluoroacetylation Reactions via SET Processes

Hydroxytrifluoroethyl and trifluoroacetyl groups are of utmost importance in biologically active compounds, but methods to tether these motifs to organic architectures have been limited. Typically, the preparation of these compounds relied on the use of strong bases or multistep routes. The renaissance of radical chemistry in photocatalytic, transition metal mediated, and hydrogen atom transfer (HAT) processes have allowed the installation of these medicinally relevant fluorinated motifs. This review provides an overview of the methods available for the direct synthesis of hydroxytrifluoroethyl- and trifluoroacetyl-derived compounds governed by single-electron transfer processes.

Visible-Light-Induced Defluorinative α-C(sp3)-H Alkylation for the Synthesis of gem-Difluoroallylated α-Trifluoromethylamines

Herein, we describe a novel and efficient photoredox catalytic Cα radical addition/defluoroalkylation coupling reaction between α-trifluoromethyl alkenes and N-trifluoroethyl hydroxylamine. A series of gem-difluoroallylated α-trifluoromethylamines were synthesized by the Cα radical addition enabled by a 1,2-H shift of the in situ-generated N-trifluoroethyl radical. Notably, this protocol is distinguished by its mild conditions, easy operation, and excellent functional group tolerability.

Metal-free photoinduced C(sp3)-H/C(sp3)-H cross-coupling to access α‑tertiary amino acid derivatives

The cross-dehydrogenative coupling (CDC) reaction is the most direct and efficient method for constructing α-tertiary amino acids (ATAAs), which avoids the pre-activation of C(sp3)-H substrates. However, the use of transition metals and harsh reaction conditions are still significant challenges for these reactions that urgently require solutions. This paper presents a mild, metal-free CDC reaction for the construction of ATAAs, which is compatible with various benzyl C-H substrates, functionalized C-H substrates, and alkyl substrates, with good regioselectivity. Notably, our method exhibits excellent functional group tolerance and late-stage applicability. According to mechanistic studies, the one-step synthesized and bench-stable N-alkoxyphtalimide generates a highly electrophilic trifluoro ethoxy radical that serves as a key intermediate in the reaction process and acts as a hydrogen atom transfer reagent. Therefore, our metal-free and additive-free method offers a promising strategy for the synthesis of ATAAs under mild conditions.

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

A visible-light-induced nickel-catalyzed cross coupling of alkyl carboxylic acids with N-trifluoroethoxyphthalimide is described. Under purple light irradiation, an α-hydroxytrifluoroethyl radical generated from a photoactive electron donor-acceptor complex between Hantzsch ester and N-trifluoroethoxyphthalimide was subsequently engaged in a nickel-catalyzed coupling reaction with in situ-activated alkyl carboxylic acids. This convenient protocol does not require photocatalysts and metal reductants, providing a straightforward and efficient access to trifluoromethyl alkyl acyloins in good yields with broad substrate compatibility. The complex bioactive molecules were also compatible with this catalytic system to afford the corresponding products.