Straightforward Synthesis of Fluorinated Enals via Photocatalytic α-Perfluoroalkenylation of Aldehydes

Visible-Light Promoted Radical Fluoroalkylation of O- and N-Substituted Alkenes

Interaction of enol ethers enol acetates, enamides and enamines with fluorinated reagents may be considered as a reliable method for the synthesis of organofluorine compounds. While classic nucleophile/electrophile substitution or addition mechanisms cannot be realized for coupling of these components, their intrinsic reactivities are revealed with the aid of photoredox catalysis. A combination of these electron donating and accepting components provides a perfect balance needed for individual redox steps, which in some cases may proceed even without a photocatalyst. The same electronic factors also support the key C,C-bond forming event involving addition of fluorinated radical at the electron rich double bond.

Photocatalytic Cascade Cyclization of Aryl Haloalkynyl Ketones Forming Cyclopenta[b]naphthalene Derivatives

An efficient metal-free, photoredox-mediated cascade cyclization of aryl 1-haloalk-5-ynyl ketones has been developed. Using catalytic amounts of eosin Y (EY) and EtNMe₂ as a reductive quencher, various aryl 1-haloalk-5-ynyl ketones have been transformed into the corresponding cyclization products in up to 98% yield. As a result, synthetic access to differently α-functionalized cyclopenta[b]naphthones and direct construction of cyclopenta[b]naphtholes has been developed.

Visible-light-induced Mn(0)-catalyzed direct C-3 mono-, di- and perfluoroalkylation reactions of 2H-indazoles

A general and efficient method for visible-light-driven fluoroalkylation, such as difluoromethylphosphonation, difluoroacetamidation, monofluoromethylation, difluoromethylation, and perfluoroalkyalation, of 2H-indazoles using an inexpensive Mn₂(CO)₁₀ photocatalyst has been developed. The present methodology affords a new series of C-3 fluoroalkylated 2H-indazole derivatives with wide functional group tolerance in good to excellent yields. Difluoromethylenated indiazoles are also prepared from difluoroester derivatives. Our mechanistic investigations support a radical pathway for the reaction.

Recent Advances in Photoinduced Perfluoroalkylation Using Perfluoroalkyl Halides as the Radical Precursors

Perfluoroalkylation is one of the most important methods for the introduction of multiple fluorine atoms into organic molecules in a single step. The use of photoinduced technology is a common strategy that uses the outstanding oxidation or reduction ability of a photo­redox catalyst in its excited state to generate perfluoroalkyl radicals from perfluoroalkyl halides. The perfluoroalkyl radicals thus obtained can undergo various subsequent reactions under mild conditions, such as ATRA reaction of alkenes, alkynes, and 1,n-enynes; carbo/heteroperfluoroalkylation of alkenes and isocyanides; and C–H/F perfluoroalkyl­ation. This allows the expedient incorporation of various perfluoroalkyl groups into the molecular motifs. Perfluorinated functional groups are still in demand in pharmaceutical and material sciences; this short review discusses recent advances in photoinduced perfluoroalkylation methodologies and technologies.

1 Introduction

2 Photocatalytic Perfluoroalkylation of Alkenes, Alkynes, and 1,n- Enynes

3 Photocatalytic Carboperfluoroalkylation or Heteroperfluoro­alkylation of Alkenes, Alkynes, Isocyanides, and Hydrazones

4 Photocatalytic ATRE Reactions of Alkenes with Perfluoroalkyl Halides­

5 Photocatalytic C–X (X = H, F) Bond Perfluoroalkylation

6 Continuous Flow Strategies in Photocatalytic Perfluoroalkylation

7 Conclusions

Water facilitated photolysis of perfluoroalkyl iodides via halogen bonding

A strategy for the efficient water facilitated photolysis of perfluoroalkyl iodide has been established for the synthesis of various perfluoroalkylated products.

Visible-light-promoted direct C3-trifluoromethylation and perfluoroalkylation of imidazopyridines

An efficient method for direct trifluoromethylation and perfluoroalkylation at C3 of imidazopyridines through visible light-promoted C-H bond functionalization was developed. Under the irradiation of a blue LED, a series of C3-perfluoroalkyl-substituted imidazopyridines were synthesized from the corresponding imidazopyridines and perfluoroalkyl iodides in moderate to good yields at room temperature. It should be mentioned that this reaction proceeded in the absence of any transition-metal catalyst, oxidant and photocatalyst.

Catalyst-Free Visible-Light-Mediated Iodoamination of Olefins and Synthetic Applications

Herein we report a catalyst- and metal-free visible-light-mediated protocol enabling the iodoamination of miscellaneous olefins. This protocol is characterized by high yields under environmentally benign reaction conditions utilizing commercially available substrates and a green and biodegradable solvent. Furthermore, the protocol allows for late-stage functionalization of bioactive molecules and can be scaled to gram quantities of product, which offers manifold possibilities for further transformations, including morpholine, piperidine, pyrrolidine, and aziridine synthesis.