Double difunctionalization of vinyl ether tethered nucleophile with electron-deficient alkene in two-molecule photoredox system.

Double difunctionalization of a vinyl ether tethered hydroxy or carbamoyl group with electron-deficient alkenes such as acrylonitrile or acrylic esters was achieved by visible-light irradiation in a two-molecule photoredox system. Use of anhydrous acetonitrile solution as a solvent promoted both dimerization of the radical cation of electron-rich alkene with electron-rich alkene and intramolecular nucleophilic addition to generate an electron-rich radical that was added to electron-deficient alkene to furnish the double difunctionalized product. A variety of electronically differentiated rich and deficient alkenes were used in the photoreaction; a simple construction of a complex carbon framework containing acetal from simple alkenes was successful under mild conditions.

Decarboxylative Side-Chain Functionalization of Aspartic/Glutamic Acids Using Two-Molecule Photoredox Catalysts.

The side-chain functionalization of aspartic/glutamic acid derivatives through photoinduced decarboxylation was achieved by using organic two-molecule photoredox catalysts without racemization under mild conditions. A facile process involving the preparation of substrates and photoinduced decarboxylative radical additions can provide easy access to the linked amino acids with carbohydrates and amino acids at the side chain.

9-Cyano-10-methoxycarbonylanthracene as a Visible Organic Photoredox Catalyst in the Two-Molecule Photoredox System.

Visible-light-induced decarboxylative and deboronative reactions using two-molecule organic photoredox catalysts, namely, phenanthrene (Phen) and biphenyl (BP), as electron donors and 9-cyano-10-methoxycarbonylanthracene 1a as an electron acceptor were achieved. The high solubility of 1a significantly improved the reaction efficiency and product yield. In addition, the facile tuning of the oxidation potential of the electron-donor molecule via the replacement of Phen with BP enabled the application of the two-molecule photoredox system to a wide range of substrates.

Visible- and UV-Light-Induced Decarboxylative Radical Reactions of Benzoic Acids Using Organic Photoredox Catalysts.

Photoinduced decarboxylative radical reactions of benzoic acids with electron-deficient alkenes, diborane, and acetonitrile under organic photoredox catalysis conditions and mild heating afforded adducts, arylboronate esters, and the reduction product, respectively. The reaction is thought to involve single-electron transfer promoted the generation of aryl radicals via decarboxylation. A diverse range of benzoic acids were found to be suitable substrates for this photoreaction. Only our two-molecule organic photoredox system can work well for the direct photoinduced decarboxylation of benzoic acids.

Sequential Intermolecular Radical Addition and Reductive Radical Cyclization of Tyrosine and Phenylalanine Derivatives with Alkenes via Photoinduced Decarboxylation: Access to Ring-Constrained γ-Amino Acids.

Sequential radical addition to alkenes and reductive radical cyclization of phenylalanine and tyrosine derivatives via photoinduced decarboxylation furnished ring-constrained γ-amino acids under mild conditions. A variety of alkenes such as acrylamides and acrylic esters could be employed in the photoinduced radical cascade cyclization. The yields of the ring-constrained γ-amino acids are dependent on the electron-accepting ability and steric hindrance of the alkene used. The proposed sequential reaction can also be applied for direct tethering of dipeptides to yield unique ring-constrained tetrapeptides.

Synthesis of 23-, 25-, 27-, and 29-Membered ( Z)-Selective Unsaturated and Saturated Macrocyclic Lactones from 16- and 17-Membered Macrocyclic Lactones and Bromoalcohols by Wittig Reaction, Yamaguchi Macrolactonization, and Photoinduced Decarboxylative Radical Macrolactonization.

A new strategy for the synthesis of 23-, 25-, 27-, and 29-membered ( Z)-selective unsaturated and saturated macrocyclic lactones from commercially available 16- and 17-membered macrocyclic lactones and bromoalcohols by Wittig reaction, Yamaguchi macrolactonization, and photoinduced decarboxylative radical macrolactonization is described. The position of the unsaturated part in the macrocyclic lactones can be controlled by changing the number of carbons in the starting materials. This protocol can provide facile access to the desired large-ring ( Z)-selective unsaturated and saturated macrocyclic lactones from simple starting materials.

Photoinduced Electron Transfer-Promoted Reactions Using Exciplex-Type Organic Photoredox Catalyst Directly Linking Donor and Acceptor Arenes.

Directly linked donor and acceptor arenes, such as phenanthrene/naphthalene/biphenyl and 1,3-dicyanobenzene were found to work as photoredox catalysts in the photoreactions of indene, 2,3-dimethyl-2-butene, and 4-methoxyphenylacetic acid. The new stable organic photocatalyst forms an intramolecular exciplex (excited complex) when irradiated in a polar solvent and shows redox catalyst activity, even at low concentrations. To the best of our knowledge, this is the first example of an intramolecular exciplex working as a redox catalyst.

Two Types of Cross-Coupling Reactions between Electron-Rich and Electron-Deficient Alkenes Assisted by Nucleophilic Addition Using an Organic Photoredox Catalyst.

Two types of photoreactions between electronically differentiated donor and acceptor alkenes assisted by nucleophilic addition using an organic photoredox catalyst efficiently afforded 1:1 or 2:1 cross-coupling adducts. A variety of alkenes and alcohols were employed in the photoreaction. Control of the reaction pathway (i.e., the formation of the 1:1 or 2:1 adduct) was achieved by varying the concentration of the alcohol used. Detailed mechanistic studies suggested that the organic photoredox catalyst acts as an effective electron mediator to promote the formation of the cross-coupling adducts.

Metal-Free Photoinduced Decarboxylative Radical Polymerization Using Carboxylic Acids as Benign Radical Initiators: Introduction of Complex Molecules into Polymer Chain Ends.

Metal-free photoinduced decarboxylative radical polymerization of aliphatic carboxylic acids with a variety of monomers was found to proceed smoothly to give the corresponding polymers under mild conditions. Complex carboxylic acids such as those of sugars, steroids, and peptides can function as benign radical initiators via decarboxylation and can be incorporated at the polymer chain ends. This synthetic methodology represents a facile introduction of molecules and functionalities to polymers by using commercially available carboxylic acids.