Iron-Catalyzed Intermolecular 1,2-Difunctionalization of Styrenes and Conjugated Alkenes with Silanes and Nucleophiles

The first iron-catalyzed 1,2-difunctionalization of styrenes and conjugated alkenes with silanes and either N or C, using an oxidative radical strategy, is described. Employing FeCl₂ and di-tert-butyl peroxide allows divergent alkene 1,2-difunctionalizations, including 1,2-aminosilylation, 1,2-arylsilylation, and 1,2-alkylsilylation, which rely on a wide range of nucleophiles, namely, amines, amides, indoles, pyrroles, and 1,3-dicarbonyls, thus providing a powerful platform for producing diverse silicon-containing alkanes.     

Ligand‐Promoted Iron(III)‐Catalyzed Hydrofluorination of Alkenes

An iron‐catalyzed hydrofluorination of unactivated alkenes has been developed. The use of a multidentate ligand and the fluorination reagent N‐fluorobenzenesulfonimide (NFSI) proved to be critical for this reaction, which afforded various fluorinated compounds in up to 94 % yield.     

Copper‐Catalyzed 1,2‐Methoxy Methoxycarbonylation of Alkenes with Methyl Formate

Reported here is a copper‐catalyzed 1,2‐methoxy methoxycarbonylation of alkenes by an unprecedented use of methyl formate as a source of both the methoxy and the methoxycarbonyl groups. This reaction transforms styrene and its derivatives into value‐added β‐methoxy alkanoates and cinnamates, as well as medicinally important five‐membered heterocycles, such as functionalized tetrahydrofurans, γ‐lactones, and pyrrolidines. A ternary β‐diketiminato‐Cu^I‐styrene complex, fully characterized by NMR spectroscopy and X‐ray crystallographic analysis, is capable of catalyzing the same transformation. These findings suggest that pre‐coordination of electron‐rich alkenes to copper might play an important role in accelerating the addition of nucleophilic radicals to electron‐rich alkenes, and could have general implications in the design of novel radical‐based transformations.     

Visible‐Light‐Induced Carbo‐2‐pyridylation of Electron‐Deficient Alkenes with Pyridinium Salts

A simple and practical visible‐light‐induced carbo‐2‐pyridylation of electron‐deficient alkenes with readily available N‐benzoylmethylpyridinium bromides is reported. More than 40 examples are presented and proceed in greater than 80 % yield (on average) with excellent regio‐ and diastereoselectivities.     

Rhodium‐Catalyzed Dehydrogenative Borylation of Aliphatic Terminal Alkenes with Pinacolborane

Aliphatic terminal alkenes react with pinacolborane at ambient temperature to afford dehydrogenative borylation compounds as the major product when iPr‐Foxap is used as the ligand with cationic rhodium(I) in the presence of norbornene, which acts as the sacrificial hydrogen acceptor. The reaction is applied to the one‐pot syntheses of aldehydes and homoallylic alcohols from aliphatic terminal alkenes.     

Dual Photoredox/Nickel‐Catalyzed Three‐Component Carbofunctionalization of Alkenes

The potential of merging photoredox and nickel catalysis to perform multicomponent alkene difunctionalizations under visible‐light irradiation is demonstrated here. Secondary and tertiary alkyl groups, as well as sulfonyl moieties can be added to the terminal position of the double bond with simultaneous arylation of the internal carbon atom in a single step under mild reaction conditions. The process, devoid of stoichiometric additives, benefits from the use of bench‐stable and easy‐to‐handle reagents, is operationally simple, and tolerates a wide variety of functional groups.     

Catalytic Intermolecular Dicarbofunctionalization of Styrenes with CO2 and Radical Precursors

A redox‐neutral intermolecular dicarbofunctionalization of styrenes with CO₂ at atmospheric pressure and carbon‐centered radicals is described. This mild protocol results in multiple C−C bond‐forming reactions from simple precursors in the absence of stoichiometric reductants, thus exploiting a previously unrecognized opportunity that complements existing catalytic carboxylation events.     

Hydroxoiridium‐Catalyzed Hydroalkylation of Terminal Alkenes with Ureas by C(sp3)−H Bond Activation

Direct alkylation of a methyl group, on di‐ and trisubstituted ureas, with terminal alkenes by C(sp³)−H bond activation proceeded in the presence of a hydroxoiridium/bisphosphine catalyst to give high yields of the corresponding addition products. The hydroxoiridium/bisphosphine complex generates an amidoiridium intermediate by reaction with ureas having an N−H bond.     

Trifluoromethylfluorosulfonylation of Unactivated Alkenes Using Readily Available Ag(O2CCF2SO2F) and N‐Fluorobenzenesulfonimide

Presented is a novel intermolecular radical trifluoromethylfluorosulfonylation of unactivated alkenes under mild reaction conditions with good functional‐group tolerance in the most atom‐economic manner by using readily available Ag(O₂CCF₂SO₂F) and N ‐fluorobenzenesulfonimide (NFSI). Both the trifluoromethyl and sulfonyl groups in the products originate from Ag(O₂CCF₂SO₂F).     

Palladium‐Catalyzed Oxidative Intermolecular Difunctionalization of Terminal Alkenes with Organostannanes and Molecular Oxygen

A cationic palladium complex catalyzes the title transformations, which are thought to proceed via a π‐allyl or π‐benzyl intermediate. The regioselectivity of the reaction (1,2‐ or 1,1‐difunctionalization) depends on the type of terminal double bond (conjugated or nonconjugated) in the substrate (see scheme) and appears to be controlled by the relative rates of β‐hydride elimination and transmetalation. DMA=dimethylacetamide, Tf=triflyl.

     

β‐Selective Aroylation of Activated Alkenes by Photoredox Catalysis

Late‐stage synthesis of α,β‐unsaturated aryl ketones remains an unmet challenge in organic synthesis. Reported herein is a photocatalytic non‐chain‐radical aroyl chlorination of alkenes by a 1,3‐chlorine atom shift to form β‐chloroketones as masked enones that liberate the desired enones upon workup. This strategy suppresses side reactions of the enone products. The reaction tolerates a wide array of functional groups and complex molecules including derivatives of peptides, sugars, natural products, nucleosides, and marketed drugs. Notably, addition of 2,6‐di‐tert‐butyl‐4‐methyl‐pyridine enhances the quantum yield and efficiency of the cross‐coupling reaction. Experimental and computational studies suggest a mechanism involving PCET, formation and reaction of an α‐chloro‐α‐hydroxy benzyl radical, and 1,3‐chlorine atom shift.     

Iron‐Catalyzed 1,2‐Addition of Perfluoroalkyl Iodides to Alkynes and Alkenes

Iron catalysis has been developed for the intermolecular 1,2‐addition of perfluoroalkyl iodides to alkynes and alkenes. The catalysis has a wide substrate scope and high functional‐group tolerance. A variety of perfluoroalkyl iodides including CF₃I can be employed. The resulting perfluoroalkylated alkyl and alkenyl iodides can be further functionalized by cross‐coupling reactions. This methodology provides a straightforward and streamlined access to perfluoroalkylated organic molecules.