Owing to their easy availability and cheapness, simple alkyl chlorides are good raw materials for introducing complex polychlorinated groups. Polychlorinated hydrocarbons units, such as di‐ or ...trichloromethyl groups, not only widely found in pesticide and bioactive molecule, but also can be as a precursor to converted into different functional groups such as −COOH, −CHO and −CO. The direct polychloroalkylation reaction by using simple alkyl chlrides has been considered to be an important tool for synthesizing complex polychlorinated compounds. This review summarizes recent developments, especially free radical strategies, in the polychloroalkylation of different substrates (such as 2‐acylpyridines, benzyl tertiary amines, alkenes, imine and 1,n‐enynes). We hope that this review provides a new perspective on this field and also provides a reference to develop environmentally friendly and sustainable methods.
Comprehensive Summary
The radical‐mediated reductive functionalization of aryl halides has been extensively studied. However, the related radical‐mediated intermolecular reductive 1,2‐diarylation of ...alkenes, using aryl halides as aryl radical sources, remains unexplored. Herein, a new electrophotocatalytic intermolecular reductive 1,2‐diarylation of alkenes is reported using aryl halides and cyanoaromatics to produce polyarylated alkanes. Using synergistic cathodic reduction and visible‐light photoredox catalysis, various electron‐rich and electron‐deficient aryl halides are combined with various alkenes and cyanoaromatics to characterize the broad substrate scope, excellent functional group compatibility, and excellent selectivity of this reaction. Mechanistic investigations reveal that this reaction may proceed via a radical process initiated by the reductive generation of aryl radicals from aryl halides and terminated by radical‐radical coupling with cyanoaromatic radical anions.
A conceptually novel electrophotocatalytic intermolecular reductive 1,2‐diarylation of alkenes with aryl halides and cyanoaromatics was reported. This provides a general tool for the incorporation of two aryl groups, including common aryl and heteroaryl groups, across an alkene scaffold. Unlike existing chemical, electrochemical, and photo‐oxidation processes, this reaction proceeds through an electrophotocatalytic reductive radical process initiated by the reductive generation of aryl radicals from aryl halides and terminated by radical–radical coupling.
A cooperative nickel and photoredox reductive catalysis for 1,4-dicarbofunctionalization of 1,3-enynes with tertiary N-methylamines and organohalides to produce tetrasubstituted allenes is presented. ...This method enables the generation of the aminoalkyl C(sp3)-centered radicals by site selective cleavage of the N-methyl C(sp3)–H bonds in tertiary N-methylamines and is extended to alkyl bromides as the electrophilic terminating regents. Mechanistic studies indicate that the reaction involves a radical process and a Ni0/NiI/NiIII catalytic cycle.
A nickel-catalyzed C–S reductive cross-coupling of alkyl halides with arylthiosilanes for producing alkyl aryl thioethers is developed. This reaction is initiated by umpolung transformations of ...arylthiosilanes followed by C–S reductive cross-coupling with alkyl halides to manage an electrophilic alkyl group onto the electrophilic sulfur atom and then construct a C(sp3)–S bond, and features exquisite chemoselectivity, excellent tolerance of diverse functional groups, and wide applications for late-stage modification of biologically relevant molecules.
A new method involving mild acryl transient-chelating-group-controlled stereoselective Rh(
i
)-catalyzed silylative aminocarbonylation of 2-alkynylanilines with CO and silanes is presented for ...producing (
Z
)-3-(silylmethylene)indolin-2-ones. Upon using an acryl transient chelating group, 2-alkynylanilines undergo an unprecedented alkyne
cis
-silylrhodation followed by aminocarbonylation to assemble (
Z
)-3-(silylmethylene)indolin-2-ones. Mechanistic studies show that acryl transient chelating effects result in the key alkyne
cis
-silylrhodation process.
Transient-chelating-group-controlled stereoselective rhodium(I)-catalyzed silylative aminocarbonylation of 2- alkynylanilines with CO and silanes toward (Z)-3-(silylmethylene)indolin-2-ones is presented.
This study systematically investigated the structural, dielectric, and ferroelectric properties of BaAl(2−2x)(Mg0.5Ti0.5)2xO4 ceramics in the 0 ≤ x ≤ 0.04 range. Single‐phase solid solutions in the ...P63 space group with hexagonal crystal symmetry were confirmed in the composition range of 0 ≤ x ≤ 0.03. The bond lengths of Al1/(Mg,Ti)–O, Al2/(Mg,Ti)–O, and Al3/(Mg,Ti)–O increased with the increase in x, as confirmed through the Rietveld refinement and evolutions of corresponding modes in Raman spectra. The temperature stability of dielectric properties improved at a composition around x = 0.03, and the dielectric constant εr ascended with the increase in x. Ultrabroad temperature stability (−100°C to 700°C) was obtained, and an optimal combination (εr = 18.5, tan δ < 10−3, −22 ppm/°C ≤ TCC ≤ +20 ppm/°C, resistivity ~4.5 × 1014 Ω·cm) was achieved for the x = 0.03 ceramic sintered at 1260°C in air for 6 hours. The increase in stability was ascribed to the variations in axial bonds, and lattice distortions were determined through high‐resolution transmission electron microscopy. The x = 0.03 ceramic could be a promising candidate for C0G or NP0 multilayer ceramic capacitors because of its low loss, high reliability, superior insulating properties and comparatively low‐cost raw materials.
Using terminal alkyne as a nontraditional one-carbon (C1) unit and silylborane as an external silicon pronucleophile, a relay palladium/copper-catalyzed silylative 5 + 1 benzannulation of ...3-acetoxy-1,4-enynes for producing polysubstituted arylsilanes, especially including bioactive motif-based analogues, in a single reaction step through benzene ring skeleton assembly and silyl intermolecular incorporation cascades is developed. Mechanistic studies show that this reaction allows the terminal sp-hybridized carbon atom in terminal alkynes as a C1 unit via cleavage of two π-bonds and one C(sp)–H bond.
An iodoarene-driven electroreductive remote C(sp3)–H arylation of unsymmetrical 1-(o-iodoaryl)alkyl ethers with cyanoarenes for the site selective synthesis of α-(hetero)aryl ethers is developed. ...With the introduction of cyanoarenes as both aryl sources and electron transfer mediators, this method includes an iodoarene-driven strategy to enable the regiocontrollable formation of two new bonds, one C(sp2)–H bond, and one C(sp2)–C(sp3) bond, in a single reaction step through the sequence of halogen atom transfer (XAT), hydrogen atom transfer (HAT), radical–radical coupling, and decyanation.
