可见光促进下氟烷基砜对芳基烯烃的自由基氟烷基化反应

自由基氟烷基化是向有机分子中引入氟烷基的一类非常重要的方法,也是目前有机化学研究的热点之一.近几年来,由于广泛的官能团兼容性和温和的反应条件等优点,可见光促进的氧化还原催化反应得到了长足的发展,已经成为化学键的构建和活化的有力工具.因此,光氧化还原催化的自由基氟烷基化反应,作为向有机化合物中引入氟烷基的有效途径,受到了广泛关注.本文报道了我们发展的氟烷基砜作为一类方便易得的新型氟烷基自由基前体,在可见光氧化还原催化下实现对烯烃的自由基氟烷基化反应.该反应可以高效地向芳基烯烃中引入三氟甲基、二氟甲基、1,1-二氟乙基、苯基二氟甲基等各种含氟烷基基团,并实现对芳基烯烃的双官能团化转化.     

Copper‐Catalyzed Carbotrifluoromethylation of Unactivated Alkenes Driven by Trifluoromethylation of Alkyl Radicals

We report herein an unprecedented protocol for radical carbotrifluoromethylation of unactivated alkenes. With Cu(OTf)₂ as the catalyst, the reaction of unactivated alkenes, TMSCF₃ and activated alkyl chlorides at room temperature provides the corresponding carbotrifluoromethylation products in satisfactory yields. Directed by trifluoromethylation of alkyl radicals, the method exhibits an excellent regioselectivity that is opposite to those driven by CF₃ radical addition.     

Enantioselective Dihalogenation of Alkenes

The dihalogenation of alkenes is one of the classic reactions in organic chemistry and a prime example of an electrophilic addition reaction. The often observed anti-selectivity in this addition reaction can be explained by the formation of a haliranium-ion intermediate. Although dihalogenations have been studied for more than a century, the development of reagent-controlled, enantioselective dihalogenation has proved to be very difficult. Only recently, significant progress has been achieved. In this review, an overview on current method development in enantioselective dihalogenation is provided and mechanistic aspects that render this transformation challenging are discussed.     

AuI-Catalyzed Haloalkynylation of Alkenes

The formal insertion of alkenes into aromatic chloro- and bromoalkynes takes place under cationic gold catalysis. This haloalkynylation reaction can be performed with cyclic, gem-disubstituted and monosubstituted alkenes, using BINAP, triazolo[4,3-b]isoquinolin-3-ylidene ligands or SPhos, respectively. The products were isolated in moderate to excellent yields and with complete diastereo- and regioselectivity; the halogen atom bonding the more substituted carbon of the alkene. Preliminary experiments showed that the enantioselective haloalkynylation of cyclopentene can be performed with (S)-BINAP to afford the insertion products with moderate to good enantioselectivities.     

Recent Developments on the Trifluoromethylation of (Hetero)Arenes

Aryl‐CF₃ as an extremely important family of fluorinated organic compounds holds wide applications in pharmaceuticals, agrochemicals, and advanced materials. Traditionally, such trifluoromethylated compounds have been synthesized from the corresponding aryl trichlorides via Cl exchange reactions (Scheme 1 ). This Focus review gives an overview over the recent development of trifluoromethylation of (hetero)arenes.     

Recent Progress in Direct Introduction of Fluorinated Groups on Alkenes and Alkynes by means of CH Bond Functionalization

The direct introduction of fluorine and fluorinated building blocks has recently attracted a lot of attention and particularly the direct functionalization of alkenes and alkynes. This review will highlight the major progress recently made in that field, with a focus on photocatalyzed transformations, base‐promoted processes, and transition metal‐catalyzed functionalization of alkenes and alkynes. Special attention will be paid to explanations of the reaction mechanisms.     

Copper-Catalyzed Defluorinative Hydroarylation of Alkenes with Polyfluoroarenes

A catalytic defluorinative hydroarylation of alkenes with polyfluoroarenes in the presence of dppbz-ligated Cu catalyst and silanes was developed. This method provides a straightforward and alternative avenue to synthetic important polyfluorinated arenes with readily available and bench-stable alkenes as latent nucleophiles, and therefore avoids conventional reliance on stoichiometric quantities of organometallic reagents. This reaction proceeds under very mild conditions and exhibits good functional group compatibility and high level of regioselectivity. The synthetic potential of this method was further demonstrated by a gram-scale synthesis, and an array of experimental studies were also carried out to elaborate the probable mechanism.     

Recent Developments in the Trifluoromethylation of Alkynes

In the last few years, the development of versatile methodologies to incorporate trifluoromethyl groups into organic molecules has attracted significant attention in synthetic chemistry. This review gives an overview over the development on the trifluoromethylation of alkynes, which have not been solely discussed before. Formation of diverse C(sp, sp², sp³)?CF₃ bonds are all covered in this review.     

Carbonylations of Alkenes with CO Surrogates

Alkene carbonylation reactions are important for the production of value‐added bulk and fine chemicals. Nowadays, all industrial carbonylation processes make use of highly toxic and flammable carbon monoxide. In fact, these properties impede the wider use of carbonylation reactions in industry and academia. Hence, performing carbonylations without the use of CO is highly desired and will contribute to the further advancement of sustainable chemistry. Although the use of carbon monoxide surrogates in alkene carbonylation reactions has been reported intermittently in the last 30 years, only recently has this area attracted significant interest. This Minireview summarizes carbonylation reactions of alkenes using different carbon monoxide surrogates.     

Manganese-Catalyzed Hydroarylation of Unactivated Alkenes

Transition-metal-catalyzed hydroarylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8-aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese-catalyzed hydroarylation of unactivated alkenes bearing diverse simple functionalities with arylboronic acids. A series of δ- and γ-arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese-catalysis regime. The method features earth-abundant manganese catalysis, easily available substrates, broad functional-group tolerance, and excellent regioselective control.     

Perfluoroalkylation of Unactivated Alkenes with Acid Anhydrides as the Perfluoroalkyl Source

An efficient perfluoroalkylation of unactivated alkenes with perfluoro acid anhydrides was developed. Copper salts play a crucial role as a catalyst to achieve allylic perfluoroalkylation with the in situ generated bis(perfluoroacyl) peroxides. Furthermore, carboperfluoroalkylation of alkene bearing an aromatic ring at an appropriate position on the carbon side chain was found to proceed under metal‐free conditions to afford carbocycles or heterocycles bearing a perfluoroalkyl group. This method, which makes use of readily available perfluoroalkyl sources, offers a convenient and powerful tool for introducing a perfluoroalkyl group onto an sp³ carbon to construct synthetically useful skeletons.     

Manganese‐Catalyzed Hydrofunctionalization of Alkenes

The manganese‐catalyzed hydrosilylation and hydroboration of alkenes has been developed using a single manganese(II) precatalyst and reaction protocol. Both reactions proceed with excellent control of regioselectivity and in high yields across a variety of sterically and electronically differentiated substrates (25 examples). Alkoxide activation, using NaO^tBu, was key to precatalyst activation and reactivity. Catalysis was achieved across various functional groups and on gram‐scale for both the developed methodologies with catalysts loadings as low as 0.5 mol %.     

Introduction of Fluorine and Fluorine‐Containing Functional Groups

Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo‐ and transition‐metal catalysis. The most challenging transformation remains the formation of the parent C? F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal—fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost‐efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field.     

Manganese‐Catalyzed Hydroarylation of Unactivated Alkenes

Transition‐metal‐catalyzed hydroarylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8‐aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese‐catalyzed hydroarylation of unactivated alkenes bearing diverse simple functionalities with arylboronic acids. A series of δ‐ and γ‐arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese‐catalysis regime. The method features earth‐abundant manganese catalysis, easily available substrates, broad functional‐group tolerance, and excellent regioselective control.     

Gallium‐Assisted Transfer Hydrogenation of Alkenes

We report a rare case of alkene transfer hydrogenation using a main‐group compound instead of a transition‐metal complex as catalyst. We disclosed that 1,4‐cyclohexadiene can be used as H₂ surrogate towards olefin reduction in the presence of [IPrGaCl₂][SbF₆]. Hydrogenative cyclizations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.     

CF3SO2Na as a Bifunctional Reagent: Electrochemical Trifluoromethylation of Alkenes Accompanied by SO2 Insertion to Access Trifluoromethylated Cyclic N‐Sulfonylimines

An unprecedented electrochemical trifluoromethylation/SO₂ insertion/cyclization process has been achieved in an undivided cell in an atom‐economic fashion. The protocol relies on tandem cyclization of N‐cyanamide alkenes by using Langlois’ reagent as a source of both CF₃ and SO₂ under direct anodically oxidative conditions, in which two C?C bonds, two C?X bonds (N?S and S?C), and two rings were formed in a single operation. This transformation enabled efficient construction of various trifluoromethylated cyclic N‐sulfonylimines from readily accessible materials.     

Current methods for asymmetric halogenation of olefins

This Minireview discusses the progress made in developing reactions where an olefin is subjected to an asymmetric halogenation. It aims to serve as a reference for the studies reported to date, including preliminary work and mechanistic studies. The current state of the art, scope, and limitations of these processes are discussed.