Recent advances in radical‐mediated transformations of 1,3‐dienes

1,3‐Dienes are a class of easily accessible and versatile feedstock chemicals that can participate in a wide range of reactions to facilitate the synthesis of various valuable allylic compounds.In the past decades,radical methodology has emerged as a powerful tool for organic synthesis by virtue of the fact that diverse highly reactive radical species can usually be generated under mild,neutral and controlled conditions,and allow for rapid generation of molecular complexity.In this review,we critically illustrate the recent advances in the field of radical‐mediated transformations of 1,3‐dienes based on the different radical precursors and working modes.Wherever possible,particular emphasis is also put on the related mechanistic studies and synthetic applications.

Remote copper-catalyzed enantioselective substitution of yne-thiophene carbonates

Here,we describe a strategy for the copper-catalyzed asymmetric heteroarylation of yne-thiophene carbonates with indoles via remote substitution.The key to the success of this strategy lies in the design of the alkynyl group at the ortho-position of the heterocycle thiophene,enabling the formation of a triarylmethane moiety via very remote substitution.Thus,the concept of remote copper-catalyzed asymmetric transformation extends not only to yne-allylic esters but also to yne-aryl esters.The reaction readily provides a diverse array of chiral triarylmethanes with high efficiency,enantioselectivity,and excellent functional group compatibility.Moreover,facile follow-up transformations underscore their potential utility in the synthesis of various enantioenriched building blocks.Preliminary mechanistic studies support the plausibility of the remote substitution pathway.

Recent advances in asymmetric synthesis of 2-substituted indoline derivatives

Enantiomerically pure 2-substituted indolines are an important class of nitrogen heterocycles that occur frequently in many alkaloid natural products and biologically active compounds.Consequently,the synthesis of such skeletons is of great significance.The past years have witnessed a number of remarkable advances in the development of efficient strategies to construct this class of chiral compounds.This review summarizes the recent advances in asymmetric synthesis of 2-substituted indoline derivatives.Due to the limitation of the length,this review only summarizes those works published from January of 2012 to January of 2019.Meanwhile,methods towards synthesis of fu sed and spirocyclic indolines will not be discussed in this review.

Development of Novel Phosphino-Oxazoline Ligands and Their Application in Asymmetric Alkynlylation of Benzylic Halides

A new set of stereochemically diverse phosphino-oxazoline ligands derived from simple L-amino acids and 2-(diphenylphosphaneyl)-benzoic acid were developed.Those mono anionic tridentated N,N,P-ligands promote the Cu-catalyzed enantioselective radical cou-pling of terminal alkynes with a broad range of benzylic halides including benzo-fused cyclicα-halides andα-silyl benzyl halides in high yield and excellent enantioselectivity under mild reaction conditions.With multi distinct sites for structural modification,a di-verse pool of chiral N,N,P-ligands is readily accessed,allowing for rapid optimization of the ligand structure for a specific substrate.Notably,the enantioselective alkynlylation of benzylic halides bonds in benzo-cyclic molecules has also been realized for the first time.

Construction of axially chiral compounds via catalytic asymmetric radical reaction

The chemistry of axially chiral compounds has emerged as a subject of increasing interest due to their widespread presence in natural products,bioactive molecules,advanced materials,and chiral ligands/catalysts.On the other hand,catalytic asymmetric radical-based transformations provide a complementary platform for the construction of enantiomerically enriched molecules that are in growing demand in the chemical and pharmaceutical in-dustries.In recent years,considerable research efforts have been devoted to the development of catalytic asymmetric radical reactions for the construction of axially chiral compounds based on the unique reactivity modes of diverse radicals.In this review,we critically illustrate these recent achievements according to different radical precursors and catalytic activation modes.Wherever possible,special emphasis is also placed on the discussion of mechanistic features underlying these works and substrate scopes.This review should be of great interest to the experts in this area,but also serve as a helpful starting point for new researchers in this field.

Copper-catalyzed asymmetric propargylic substitution of anthrones and propargylic esters

Anthrones are key structural motifs in many natural products, bioactive compounds and pharmaceutical chemicals. Earth-abundant-metal-catalyzed asymmetric functionalization of anthrones has not proved to be viable. Herein, we disclosed a highly enantioselective propargylic substitution of anthrones with propargylic esters using copper salts with chiral N, N, P-ligand. This strategy is amenable to a broad range of substrates, uses readily available starting materials, provides excellent yields with remarkable enantioselectivity under mild conditions, and enables attractive products diversification routes.

Practical C–P bond formation via heterogeneous photoredox and nickel synergetic catalysis

An efficient C–P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis.This platform utilizing cadmium sulfide semiconductors as heterogeneous photocatalysts and nickel complexes as transition metal catalysts provided a variety of organophosphorus compounds from readily available aryl and vinyl halides,as well as aryl triflates,with generally a good-to-excellent reaction efficiency(31 examples,46%-98%yields).The current protocol features mild reaction conditions,a broad substrate scope,recyclability of photocatalysts,and inexpensive catalysts,thus defining the practical and economic proprieties of the present catalyst system.

Recent Developments in Copper(Ⅰ)-Catalyzed Enantioselective Alkynylation Reactions via a Radical Process

Alkynes are one of the most significant functional groups in organic chemistry and great efforts have been made to explore efficient approach for the construction of chiral alkynes.The asymmetric C(sp^(3))–C(sp)cross-coupling provides a significant complementary strategy through radical-initiated process.However,the stereocontrol of highly reactive and unstable radical intermediate has been a challenge for decades.To address this problem,a variety of chiral ligands are developed for initiating the reaction and achieving enantiocontrol of alkyl radicals.This review summarizes recent developments in copper-catalyzed enantioselective alkynylation of prochiral alkyl radicals and their brief mechanistic studies.

Recent advances in visible-light photoredox-catalyzed nitrogen radical cyclization

Visible-light photoredox catalysis is a powerful and attractive strategy for organic molecule activation and new reaction design owing to its environmental-friendly characteristics and unique catalytic mechanisms,and has found wide applications in organic synthesis.This catalytic strategy enables controllable generation of diverse nitrogen-centered radicals(NCRs)under mild conditions,providing access to construction of diverse nitrogencontaining compounds.In this review,we critically illustrate the recent advances in the field of visible-light photoredox-catalyzed cyclization of nitrogen-centered radicals,based on the different radical precursors and activation modes.Wherever possible,particular emphasis is also put on working models and synthetic applications.

Azetidine synthesis enabled by photo-induced copper catalysis via [3+1] radical cascade cyclization

Azetidines are an important type of saturated,highly strained,fourmembered,nitrogen-containing heterocyclic compound.These compounds serve as important raw materials,intermediates,and catalysts in organic synthesis,as well as important active units in amino acids,alkaloids,and pharmaceutically active compounds.Thus,the development of an efficient and concise method to construct azetidines is of great significance in multiple disciplines.In this work,we reported on the photo-induced copper-catalyzed radical annulation of aliphatic amines with alkynes to produce azetidines.

Dual photoredox and cobalt catalysis enpowers site-selective allylic amination

The development of a highly efficient,selective and atom-economical method for the construction of allylic amines are a challenge in green synthetic chemistry.In a recent work published in Nature Catalysis,Lei,Qi,and coworkers reported that the combination of a photoredox catalyst and cobaloxime catalyst enables site-selective allylic amination of various olefins with secondary alkyl amines,affording the valuable tertiary aliphatic allylamines,without the need for external oxidants.