Copper-Catalyzed Azide-Ynamide Cyclization to Generate α-Imino Copper Carbenes: Divergent and Enantioselective Access to Polycyclic N-Heterocycles

Copper-Catalyzed [2,3]-Sigmatropic Rearrangement of Azide-Ynamides via Selenium Ylides

A copper-catalyzed [2,3]-sigmatropic rearrangement of azide-ynamides via selenium ylides is disclosed, which leads to the practical and divergent synthesis of a variety of tricyclic heterocycles bearing a quaternary carbon stereocenter in generally moderate to excellent yields. Significantly, this method represents the first [2,3]-sigmatropic rearrangement of the selenium ylide based on alkynes and an unprecedented [2,3]-sigmatropic rearrangement via α-imino copper carbenes.

Copper-Catalyzed Synthesis of Furan-Tethered Benzocyclobutenes via Carbene-Mediated 1,4-Sulfinate Migration-Annulation

A copper-catalyzed intramolecular cascade reaction of conjugated enynones has been achieved via a pivotal 1,4-sulfinate migration step. This process leverages a cost-effective and ecofriendly copper salt as catalyst, enabling the efficient construction of five- and four-membered rings in a rapid, sequential manner, producing furan-tethered benzocyclobutenes in good to excellent yields under mild conditions. The reaction is characterized by 100% atom economy, outstanding efficiency, and excellent diastereoselectivity in the cases studied. The robustness of this method is evidenced by its compatibility with air exposure and the use of undistilled, commercially available solvents, further enhancing its practicality.

NQNHC Ligand-Enabled Cu(I)-Catalyzed Double Hydroamination: A Regio- and Chemoselective Bicyclization of o-Amino 1,6-Diyne

In this work, we have developed an efficient method for the intramolecular double hydroamination of aniline by employing o-amino 1,6-diyne as a potential starting material. This protocol enables easy access to bioactive motif 3,4-dihydro-1H-[1,4]oxazino[4,3-a]indole through an intramolecular cascade bicyclization and concomitant isomerization pathway in one pot. This transformation has been effectively achieved by utilizing a stereoelectronically tuned, π-accepting NHC-supported copper(I) system. During ligand optimization trials, naphthoquinone-annulated N-heterocyclic carbene, Nq(IDipp) [1,3-bis(2,6-diisopropylphenyl)-4,5-naphthoquino-imidazolidene]-supported copper(I) complexes of the type Nq(IDipp)CuX (X = Cl or I) were synthesized and fully characterized using various spectroscopic techniques. For this conversion, NHC plays a crucial role in providing the optimum electron density around the metal center. It is a highly regio- and chemoselective transformation with a high atom economy and uses cheap, environmentally benign copper-based catalysts. Furthermore, a plausible mechanism has been proposed on the basis of experimental observations and literature support.

Hetero Diels-Alder reactions of isolable N-borylenamines

A new strategy for N-borylenamines by reaction of 2-alkynyl benzyl azides with B(C6F5)3 was developed. This novel 1,3-carboboration reaction proceeded via a 5-exo-dig cyclization/formal 1,1-carboboration/B(C6F5)2 shift reaction sequence. Additionally, N-borylenamines can undergo hetero Diels-Alder (HDA) reactions with a variety of dienophiles. Our results are an attractive complement to HDA reactions.

Copper-Catalyzed [2 + 2] Cyclization/Ring Expansion of Ene-Ynamides: Construction of Medium- and Large-Sized Rings

Catalytic cyclization of enynes is an efficient approach for the preparation of cyclic compounds, and a large variety of four- to six-membered rings could be synthesized using this method. However, it has been rarely employed for the construction of medium- and large-sized rings. Herein, we describe a copper-catalyzed cycloisomerization of ene-ynamides through a [2 + 2] cyclization/electrocyclic ring opening cascade, leading to the atom-economical assembly of indole-fused medium- and large-sized rings in moderate to excellent yields under mild reaction conditions. Importantly, the synthetic utility of this reaction was demonstrated by the convenient synthesis of iprindole.

Gold-Catalyzed Cyclization of Yndiamides with Isoxazoles via α-Imino Gold Fischer Carbenes

Gold catalysis is an important method for alkyne functionalization. Here we report the gold-catalyzed formal [3+2] aminative cyclization of yndiamides and isoxazoles in a direct synthesis of polysubstituted diaminopyrroles, which are important motifs in drug discovery. Key to this process is the formation, and subsequent cyclization, of an α-imino gold Fischer carbene, which represents a new type of gold carbene intermediate. The reaction proceeds rapidly under mild conditions, with high regioselectivity being achieved by introducing a subtle steric bias between the nitrogen substituents on the yndiamide. DFT calculations revealed that the key to this regioselectivity was the interconversion of isomeric gold keteniminiun ions via a low-barrier π-complex transition state, which establishes a Curtin-Hammett scenario for isoxazole addition. By using benzisoxazoles as substrates, the reaction outcome could be switched to a formal [5+2] cyclization, leading to 1,4-oxazepines.

Copper-catalyzed atroposelective formal [4+1] annulation of 1,2-diketones with vinyl cations

The enantioselective transformation of easily accessible 1,2-diketones represents a quick pathway towards enantioenriched molecules. Herein, we disclose a copper-catalyzed atroposelective formal [4+1] annulation of 1,2-diketones with vinyl cations, enabling the efficient and atom-economical construction of axially chiral arylpyrroles bearing 1,3-dioxole moieties with good to excellent enantioselectivities under mild reaction conditions. Importantly, this methodology constitutes the first enantioselective formal [4+1] annulation of 1,2-diketones.

Copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles

One-carbon homologation reactions based on one-carbon insertion into the N-O bond of heterocycles have received tremendous interest over the past decades. However, these protocols have to rely on the use of hazardous and not easily accessible diazo compounds as precursors, and examples of the relevant asymmetric catalysis have not been reported. Here we show that a copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles involving one-carbon insertion into the heterocyclic N-O bond via non-diazo approach. This method enables practical and atom-economic synthesis of valuable pyrrole-substituted oxadiazines in generally moderate to good yields under mild reaction conditions. In addition, the possibility of such an asymmetric formal (5 + 1) annulation also emerges.

Organocatalytic intramolecular (4 + 2) annulation of enals with ynamides: atroposelective synthesis of axially chiral 7-aryl indolines

Catalytic enantioselective transformation of alkynes has become a powerful tool for the synthesis of axially chiral molecules. Most of these atroposelective reactions of alkynes rely on transition-metal catalysis, and the organocatalytic approaches are largely limited to special alkynes which act as the precursors of Michael acceptors. Herein, we disclose an organocatalytic atroposelective intramolecular (4 + 2) annulation of enals with ynamides. This method allows the efficient and highly atom-economical preparation of various axially chiral 7-aryl indolines in generally moderate to good yields with good to excellent enantioselectivities. Computational studies were carried out to elucidate the origins of regioselectivity and enantioselectivity. Furthermore, a chiral phosphine ligand derived from the synthesized axially chiral 7-aryl indoline was proven to be potentially applicable to asymmetric catalysis.

Base-Promoted Intramolecular Addition of Vinyl Cyclopropanecarboxamides to Access Conformationally Restricted Aza[3.1.0]bicycles

3-Azabicyclo[3.1.0]hexanes are common structural components in natural products and bioactive compounds. Traditionally, the metal-mediated cyclopropanation domino reaction of chain enzymes is the most commonly used strategy for the construction of this type of aza[3.1.0]bicycle derivative. In this study, a base-promoted intramolecular addition of alkenes used to deliver conformationally restricted highly substituted aza[3.1.0]bicycles is reported. This reaction was tailor-made for saturated aza[3.1.0] bicycle-containing fused bicyclic compounds that may be applied in the development of concise and divergent total syntheses of bioactive compounds.

Copper-catalyzed enantioselective diyne cyclization via C(sp2)-O bond cleavage

The functionalization of etheric C-O bonds via C-O bond cleavage is an attractive strategy for the construction of C-C and C-X bonds in organic synthesis. However, these reactions mainly involve C(sp3)-O bond cleavage, and a catalyst-controlled highly enantioselective version is extremely challenging. Here, we report a copper-catalyzed asymmetric cascade cyclization via C(sp2)-O bond cleavage, allowing the divergent and atom-economic synthesis of a range of chromeno[3,4-c]pyrroles bearing a triaryl oxa-quaternary carbon stereocenter in high yields and enantioselectivities. Importantly, this protocol not only represents the first [1,2]-Stevens-type rearrangement via C(sp2)-O bond cleavage, but also constitutes the first example of [1,2]-aryl migration reactions via vinyl cations.

Copper-Catalyzed Tandem Cyclization/Direct C(sp2)-H Annulation of Azide-Ynamides via α-Imino Copper Carbenes: Access to Azepino[2,3-b:4,5-b']diindoles

A novel copper-catalyzed tandem cyclization/direct C(sp²)-H annulation of phenyl azide-ynamides via α-imino copper carbenes has been developed, which provides a concise and flexible approach for the construction of a range of valuable azepino[2,3-b:4,5-b']diindoles in mostly good to excellent yields with high chemoselectivities. This tandem reaction also exhibits a broad substrate scope, excellent functional group tolerance, simple operation, and mild reaction conditions.

Brønsted acid-catalyzed asymmetric dearomatization for synthesis of chiral fused polycyclic enone and indoline scaffolds

In the past two decades, substantial advances have been made on the asymmetric alkyne functionalization by the activation of inert alkynes. However, these asymmetric transformations have so far been mostly limited to transition metal catalysis, and chiral Brønsted acid-catalyzed examples are rarely explored. Here, we report a chiral Brønsted acid-catalyzed dearomatization reaction of phenol- and indole-tethered homopropargyl amines, allowing the practical and atom-economical synthesis of a diverse array of valuable fused polycyclic enones and indolines bearing a chiral quaternary carbon stereocenter and two contiguous stereogenic centers in moderate to good yields with excellent diastereoselectivities and generally excellent enantioselectivities (up to >99% enantiomeric excess). This protocol demonstrates Brønsted acid-catalyzed asymmetric dearomatizations via vinylidene-quinone methides.

Construction of Spirolactams by Unexpected Oxidative Cyclization of Alkenyl Diynes via Copper Catalysis

A copper-catalyzed oxidative cyclization of alkenyl N-propargyl ynamides is described. This protocol enables the practical synthesis of diverse spirocyclic γ-lactams bearing an exocyclic double bond with generally high Z/E selectivity in moderate to good yields. Importantly, this copper-catalyzed oxidative cyclization demonstrates a distinctive selectivity in comparison with the related gold catalysis.

Copper-Catalyzed Enantioselective Doyle-Kirmse Reaction of Azide-Ynamides via α-Imino Copper Carbenes

[2,3]-Sigmatropic rearrangement reaction involving sulfonium ylide (Doyle-Kirmse reaction) generated from metal carbenes represents one of the powerful methods for the construction of C(sp³ )-S and C-C bonds. Although significant advances have been achieved, the asymmetric versions via the generation of sulfonium ylides from metal carbenes have been rarely reported to date, and they have so far been limited to diazo compounds as metal carbene precursors. Here, we describe a copper-catalyzed enantioselective Doyle-Kirmse reaction via azide-ynamide cyclization, leading to the practical and divergent assembly of an array of chiral [1,4]thiazino[3,2-b]indoles bearing a quaternary carbon stereocenter in generally moderate to excellent yields and excellent enantioselectivities. Importantly, this protocol represents a unique catalytic asymmetric Doyle-Kirmse reaction via a non-diazo approach and an unprecedented asymmetric [2,3]-sigmatropic rearrangement via α-imino metal carbenes.

An unexpected synthesis of azepinone derivatives through a metal-free photochemical cascade reaction

Azepinone derivatives are privileged in organic synthesis and pharmaceuticals. Synthetic approaches to these frameworks are limited to complex substrates, strong bases, high power UV light or noble metal catalysis. We herein report a mild synthesis of azepinone derivatives by a photochemical generation of 2-aryloxyaryl nitrene, [2 + 1] annulation, ring expansion/water addition cascade reaction without using any metal catalyst. Among the different nitrene precursors tested, 2-aryloxyaryl azides performed best under blue light irradiation and Brønsted acid catalysis. The reaction scope is broad and the obtained products underwent divergent transformations to afford other related compounds. A computational study suggests a pathway involving a step-wise aziridine formation, followed by a ring-expansion to the seven-membered heterocycle. Finally, water is added in a regio-selective manner, this is accelerated by the added TsOH.

Multicomponent Direct Assembly of N-Heterospirocycles Facilitated by Visible-Light-Driven Photocatalysis

N-heterospirocycles are interesting structural units found in both natural products and medicinal compounds but have relatively few reliable methods for their synthesis. Here, we enlist the photocatalytic generation of N-centered radicals to construct β-spirocyclic pyrrolidines from N-allylsulfonamides and alkenes. A variety of β-spirocyclic pyrrolidines have been constructed, including drug derivatives, in moderate to very good yields. Further derivatization of the products has also been demonstrated as has a viable scale-up procedure, making use of flow chemistry techniques.

Azides in the Synthesis of Various Heterocycles

In this review, we focus on some interesting and recent examples of various applications of organic azides such as their intermolecular or intramolecular, under thermal, catalyzed, or noncatalyzed reaction conditions. The aforementioned reactions in the aim to prepare basic five-, six-, organometallic heterocyclic-membered systems and/or their fused analogs. This review article also provides a report on the developed methods describing the synthesis of various heterocycles from organic azides, especially those reported in recent papers (till 2020). At the outset, this review groups the synthetic methods of organic azides into different categories. Secondly, the review deals with the functionality of the azido group in chemical reactions. This is followed by a major section on the following: (1) the synthetic tools of various heterocycles from the corresponding organic azides by one-pot domino reaction; (2) the utility of the chosen catalysts in the chemoselectivity favoring C−H and C-N bonds; (3) one-pot procedures (i.e., Ugi four-component reaction); (4) nucleophilic addition, such as Aza-Michael addition; (5) cycloaddition reactions, such as [3+2] cycloaddition; (6) mixed addition/cyclization/oxygen; and (7) insertion reaction of C-H amination. The review also includes the synthetic procedures of fused heterocycles, such as quinazoline derivatives and organometal heterocycles (i.e., phosphorus-, boron- and aluminum-containing heterocycles). Due to many references that have dealt with the reactions of azides in heterocyclic synthesis (currently more than 32,000), we selected according to generality and timeliness. This is considered a recent review that focuses on selected interesting examples of various heterocycles from the mechanistic aspects of organic azides.

Synthesis of Axially Chiral N-Arylindoles via Atroposelective Cyclization of Ynamides Catalyzed by Chiral Brønsted Acids

In recent years, asymmetric catalysis of ynamides has attracted much attention, but these reactions mostly constructed central chirality, except for a few examples on the synthesis of axially chiral compounds which exclusively relied on noble-metal catalysis. Herein, a facile access to axially chiral N-heterocycles enabled by chiral Brønsted acid-catalyzed 5-endo-dig cyclization of ynamides is disclosed, which represents the first metal-free protocol for the construction of axially chiral compounds from ynamides. This method allows the practical and atom-economical synthesis of valuable N-arylindoles in excellent yields with generally excellent enantioselectivities. Moreover, organocatalysts and ligands based on such axially chiral N-arylindole skeletons are demonstrated to be applicable to asymmetric catalysis.

Photoinduced ynamide structural reshuffling and functionalization

The radical chemistry of ynamides has recently drawn the attention of synthetic organic chemists to the construction of various N-heterocyclic compounds. Nevertheless, the ynamide-radical chemistry remains a long-standing challenge for chemists due to its high reactivity, undesirable byproducts, severe inherent regio- and chemoselective problems. Importantly, the ynamide C(sp)-N bond fission remains an unsolved challenge. In this paper, we observe Photoinduced radical trigger regio- and chemoselective ynamide bond fission, structural reshuffling and functionalization of 2-alkynyl-ynamides to prepare synthetically inaccessible/challenging chalcogen-substituted indole derivatives with excellent step/atom economy. The key breakthroughs of this work includes, ynamide bond cleavage, divergent radical precursors, broad scope, easy to handle, larger-scale reactions, generation of multiple bonds (N-C(sp²), C(sp²)-C(sp²), C(sp²)-SO₂R/C-SR, and C-I/C-Se/C-H) in a few minutes without photocatalysts, metals, oxidants, additives. Control experiments and ¹³C-labeling experiments supporting the conclusion that sulfone radicals contribute to ynamide structural reshuffling processes via a radical pathway.

Although ynamides have emerged as a versatile class of compounds for organic synthesis, the radical chemistry of ynamides usually proceeds with the expected connectivity largely intact. Here the authors show a methodology by which the C(sp)–N bond undergoes scission, alkyne migration and functionalization under blue LED light in the absence of metals or additives.

Palladium-Catalyzed Regioselective Arylalkenylation of Ynamides

A cationic palladium-catalyzed arylalkenylation of ynamides is presented. The putative keteniminium arylpalladium intermediate likely dictates the regioselective carbopalladation of the ynamide to form a vinylpalladium species. The capture of this complex by the olefin yields linear conjugated β-alkenyl aminodienes (especially with trans selectivity). The transformation features a broad scope with labile functional group tolerance and makes 42 unusual molecular scaffolds with structural diversity. DFT studies provide valuable insights into the reaction mechanism.

Copper-catalyzed B−H bond insertion reaction of azide-ynamide with borane adducts via α-imino copper carbenes

A new copper-catalyzed B−H bond insertion reaction between azide-ynamides and borane adducts has been developed, which represents the first B−H bond insertion into α-imino metal carbenes. This protocol enables the...

Efficient synthesis of tetracyclic γ-lactams via gold-catalyzed oxidative cyclization of alkenyl diynes

An efficient gold-catalyzed cascade cyclization of alkenyl diynes involving alkyne oxidation, carbene-alkyne metathesis and cyclopropanation has been developed, furnishing a series of tetracyclic γ-lactams bearing one quaternary carbon center and...

Metal-free dearomatization reactions of naphthol-ynamides for the divergent and enantioselective synthesis of azaspirocycles

An efficient Brønsted acid (BA) catalyzed intramolecular dearomatization cyclization of naphthol-ynamides has been developed, enabling the practical and divergent synthesis of two azaspirocycles in high yields.

Copper(I)-catalysed intramolecular hydroarylation-redox cross-dehydrogenative coupling of N-propargylanilines with phosphites

Intramolecular hydroarylation-redox cross-dehydrogenative coupling of N-propargylanilines with phosphite diesters proceeded in the presence of Cu(I)-catalysts (20 mol%) to selectively give 2-phosphono-1,2,3,4-tetrahydroquinolines in good yields with 100% atomic utilization. P-H and two C-H bonds are activated at once and these hydrogen atoms are trapped by a propargylic triple bond in the molecule.

Copper-Catalyzed Si-H Bond Insertion Reaction of N-Propargyl Ynamides with Hydrosilanes

Transition-metal-catalyzed Si-H bond insertion reactions are generally limited to stabilized diazo compounds. An efficient copper-catalyzed Si-H bond insertion reaction of N-propargyl ynamides with hydrosilanes is described, allowing practical and atom-economic construction of valuable organosilanes in generally moderate to excellent yields under mild reaction conditions. Notably, this reaction constitutes a new method of Si-H bond insertion reaction involving vinyl cations as key intermediates.

Catalytic Enantioselective Synthesis of 2,3-Dihydrobenzo[b]oxepines via Asymmetric Oxetane Opening by Internal Carbon Nucleophiles

An intramolecular C-C formation process based on catalytic asymmetric oxetane opening by carbon nucleophiles has been developed, which provides rapid access to a range of valuable enantioenriched 2,3-dihydrobenzo[b]oxepines. With the combination of Sc(OTf)₃ and a Box ligand, good chemical efficiency and enantioselectivity were achieved under mild conditions. The products are also useful precursors to other valuable structures, such as the bicyclo[3.2.2]nonane derivatives.

Copper-Catalyzed Asymmetric Diyne Cyclization via [1,2]-Stevens-Type Rearrangement for the Synthesis of Chiral Chromeno[3,4-c]pyrroles

Here, we report a copper-catalyzed asymmetric cascade cyclization/[1,2]-Stevens-type rearrangement via a non-diazo approach, leading to the practical and atom-economic assembly of various valuable chiral chromeno[3,4-c]pyrroles bearing a quaternary carbon stereocenter in generally moderate to good yields with wide substrate scope and excellent enantioselectivities (up to 99 % ee). Importantly, this protocol not only represents the first example of catalytic asymmetric [1,2]-Stevens-type rearrangement based on alkynes but also constitutes the first asymmetric formal carbene insertion into the Si-O bond.

Discovery of Novel Polycyclic Heterocyclic Derivatives from Evodiamine for the Potential Treatment of Triple-Negative Breast Cancer

Evodiamine (Evo) is a quinazolinocarboline alkaloid found in Evodia rutaecarpa and exhibits moderate antiproliferative activity. Herein, we report using a scaffold-hopping approach to identify a series of novel polycyclic heterocyclic derivatives based on Evo as the topoisomerase I (Top1) inhibitor for the treatment of triple-negative breast cancer (TNBC), which is an aggressive subtype of breast cancer with limited treatment options. The most potent compound 7f inhibited cell growth in a human breast carcinoma cell line (MDA-MB-231) with an IC₅₀ value of 0.36 μM. Further studies revealed that Top1 was the target of 7f, which directly induced irreversible Top1-DNA covalent complex formation or induced an oxidative DNA lesion through an indirect mechanism mediated by reactive oxygen species. More importantly, in vivo studies showed that 7f exhibited potent antitumor activity in a TNBC-patient-derived tumor xenograft model. These results suggest that compound 7f deserves further investigation as a promising candidate for the treatment of TNBC.

Gold-catalyzed oxidative cyclization of amide-alkynes: access to functionalized γ-lactams

An efficient gold-catalyzed oxidative cyclization of amide-alkynes is developed. A series of functionalized γ-lactams are easily accessed by employing this strategy. The tandem reaction proceeds through alkyne oxidation, carbene/alkyne metathesis, and donor/donor carbene oxidation.

Brønsted Acid Catalyzed Dearomatization by Intramolecular Hydroalkoxylation/Claisen Rearrangement: Diastereo- and Enantioselective Synthesis of Spirolactams

Described herein is a novel Brønsted acid catalyzed intramolecular hydroalkoxylation/Claisen rearrangement, allowing the practical and atom-economic synthesis of a range of valuable spirolactams from readily available ynamides in generally good to excellent yields with excellent diastereoselectivities and broad substrate scope. Importantly, an unexpected dearomatization of nonactivated arenes and heteroaromatic compounds is involved in this tandem sequence. Moreover, an asymmetric version of this tandem cyclization was also achieved by efficient kinetic resolution by chiral phosphoric acid catalysis. In addition, the [3,3]-rearrangement is shown to be kinetically preferred over the related [1,3]-rearrangement by theoretical calculations.

Copper-Catalyzed Cyclization of N-Propargyl Ynamides with Borane Adducts through B-H Bond Insertion

An efficient copper-catalyzed cyclization of N-propargyl ynamides with borane adducts through B-H bond insertion has been developed. A series of valuable organoboron compounds are constructed in generally good yields with a wide substrate scope and good functional group tolerance under mild reaction conditions. Importantly, this protocol via vinyl cation intermediates constitutes a novel way of B-H bond insertion.

(4,5,8)-Connected Cationic Coordination Polymer Material as Explosive Chemosensor Based on the in Situ Generated AIE Tetrazolyl-Tetraphenylethylene Derivative

A multidentate tetrazole molecule based on a TPE core, tetrakis[4-(1H-tetrazol-5-yl)phenyl]ethylene (H₄ttpe) with combined advantages of two functional groups, was synthesized by cycloaddition reaction of the corresponding organic benzonitrile derivative and azide salt. Coordination self-assembly of the in situ formed aggregation-induced emission polytetrazole luminogen with cadmium(II) ion produces an unprecedented tetrazolyl-TPE-based microporous cationic metal-organic framework (MOF) with an unusual (4,5,8T14)-connected net of {[Cd₄(H₄ttpe)₂Cl₅]·(N₃)₃}, in which the H₄ttpe serves as the first undeprotonated tetrazole ligand of octa-coordinating bridging mode. We investigate, for the first time, the utilization of the luminescent MOF containing a TPE core decorated with tetrazolyl terminals for explosive detection based on the change in fluorescence intensity, which shows high selectivity and efficiency in fluorescence quenching toward TNP detection in water solution.

Gold-Catalyzed Transformation of Ynamides

Ynamide, a unique species with inherited polarization of nitrogen lone pair electron to triple bond, has been largely used for the developement of novel synthetic methods and the construction of unusual N-bearing heterocycles. The reaction versatility of ynamide on umpolung reactivity, radical reactions and asymmetric synthesis have been recently reviewed. This review provides an overall scenic view into the gold catalyzed transformation of ynamides. The ynamides reactivity towards nitrogen-transfer reagents, such as azides, nitrogen ylides, isoxazoles, and anthranils; oxygen atom-transfer reagents, like nitrones, sulfoxides, and pyridine N-oxides; and carbon nucleophiles under gold catalysis are herein uncovered. The scope as well the mechanistic insights of each reaction is also briefed.

Copper-catalyzed asymmetric cyclization of alkenyl diynes: method development and new mechanistic insights

Metal carbenes have proven to be one of the most important and useful intermediates in organic synthesis, but catalytic asymmetric reactions involving metal carbenes are still scarce and remain a challenge. Particularly, the mechanistic pathway and chiral induction model in these asymmetric transformations are far from clear. Described herein is a copper-catalyzed asymmetric cyclization of alkenyl diynes involving a vinylic C(sp²)–H functionalization, which constitutes the first asymmetric vinylic C(sp²)–H functionalization through cyclopentannulation. Significantly, based on extensive mechanistic studies including control experiments and theoretical calculations, a revised mechanism involving a novel type of endocyclic copper carbene via remote-stereocontrol is proposed, thus providing new mechanistic insight into the copper-catalyzed asymmetric diyne cyclization and representing a new chiral control pattern in asymmetric catalysis based on remote-stereocontrol and vinyl cations. This method enables the practical and atom-economical construction of an array of valuable chiral polycyclic-pyrroles in high yields and enantioselectivities.

A copper-catalyzed asymmetric cyclization of alkenyl diynes involving a vinylic C(sp²)–H functionalization is reported, enabling the construction of various valuable chiral polycyclic-pyrroles in high yields and enantioselectivities.