Practical Singly and Doubly Electrophilic Aminating Agents: A New, More Sustainable Platform for Carbon-Nitrogen Bond Formation

Organocatalytic Electrophilic Arene Amination: Rapid Synthesis of 2-Quinolones

For decades, the synthesis of 2-quinolones, a crucial structural motif in pharmaceuticals and agrochemicals, has relied heavily on costly noble metal complexes and structurally complex ligands. Despite considerable efforts from synthetic chemists, a mild, metal-free, environmentally friendly, and cost-effective approach has remained elusive. This study introduces a robust, metal-free synthetic platform that leverages an innovative organoiodine-catalyzed electrophilic arene C(sp2)-H amination strategy to efficiently produce a wide range of new and modifiable 2-quinolones. Moreover, this study allows ready synthetic access to novel 8-aryl-substituted 2-quinolones, uncovering new chemical spaces with significant potential for medicinal applications.

Recent synthetic strategies for the functionalization of fused bicyclic heteroaromatics using organo-Li, -Mg and -Zn reagents

This review highlights the use of functionalized organo-Li, -Mg and -Zn reagents for the construction and selective functionalization of 5- and 6-membered fused bicyclic heteroaromatics. Special attention is given to the discussion of advanced syntheses for the preparation of highly functionalized heteroaromatic scaffolds, including quinolines, naphthyridines, indoles, benzofurans, benzothiophenes, benzoxazoles, benzothiazoles, benzopyrimidines, anthranils, thienothiophenes, purine coumarins, chromones, quinolones and phthalazines and their fused heterocyclic derivatives. The organometallic reagents used for the desired functionalizations of these scaffolds are generally prepared in situ using the following methods: (i) through directed selective metalation reactions (DoM), (ii) by means of halogen/metal exchange reactions, (iii) through oxidative metal insertions (Li, Mg, Zn), and (iv) by transmetalation reactions (organo-Li and Mg transmetalations with ZnCl2 or ZnO(Piv)2). The resulting reactive organometallic reagents allow a wide range of C-C, C-N and C-X cross-coupling reactions with different electrophiles, employing in particular Kumada or Negishi protocols among other transition metal (Pd, Ni, Co, Cu, Cr, Fe, etc.)-catalyzed processes. In addition, key developments concerning selective metalation techniques will be presented, which rely on the use of RLi, LDA and TMP metal bases. These methods are now widely employed in organic synthetic chemistry and have proven to be particularly valuable for drug development programs in the pharmaceutical industry. New and improved protocols have resulted in many Li, Mg and Zn organyls now being compatible with functionalized aryl, heteroaryl, alkenyl, alkynyl and alkyl compounds even in the presence of labile functional groups, making these reagents well-suited for C(sp2)-C(sp2), C(sp2)-C(sp) and C(sp2)-C(sp3) cross-coupling reactions with fused heteroaryl halides. In addition, the use of some transition metal-catalyzed processes occasionally allows a reversed role of the reactants in cross-coupling reactions, providing alternative synthetic routes for the preparation of fused heteroaromatic-based bioactive drugs and natural products. In line with this, this article points to novel methods for the functionalization of bicyclic heteroaromatic scaffolds by organometallic reagents that have been published in the period 2010-2023.

H-Bond Donor-Directed Switch of Diastereoselectivity in the Enantioselective Intramolecular Aza-Henry Reaction of Ketimines

We report an H-bond donor controlled diastereoselective switchable intramolecular aza-Henry reaction of ketimines derived from α-ketoesters and 2-(2-nitroethyl)anilines, allowing facile access to chiral tetrahydroquinolines bearing an aza-quaternary carbon stereocenter, which are privileged scaffold for medicinal researches. While newly developed cinchona alkaloid derived phosphoramide-bearing quaternary ammonium salt C2 selectively give cis-adducts in up to 20 : 1 dr and 99 % ee, the corresponding urea-bearing analogue C8 preferentially give trans-adducts in up to 20 : 1 dr and 99 % ee.

Domino Sequence of Ketimization and Electrophilic Amination for an Inverse Aza Intramolecular Morita-Baylis-Hillman Adduct

Morita-Baylis-Hillman (MBH) reaction, typically catalyzed by a Lewis base, is a popular and useful method for C-C bond formation. Unfortunately, it is limited by a slow reaction rate and has sensitivity toward steric and electronic parameters. Despite tremendous efforts, the versatility of the reaction keeps the quest open for new mechanistic and catalytic pathways. Here, we have reported a Bro̷nsted acid-catalyzed, electrophilic amination (Umpolung of imine) as a method for an inverse Aza Intramolecular MBH adduct in the form of 2-acylindole. Umpolung of imine with nitrogen acting as an electrophilic center has been achieved. Interestingly, the reaction was also shown to occur under catalyst-free conditions also. The expected products of ketimine formation, 6π electrocyclization, or quinoline formation were least/not observed. A large number of examples have demonstrated the reaction strength. β-aryl-substituted acrylate and acrylamide (cinnamates and cinnamides), which are extremely sluggish in conventional MBH chemistry, are the highlights of the developed methodology. The annulated product exhibited keto-enol tautomerism, which was proven by 1H NMR integrals. As an application, another tandem reaction in the form of Michael addition on a highly complex amine was carried out to provide spiro-annulated indole.

Synthesis of Diarylamines via Nitrosonium-Initiated C-N Bond Formation

Electron-rich diarylamines, exemplified by anisole-derived amines, play pivotal roles in process chemistry, pharmaceuticals, and materials. In this study, homo-diarylamines were synthesized directly from the C-H activation of electron-rich arenes by sodium nitrate/trifluoroacetic acid and the successive treatment of iron powder. Mechanistic investigations reveal that nitrosoarene serves as the reaction intermediate, and the formation of the second C-N bond between the resulting nitrosoarene and electron-rich arene is catalyzed by the nitrosonium ion (NO+). Thus, hetero-diarylamines were synthesized using preformed nitrosoarenes and various electron-rich arenes. This reaction complements a range of cross-coupling reactions catalyzed by transition metal catalysts.

Preparation of Vitamin-g-Lignin Nanohybrids with Excellent Biological Activity and Fluorescence Performance

As a natural renewable biomacromolecule, lignin has some inherently interesting properties such as fluorescence, antioxidation, and antibacterial performance. However, the unsatisfactory fluorescence and biological activities have greatly limited their value-added and large-scale applications. In this work, lignin nanoparticles (LNPs) grafted with vitamin B1 hybrid nanoparticles (LEVs) were obtained by using ethylenediamine and different contents of vitamin B1 through a simple hydrothermal method. The chemical structure, fluorescence properties, and bioactivity were characterized to assess the effects of ethylenediamine and vitamin B1 on the properties of LEVs. It was found that the fluorescence performance of synthesized LEV particles was improved with the increase in the amount of vitamin B1. The free radical scavenging rate (RSA, %) increased to 97.8%, while the antibacterial rates reached up to 99.9%. The antibacterial activity of LEV involved multiple combined mechanisms. The introduction of imine, amide groups, and positively charged VB1 of LEV will make it easier to interact with the negatively charged bacterial phospholipid membranes and cause bacterial lysis and death. Then, the PVA/LEV hydrogel composites were prepared by the freezing-thawing method, and the results showed that PVA/LEV hydrogels had more comprehensive performance such as improved mechanical properties and antioxidant and antibacterial activities, resulting in its great potential to be used as an efficient biomedical material.

Organocatalytic aromatization-promoted umpolung reaction of imines

The umpolung functionalization of imines bears vast synthetic potential, but polarity inversion is less efficient compared with the carbonyl counterparts. Strong nucleophiles are often required to react with the N-electrophiles without catalytic and stereochemical control. Here we show an effective strategy to realize umpolung of imines promoted by organocatalytic aromatization. The attachment of strongly electron-withdrawing groups to imines could enhance the umpolung reactivity by both electronegativity and aromatic character, enabling the direct amination of (hetero)arenes with good efficiencies and stereoselectivities. Additionally, the application of chiral Brønsted acid catalyst furnishes (hetero)aryl C-N atropisomers or enantioenriched aliphatic amines via dearomative amination from N-electrophilic aromatic precursors. Control experiments and density functional theory calculations suggest an ionic mechanism for the umpolung reaction of imines. This disconnection expands the options to forge C-N bonds stereoselectively on (hetero)arenes, which represents an important synthetic pursuit, especially in medicinal chemistry.

Exploiting N-Centered Umpolung Reactivity of α-Iminomalonates for the Synthesis of N-Sulfenylimines and Sulfonamides

An efficient and interesting N-centered umpolung method has been disclosed to construct beneficial S-N bonds, furnishing N-sulfenylimines, which can readily be converted into the corresponding sulfonamide derivatives in a one-pot sequential operation. N-Sulfenylimines are potent intermediates in organic synthesis, whereas sulfonamides are of major molecular interest due to their rich biological activities and wide applicability in medicinal chemistry. Owing to the simple reaction conditions and setup, this protocol displays a broad and versatile substrate scope, resulting in excellent functional group tolerability toward the synthesis of both N-sulfenylimines and sulfonamides. A density functional theory (DFT) computed and experimentally supported convenient mechanism has been proposed for this unique method.

General Ir-Catalyzed N-H Insertions of Diazomalonates into Aliphatic and Aromatic Amines

A general N-H insertion reactivity of acceptor-acceptor diazo malonate reagents is reported using [Ir(cod)Cl]2 as catalyst. A large range of amines, primary and secondary, aliphatic and aromatic, is possible. Mild temperatures, perfect substrate/reactant stoichiometry, and good functional group compatibility render the process particularly attractive for the (late-stage) functionalization of amines.

Clay based heterogeneous catalysts for carbon-nitrogen bond formation: a review

Clay and modified clay-based catalysts are widely used in organic transformation. Owing to the interlayer ions and good ion exchange capacity of clay, replacement with another ion and incorporation of different nanomaterials can be done. Due to these significant properties of clay, it can be utilized in the synthesis of various organic compounds. Carbon-nitrogen bonded compounds possess diverse applications in different fields. These compounds are prepared using different solid acid heterogeneous catalysts. This review presents a detailed discussion on clay used for the carbon-nitrogen bond formation reaction, such as the Biginelli reaction and A3 and KA2 coupling reactions. Additionally, other C-N bond formation reactions using various clay-based catalysts such as bentonite, montmorillonite, hydrotalcite and halloysite clay with various metals, metal oxides, Kegging type heteropoly acid and various nanomaterial incorporated clay heterogeneous catalysts are discussed.

Preparation of Aromatic and Heterocyclic Amines by the Electrophilic Amination of Functionalized Diorganozincs with Polyfunctional O-2,6-Dichlorobenzoyl Hydroxylamines

We report a catalyst-free electrophilic amination, which enables the synthesis of aromatic and heterocyclic amines. By subjecting diarylzinc or diheteroarylzinc compounds to readily accessible O-2,6-dichlorobenzoyl hydroxylamines in the presence of MgCl2 in dioxane at a temperature of 60 °C (8-16 h). This new electrophilic amination allowed an expedited synthesis of two pharmaceutically significant compounds: vortioxetine is a key intermediate of delamanid. This approach offers opportunities for the streamlined synthesis of amine-based molecules in the pharmaceutical industry.

Nitrenium ions as new versatile reagents for electrophilic amination

Herein we report the utilization of N-heterocyclic nitrenium ions - easily prepared, bench-stable and non-oxidating nitrogen sources for the efficient electrophilic amination of aliphatic and aromatic organometallic nucleophiles, towards the facile and general preparation of primary amines. To this end, a plethora of abundant organolithium and organomagnesium reagents were combined with nitrenium salts to generate a variety of previously unexplored N-alkyl and N-aryl triazanes. Through the simple hydrogenolysis of these relatively stable triazanes, we have prepared a diverse scope of primary amines, including linear and branched aliphatic as well as (hetero)aromatic amines possessing various stereo-electronic substituents. Furthermore, we present the facile synthesis of valuable 15N-labelled primary amines from easily prepared 15N-labelled nitrenium salts, as well as a one-pot approach to biologically relevant primary amines. Finally, a recyclable variant of the nitrenium precursor was prepared and a simple recovery protocol was developed to improve the atom-economy of this procedure.

Synthesis of Indoles Using the Electrophilic Potential of Diazirines

The electrophilic potential of diazirines has been utilized to obtain N-substituted diaziridines that are directly hydrolyzed to produce monosubstituted hydrazines. The hydrazines can undergo the Fisher process with enolizable carbonyls to yield multiple indole derivatives in moderate to high yields. The N-metalated diaziridine intermediates can undergo isomerization prior to electrophilic substitution, to form N,N-disubstituted hydrazones. The latter react with enolizable carbonyls to produce N-protected indole derivatives in a single step. This protocol was used to efficiently synthesize indomethacin, an anti-inflammatory drug.

Step-Economic Total Synthesis of Melosatin A from Eugenol

An efficient and straightforward route toward the isatin-type natural product melosatin A is reported, employing a trisubstituted aniline as a key intermediate. The latter was synthesized in 4 steps and 60% overall yield from eugenol, through its regioselective nitration, sequentially followed by a Williamson methylation, an olefin cross-metathesis with 4-phenyl-1-butene and the simultaneous reduction of olefin and nitro groups. The final step, a Martinet cyclocondensation of the key aniline with diethyl 2-ketomalonate, provided the natural product with 68% yield.

Discovery of a simple iron catalyst reveals the intimate steps of C-H amination to form C-N bonds

Formation of ubiquitous C-N bonds traditionally uses prefunctionalized carbon precursors. Recently, metal-catalyzed amination of unfunctionalized C-H bonds with azides has become an attractive and atom-economic strategy for C-N bond formation, though all catalysts contain sophisticated ligands. Here, we report Fe(HMDS)2 (HMDS = N(SiMe3)2 -) as an easy-to-prepare catalyst for intramolecular C-H amination. The catalyst shows unprecedented turnover frequencies (110 h-1 vs. 70 h-1 reported to date) and requires no additives. Amination is successful for benzylic and aliphatic C-H bonds (>80% yield) and occurs even at room temperature. The simplicity of the catalyst enabled for the first time comprehensive mechanistic investigations. Kinetic, stoichiometric, and computational studies unveiled the intimate steps of the C-H amination process, including the resting state of the catalyst and turnover-limiting N2 loss of the coordinated azide. The high reactivity of the iron imido intermediate is rationalized by its complex spin system revealing imidyl and nitrene character.

From the bottle: simple iron salts for the efficient synthesis of pyrrolidines via catalytic C-H bond amination

Commercially available iron salts FeX2 are remarkably active catalysts for pyrrolidine formation from organic azides via direct C-H bond amination. With FeI2, amination is fast and selective, (<30 min for 80% yield at 2 mol% loading), TONs up to 370 are reached with just 0.1 mol% catalyst, different functional groups are tolerated, and a variety of C-H bonds were activated.

Diisopropyl 2-[(4-nitro-benzo-yl)amino]-propane-dioate

The title compound, C16H20N2O7, crystallizes in the space group C2 with two mol-ecules in the asymmetric unit. The crystal packing shows O⋯π inter-actions between the two mol-ecules.

Iminologous epoxide ring-closure

The discovery of new reactions enables chemists to attain a better understanding of fundamental chemical reactivity and push the boundaries of organic synthesis. Our understanding and manipulation of high-energy states such as reactive conformations, intermediates, and transition structures contribute to this field. Herein we interrogate epoxide ring-closure by inserting the C[double bond, length as m-dash]N functionality into a well-known precursor to nucleophilic epoxide ring-closure. The synthesis of tetrasubstituted, nitrile-tethered epoxides takes place via activation of iminologous diols followed by fragmentation. Mechanistic study reveals the transformation to be stereospecific, which is consistent with the concerted nature of the epoxide ring-closure.

Rh(I)-Catalyzed Coupling of Azides with Boronic Acids Under Neutral Conditions

Because of the importance of polyfunctional amines, C-N bond formation is important in synthetic organic chemistry. Here we present a neutral amination reaction using azides as the nitrogen source and arylboronic acids with a rhodium(I) catalyst to afford alkyl-aryl and aryl-aryl secondary amines. Natural products and pharmaceutical derivatives were applied, and gram-scale reactions were performed, which demonstrated the utility. Mechanistic experiments and DFT calculations suggested that the reaction involves a metal-nitrene intermediate.

Traceless Benzylic C-H Amination via Bifunctional N-Aminopyridinium Intermediates

C-H amination reactions provide the opportunity to streamline the synthesis of nitrogen-containing organic small molecules. The impact of intermolecular C-H amination methods, however, is currently limited the frequent requirement for the amine precursors to bear activating groups, such as N-sulfonyl substituents, that are both challenging to remove and not useful synthetic handles for subsequent derivatization. Here, we introduce traceless nitrogen activation for C-H amination-which enables application of selective C-H amination chemistry to the preparation of diverse N-functionalized products-via sequential benzylic C-H N-aminopyridylation followed by Ni-catalyzed C-N cross-coupling with aryl boronic acids. Unlike many C-H amination reactions that provide access to protected amines, the current method installs an easily diversifiable synthetic handle that serves as a lynchpin for C-H amination, deaminative N-N functionalization sequences.

Aza-Quasi-Favorskii Reaction: Construction of Highly Substituted Aziridines through a Concerted Multibond Rearrangement Process

A new molecular rearrangement, the aza-Quasi-Favorskii rearrangement, has been developed for the construction of highly substituted aziridines. Electron-deficient O-sulfonyl oximes react readily with α,α-disubstituted acetophenone-derived enolates to furnish highly substituted aziridines via this unprecedented domino process. In-depth computational studies reveal an asynchronous yet concerted nitrenoid-type rearrangement pathway.

Reactivity Umpolung of the C═N Bond in Quinoxaline Scaffold Enabling Direct Nucleophilic Attack of Alkyl Grignard Reagents at the N-Terminus

The reactivity umpolung of the C═N bond in the quinoxaline scaffold has been successfully realized for the first time by introduction of a formyl or an acyl group adjacent to the C-position of the C═N moiety. The reversed reactivity of the C═N bond thus enabled direct nucleophilic attack of alkyl Grignard reagents at the N-terminus rather than the C-terminus, thereby providing an unprecedented and efficient method for the synthesis of quinoxalin-2(1H)-one derivatives involving a tandem N-alkylation/C─C bond cleavage process.

Light-Promoted Low-Valent-Tungsten-Catalyzed Ambient Temperature Amination of Boronic Acids with Nitroaromatics

Triggering C-N bond formation with nitroaromatics and boronic acids at mild conditions is highly desirable, since most prior works were carried out under harsh conditions and sometimes suffered from poor chemo- or regioselectivity. Herein, a low-valent-tungsten-catalyzed reaction that enables the ambient temperature amination of boronic acids with nitroaromatics is disclosed. With readily available W(CO)₆ as a precatalyst under external-photosensitizer-free conditions, nitroaromatics smoothly undergo C-N coupling reactions with their boronic acid partners, delivering structurally diverse secondary amines in good yields (>50 examples, yields up to 96%). This methodology is both scalable and highly chemoselective and engages both aliphatic and aromatic boronic acid partners. The catalysis is initiated by the deoxygenation of nitroaromatics by a trans-[W(CO)₄(PPh₃)₂] (trans-W, PPh₃ = triphenylphosphine) complex, which forms in situ via ligand replacement.

Understanding OxymaPure as a Peptide Coupling Additive: A Guide to New Oxyma Derivatives

An in silico study, using the GALAS algorithm available in ACD/PhysChem Suite, was performed to calculate the pK _a(s) of various oximes with potential application as peptide coupling additives. Among the known oximes and predicted structures, OxymaPure is superior based on the pK _a values calculated, confirming the results described in the literature and validating this algorithm for further use in that field. Among the nondescribed oximes, based on pK _a calculation, ethyl 2-(hydroxyimino)-2-nitroacetate seems to be a potential candidate to be used as an additive during peptide coupling.

Electrophilic Aminating Agents in Total Synthesis

Classical amination methods involve the reaction of a nitrogen nucleophile with an electrophilic carbon center; however, in recent years, umpoled strategies have gained traction where the nitrogen source acts as an electrophile. A wide range of electrophilic aminating agents are now available, and these underpin a range of powerful C-N bond-forming processes. In this Review, we highlight the strategic use of electrophilic aminating agents in total synthesis.

Exploiting Iminoquinones as Electrophilic at Nitrogen "N+" Synthons for C-N Bond Construction

New methods for C-N bond construction exploiting the N-centered electrophilic character of iminoquinones are reported. Iminoquinones, generated in situ via the condensation of o-vinylanilines with benzoquinones, undergo acid-catalyzed cyclization to afford N-arylindoles in excellent yields. Under similar reaction conditions, homoallylic amines react analogously to afford N-arylpyrroles. Additionally, organometallic nucleophiles are shown to add to the nitrogen atom of N-alkyliminoquinones to provide amine products. Finally, iminoquinones are shown to be competent electrophiles for copper-catalyzed hydroamination.

Discovery of 3,5-Dimethyl-4-Sulfonyl-1H-Pyrrole-Based Myeloid Cell Leukemia 1 Inhibitors with High Affinity, Selectivity, and Oral Bioavailability

Myeloid cell leukemia 1 (Mcl-1) protein is a key negative regulator of apoptosis, and developing Mcl-1 inhibitors has been an attractive strategy for cancer therapy. Herein, we describe the rational design, synthesis, and structure-activity relationship study of 3,5-dimethyl-4-sulfonyl-1H-pyrrole-based compounds as Mcl-1 inhibitors. Stepwise optimizations of hit compound 11 with primary Mcl-1 inhibition (52%@30 μM) led to the discovery of the most potent compound 40 with high affinity (K_d = 0.23 nM) and superior selectivity over other Bcl-2 family proteins (>40,000 folds). Mechanistic studies revealed that 40 could activate the apoptosis signal pathway in an Mcl-1-dependent manner. 40 exhibited favorable physicochemical properties and pharmacokinetic profiles (F% = 41.3%). Furthermore, oral administration of 40 was well tolerated to effectively inhibit tumor growth (T/C = 37.3%) in MV4-11 xenograft models. Collectively, these findings implicate that compound 40 is a promising antitumor agent that deserves further preclinical evaluations.

Cobalt-Catalyzed Umpolung Alkylation of Imines To Generate α-Branched Aliphatic Amines

Here we report a general and mild approach to prepare α-branched aliphatic amines from imines. This method capitalizes on a cobalt-catalyzed umpolung alkylation of imines, employs easily available reaction partners, and demonstrates a broad substrate scope. Mechanistic studies suggest this transformation occurs by a radical pathway.

Cu(I)-Catalyzed [2 + 2 + 1] Cycloaddition of Amines, Alkynes, and Ketenes: An Umpolung and Regioselective Approach to Full-Substituted β-Pyrrolinones

Described here is a Cu-catalyzed [2 + 2 + 1] modular synthesis of full-substituted β-pyrrolinones from simple amines, alkynes, and α-diazo-β-ketoesters. This approach involving the regioselective C-nucleophilic attack of enamines, uncommon C-nucleophilic addition to ketenes, and umpolung of imines enables the direct synthesis of full-substituted β-pyrrolinones, which were hardly constructed by traditional synthetic strategies.

Regio- and Enantioselective Palladium-Catalyzed Asymmetric Allylation of N-Fluorenyl Trifluoromethyl Imine

A palladium-catalyzed asymmetric allylation of N-fluorenyl trifluoromethyl imine with allylic acetates is disclosed. This method provides scalable and efficient access to polysubstituted chiral α-trifluoromethyl amines bearing two adjacent stereocenters and one allyl group in high yields with excellent regio-, diastereo-, and enantioselectivity. Importantly, this method also provides a powerful strategy for the synthesis of both regioisomeric products and the regioselectivity is controlled by the chiral catalysts and optically active substrates.

Total synthesis of isatindigotindoline C

Total synthesis of isatindigotindoline C, a 3,3'-spiropyrrolidine oxindole alkaloid, is achieved in two steps using an exo-selective decarboxylative 1,3-dipolar cycloaddition as the key step. The synthesis verifies the originally assigned relative anti-stereochemistry for the bis-oxindole core of isatindigotindoline C.

Regiodivergent Intramolecular Nucleophilic Addition of Ketimines for the Diverse Synthesis of Azacycles

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N-functionalized indoles and tetrahydroquinolines, by the control of reaction at the N-terminus and C-terminus, respectively. Using ketimines derived from 2-(2-nitroethyl)anilines with isatins or α-ketoesters, the regioselective N-attack reaction gives N-functionalized indoles, while the catalytic enantioselective C-attack reaction affords chiral tetrahydroquinolines featuring an α-tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen-bonding interactions may greatly facilitate such unusual N-attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (-)-psychotrimine, and the construction of various fused aza-heterocycles.

Synthesis of Structurally Diverse 3-, 4-, 5-, and 6-Membered Heterocycles from Diisopropyl Iminomalonates and Soft C-Nucleophiles

Herein, we present a general synthetic strategy for the preparation of 3-, 4-, 5-, and 6-membered heterocyclic unnatural amino acid derivatives by exploiting facile Mannich-type reactions between readily available N-alkyl- and N-aryl-substituted diisopropyl iminomalonates and a wide range of soft anionic C-nucleophiles without using any catalyst or additive. Fully substituted aziridines were obtained in a single step when enolates of α-bromo esters were employed as nucleophiles. Enantiomerically enriched azetidines, γ-lactones, and tetrahydroquinolines were obtained via a two-step catalytic asymmetric reduction and cyclization sequence from ketone enolate-derived adducts. Finally, highly substituted γ-lactams were prepared in one pot from adducts obtained using acetonitrile-derived carbanions. Overall, this work clearly demonstrates the utility of iminomalonates as highly versatile building blocks for the practical and scalable synthesis of structurally diverse heterocycles.

Direct Amination of Arenes with Azodicarboxylates Catalyzed by Bisulfate Salt/HFIP Association

A mild and efficient amination of arenes with azodicarboxylates using potassium bisulfate (KHSO4) as the catalyst in 1,1,1,3,3,3-hexafluoro-2-propanol has been developed. This protocol allowed the amination of a broad range of arenes leading to corresponding hydrazides in good to excellent yields.

Cu(II)-Mediated N-H and N-Alkyl Aryl Amination and Olefin Aziridination

Cu(II)-mediated direct NH₂ and NH alkyl aryl aminations and olefin aziridinations are described. These room-temperature, one-pot, environmentally friendly procedures replace costly Rh₂ catalysts and, in some instances, display important differences with comparable Rh₂- and Fe-supported reactions.

Synthesis of Arenesulfonyl Fluorides via Sulfuryl Fluoride Incorporation from Arynes

Transition-metal-free multicomponent reactions involving aryne precursors, secondary amines, and sulfuryl fluoride are reported herein. Zwitterionic intermediates formed from the reaction of arynes with amine nucleophiles can capture SO₂F₂ under mild conditions, offering a novel and practical protocol for the synthesis of 2-dialkyl-, 2-alkylaryl-, or 2-diarylamino-substituted arenesulfonyl fluoride derivatives in good to excellent yields.

Regiospecific N-Arylation of Aliphatic Amines under Mild and Metal-Free Reaction Conditions

A transition metal‐free N‐arylation of primary and secondary amines with diaryliodonium salts is presented. Both acyclic and cyclic amines are well tolerated, providing a large set of N‐alkyl anilines. The methodology is unprecedented among metal‐free methods in terms of amine scope, the ability to transfer both electron‐withdrawing and electron‐donating aryl groups, and efficient use of resources, as excess substrate or reagents are not required.