Regio- and Chemoselective Mono- and Bisnitration of 8-Amino quinoline Amides with Fe(NO3)3·9H2O as Promoter and Nitro Source

Late-Stage C-H Nitration of Unactivated Arenes by Fe(NO3)3·9H2O in Hexafluoroisopropanol

Operationally simple and generally applicable arene nitration with cheap and easily accessible chemicals has been a long-sought transformation in the synthetic organic community. In this work, we realized this goal with nontoxic and inexpensive Fe(NO3)3·9H2O as the nitro source and easily recyclable solvent hexafluoroisopropanol as the promotor via a network of hydrogen-bonding interactions. As a result of the relative mildness and high reliability of this protocol, late-stage nitration of various highly functionalized natural products and commercially available drugs was realized.

Microwave-accelerated cross-dehydrogenative-coupling (CDC) of N-(quinolin-8-yl)amides with acetone/acetonitrile under metal-free conditions

A highly selective remote C(sp³)-H acetonation of N-(quinolin-8-yl)amide scaffolds at the C5-position under microwave irradiation has been developed. In the absence of a transition-metal-catalyst, benzoyl peroxide (BPO)-promoted cross-dehydrogenation coupling (CDC) of N-(quinolin-8-yl)amides with acetone/acetonitrile occurred smoothly to generate the corresponding 5-acetonated/acetonitriled N-(quinolin-8-yl)amides in good yields. The transformation is operationally simple, rapid, easily scaled-up to the gram scale, and shows a broad substrate scope.

Nitration of Pyrrolo[2,1-a]isoquinolines

We have successfully modified a series of pyrrolo[2,1-a]isoquinolines via direct nitration under mild reaction conditions. Easily accessible nitrates including CAN, Cu(NO₃)₂·H₂O, and Fe(NO₃)₃·9H₂O all can serve as effective nitrating reagents for functionalizing pyrrolo[2,1-a]isoquinolines. Various nitro-bearing pyrrolo[2,1-a]isoquinolines have been efficiently prepared in acceptable to good yields.

Copper-catalyzed selective C5-H bromination and difluoromethylation of 8-aminoquinoline amides using ethyl bromodifluoroacetate as the bifunctional reagent

A simple and effective method for the copper-catalyzed selective C5-H bromination and difluoromethylation of 8-aminoquinoline amides with ethyl bromodifluoroacetate as the bifunctional reagent was developed. The combination of cupric catalyst and alkaline additive results in a C5-bromination reaction, whereas cuprous catalyst combined with silver additive results in the C5-difluoromethylation reaction. This method has a broad substrate scope and allows for easy and convenient access to desired C5-functionalized quinolones with good to excellent yields.

Synthesis, Characterization, Pharmacogenomics, and Molecular Simulation of Pyridinium Type of Ionic Liquids and Their Applications

Substituted pyridinium bromides are prepared by conventional and solvent-free greener methods. The solvent-free solid-phase (greener) method is superior to the conventional method because of its nontoxic nature, simple reaction setup procedure, and twenty times less time consumption. Column chromatography and toxic organic solvents are avoided. Substituted pyridinium salts 1-2(a-c) show excellent catalytic response in the preparation of β-amino carbonyl derivatives using the conventional approach. Pharmacokinetics is very important in target validation and in shifting a lead compound into a drug. The physicochemical properties discussed here can be used effectively in the drug designing candidate, which is a cumbersome process in clinical research. In addition, molecular simulations are demonstrated, and compounds 1-2(a-c) possess the most potent VEGFR-2 kinase protein inhibitory activities, and most interestingly, compound 2a strongly binds and regulates the VEGFR-2 kinase activity in therapeutic approaches and cancer prevention.

Improved Regioselective Mononitration of Naphthalene over Modified BEA Zeolite Catalysts

HBEA zeolite modified with highly electronegative cations is a highly efficient and reusable catalyst for the nitration of naphthalene with nitric acid, which has been successfully prepared in this work. Catalytic selective mononitration of naphthalene was investigated. The ratio of 1-nitronaphthalene isomer to 2-nitronaphthalene could reach 19.2, with a moderate yield of 68.2%, when the reaction was carried out in 1,2-dichloroethane, with 1.0 mmol naphthalene, 0.22 mL nitric acid (95%), and 0.10 g HBEA-25 at −15 °C. The effects of reaction temperature and the quantity of zeolites on 1-nitronaphthalene were also studied. The catalyst is readily recyclable, and we believe this to be a major step forward in the area of clean technology for aromatic nitration.

Iron(III)-catalyzed α-cyanation and carbonylation with 2-pyridylacetonitrile: divergent synthesis of α-amino nitriles and tetrahydroisoquinolinones

Iron-catalyzed oxidative synthesis of N-aryl-substituted tetrahydroisoquinolines (THIQs) toward tetrahydroisoquinoline-based derivatives is reported. A wide range of α-amino nitriles and tetrahydroisoquinolinones are synthesized in moderate to good yields. This approach involves a new organic nitrile source, a cheap iron catalyst under an oxygen atmosphere, and temperature-controlled divergent synthesis and features complete selectivity and operational simplicity.

Oxidative functionalization of alkylidenecyclopropanes and alkylidenecyclobutanes: a versatile platform to access nitrated cyclopropanes and cyclobutanes

A divergent radical nitration of alkylidenecyclopropanes (ACPs) and alkylidenecyclobutanes (ACBs) with Fe(NO₃)₃·9H₂O or AgNO₂ has been achieved, affording three categories of products including β-nitro alcohol, α-nitro ketone and nitro nitratosation products with yields up to 90%. Particularly, the cyclopropyl and cyclobutyl rings were conserved in the products. The applicability of this method was demonstrated by the scale-up experiment and reduction of the nitro into an amino group. Preliminary mechanistic studies suggested that the nitro radical was involved in the reaction process.

Metal-free regioselective nitration of quinoxalin-2(1H)-ones with tert-butyl nitrite

A metal-free coupling of quinoxalin-2(1H)-ones with tert-butyl nitrite has been developed. Distinctly from the previous functionalization of quinoxalin-2(1H)-ones, this nitration reaction took place selectively at the C7 or C5 position of the phenyl ring, affording a series of 7-nitro and 5-nitro quinoxalin-2(1H)-ones in moderate to good yields. Preliminary mechanistic studies revealed that the reaction may involve a radical process.

3-Nitro-coumarin synthesis via nitrative cyclization of aryl alkynoates using tert-butyl nitrite

We report a one-pot metal-free synthesis of 3-nitro-coumarins from aryl alkynoates using TBN (tert-butyl nitrite) as the sole reagent. The radical triggered cyclization and nitration of the aryl alkynoates proceeded in a cascaded manner via nitro radical addition to alkynoates, then 5-exo-trig spirocyclization and ester migration.

Metal-free regioselective C5-cyanoalkylation of the 8-aminoquinolineamides/sulfonamides via oxidative cross-dehydrogenative coupling with alkylnitriles

A practical, versatile and Metal-free regioselective C5-cyanoalkylation of the 8-aminoquinolineamides/sulfonamides with acetonitrile has been described.

Room-Temperature Synthesis of Isoindolone Spirosuccinimides: Merger of Visible-Light Photocatalysis and Cobalt-Catalyzed C-H Activation

A room-temperature C-H bond functionalization of benzamides has been developed by merging a photocatalyst with a cobalt catalyst for the synthesis of isoindolone spirosuccinimides. The reaction proceeds in aerobic conditions and does not require any sacrificial external oxidants such as Ag(I) or Mn(III) salts. Visible light activates the photocatalyst, and it acts as an electron-transfer reagent and helps in the fundamental organometallic steps by modulating the oxidation state of the cobalt complex. This C-H bond functionalization and spirocyclization showed wide substrate scope and good functional group tolerance. A possible reaction mechanism was proposed from the experimental outcome, showing that C-H bond activation is irreversible and not the rate-determining step.

Three-component ruthenium-catalyzed remote C-H functionalization of 8-aminoquinoline amides

Multicomponent reactions can efficiently construct complex molecular structures from simple precursors. Herein, a novel ruthenium-catalyzed three-component highly selective remote C-H functionalization of 8-aminoquinoline amides has been described. The reaction tolerates a wide range of functional groups, producing arylation/difluoroalkylation products of olefins with potential biological activity and pharmaceutical value. Radical scavenging and radical clock experiments show that a free radical process is involved and a H/D exchange experiment suggests that the reaction might involve ortho-C-H activation of the aromatic ring. A possible mechanism is proposed.

Recent advances in nitro-involved radical reactions

Significant progress in the chemistry of nitro radicals has been witnessed in the past decades, providing efficient and rapid access to nitro-containing compounds. This review describes recent advances in nitro-involved radical reactions, and summarizes various transformations.

Iron-Catalyzed Regioselective Remote C(sp2)-H Carboxylation of Naphthyl and Quinoline Amides

Iron(III)-catalyzed regioselective direct remote C-H carboxylation of naphthyl and quinoline amides was developed using CBr₄ and alcohol. The reaction involves a radical pathway using a coordination activation strategy and single electron transfer process. The use of sustainable iron catalysis, selectivity, and the substrate scope are the important practical features.

Visible Light-Promoted Photocatalytic C-5 Carboxylation of 8-Aminoquinoline Amides and Sulfonamides via a Single Electron Transfer Pathway

An efficient photocatalytic method was developed for the remote C5-H bond carboxylation of 8-aminoquinoline amide and sulfonamide derivatives. This methodology uses in situ generated ^•CBr₃ radical as a carboxylation agent with alcohol and is further extended to a variety of arenes and heteroarenes to synthesize the desired carboxylated product in moderate-to-good yields. The reaction proceeding through a single electron transfer pathway was established by a control experiment, and a butylated hydroxytoluene-trapped aryl radical cation intermediate in high-resolution mass spectrometry was identified.

Mild Nitration of Pyrazolin-5-ones by a Combination of Fe(NO3 )3 and NaNO2 : Discovery of a New Readily Available Class of Fungicides, 4-Nitropyrazolin-5-ones

4-Nitropyrazolin-5-ones have been synthesized by the nitration of pyrazolin-5-ones at room temperature by employing the Fe(NO₃ )₃ /NaNO₂ system. The method demonstrated selectivity towards the 4-position of pyrazolin-5-ones even in the presence of NPh and allyl substituents, which are sensitive to nitration. It was shown that other systems containing Fe^III and nitrites, namely Fe(NO₃ )₃ /tBuONO, Fe(ClO₄ )₃ /NaNO₂ , and Fe(ClO₄ )₃ /tBuONO, were also effective. Presumably, Fe^III oxidizes the nitrite (NaNO₂ or tBuONO) to form the NO₂ free radical, which serves as the nitrating agent for pyrazolin-5-ones. The synthesized 4-nitropyrazolin-5-ones were discovered to be a new class of fungicides. Their in vitro activities against phytopathogenic fungi were found comparable or even superior to those of commercial fungicides (fluconazole, clotrimazole, triadimefon, and kresoxim-methyl). These results represent a promising starting point for the development of a new type of plant protection agents that can be easily synthesized from widely available reagents.

Selective synthesis of β-nitrated N-heterocycles and N-nitroso-2-alkoxyamine aldehydes from inactivated cyclic amines promoted by tBuONO and oxoammonium salt

Solvent-dependent-controlled selective synthesis of β-nitrated N-heterocycles and N-nitroso chain 2-alkoxyamine aldehydes has been successfully realized via^tBuONO and oxoammonium salt promoted cascade reactions of inactivated cyclic amines.

Ruthenium-catalyzed remote C5-sulfonation of N-alkyl-8-aminoquinolines

Ruthenium-catalyzed remote C–H sulfonation of 8-aminoquinolines with single C5-selectivity.