Synthesis, Characterization, and Reactivity of a Hypervalent-Iodine-Based Nitrooxylating Reagent

Silver-Catalyzed Decarboxylative Nitrooxylation of Aliphatic Carboxylic Acids

Here, we present a silver-catalyzed decarboxylative nitrooxylation via a radical-based approach. The substrate scope of this reaction prototype extends to nonactivated primary and secondary carboxylic acids. This protocol provides a practical method for the synthesis of an unprecedented family of organic nitrates and exhibits wide functional group compatibility. Preliminary mechanistic studies reveal that a high-valent silver(II) nitrate complex is a versatile NO3 resource pool, allowing for facile C-O bond formation.

Preparation of a benziodazole-type iodine(III) compound and its application as a nitrating reagent for synthesis of furazans via a copper-catalyzed cascade process

The existing hypervalent I(III) reagents bearing ONO2 group are limited in types and their applications primarily focused on the nitrooxylation reactions featuring a fully-exo fashion. Herein, a benziodazole-type O2NO-I(III) compound was prepared and its reaction with β-monosubstituted enamines in the presence of CuI could trigger a radical nitration/cyclization/dehydration cascade to provide a series of less explored but biologically interesting furazan heterocycles. Mechanistically, the benziodazole-type O2NO-I(III) compound acts as a nitrating reagent and incorporates its NO moiety into the final furazan product in a fully-endo model, a process of which was proposed to involve nitration, cyclization and dehydration.

Mechanochemistry Drives Alkene Difunctionalization via Radical Ligand Transfer and Electron Catalysis

A general and modular protocol is reported for olefin difunctionalization through mechanochemistry, facilitated by cooperative radical ligand transfer (RLT) and electron catalysis. Utilizing mechanochemical force and catalytic amounts of 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), ferric nitrate can leverage nitryl radicals, transfer nitrooxy-functional group via RLT, and mediate an electron catalysis cycle under room temperature. A diverse range of activated and unactivated alkenes exhibited chemo- and regioselective 1,2-nitronitrooxylation under solvent-free or solvent-less conditions, showcasing excellent functional group tolerance. Mechanistic studies indicated a significant impact of mechanochemistry and highlighted the radical nature of this nitrative difunctionalization process.

Organohypervalent heterocycles

This review summarizes the structural and synthetic aspects of heterocyclic molecules incorporating an atom of a hypervalent main-group element. The term "hypervalent" has been suggested for derivatives of main-group elements with more than eight valence electrons, and the concept of hypervalency is commonly used despite some criticism from theoretical chemists. The significantly higher thermal stability of hypervalent heterocycles compared to their acyclic analogs adds special features to their chemistry, particularly for bromine and iodine. Heterocyclic compounds of elements with double bonds are not categorized as hypervalent molecules owing to the zwitterionic nature of these bonds, resulting in the conventional 8-electron species. This review is focused on hypervalent heterocyclic derivatives of nonmetal main-group elements, such as boron, silicon, nitrogen, carbon, phosphorus, sulfur, selenium, bromine, chlorine, iodine(III) and iodine(V).

Manganese(III) Nitrate Complexes as Bench-Stable Powerful Oxidants

We report herein a convenient one-pot synthesis for the shelf-stable molecular complex [Mn(NO3)3(OPPh3)2] (2) and describe the properties that make it a powerful and selective one-electron oxidation (deelectronation) reagent. 2 has a high reduction potential of 1.02 V versus ferrocene (MeCN) (1.65 vs normal hydrogen electrode), which is one the highest known among readily available redox agents used in chemical synthesis. 2 exhibits stability toward air in the solid state, can be handled with relative ease, and is soluble in most common laboratory solvents such as MeCN, dichloromethane, and fluorobenzene. 2 is substitutionally labile with respect to the coordinated (pseudo)halide ions enabling the synthesis of other new Mn(III) nitrato complexes also with high reduction potentials ranging from 0.6 to 1.0 V versus ferrocene.

Palladium-catalyzed C(sp3)-H nitrooxylation of masked alcohols

A palladium-catalyzed β-C(sp³)-H nitrooxylation of aliphatic alcohols with AgNO₂ is reported. An 8-formylquinoline-derived oxime is installed as an exo-type directing group for sp³ C-H activation and selectfluor acts as the oxidant. The reaction tolerates a variety of functional groups and shows good selectivity for β-C-H nitrooxylation of alcohols.

Synthesis of acyloxy-2H-azirine and sulfonyloxy-2H-azirine derivatives via a one-pot reaction of β-enamino esters, PIDA and carboxylic acid or sulfonic acid

PIDA mediated oxidative acyloxylation/azirination and sulfonyloxylation/azirination of β-enamino esters were investigated. A series of functionalized acyloxy-2H-azirine and sulfonyloxy-2H-azirine derivatives was synthesized in moderate to good yields. This represents the first oxidative sulfonyloxylation/azirination of β-enamino esters with PIDA and sulfonic acid for access to sulfonyloxy-2H-azirine. Hypervalent iodine reagents enable cascade C-O/C-N bond formation. Furthermore, a possible reaction pathway was proposed based on the experimental results.

Asymmetric catalytic nitrooxylation and azidation of β-keto amides/esters with hypervalent iodine reagents

Chiral Lewis acid-catalyzed enantioselective nitrooxylation and azidation of cyclic and acyclic β-keto amides/esters with hypervalent iodine(iii) reagents.

Reactions promoted by hypervalent iodine reagents and boron Lewis acids

Understanding the role of boranes in hypervalent iodine chemistry will open up new reactivities which can be utilised in organic synthesis. Due to similar reactivities, λ3-iodanes have presented themselves as viable alternatives for many transformations dominated by transition metals whilst mitigating some of the associated drawbacks of metal systems. As showcased by recent reports, boranes can adopt a dual role in hypervalent iodine chemistry that surpasses mere activation of the hypervalent iodine reagent. Increased efforts to harness this potential with diverse boranes will uncover exciting reactivity with high applicability across various disciplines including adoption in the pharmaceutical sciences. This review will be relevant to the wider synthetic community including organic, inorganic, materials, and medicinal chemists due to the versatility of hypervalent iodine chemistry especially in combination with borane activation or participation. We aim to highlight the development of hypervalent iodine compounds including their structure, bonding, synthesis and utility in metal-free organic synthesis in combination with Lewis acidic boranes.

Synthesis, Characterization of Spirocyclic λ3 -Iodanes and Their Application to Prepare 4,1-Benzoxazepine-2,5-diones and 1,3-Diynes

Herein, a [3+2] cycloaddition of aza-oxyallylic cations with ethynylbenziodoxolones for synthesis of new λ³ -iodanes containing spirocyclic 4-oxazolidinone has been developed. This cyclic λ³ -iodanes display stability in air and excellent solubility in organic solvent. Using them as substrate, both the 4,1-benzoxazepine-2,5-diones and symmetrical 1,3-diynes derivatives were afforded in high yield under copper(I)-catalyzed conditions.

Zinc-catalyzed asymmetric nitrooxylation of β-keto esters/amides with a benziodoxole-derived nitrooxy transfer reagent

Zinc-catalyzed asymmetric nitrooxylation to afford a series of α-nitrooxy β-keto esters/amides in high yields and with low to moderate enantioselectivities has been disclosed.