Mechanism of oxidative amidation of nitroalkanes with oxygen and amine nucleophiles using electrophilic iodine

Recently, we developed a direct way to oxidatively convert primary nitroalkanes into amides. This entailed mixing an iodonium source with an amine, a base, and oxygen. Herein, we systematically investigated the mechanism and likely intermediates. We conclude that an amine-iodonium complex first forms through N-halogen bonding. This complex reacts with aci-nitronates to give both alpha-iodo and alpha-,alpha-diiodo nitroalkanes. These iodinated species can act as alternative sources of electrophilic iodine and also generate an extra equimolar amount of “I+” under O2. In particular, evidence supports alpha-,alpha-diiodo nitroalkanes reacting with molecular oxygen to form a peroxy adduct; alternatively, these tetrahedral intermediates rearrange anaerobically into a cleavable nitrite ester. In either case, activated esters are proposed form, which eventually react with nucleophilic amines in a traditional fashion

Sterically demanding oxidative amidation of alpha-substituted malononitriles with amines using O2

An efficient amidation method between readily available 1,1-dicyanoalkanes and chiral or non-chiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of alpha-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile alpha-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles

A Recyclable Metal-Organic Framework as a Dual Detector and Adsorbent for Ammonia

Recyclable materials for simultaneous detection and uptake of ammonia (NH3) are of great interest due to the hazardous nature of NH3. The structural versatility and porous nature of metal-organic frameworks (MOFs) make them ideal candidates for NH3 capture. Herein, the synthesis of a water-stable and porous 3-dimensional Cu-II-based MOF (SION-10) displaying a ship-in-a-bottle structure is reported; the pores of the host SION-10 framework accommodate mononuclear Cu-II-complexes. SION-10 spontaneously uptakes NH3 as a result of two concurrent mechanisms: chemisorption due to the presence of active Cu-II sites and physisorption (bulk permanent porosity). The color of the material changes from green to blue upon NH3 capture, with the shifts of the UV/Vis absorption bands clearly seen at NH3 concentrations as low as 300 ppm. SION-10 can be recovered upon immersion of SION-10 superset of NH3 in water and can be further reused for NH3 capture for at least three cycles

Oxidation of Alcohols and Activated Alkanes with Lewis Acid-Activated TEMPO

The reactivity of MCl3(η(1)-TEMPO) (M = Fe, 1; Al, 2; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) with a variety of alcohols, including 3,4-dimethoxybenzyl alcohol, 1-phenyl-2-phenoxyethanol, and 1,2-diphenyl-2-methoxyethanol, was investigated using NMR spectroscopy and mass spectrometry. Complex 1 was effective in cleanly converting these substrates to the corresponding aldehyde or ketone. Complex 2 was also able to oxidize these substrates; however, in a few instances the products of overoxidation were also observed. Oxidation of activated alkanes, such as xanthene, by 1 or 2 suggests that the reactions proceed via an initial 1-electron concerted proton-electron transfer (CPET) event. Finally, reaction of TEMPO with FeBr3 in Et2O results in the formation of a mixture of FeBr3(η(1)-TEMPOH) (23) and [FeBr2(η(1)-TEMPOH)]2(μ-O) (24), via oxidation of the solvent, Et2O

Site-Selective Benzylic C–H Hydroxylation in Electron-Deficient Azaheterocycles

Benzylic C–H bonds can be converted into numerous functional groups, often by mechanisms that involve hydrogen atom transfer at the key bond breaking step. The abstracting species is most often an electrophilic radical, which makes these reactions best suited to electron-rich C–H bonds to achieve appropriate polarity matching. Thus, electron deficient systems such as pyridine and pyrimidine are relatively unreactive, and relatively underrpresented in substrate scopes. In this report, we describe a new method for benzylic hydroxylation—essentially an unknown reaction in the case of pyrimidines—that makes use of an iodine(III) reagent to affords very high selectivity towards electron-deficient azaheterocycles in substrates with more than one reactive position and prevents over-oxidation to carbonyl products. The identification of key reaction byproducts supports a mechanism that involves radical coupling in the bond forming step

ChemInform Abstract: A General Approach to the Enantioselective α-Oxidation of Aldehydes via Synergistic Catalysis.

A new enantioselective α-oxidation of aldehydes has been accomplished using TEMPO and a synergistic combination of copper and organic catalysis. Expanding upon recently reported mechanistic studies, these mild catalytic conditions provide stable aldehyde products bearing a wide array of electronically and sterically diverse substructures. The utility of these oxidized products is highlighted by subsequent derivatization to a variety of common chiral synthons, without loss in enantiopurity

Combined Iron/Hydroxytriazole Dual Catalytic System for Site Selective Oxidation Adjacent to Azaheterocycles

This report details a new method for site-selective methylene oxidation adjacent to azaheterocycles. A dual catalysis approach, utilizing both an iron Lewis acid and an organic hydroxylamine catalyst, proved highly effective. We demonstrate that this method provides complementary selectivity to other known catalytic approaches and represents an improvement over current heterocycle-selective reactions that rely on stoichiometric activation

Tetraarylborate polymer networks as single-ion conducting solid electrolytes

A new family of solid polymer electrolytes based upon anionic tetrakis(phenyl)borate tetrahedral nodes and linear bis-alkyne linkers is reported. Sonogashira polymerizations using tetrakis(4-iodophenyl)borate, tetrakis(4-iodo-2,3,5,6-tetrafluorophenyl)borate and tetrakis(4-bromo-2,3,5,6-tetrafluorophenyl)borate delivered highly cross-linked polymer networks with both 1,4-diethynylbeznene and a tri(ethylene glycol) substituted derivative. Promising initial conductivity metrics have been observed, including high room temperature conductivities (up to 2.7 × 10[superscript −4] S cm[superscript −1]), moderate activation energies (0.25–0.28 eV), and high lithium ion transport numbers (up to t[superscript Li+] = 0.93). Initial investigations into the effects of important materials parameters such as bulk morphology, porosity, fluorination, and other chemical modification, provide starting design parameters for further development of this new class of solid electrolytes