Cobalt-Catalyzed Regioselective Ortho C(sp2)-H Bond Nitration of Aromatics through Proton-Coupled Electron Transfer Assistance

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.

Acid-Free Copper-Catalyzed Electrophilic Nitration of Electron-Rich Arenes with Guanidine Nitrate

A practical copper-catalyzed nitration of electron-rich arenes with trimethylsilyl chloride and guanidine nitrate is reported. A variety of nitrated products were generated in moderate to excellent yields (32-99%) at ambient temperature under acid-free, open-flask, and operationally simple conditions.

Synthesis and Chiroptical Properties of Planar Chiral Azahelicenes Based on [2.2]Paracyclophane

Three pairs of planar chiral heteroarenes were synthesized using palladium-catalyzed Buchwald-Hartwig coupling and hypervalent iodine-mediated oxidative cyclization from optically pure 4-amino[2.2]paracyclophane. Among them, an enantiomer of planar chiral azahelicene was found to have circularly polarized luminescence activity that was remarkably stronger than that of planar chiral heteroarenes.

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.

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

A comprehensive overview of directing groups applied in metal-catalysed C-H functionalisation chemistry

The present review is devoted to summarizing the recent advances (2015-2017) in the field of metal-catalysed group-directed C-H functionalisation. In order to clearly showcase the molecular diversity that can now be accessed by means of directed C-H functionalisation, the whole is organized following the directing groups installed on a substrate. Its aim is to be a comprehensive reference work, where a specific directing group can be easily found, together with the transformations which have been carried out with it. Hence, the primary format of this review is schemes accompanied with a concise explanatory text, in which the directing groups are ordered in sections according to their chemical structure. The schemes feature typical substrates used, the products obtained as well as the required reaction conditions. Importantly, each example is commented on with respect to the most important positive features and drawbacks, on aspects such as selectivity, substrate scope, reaction conditions, directing group removal, and greenness. The targeted readership are both experts in the field of C-H functionalisation chemistry (to provide a comprehensive overview of the progress made in the last years) and, even more so, all organic chemists who want to introduce the C-H functionalisation way of thinking for a design of straightforward, efficient and step-economic synthetic routes towards molecules of interest to them. Accordingly, this review should be of particular interest also for scientists from industrial R&D sector. Hence, the overall goal of this review is to promote the application of C-H functionalisation reactions outside the research groups dedicated to method development and establishing it as a valuable reaction archetype in contemporary R&D, comparable to the role cross-coupling reactions play to date.

Regiocontrolled Synthesis of α-Sulfonylmethyl o-Nitrostyrenes via ZnI2-Mediated Sulfonylation and AgNO2/Pd(PPh3)4-Promoted o-Nitration

We report herein the AgNO₂/Pd(PPh₃)₄-promoted regiocontrolled o-nitration of α-sulfonylmethylstyrenes in MeNO₂ with good yields. The o-nitration process provides a series of sulfonyl o-nitrostyrenes. Substituted α-sulfonylmethylstyrenes were synthesized from ZnI₂-mediated sulfonylation of substituted α-methylstyrenes and sodium sulfinates (RSO₂Na) in MeCN with good to excellent yields. The structures of the key products were confirmed by X-ray crystallography. A plausible mechanism has been proposed herein.