11. The photo-induced cleavage of C(sp2)–Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence. The photochemical reaction tolerates a panel of functional groups including esters, alcohols, amides, cyano and alkenes (27 examples, 50–88% yields), and can be used to prepare polycyclic compounds and perform the functionalization of natural product analogues in moderate to good yields. Mechanistic experiments, including time-resolved absorption spectroscopy, are supportive of photo-induced electron transfer between the indole substrate and DIPEA, with the formation of radical intermediates in the photoinduced dearomatization reaction. Chem. Sci., 2021, 12, 14050–14058. DOI: 10.1039/d1sc04258k.
10. Herein, we describe a soluble iron(II)-phthalocyanine, [FeII(tBu4Pc)(py)2] (Pc = phthalocyaninato(2–)), as an effective catalyst in intramolecular C(sp3)–H bond amination, with alkyl azides as the nitrogen source, to afford the amination products in moderate to excellent yields with a broad substrate scope. Chem. Commun., 2021, 57, 10711–10714. DOI: 10.1039/d1cc04573c.
9. A series of platinum(II) complexes supported by terphenyl diacetylide as well as diimine or bis-N-heterocyclic carbene (NHC) ligands have been prepared. The diacetylide ligands adopt a cis coordination mode featuring non-planar terphenyl moieties as revealed by X-ray crystallographic analyses. The electrochemical, photophysical and photochemical properties of these platinum(II) complexes have been investigated. These platinum(II) diimine complexes show broad emission with peak maxima from 566 nm to 706 nm, with two of them having emission quantum yields >60% and lifetimes <2 μs in solutions at room temperature, whereas the platinum(II) diacetylide complexes having bis-Nheterocyclic carbene instead of diimine ligand display photoluminescence with quantum yields of up to 28% in solutions and excited state lifetimes of up to 62 μs at room temperature. Application studies revealed that one of the complexes can catalyze photoinduced aerobic dehydrogenation of alcohols and alkenes, and a relatively non-toxic water-soluble Pt(II) complex displays anti-angiogenic activity. Chem Asian J. 2021, 16, 2978–2992. DOI: 10.1002/asia.202100756.
8. Metal-catalyzed C@N bond formation reactions via acylnitrene transfer have recently attracted much attention, but direct detection of the proposed acylnitrenoid/acylimido M-(NCOR) (R=aryl or alkyl) species in these reactions poses a formidable challenge. Herein, we report on Ru(NCOR) intermediates in C@N bond formation catalyzed by [RuIV-(Por)Cl2]/N3COR, a catalytic method applicable to aziridine/ oxazoline formation from alkenes, amination of substituted indoles, a-amino ketone formation from silyl enol ethers, amination of C(sp3)@Hbonds, and functionalization of natural products and carbohydrate derivatives (up to 99% yield). Experimental studies, including HR-ESI-MS and EPR measurements, coupled with DFT calculations, lend evidence for the formulation of the Ru(NCOR) acylnitrenoids as a RuV-imido species. Angew. Chem. Int. Ed. 2021, 60, 18619 – 18629. DOI: 10.1002/anie.202100668.
7. Photoinduced hydroarylation of alkenes is an appealing synthetic strategy for arene functionalization. Herein, we demonstrated that aryl radicals generated from electrondeficient aryl chlorides/bromides could be trapped by an array of terminal/internal aryl alkenes in the presence of [Pt-(O^N^C^N)] under visible-light (410 nm) irradiation, affording anti-Markovnikov hydroarylated compounds in up to 95% yield. Besides, a protocol for [Pt(O^N^C^N)]-catalyzed intramolecular photocyclization of acrylanilides to give structurally diverse 3,4-dihydroquinolinones has been developed. Angew. Chem. Int. Ed. 2021, 60, 1383 – 1389. DOI: 10.1002/anie.202011841.
6. A panel of natural aliphatic tertiary alkaloids (R3N) were directly converted to R3N+–NH− (without the need to prepare protected aminimides R3N+–NR′− followed by deprotection) by [Mn(TDCPP)Cl]-catalysed N-amination reaction, with O-(2,4-dinitrophenyl)hydroxylamine as the nitrogen source, in up to 98% yields under mild reaction conditions. (Chemical Communications 2020, 56, 9102–9105. DOI: 10.1039/D0CC02934C)
5. Direct C–H bond functionalization catalyzed by non-precious transition metals is an attractive strategy in synthetic chemistry. Compared with the precious metals rhodium, palladium, ruthenium, and iridium commonly used in this field, catalysis based on non-precious metals, especially the earth-abundant ones, is appealing due to the increasing demand for environmentally benign and sustainable chemical processes. Herein, developments in iron- and cobalt-catalyzed C(sp3)–H bond functionalization reactions are described, with an emphasis on their applications in organic synthesis, i.e., the synthesis of natural products and pharmaceuticals and/or their modification. (Chem. Soc. Rev. 2020, 49, 5310--5358; https://doi.org/10.1039/D0CS00340A)
4. Ruthenium porphyrin catalysed direct intermolecular amino-oxyarylation of alkenes including styrenes and 1,3-dienes to give primary amines with O-(2,4-dinitrophenyl)hydroxylamine as the amine source was achieved in moderate to good yields under mild reaction conditions. Spectroscopic analyses revealed that a ruthenium nitrido complex was the key reaction intermediate for the amino-oxyarylation reaction.(Chem. Commun. 2020, 56, 137--140; https://doi.org/10.1039/C9CC08043K)
3. Transition-metal-catalyzed direct CeH bond amination is an attractive strategy in preparation of nitrogen containing molecules which are common in naturally occurring and pharmaceutically important compounds. Comparing to the precious metals commonly used in this reaction, non-precious metals such as iron are abundant in earth, relatively low toxic, and more biocompatible, which meet the increasing demand for environmentally benign and sustainable chemical processes. In this review, we described the development in iron catalyzed C-H bond amination reactions from historical landmarks to recent achievements, and placed emphasis on their applications in organic synthesis, i.e. natural product synthesis and/or modification.(Tetrahedron 2019, 75, 130607; https://doi.org/10.1016/j.tet.2019.130607)
2. Ruthenium(II) complexes bearing a tridentate bis(N‐heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N‐substituted imine group. The RuIII–amido intermediates have been characterized by 1H NMR, UV/Vis, ESI‐MS, and X‐ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism.(Chem. Eur. J. 2019, 25, 10828–10833; https://doi.org/10.1002/chem.201903012)
1. Metal‐catalyzed intramolecular C−H amination of alkyl azides constitutes an appealing approach to alicyclic amines; challenges remain in broadening substrate scope, enhancing regioselectivity, and applying the method to natural product synthesis. Herein we report an iron(III) porphyrin bearing axial N‐heterocyclic carbene ligands which catalyzes the intramolecular C(sp3)–H amination of a wide variety of alkyl azides under microwave‐assisted and thermal conditions, resulting in selective amination of tertiary, benzylic, allylic, secondary, and primary C−H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re‐bound mechanism for the amination reaction. The reaction has been applied to the syntheses of tropane, nicotine, cis‐octahydroindole, and leelamine derivatives.(Angew. Chem. Int. Ed. 2018, 57, 11947–11951; https://doi.org/10.1002/anie.201806059)
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