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Dichloromethane, as a readily available and inexpensive C 1 synthon is proposed as a powerful building block for cyclopropanation of alkenes under mild conditions. Herein, we report a highly efficient and versatile dual photoredox system, involving a nickel aminopyridine coordination complex and a photocatalyst, for the cyclopropanation of aromatic olefins using dichloromethane, under visible-light irradiation. The cyclopropanation protocol has been successfully applied at gram scale. Mechanistic studies suggest a Ni(II) pyridyl radical complex as the key intermediate for the homolytic cleavage of the C sp3 -Cl bond, generating a chloromethyl radical that is captured by the olefin coupling partner. Our findings also highlight the versatility of this methodology. By directing the radical/polar crossover process, we were able to selectively drive the reaction towards either the formation of cyclopropyl derivatives or the corresponding non-cyclic alkyl chloride products. The methodology also successfully apply to geminal dichloroalkanes, including the formation of spiro[2,2] compounds. Moreover, our methodology extends to the synthesis of deuterium-labelled cyclopropanes, demonstrating its utility in isotopic labelling and broadening its applicability in chemical synthesis and drug development., (© 2024 Wiley-VCH GmbH.)

The construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long-standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO 2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO 2 -to-CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso-tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br 2 ] (2,2'-bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non-sacrificial electrodes. The reaction can be directly scaled up to gram-scale and operates effectively at a CO 2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO 2 reduction is key in the formation of the [Ni(bpy)(CO) 2 ], which is proposed as the catalytic intermediate responsible for the C-C bond formation in the carbonylation steps., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The inertness of chloroalkanes has precluded them as coupling partners for cross-coupling reactions. Herein we disclose a general strategy for the activation of inert alkyl chlorides through photoredox catalysis and their use as coupling partners with alkenes. The catalytic system is formed by [Ni(OTf)(Py 2 Ts tacn)](OTf) (1 Ni ), which is responsible for the Csp 3 -Cl bond activation, and [Ir( NMe2 bpy)(ppy) 2 ]PF 6, (PC Ir NMe2 ), which is the photoredox catalyst. Combined experimental and theoretical studies show an in situ photogenerated Ni I intermediate ([Ni(Py 2 Ts tacn)] + ) which is catalytically competent for the Csp 3 -Cl bond cleavage via a S N 2 mechanism for primary alkyl chlorides, forming carbon-centered free radicals, which react with the olefin leading to the formation of the Csp 3 -Csp 3 bond. These results suggest inert alkyl chlorides can be electrophiles for developing new intermolecular strategies in which low-valent aminopyridine nickel complexes act as key catalytic species., (© 2022 Wiley-VCH GmbH.)

The chemical inertness of abundant and commercially available alkyl chlorides precludes their widespread use as reactants in chemical transformations. Presented in this work is a metallaphotoredox methodology to achieve the catalytic intramolecular reductive cyclization of unactivated alkyl chlorides with tethered alkenes. The cleavage of strong C(sp 3 )-Cl bonds is mediated by a highly nucleophilic low-valent cobalt or nickel intermediate generated by visible-light photoredox reduction employing a copper photosensitizer. The high basicity and multidentate nature of the ligands are key to obtaining efficient metal catalysts for the functionalization of unactivated alkyl chlorides., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

We report here the first purely organometallic fac-[Mn I (CO) 3 (bis- Me NHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO 2 to CO, exceeding 100 turnovers with excellent faradaic yields (η CO ≈95 %) in anhydrous CH 3 CN. Under the same conditions, a maximum turnover frequency (TOF max ) of 2100 s -1 was measured by cyclic voltammetry, which clearly exceeds the values reported for other manganese-based catalysts. Moreover, the addition of water leads to the highest TOF max value (ca. 320 000 s -1 ) ever reported for a manganese-based catalyst. A Mn I tetracarbonyl intermediate was detected under catalytic conditions for the first time., (© 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2 O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2 O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97%ee) in short reaction times., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Breaking the chain: Reaction of a zirconium hydrazinediide with organoazides gives 2-pentazene-1,4-diyl complexes, such as [Zr(N(2) (TBS)N(py)){N(Ad)N(3)NPh(2)}] (C gray, N blue, Si green, Zr turquoise), by formal [2+3] cycloaddition. Bonding within the N(5) chain is investigated using density functional calculations. These complexes thermally eject N(2) to give side-on bonded diazenides.