Lewis acid assisted Brønsted acid catalysed decarbonylation of Isocyanates: a combined DFT and experimental study

An efficient and mild reaction protocol for the decarbonylation of isocyanates has been developed using catalytic amounts of Lewis acidic boranes. The electronic nature (electron withdrawing, electron neutral, and electron donating) and the position of the substituents (ortho/meta/para) bound to isocyanate controls the chain length and composition of the products formed in the reaction. Detailed DFT studies were undertaken to account for the formation of the mono/di‐carboxamidation products and benzoxazolone compounds

Investigation of structure-directing interactions within copper(i)thiocyanate complexes through X-ray analyses and non-covalent interaction (NCI) theoretical approach

Herein, we reported the synthesis of copperIJI) thiocyanate complexes with ortho-pyridinyl carbohydrazones containing a thiophene (L1) or a furyl ring (L2) as a mixture of two different crystals for each compound, linkage isomers of C1N, [CuIJNCS)IJL1)PPh3] and C1S, [Cu(SCN)(L1)PPh3], for L1, whereas monomeric and polymeric structures C2N, [Cu(NCS)(L2)PPh3], and C2P, [–(NCS)Cu(L2)–]n, for L2. Crystallographic information and theoretical calculations, mainly noncovalent interaction reduced density gradient (NCI-RDG) analyses, were pursued to generate a profound understanding of the structure-directing interactions in these complexes. The supramolecular assemblies are first driven by cooperative π⋯π interactions and hydrogen bonds followed by CH⋯π, S⋯S and S⋯π linkages. In the case of the linkage isomers, intermolecular interactions may have a significant role in the formation of the less stable S-bound isomer C1S

Kinetics of N2 Release from Diazo Compounds: A Combined Machine Learning-Density Functional Theory Study

Diazo compounds are commonly employed as carbene precursors in carbene transfer reactions during a variety of functionalization procedures. Release of N2 gas from diazo compounds may lead to carbene formation, and the ease of this dissociation is highly dependent on the characteristics of the substituents located in the vicinity of the diazo moiety. A quantum mechanical density functional theory assisted by machine learning was used to investigate the relationship between the chemical features of diazo compounds and the activation energy required for the N2 dissociation. Our results suggest that diazo molecules possessing a higher positive partial charge on the carbene carbon and more negative charge on the terminal nitrogen, encounter a lower energy barrier. A more positive C charge decreases the π-donor ability of the carbene lone pair to the π∗ orbital of N2 , while the more negative N charge is a result of a weak interaction between N2 lone pair and vacant p orbital of the carbene. The findings of this study can pave the way for molecular engineering for the purpose of carbene generation which serves as a crucial intermediate for many chemical transformations in synthetic chemistry

Kinetics of N2 Release from Diazo Compounds: A Combined Machine Learning-Density Functional Theory Study

Total potential (E) and Thermal correction to Gibbs Free Energies obtained using SMD/M06-2X/def2-TZVP//SMD/M06-2X/6-31G(d) level of theory in dichloroethane and Cartesian coordinates for all of the calculated structures. dataset Python Machine Learning Scrip

Rhodium-catalysed tetradehydro-Diels-Alder reactions of enediynes: Via a rhodium-stabilized cyclic allene

The Royal Society of Chemistry. Efficient methods for the synthesis of fused-aromatic rings is a critical endeavour in the creation of new pharmaceuticals and materials. A direct method for preparing these systems is the tetradehydro-Diels-Alder reaction, however this is limited by the need for harsh reaction conditions. A potential, but underdeveloped, route to these systems is via transition metal-catalysed cycloaromatisation of ene-diynes. Herein, tethered unconjugated enediynes have been shown to undergo a facile room-temperature RhI-catalysed intramolecular tetradehydro-Diels-Alder reaction to produce highly substituted isobenzofurans, isoindolines and an indane. Furthermore, experimental and computational studies suggest a novel mechanism involving an unprecedented and complex RhI/RhIII/RhI/RhIII redox cycle involving the formation of an unusual strained 7-membered rhodacyclic allene intermediate and a RhIII-stabilized 6-membered ring allene complex

Supramolecular assemblies of organotin(IV)-diphosphoryl adducts: insights from X-rays and DFT

Mono-, di- and tri-phenyltin(IV) adducts containing a neutral diphosphoryl ligand, Ph2P(O)OC6H4OP(O) Ph-2, were synthesized and characterized. These 2 : 1 adducts of two trans-organotin(IV) moieties and the bridging ligand all crystallize around a centre of inversion. The influence of tin-substituents on the building up of multidimensional architectures, as well as, strength of the Sn-O interactions are discussed in terms of geometrical parameters, Hirshfeld surface analysis and theoretical calculations. The CH center dot center dot center dot Cl interactions make a substantial contribution to directing 1D self-assembly of the tin adducts. Replacement of Cl atoms with Ph groups on tin(IV) in these complexes has increased the probability of CH center dot center dot center dot pi and H center dot center dot center dot H interactions and weakens the Sn-O bonds. QTAIM and NBO analyses reveal that the Sn-O interactions are principally electrostatic in nature (donor-acceptor like) with only a small amount of covalence increasing from the tri-to the mono-phenyltin adduct

Mechanism of CO2 Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Carbon dioxide reduction reaction (CO2RR) is a promising method for converting CO2 into value-added products. CO2RR over single-atom catalysts (SACs) is widely known to result in chemical compounds such as carbon monoxide and formic acid that contain only one carbon atom (C1). Indeed, at least two active sites are commonly believed to be required for C–C coupling to synthesize compounds, such as ethanol and propylene (C2+), from CO2. However, experimental evidence suggests that iron phthalocyanine (PcFe), which possesses only a single metal center, can produce a trace amount of C2+ products. To the best of our knowledge, the mechanism by which C2+ products are formed over a SAC such as PcFe is still unknown. Using density functional theory (DFT), we analyzed the mechanism of the CO2RR to C1 and C2+ products over PcFe. Due to the high concentration of bicarbonate at pH 7, CO2RR competes with HCO3– reduction. Our computations indicate that bicarbonate reduction is significantly more favorable. However, the rate of this reaction is influenced by the H3O+ concentration. For the formation of C2+ products, our computations reveal that C–C coupling proceeds through the reaction between in situ-formed CO and PcFe(“0”)–CH2 or PcFe(“-I”)–CH2 intermediates. This reaction step is highly exergonic and requires only low activation energies of 0.44 and 0.24 eV for PcFe(“0”)–CH2 and PcFe(“-I”)–CH2. The DFT results, in line with experimental evidence, suggest that C2+ compounds are produced over PcFe at low potentials whereas CH4 is still the main post-CO product. Validerad;2024;Nivå 2;2024-04-12 (joosat);Funder: Jane and Aatos Erkko Foundation; Dr. Barbara Mez-Starck foundation;Full text: CC BY license</p

An unexpected synthesis of azepinone derivatives through a metal-free photochemical cascade reaction

Funding Information: L.S. and X.T. are grateful to the CSC (China Scholarship Council) for a PhD fellowship. We gratefully acknowledge the generous allocation of computing time from the Australian National Computational Infrastructure and University of Tasmania, and the Australian Research Council (grant number DP180100904) for financial support. We thank Petra Krämer for her UV-vis measurements. Publisher Copyright: © 2023, The Author(s).Azepinone derivatives are privileged in organic synthesis and pharmaceuticals. Synthetic approaches to these frameworks are limited to complex substrates, strong bases, high power UV light or noble metal catalysis. We herein report a mild synthesis of azepinone derivatives by a photochemical generation of 2-aryloxyaryl nitrene, [2 + 1] annulation, ring expansion/water addition cascade reaction without using any metal catalyst. Among the different nitrene precursors tested, 2-aryloxyaryl azides performed best under blue light irradiation and Brønsted acid catalysis. The reaction scope is broad and the obtained products underwent divergent transformations to afford other related compounds. A computational study suggests a pathway involving a step-wise aziridine formation, followed by a ring-expansion to the seven-membered heterocycle. Finally, water is added in a regio-selective manner, this is accelerated by the added TsOH.Peer reviewe