We have quantum chemically investigated how solvation influences the competition between the S N 2 and E2 pathways of the model F – + C 2 H 5 Cl reaction. The system is solvated in a stepwise manner by going from the gas phase, then via microsolvation of one to three explicit solvent molecules, then last to bulk solvation using relativistic density functional theory at (COSMO)-ZORA-OLYP/QZ4P. We explain how and why the mechanistic pathway of the system shifts from E2 in the gas phase to S N 2 upon strong solvation of the Lewis base (i.e., nucleophile/protophile). The E2 pathway is preferred under weak solvation of the system by dichloromethane, whereas a switch in reactivity from E2 to S N 2 is observed under strong solvation by water. Our activation strain and Kohn–Sham molecular orbital analyses reveal that solvation of the Lewis base has a significant impact on the strength of the Lewis base. We show how strong solvation furnishes a weaker Lewis base that is unable to overcome the high characteristic distortivity associated with the E2 pathway, and thus the S N 2 pathway becomes viable.
An iron-catalysed carbene transfer reaction of diazo compounds to isocyanides has been developed. The resulting ketenimines are trapped in situ with various bisnucleophiles to access a range of densely functionalized heterocycles (pyrimidinones, dihydropyrazolones, 1H-tetrazoles) in a onepot process. The electron-rich Hieber anion ([Fe(CO) 3 NO] À ) facilitates efficient catalytic carbene transfer from acceptortype α-diazo carbonyl compounds to isocyanides, providing a cost-efficient and benign alternative to similar noble metalcatalysed processes. Based on DFT calculations a plausible reaction mechanism for activation of the α-diazo carbonyl carbene precursor and ketenimine formation is provided.
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