ABSTRACT
Applications of TEMPO. catalysis for the development of redox-neutral transformations are rare. Reported here is the first TEMPO. -catalyzed, redox-neutral C-H di- and trifluoromethoxylation of (hetero)arenes. The reaction exhibits a broad substrate scope, has high functional-group tolerance, and can be employed for the late-stage functionalization of complex druglike molecules. Kinetic measurements, isolation and resubjection of catalytic intermediates, UV/Vis studies, and DFT calculations support the proposed oxidative TEMPO. /TEMPO+ redox catalytic cycle. Mechanistic studies also suggest that Li2 CO3 plays an important role in preventing catalyst deactivation. These findings will provide new insights into the design and development of novel reactions through redox-neutral TEMPO. catalysis.
Subject(s)
Hydrocarbons, Aromatic/chemistry , Hydrocarbons, Fluorinated/chemical synthesis , Cyclic N-Oxides , Density Functional Theory , Free Radicals/chemical synthesis , Free Radicals/chemistry , Hydrocarbons, Fluorinated/chemistry , Kinetics , Molecular Structure , Oxidation-ReductionABSTRACT
Ab initio calculations are used to demonstrate the existence of a nonvalence temporary anion shape resonance for a model (H2O)4 cluster system with no net dipole moment. The cluster is composed of two water dimers, the distance between which is varied. Each dimer possesses a weakly bound nonvalence anion state. For large separations of the dimer subunits, there are two bound nonvalence anion states (of Ag and B2u symmetry) corresponding to the symmetric and asymmetric combinations of the nonvalence anion states of the two dimer subunits. As the separation between the dimer subunits is decreased, the B2u anion increases in energy and becomes a temporary anion shape resonance. The real part of the resonance energy is determined as a function of the distance between the dimers and is found to increase monotonically from just above threshold to 28 meV for the range of geometries considered. Over this same range of geometries, the resonance half-width varies from 0 to 21 meV. The B2u anion, both when bound and when temporary, has a very diffuse charge distribution. The effective radial potential for the interaction of the excess electron with the cluster has a barrier at large distance arising from the electron-quadrupole interaction in combination with the repulsive angular momentum ( l = 1) contribution. This barrier impacts both the resonance energy and its lifetime.
