40529-24-6Relevant academic research and scientific papers
An experimental and theoretical study of the type C enone rearrangement: Mechanistic and exploratory organic photochemistry
Zimmerman, Howard E.,Nesterov, Evgueni E.
, p. 5422 - 5430 (2007/10/03)
We recently described a new photochemical rearrangement which we termed a Type C process. The reaction involves a δ to α aryl migration in 5-disubstituted cyclohexenones also having bulky C-3 substituents. In contrast to most cyclohexenone rearrangements, the reaction occurs via a twisted π-π* excited triplet rather than the usual n-π* state. The electronic nature of the rearrangement was assessed using migration selectivity with p-anisyl and p-cyanophenyl groups. A synthesis of the reactants was elaborated, and the product structures were established by X-ray and NMR analysis. The reaction mechanism was established further with DFT and CASSCF computations. In the latter, localized NBO basis orbitals permitted proper selection of the active space. The nature of the diradical intermediates as well as the transition states was established computationally. Sensitization experiments with regioselectivities the same as those in direct irradiation confirmed the triplet multiplicity of the process.
Quantitative cavities and reactivity in stages of crystal lattices: Mechanistic and exploratory organic photochemistry
Zimmerman, Howard E.,Nesterov, Evgueni E.
, p. 2818 - 2830 (2007/10/03)
In continuing our research on solid-state organic photochemistry, we have been investigating the phenomenon of reactivity in stages. In this study we present new examples where the photochemical reactivity changes discontinuously at some point in the conversion. In these instances, the reaction course of the solid differs from that in solution. One example is the reaction of 2-methyl-4,4-diphenylcyclohexenone, where an unusual reaction course was encountered in the solid state; and, of two possible mechanisms, one was established by isotopic labeling. A second case is that of 4,5,5-triphenylcyclohexenone. The solid-state reaction of this enone was found to give a new photochemical transformation, the Type C rearrangement, a process that involves a δ to α aryl migration. In the case of 3-tert-butyl-5,5-diphenylcyclohexenone the Type C rearrangement occurred even in solution. The stage behavior was investigated using X-ray analysis and Quantum Mechanics/Molecular Mechanics computations. This permitted us to determine the sources and details of the stage phenomenon. The analysis revealed how a product molecule as a neighbor affects reactivity. The computations were employed to follow the course of a solid-state reaction from reactant through the succeeding stages. Additionally, the Delta-Density Analysis was utilized to ascertain the electronic nature of molecular changes. Besides product composition changing with extent of conversion, the reaction quantum yield was found to change as one stage gave way to a succeeding one.
