Theoretical insights on product selectivity in diradical-mediated thermal rearrangements.

摘要

Electronic structure calculations have led to the interpretation of experimental results for intramolecular rearrangements that yield complex or unusual product distributions.; Chapter 1 presents calculations on the degenerate rearrangement of bicyclo[3.1.0]hex-2-ene. DFT, CASSCF, and CASPT2 quantum mechanical calculations map the details of the potential energy landscape for the reaction. A dynamical hypothesis is offered to explain the observed nonstatistical product distribution.; Chapters 2 and 3 describe the results of CASPT2//UB3LYP calculations on the rearrangements of deuterium- and methyl-labeled 6-methylenebicyclo[3.2.0]hept-2-ene. Kinetic models are derived from calculations, and comparison to experimental results is achieved through mathematical techniques. For the parent reaction, an effect of non-statistical post-transition state dynamics is deduced based on fit to experiment and analysis of the potential energy surface shape.; B3LYP calculations in Chapter 4 detail the routes to several products from two phenylcarbenes capable of intramolecular oxonium ylide formation. The kinetic and thermodynamic feasibility of ylide formation and persistence is evaluated, and competition among ylide decomposition pathways is investigated vis-a-vis pertinent experimental results.; In Chapter 5, CBS-QB3 calculations are used to evaluate the possibility of a concerted or stepwise [1,3] hydrogen shift in an O--substituted propylene system. An unexpectedly low-energy, highly dissociative, but nevertheless concerted antarafacial H-[1,3] transition state is indicated by CBS-QB3 as well as the RHF and MP2 methods.; Chapter 6 outlines an experimental test of a computationally predicted redox behavior of 1,2-diphenyl[b]naphthocyclobutene. A preliminary experimental trial is reported.