Computational studies on complex reaction mechanics

Molecular modeling with density functional and higher level methods was used to study mechanisms for the reactions of carbonyl compounds with ozone, the Doering-Moore-Skattebol Rearrangement, bis-lactam cyclizations, and thermal rearrangements of ortho-ethynyltoluene. Ozonation of both formaldehyde and acetone can proceed by one of two slow pathways: stepwise addition across the carbonyl group or hydrogen atom abstraction. The Doering-Moore-Skattebol Rearrangement proceeds as a triangular lithium-halogen carbenoid, opening stereospecifically to an allene, with lithium-halogen dissociation occurring after the transition state. Bis-lactam cyclization is rapid, reversible, and thermodynamically controlled. The experimentally observed major product is confirmed by computations as thermodynamically most stable. Thermal rearrangements of o-ethynyltoluene proceed through competitive [1,2] and [1,5] H-shifts. Chrysene is formed as a minor product by dimerization of a novel intermediate, orthoxylallene