Controlling Selectivity by Controlling the Path of Trajectories.

Area of Science:

• Organic Chemistry
• Reaction Mechanism Studies
• Computational Chemistry

Background:

• Sigmatropic rearrangements are fundamental organic reactions.
• Controlling selectivity in [1,2]- and [2,3]-sigmatropic rearrangements remains a challenge.
• Dynamic trajectories offer a new perspective on reaction control.

Purpose of the Study:

• To investigate the role of dynamic trajectories in controlling sigmatropic rearrangement selectivity.
• To develop a counterintuitive strategy for promoting [2,3]-sigmatropic selectivity.
• To apply this strategy to Stevens/Sommelet-Hauser rearrangements of ammonium ylides.

Main Methods:

• Analysis of dynamic trajectories.
• Kinetic isotope effect measurements.
• Crossover experiments.
• Computational modeling.

Main Results:

• A hypothesis was proposed: thermodynamically disfavoring the [2,3] rearrangement promotes selectivity by creating later transition states.
• This hypothesis was successfully applied to Stevens/Sommelet-Hauser rearrangements.
• Experimental and computational data support trajectory path control over selectivity.

Conclusions:

• Dynamic trajectories provide a powerful tool for controlling the selectivity of sigmatropic rearrangements.
• The developed strategy offers a new method for directing Stevens/Sommelet-Hauser rearrangements.
• Understanding reaction dynamics is key to designing selective chemical transformations.