Improving Methods for Enantioselective Organophosphorus Synthesis by A Chiral Nucleophile-Metal Bifunctional Catalytic System

Improving Methods for Enantioselective Organophosphorus Synthesis by A Chiral Nucleophile-Metal Bifunctional Catalytic System

Presenter(s)

Jackson Thomas Shuman

Comments

Presentation: 1:40-2:00, Kennedy Union 211

Description

The use of Benzotetramisole (BTM) as a catalyst is a promising strategy for enantioselective organophosphorus synthesis since the reaction has been previously reported by Numan and Brichacek and has been tested in Dr. Erb’s research laboratory. However, the yields are only moderate (46-58%) and the enantiomeric excess (ee) of the purified product are poor, with 62% being the highest reported ee [1]. Preliminary computational data performed in the Erb lab has revealed that the cause of the lower ee (and possibly yield) could be the ability of the intermediate to adopt different conformations that are similar in energy but would give a mixture of chirality in the product. The addition of a metal ion could result in the formation of a ring structure, providing a firm anchor that prevents rotation of the Phosphorus-Nitrogen bond, and thus would form two possible intermediates. Locking the rotation of the intermediate prevents the relief of steric strain between groups on the substrate and the organocatalyst in one conformation, thus making one intermediate much higher in energy, less stable, and less likely to form. The other intermediate would also be locked in place in a similar way but has lower steric strain and thus would be more favorable. It may even be possible that the higher energy intermediate can isomerize to form the lower energy intermediate. Following this, bimolecular substitution by a nucleophile, such as an alcohol, would release of the catalyst and provide the product in improved enantioselectivity or yield.

Publication Date

4-17-2024

Project Designation

Honors Thesis

Primary Advisor

Jeremy M. Erb

Primary Advisor's Department

Chemistry

Keywords

Stander Symposium, College of Arts and Sciences

Institutional Learning Goals

Scholarship

Improving Methods for Enantioselective Organophosphorus Synthesis by A Chiral Nucleophile-Metal Bifunctional Catalytic System

Share

COinS