Nuyen_MastersThesis_FinalDraft.pdf

Reason: Files contain content that will be used for a manuscript that has not yet been published.

1

year(s)

6

month(s)

30

day(s)

until file(s) become available

COBALT-CATALYZED ENANTIOSELECTIVE RING OPENING OF UNSTRAINED HETEROCYCLES VIA VINYLIDENE ADDITION AND BETA-HETEROATOM ELIMINATION

thesis
posted on 26.04.2022, 17:35 authored by Courtney E NuyenCourtney E Nuyen

 Ring opening of heterocyclic compounds through C-X bond cleavage is a useful strategy that provides rapid access to highly functionalized acyclic building blocks. In recent years, much work has focused on using transition metal catalysts to activate the C-X bonds of heterocycles and initiate ring opening. Metal-catalyzed ring opening of unstrained heterocycles is less prevalent than catalytic activation of strained heterocycles, which is advantageously driven by relief of ring strain. Methods for catalytic ring activation of unstrained heterocycles exist but are limited. Herein, we report the use of chiral cobalt complexes as catalysts for enantioselective ring opening of dihydrofuran and nitrogen-protected pyrrolines by utilizing dichloroalkenes as vinylidene precursors, Zn as a reductant, and ZnCl2 as an additive. Based on preliminary mechanistic studies, we believe this method proceeds through [2 + 2] cycloaddition between the ligated cobalt vinylidene species and the heterocycle, followed by β-heteroatom elimination, cobalt to zinc transmellation, and protonation to give rise to synthetically useful chiral allylic alcohol and amine products. 

History

Degree Type

Master of Science

Department

Chemistry

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

Christopher Uyeda

Additional Committee Member 2

Ryan Altman

Additional Committee Member 3

Mingji Dai