Event Title

Visible Light-Promoted Additions of Potassium Organotrifluoroborates to Imines

Poster Number

40

Faculty Mentor

James M. Hanna Jr., Ph.D.

College

College of Arts and Sciences

Department

Department of Chemistry, Physics, and Geology

Location

Richardson Ballroom

Start Date

21-4-2017 2:15 PM

Description

Recently, the use of visible light combined with a suitable photocatalyst to promote key bond-forming steps in organic synthesis has emerged as a viable strategy to achieve a number of important synthetic transformations. Visible light passes through ordinary glass, and organic substrates do not typically absorb wavelengths in the visible range, providing a significant advantage of this method over traditional ultraviolet (UV) photochemistry. The photocatalyst involved is often a ruthenium or iridium polypyridyl complex, which absorbs light in the visible range to give a relatively long-lived excited state. This photo-excited catalyst then mediates the formation of radicals from organic substrates, through a series of single-electron-transfer (SET) events; the organic radicals thus generated engage in downstream reactions, leading to the final product(s). We have begun exploring this strategy as a means to effect formal additions of potassium organotrifluoroborates to imines. We have found that irradiation of an argon-sparged dichloromethane solution of potassium benzyltrifluoroborate, benzalaniline, and diphenylphosphate in the presence of Ir-dF(CF3)-dtb at room temperature using blue LEDs (450 nm) yielded the expected addition product in 76% isolated yield; only traces of homocoupling products could be detected. Control experiments established that catalyst and light are both required for reaction; the elimination of diphenylphosphate led to a slightly lower yield. Light/dark experiments seemed to favor a single-cycle mechanism rather than a radical-chain mechanism.

Previously Presented/Performed?

68th Southeastern Regional Meeting of the American Chemical Society (SERMACS), Columbia, South Carolina, October 2016

Grant Support?

Supported by a grant from the National Institutes of Health IDeA Networks for Biomedical Research Excellence (NIH-INBRE)

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Apr 21st, 2:15 PM

Visible Light-Promoted Additions of Potassium Organotrifluoroborates to Imines

Richardson Ballroom

Recently, the use of visible light combined with a suitable photocatalyst to promote key bond-forming steps in organic synthesis has emerged as a viable strategy to achieve a number of important synthetic transformations. Visible light passes through ordinary glass, and organic substrates do not typically absorb wavelengths in the visible range, providing a significant advantage of this method over traditional ultraviolet (UV) photochemistry. The photocatalyst involved is often a ruthenium or iridium polypyridyl complex, which absorbs light in the visible range to give a relatively long-lived excited state. This photo-excited catalyst then mediates the formation of radicals from organic substrates, through a series of single-electron-transfer (SET) events; the organic radicals thus generated engage in downstream reactions, leading to the final product(s). We have begun exploring this strategy as a means to effect formal additions of potassium organotrifluoroborates to imines. We have found that irradiation of an argon-sparged dichloromethane solution of potassium benzyltrifluoroborate, benzalaniline, and diphenylphosphate in the presence of Ir-dF(CF3)-dtb at room temperature using blue LEDs (450 nm) yielded the expected addition product in 76% isolated yield; only traces of homocoupling products could be detected. Control experiments established that catalyst and light are both required for reaction; the elimination of diphenylphosphate led to a slightly lower yield. Light/dark experiments seemed to favor a single-cycle mechanism rather than a radical-chain mechanism.