Event Title

Visible-Light-Induced Alkylation of Aryl Aldimines with Potassium Organotrifluoroborates Enabled by an Organic Photocatalyst

Poster Number

044

Faculty Mentor

James M. Hanna Jr., Ph.D.

College

College of Arts and Sciences

Department

Department of Chemistry, Physics, and Geology

Location

Richardson Ballroom – DiGiorgio Campus Center

Start Date

12-4-2019 2:15 PM

End Date

April 2019

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. 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, which may engage organic substrates in a series of single-electron-transfer (SET) events. The organic radicals thus generated participate in downstream reactions leading to the final product(s). Our group has previously employed this strategy for the alkylation of aldimines with potassium organotrifluoroborates using transition-metal photocatalysts. However, because of the much lower cost of organic photocatalysts (~$50/mmol for acridinium-based catalysts vs ~$1000/mmol for Ir-based catalysts), we desired to explore the use of organic photocatalysts in this transformation. Several organic photocatalysts and solvents were screened; the optimum conditions were found to require the photocatalyst 9-mesityl-10-methylacridinium tetrafluoroborate (Mes-Acr-Me) in dichloromethane solvent. Thus, a dichloromethane solution of potassium isopropyltrifluoroborate and variously substituted benzalanilines, when irradiated with blue LEDs in the presence of Mes-Acr-Me under argon, resulted in good yields of the desired α-arylamine adducts.

Previously Presented/Performed?

Southeast Regional Meeting of the American Chemical Society (SERMACS), Augusta, Georgia, November, 2018

Grant Support?

Supported by the Donors of the American Chemical Society Petroleum Research Fund and by an SC-INBRE grant from the National Institute for General Medical Sciences (NIH-NIGMS)

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Apr 12th, 2:15 PM Apr 12th, 4:15 PM

Visible-Light-Induced Alkylation of Aryl Aldimines with Potassium Organotrifluoroborates Enabled by an Organic Photocatalyst

Richardson Ballroom – DiGiorgio Campus Center

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. 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, which may engage organic substrates in a series of single-electron-transfer (SET) events. The organic radicals thus generated participate in downstream reactions leading to the final product(s). Our group has previously employed this strategy for the alkylation of aldimines with potassium organotrifluoroborates using transition-metal photocatalysts. However, because of the much lower cost of organic photocatalysts (~$50/mmol for acridinium-based catalysts vs ~$1000/mmol for Ir-based catalysts), we desired to explore the use of organic photocatalysts in this transformation. Several organic photocatalysts and solvents were screened; the optimum conditions were found to require the photocatalyst 9-mesityl-10-methylacridinium tetrafluoroborate (Mes-Acr-Me) in dichloromethane solvent. Thus, a dichloromethane solution of potassium isopropyltrifluoroborate and variously substituted benzalanilines, when irradiated with blue LEDs in the presence of Mes-Acr-Me under argon, resulted in good yields of the desired α-arylamine adducts.