Visible-Light Promoted Reactions of Potassium Organotrifluoroborates with Benzalaniline
College
College of Arts and Sciences
Department
Chemistry, Physics, Geology, & the Environment
Abstract
The α-arylamine motif is present in about 10% of the top 100 drugs sold in the United States. A way to form this motif is the addition of organometallics to aromatic imines. In many cases, this approach is limited by the poor electrophilicity of the azomethine carbon of imines, which causes undesired enolization, reduction, or coupling reactions. 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. 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). Due to the generally low toxicity, relative stability, ease of synthesis, and functional group tolerance of potassium organotrifluoroborates, we have begun exploring this strategy as a means to effect formal additions of these organometallics to aromatic imines. We have found that irradiation of an argon-sparged dichloromethane solution of potassium allyltrifluoroborate and benzalaniline in the presence of Ir-dF(CF3)-dtb at room temperature using blue LED floodlights (450 nm) produced N-Phenyl-α-2-propen-1-yl-benzenemethanamine in 70% yield. Control experiments established that light and catalyst are required for reaction success. Various other potassium organotrifluoroborates have been tested under these conditions, with various degrees of success.
Honors Thesis Committee
James M. Hanna Jr., Ph.D.; Robin K. Lammi, Ph.D.; and Takita F. Sumter, Ph.D.
Course Assignment
CHEM 551, 552H – Hanna
Recognized with an Award?
Winner, Outstanding Presentation in Photocatalysis, Gulf Coast Undergraduate Research Symposium, Rice University, October 2016
Previously Presented/Performed?
Gulf Coast Undergraduate Research Symposium, Rice University, October 2016
Grant Support?
Supported by a grant from the National Institutes of Health IDeA Networks for Biomedical Research Excellence (NIH-INBRE)
Start Date
21-4-2017 1:00 PM
Visible-Light Promoted Reactions of Potassium Organotrifluoroborates with Benzalaniline
West Center, Room 219
The α-arylamine motif is present in about 10% of the top 100 drugs sold in the United States. A way to form this motif is the addition of organometallics to aromatic imines. In many cases, this approach is limited by the poor electrophilicity of the azomethine carbon of imines, which causes undesired enolization, reduction, or coupling reactions. 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. 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). Due to the generally low toxicity, relative stability, ease of synthesis, and functional group tolerance of potassium organotrifluoroborates, we have begun exploring this strategy as a means to effect formal additions of these organometallics to aromatic imines. We have found that irradiation of an argon-sparged dichloromethane solution of potassium allyltrifluoroborate and benzalaniline in the presence of Ir-dF(CF3)-dtb at room temperature using blue LED floodlights (450 nm) produced N-Phenyl-α-2-propen-1-yl-benzenemethanamine in 70% yield. Control experiments established that light and catalyst are required for reaction success. Various other potassium organotrifluoroborates have been tested under these conditions, with various degrees of success.
