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Dual Role of Visible Light-Activated 1,4-Dihydropyridine Anions: Alkyl Radical Precursors and Photoreductants in Organic Transformations /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Dual Role of Visible Light-Activated 1,4-Dihydropyridine Anions: Alkyl Radical Precursors and Photoreductants in Organic Transformations /Prasadi Gallage.
Author:	Gallage, Prasadi,
Description:	1 electronic resource (322 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Notes:	Advisors: Pitre, Spencer P. Committee members: Nelson, Toby L.; Vasquez, Yolanda; Miller, David C.; Montgomery, Mckale.
Contained By:	Dissertations Abstracts International86-06B.
Subject:	Chemistry.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31485000
ISBN:	9798346854241

Dual Role of Visible Light-Activated 1,4-Dihydropyridine Anions: Alkyl Radical Precursors and Photoreductants in Organic Transformations /
Gallage, Prasadi,

Dual Role of Visible Light-Activated 1,4-Dihydropyridine Anions: Alkyl Radical Precursors and Photoreductants in Organic Transformations /Prasadi Gallage. - 1 electronic resource (322 pages)

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

1,4-Dihydropyridines (DHPs), characterized by a pyridine ring with hydrogen atoms attached to both the nitrogen and C-4 positions, are essential compounds in modern organic synthesis. Their versatile reactivity allows them to participate in a wide range of chemical transformations, making them essential in the synthesis of pharmaceuticals, agrochemicals, and other valuable compounds across various industries. DHP derivatives, such as Hantzsch esters and C-3,5 nitrile DHPs, are extensively studied as hydrogen atom donors in numerous transformations initiated by transition metal or photoredox catalysis. Additionally, 4-alkyl-1,4-DHPs also serve as alkyl radical precursors in photoredox transformations, undergoing SET oxidative cleavage in the presence of a photoredox catalyst to generate carbon-centered radicals. Recent research in our lab has shown that DHPs can be deprotonated in the presence of a suitable base to form the corresponding anion in-situ, resulting in a significant redshift in their absorption and allowing them to serve as strong visible light-absorbing reagents. Using this strategy, we developed a visible light-mediated direct photolysis method to generate alkyl radicals from 4-tert-alkyl-1,4-DHPs, facilitating photochemical Giese reactions with various Michael acceptors without the need for a photocatalyst or external oxidant. We then evaluated the DHP anion as a photoactive single-electron reductant. Studies on their chemical and light-absorbing properties revealed that 1,4-DHP anions possess excited states with strong reducing abilities, with excited state oxidation potentials around ˗2.6 V vs. SCE. This led to the development of a method for the reductive dehaloborylation of aryl chlorides and the extension of reaction conditions for the detosylation of N-tosyl aryl amines. We further advanced this approach to achieve ketyl radical formation from aromatic aldehydes, resulting in homocoupling to form symmetrically substituted 1,2-diols. Additionally, we achieved the reductive coupling of aromatic imines and the reductive intermolecular cyclization of aromatic aldehydes to form the corresponding lactones. Ongoing efforts aim to demonstrate the protocol's effectiveness for the generation of ketyl radicals from aliphatic aldehydes and ketones. These findings underscore the significant potential of 1,4-DHPs in advancing organic synthesis by offering efficient, mild, and versatile methodologies for a variety of chemical transformations.

English

ISBN: 9798346854241Subjects--Topical Terms:

188628
Chemistry.
Subjects--Index Terms:

Dihydropyridine chemistry

Dual Role of Visible Light-Activated 1,4-Dihydropyridine Anions: Alkyl Radical Precursors and Photoreductants in Organic Transformations /
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520 $a 1,4-Dihydropyridines (DHPs), characterized by a pyridine ring with hydrogen atoms attached to both the nitrogen and C-4 positions, are essential compounds in modern organic synthesis. Their versatile reactivity allows them to participate in a wide range of chemical transformations, making them essential in the synthesis of pharmaceuticals, agrochemicals, and other valuable compounds across various industries. DHP derivatives, such as Hantzsch esters and C-3,5 nitrile DHPs, are extensively studied as hydrogen atom donors in numerous transformations initiated by transition metal or photoredox catalysis. Additionally, 4-alkyl-1,4-DHPs also serve as alkyl radical precursors in photoredox transformations, undergoing SET oxidative cleavage in the presence of a photoredox catalyst to generate carbon-centered radicals. Recent research in our lab has shown that DHPs can be deprotonated in the presence of a suitable base to form the corresponding anion in-situ, resulting in a significant redshift in their absorption and allowing them to serve as strong visible light-absorbing reagents. Using this strategy, we developed a visible light-mediated direct photolysis method to generate alkyl radicals from 4-tert-alkyl-1,4-DHPs, facilitating photochemical Giese reactions with various Michael acceptors without the need for a photocatalyst or external oxidant. We then evaluated the DHP anion as a photoactive single-electron reductant. Studies on their chemical and light-absorbing properties revealed that 1,4-DHP anions possess excited states with strong reducing abilities, with excited state oxidation potentials around ˗2.6 V vs. SCE. This led to the development of a method for the reductive dehaloborylation of aryl chlorides and the extension of reaction conditions for the detosylation of N-tosyl aryl amines. We further advanced this approach to achieve ketyl radical formation from aromatic aldehydes, resulting in homocoupling to form symmetrically substituted 1,2-diols. Additionally, we achieved the reductive coupling of aromatic imines and the reductive intermolecular cyclization of aromatic aldehydes to form the corresponding lactones. Ongoing efforts aim to demonstrate the protocol's effectiveness for the generation of ketyl radicals from aliphatic aldehydes and ketones. These findings underscore the significant potential of 1,4-DHPs in advancing organic synthesis by offering efficient, mild, and versatile methodologies for a variety of chemical transformations.
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653 $a Aryl chlorides
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