Sensitizer-free photochemical regeneration of benzimidazoline organohydride

21 April 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Organohydrides are an important class of organic compounds that can provide hydride anions for chemical and biochemical reactions, as demonstrated by reduced nicotinamide adenine dinucleotide serving as an important natural redox cofactor. The coupling of hydride transfer from the organohydride to the substrate and subsequent regeneration of the organohydride from its oxidized form can realize organohydride-catalyzed reduction reactions. Depending on the structure of the organohydride, its hydridicity and ease of regeneration vary. Benzimidazoline (BIH) is one of the strongest synthetic C–H hydride donors; however, its reductive regeneration requires highly reducing conditions. In this study, we synthesized various oxidized and reduced forms of BIH derivatives with aryl groups at the 2-position and investigated their photophysical and electrochemical properties. 4-(Dimethylamino)phenyl-substituted BIH exhibited salient red-shifted absorption compared to other synthesized BIH derivatives, and visible-light-driven regeneration without using an external photosensitizer was achieved. This knowledge has significant implications for the future development of solar-energy-based catalytic photoreduction technologies that utilize organohydride regeneration strategies.

Keywords

photosensitizer
organohydride
benzimidazoline

Supplementary materials

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Description
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Supporting Information
Description
Photographic image of photoirradiation system; cyclic voltammograms; crystallographic data; copies of 1H and 13C{1H} NMR spectra; and Cartesian coordinates of all optimized and transition state structures
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