Carbene-catalysed reductive coupling of nitrobenzyl bromides and activated ketones or imines via single-electron-transfer process

Benzyl bromides and related molecules are among the most common substrates in organic synthesis. They are typically used as electrophiles in nucleophilic substitution reactions. These molecules can also be activated via single-electron-transfer (SET) process for radical reactions. Representative rec...

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Veröffentlicht in:Nature communications 2016-09, Vol.7 (1), p.12933-12933, Article 12933
Hauptverfasser: Li, Bao-Sheng, Wang, Yuhuang, Proctor, Rupert S. J., Zhang, Yuexia, Webster, Richard D., Yang, Song, Song, Baoan, Chi, Yonggui Robin
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Sprache:eng
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Zusammenfassung:Benzyl bromides and related molecules are among the most common substrates in organic synthesis. They are typically used as electrophiles in nucleophilic substitution reactions. These molecules can also be activated via single-electron-transfer (SET) process for radical reactions. Representative recent progress includes α-carbon benzylation of ketones and aldehydes via photoredox catalysis. Here we disclose the generation of (nitro)benzyl radicals via N -heterocyclic carbene (NHC) catalysis under reductive conditions. The radical intermediates generated via NHC catalysis undergo formal 1,2-addition with ketones to eventually afford tertiary alcohol products. The overall process constitutes a formal polarity-inversion of benzyl bromide, allowing a direct coupling of two initially electrophilic carbons. Our study provides a new carbene-catalysed reaction mode that should enable unconventional transformation of (nitro)benzyl bromides under mild organocatalytic conditions. Benzyl bromides can be activated for radical reactions by photocatalytic single electron transfer. Here the authors show that N -heterocyclic carbenes are also capable of activating this pathway for nitrobenzyl bromides, and that the radical intermediates can add to the carbonyl group of ketones.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms12933