A Pyridine–Pyridine Cross‐Coupling Reaction via Dearomatized Radical Intermediates
A pyridine–pyridine coupling reaction has been developed between pyridyl phosphonium salts and cyanopyridines using B2pin2 as an electron‐transfer reagent. Complete regio‐ and cross‐selectivity are observed when forming a range of valuable 2,4′‐bipyridines. Phosphonium salts were found to be the onl...
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Published in | Angewandte Chemie International Edition Vol. 58; no. 42; pp. 14882 - 14886 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
WEINHEIM
Wiley
14.10.2019
Wiley Subscription Services, Inc |
Edition | International ed. in English |
Subjects | |
Online Access | Get full text |
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Summary: | A pyridine–pyridine coupling reaction has been developed between pyridyl phosphonium salts and cyanopyridines using B2pin2 as an electron‐transfer reagent. Complete regio‐ and cross‐selectivity are observed when forming a range of valuable 2,4′‐bipyridines. Phosphonium salts were found to be the only viable radical precursors in this process, and mechanistic studies indicate that the process does not proceed through a Minisci‐type coupling involving a pyridyl radical. Instead, a radical–radical coupling process between a boryl phosphonium pyridyl radical and a boryl‐stabilized cyanopyridine radical explains the C−C bond‐forming step.
Pyridyl phosphonium salts react with cyanopyridines and B2pin2 to form 2,4‐bipyridines with complete regiocontrol. Mechanistic studies support a radical–radical coupling process between two boryl‐stabilized pyridyl radical anions rather than a Minisci‐type pathway, and the process is unique to pyridyl phosphonium salts. |
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Bibliography: | These authors contributed equally to this work. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1433-7851 1521-3773 |
DOI: | 10.1002/anie.201906267 |