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Alkoxide‐Promoted Selective Hydroboration of N ‐Heteroarenes: Pivotal Roles of in situ Generated BH 3 in the Dearomatization Process
Author(s) -
Jeong Eunchan,
Heo Joon,
Park Sehoon,
Chang Sukbok
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201901214
Subject(s) - hydroboration , chemistry , alkoxide , catalysis , hydride , pyridine , borohydride , borylation , adduct , borane , selectivity , combinatorial chemistry , organic chemistry , metal , aryl , alkyl
While numerous organo(metallic)catalyst systems were documented for dearomative hydroboration of N‐ aromatics, alkoxide base catalysts have not been disclosed thus far. Described herein is the first example of alkoxide‐catalyzed hydroboration of N‐ heteroaromatics including pyridines, providing a broad range of reduced N‐ heterocycles with high efficiency and selectivity. Mechanistic studies revealed an unprecedented counterintuitive dearomatization pathway, in which 1) pyridine‐BH 3 adducts undergo a hydride attack by alkoxyborohydrides, 2) in situ generated BH 3 serves as a catalytic promoter, and 3) 1,4‐dihydropyridyl borohydride is in a predominant resting state.