Deprotonative Metalation of Chloro- and Bromopyridines Using Amido-Based Bimetallic Species and Regioselectivity-Computed CH Acidity Relationships
作者:Katia Snégaroff、Tan Tai Nguyen、Nada Marquise、Yury S. Halauko、Philip J. Harford、Thierry Roisnel、Vadim E. Matulis、Oleg A. Ivashkevich、Floris Chevallier、Andrew E. H. Wheatley、Philippe C. Gros、Florence Mongin
DOI:10.1002/chem.201101993
日期:2011.11.18
A series of chloro‐ and bromopyridines have been deprotometalated by using a range of 2,2,6,6‐tetramethylpiperidino‐based mixed lithium–metal combinations. Whereas lithium–zinc and lithium–cadmium bases afforded different mono‐ and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium–copper combination, as demonstrated by subsequent
Ultrafast Halogen Dance Reactions of Bromoarenes Enabled by Catalytic Potassium Hexamethyldisilazide
作者:Kengo Inoue、Atsunori Mori、Kentaro Okano
DOI:10.1002/chem.202400104
日期:2024.4.22
Lochmann–Schlosser base, a stoichiometric combination of nBuLi and KOtBu, is commonly used as a superbase for deprotonating a wide range of organic compounds. In the present study, we report that catalytic potassium hexamethyldisilazide (KHMDS) exhibits higher catalytic activity than KOtBu for successive bromine–metal exchanges. Accordingly, 1–10 mol% of KHMDS dramatically enhances halogen dance reactions to introduce various electrophiles to bromopyridine, bromoimidazole, bromothiophene, bromofuran, and bromobenzene derivatives with the bromo group translocated from the original position. A dual catalytic cycle is proposed to explain the ultrafast bromine transfer.