-
Notifications
You must be signed in to change notification settings - Fork 0
Bromination of ketones
The protocol used is linked at the start of each attempt listed.
KBS38-1 - NBS method, 90% conversion
KBS38-2 - HBr method, 67% conversion
KBS38-3 - 89% NBS method
KBS38-3 - 95% NBS method
KBS39-1 - 32%
KBS39-2 - 35%
KBS40-1 - 89%
KBS40-2 - 94%
KBS40-3 - 87%
KBS41-1 - 72%
KBS41-2 - 77%
KBS42-1 - 71%
KBS42-2 - product not recovered
KBS42-3 - tbd
KBS42-4 - 77%
Started off with NBS/tosic acid. This is not the radical Wohl-Ziegler type reaction. Previous efforts to brominate ketones required the use of HBr in acetic acid/Br2 - this will be the second route explored.
Another alternative is CuBr2 in ethyl acetate (ref 1, ref 2.) but this seems to primarily work on phenyl compounds.
NBS/tosic acid method is established to work on phenyl compounds. It is possible that the nitrogen complicates the reaction in the case of pyridinyl ketones. E.g. see ref 1 where CuBr2 is used for phenyl compounds but HBr is used for pyridinyl rings. Also ref 3.
Pyridinium tribromide is sometimes used an alternative source of Br (in place of Br2) - see ref 4.