Those notes sound like some poorly thought generalizations rather than something that poster got from the article. Why don't you check the reference?
That is the only reasonable way to verify that info.
I never heard of DMF being used in any radical reactions (it would be among the last choices) and I would expect that particular substrate to undergo
electrophilic bromination in such a solvent. If I remember correctly, dichloromethane was found unsuitable already in the seminal papers by Wohl and
Ziegler (not "zeiglar"!). Chloroform works in some cases. So do some other halogenated solvents (1,2-dichloro or 1,2-dibromo -ethane, chlorobenzene,
etc., but I don't really remember and you should check the literature anyway).
If you read the first page of patent application US2006217569 you will find a nice review with references about solvents suitable for use with radical
initiators or photobromination. DMF is not mentioned. It also appears that CCl4 is the solvent with the wider scope, but other solvents with difficult
to abstract hydrogens often give comparable yields on specific substrates (acetonitrile, methyl acetate, etc.).
3-Bromotoluene is a liquid so you don't really need an additional solvent. The choice of solvents is wider if you use visible light instead of
dibenzoyl peroxide or AIBN. Also, a light bulb or sunlight is less costly.
You can also avoid using NBS altogether. In situ formed bromine from HBr+H2O2(aq) or bromide/H2SO4/H2O2 also works on liquid substrates when using
light as a radical chain reaction initiator. I misplaced the articles (there were at least two on this topic), but I'm sure you can find the
references on your own if you try.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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