I would like to boronate 2-bromo-6-nitro-naphtalene using nBuLi and quenching with 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. Since there is no alpha proton to the nitro, and that the nitro group is not known to be a strong DMG (Direct ortho metalation group), theory seems to be on my side. I would love to hear from anyone who has experience using nBuLi on nitroarenes or knows of other side reactions to be aware of! Thank you
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2$\begingroup$ Sorry, but can you give a reference for a successful lithiation of a nitrocompound? I'm fairly certain that nitrogroup shall react. $\endgroup$– permeakraCommented Jun 20 at 6:10
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$\begingroup$ I don't have any! Which is also why i am asking! $\endgroup$– The Red Man Jolan BonelliCommented Jun 21 at 3:18
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1 Answer
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Aryl nitro groups will not stand lithiation conditions. The solution to your problem is a Pd catalysed Miyaura borylation between your substrate and pinacol borane.
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$\begingroup$ Thanks! I am aware of the Miyaura borylation, but it doesn't work very well and the purification is annoying as Bpin and my compound have similar polarity. Nevertheless, do you have any ideas on why the nitro group won't stand ? $\endgroup$ Commented Jun 20 at 6:37
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1$\begingroup$ How about preparing the aryl magnesium by Knochel exchange and quenching with trimethyl borate? See onlinelibrary.wiley.com/doi/10.1002/anie.200300579 $\endgroup$ Commented Jun 20 at 6:53
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1$\begingroup$ Also note: a colleague has advised me that you can do the Li-Hal exchange in the presence of nitro groups if you run with tBuLi at -100C $\endgroup$ Commented Jun 20 at 19:57
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1$\begingroup$ What is the next proposed step for your product? $\endgroup$ Commented Jun 21 at 6:23
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2$\begingroup$ @TheRedManJolanBonelli Don't forget that a slow addition/cannulation can transfer the reagents/reagent solutions cooled -- possibly not perfectly $\pu{-78 ^\circ{}C}$, but significantly cooler than just by a brine/water ice bath. $\endgroup$ Commented Jun 21 at 15:58