I tried a lot to prepare Grignard reagent of 3-nitrobenzyl bromide but failed even i tried with freshly prepared THF using catalytic amount of iodine by slightly warm the reaction mixture. Even I heated the reaction mixture for long time i only getting my staring material.However, reaction going smoothly with simple benzyl bromide. Is there any trick to prepare or procedure for its synthesis?.
Thanks.
The preparation of the Grignard reagents successfully depends up on the use of moisture free solvent. Use double distilled dry ether . 3-nitrobenzyl bromide may be lacrimatory . During preparation of Grignard reagent 3-nitrobenzyl bromide should distilled under vacuum then it should be used to react with fresh Mg metal get to good results.
Since you have the active nitro group,you may end up with Grignard rgts as the following case: 1,2-Addition of Alkyl Grignard Reagents to the Nitro Group: Simple Access to
2-[Alkyl(hydroxy)amino]pyridine N-Oxides and 2-Alkylaminopyridine
N-Oxides;
You may need to change your strategy in achieving your desired target.
In several Grignard reactions, initiation is problem; once initiated it can progress well. It also depends on MC of reagents & Mg quality.
Sometimes Grignard reactions can be initiated with small portion of bromo reagent at higher concentration of about 20-30%w/v in solvent at appropriate temp. in the presence of cat. I2.
After initiation, remaining bromo reagent & solvent can be added under N2 and reagent can be prepared.
Nitro groups react with grignards unless there is some additional stabilisation present.
In which case they can be prepared by magnesium halogen exchange, using the likes of a Knochel transmetallation. However a benzylic bromide is too unreactive to generate in this fashion.
You most likely will not be able to prepare your desired grignard reagent. I suggest finding an alternative option. What did you intend to do with this grignard?
Keep it all dry and use 1,2-dibromoethane to activate. I have been dry stirring the Mg turnings for 20 mins. Then add 10% of the solvent/reactant mixture to the turnings. After this turn off the stirring and syringe the dibromoethane directly into the turnings. The turnings in the mixture should start evolving ethene gas off the surface when activated. Then syringe the other 90% into the reaction flask. Be careful of thermal runaway. Keep an ice bath close.
I agree with the view point of Dr. Chen and Harris that nitro group can react with grignard reagent but in my case i am getting only starting
i want to react Grignard reagent with chlorodiisopropylsilane and finally want to reduced nitro group
Hi,
I am also working on grignard reaction. But can u tell me how u r monitoring the progress of ur reaction. Because grignard reagent formation cannot be monitored by tlc
Hi,
You can review the following literature to optimize your experimental procedures.
[1]Zhao, Hong; et al. Hydrothermal syntheses and crystal structures of two Zn(II) complexes with 1-substituted-1H-[1,2,3]-triazole-4-carboxylic acid. Journal of Coordination Chemistry (2011), 64(15), 2735-2745.
[2] Dinda, Milan; et al. Solar Photothermochemical Reaction and Supercritical CO2 Work up for a Fully Green Process of Preparation of Pure p-Nitrobenzyl Bromide. Environmental Science & Technology (2013), 47(18), 10535-10540.
[3] Ghaffarzadeh, Mohammad; et al. H2O2-HBr: A metal-free and organic solvent-free reagent system for the synthesis of arylaldehydes from methylarenes. Journal of Chemical Sciences (Bangalore, India) (2009), 121(2), 177-182.
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