Hi all,
I am currently having problems trying to reduce some differently positioned cyanopyrenes to the corresponding aminomethylpyrenes. They are extremely insoluble.
I have had limited success with butanol/Raney-Ni/H2, getting about 20% yield and a very messy column. I've not isolated any product when trying Red-Al/Toluene, LiAlH4/THF, BH3/THF, Pd/C/H2/Ethyl Acetate/MeOH and a Ni2B method. Anyone have any tricks for these kinds of reductions?
Dear Tom,
when using Ni2B, did you apply in situ method with NiCl2/NaBH4? Works normally well..
Astonishing that all other mentioned methods did not succed!
please try DMF or NMP as solvent and ammonium formiate as reducing agent.
Cheers for the responses guys!
@ Lars
I did generate the Ni2B in situ from NiCl2/NaNH4, but I was utilising a method that involved trapping the amine with Boc anhydride, to minimise any imine-amine dimerisation. So I could try it again under more conventional conditions.
@Helmut
NMP is an interesting proposition, my feeling is probably that this is a solubility problem. We prepared the compounds using NMP so that bodes well. Presumably you mean ammonium formate with Pd/C? Is this more effective than H2?
OK, you may also try Pd/C and methyl-cyclohexene as H2 transfer agent.
Methyl-cyclohexene easily forms toluene plus hydrogen at elevated temperature (around 100 °C). We have performed this reaction readily in a CEM microwave oven.
Conditions are required for reduction of cyanopyrenes use H2 gas in presence of PtO2 catalyst. The cyano group is reduced to amino group.
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