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High-yielding nitrostyrene catalyst

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Barium:
I have been searching and searching and trying and trying for years to find a cheap  condensation/dehydration catalyst which doesn't require refluxing GAA or nitromethane to get good yields. Finally I have found it. Methylamine.

A general method for nitrostyrenes is as follows:

100 mmol of a aromatic aldehyde
105 mmol nitromethane or nitroethane
15-20 mmol methylamine as a 10-20% aqueous solution
Enough MeOH, EtOH or IPA to make the mixture stirable. Usually about 25 ml

To a 250 ml rb-flask equipped with a magnetic stirbar is added the aromatic aldehyde, nitromethane and the alcohol. Sirring is started and the aqueous methylamine solution is added in one portion. The reaction flask is placed in a water bath and heated to 40-50°C. The reaction progress can be monitored by TLC to see when the aldehyde is consumed. In most cases 45 minutes in the water bath is enough.
When the reaction is over 25 mmol GAA is added to the reaction mixture and the flask is placed in the freezer until the crystallisation is complete [1]. The solids are then broken up with a spatula, transferred to a filter funnel and washed with water to remove most of the methylamine acetate. The nitrostyrene is then recrystallised from MeOH, EtOH or IPA.


1-phenyl-2-nitroethene, 92%
1-phenyl-2-nitropropene, 93%
1-(4-ethoxyphenyl)-2-nitroethene, 88%
1-(4-ethoxyphenyl)-2-nitropropene, 90%
1-(2-methoxyphenyl)-2-nitroethene, 94%
1-(2-methoxyphenyl)-2-nitropropene, 89%
1-(4-methoxyphenyl)-2-nitroethene, 92%
1-(4-methoxyphenyl)-2-nitropropene, 88%
1-(2,4-dimethoxyphenyl)-2-nitroethene, 97%
1-(2,4-dimethoxyphenyl)-2-nitropropene, 74%
1-(2,5-dimethoxyphenyl)-2-nitroethene, 97%
1-(2,5-dimethoxyphenyl)-2-nitropropene, 89%
1-(2,4,5-trimethoxyphenyl)-2-nitroethene, 89%
1-(2,4,5-trimethoxyphenyl)-2-nitropropene, 94%
1-(2,4,6-trimethoxyphenyl)-2-nitroethene, 95%
1-(2,4,6-trimethoxyphenyl)-2-nitropropene, 96%
1-(3,4,5-trimethoxyphenyl)-2-nitroethene, 92%
1-(3,4,5-trimethoxyphenyl)-2-nitropropene, 93%


3-(2-nitrovinyl)-1H-indole, 79%
3-(2-nitropropenyl)-1H-indole, 72%
5-methoxy-3-(2-nitrovinyl)-1H-indole, 83%
5-methoxy-3-(2-nitropropenyl)-1H-indole, 91%

[1] In case of 1-(2,5-dimethoxyphenyl)-2-nitroethene crystallisation occurs during the reaction. After 20 minutes at 50°C the reaction mixture becomes a bright neon-orange solid cake.

pHarmacist:
Thank you sooo much for telling us about methylamine's use! Personally I'm going to have a lot of benefit from this in Henry's condensation. You've just opened my eyes! Are you actually talking about isolated yields, that YOU got?

If Barium does it, it will work!

Sunlight:
To this Rhodium's link:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenethylamines.dibah.html

They used four methods to prepare nitrostyrenes, methanolic methylamine 16-20 %, aqueous ethylamine 70 %, ethanol KOH and ammonium acetate acetic acid. Results show that using methods first or second, an apparent 90 % + yield of nitrostyrenes from piperonal and veratraldehyde are really 50-60 % due nitrostyrene is contaminated with high molecular mass products.
Anyway in Michael Valentine' Psychedelic Chemistry methanolic methylamine is proposed to get the 3,4,5 nitro, with an unespecefied yield. It's not a very good book.
And for example, 3,4,5 trimethoxy benzaldehyde condensation with cyclohexylamine in methanol yield a strange product that it is not the styrene. TLC aids almost nothing in this case because this product is not soluble in methanol.
Have you performed any analytical procecure to determine the purity of the products you got with this attractive method ?

GC_MS:
Must...find...benzaldehydes...Start...synthesis...aaaargh! Nice to hear you're still alive Ba  ;)

Barium:
The following nitrostyrenes has been reduced to the corresponding nitroalkanes using the EtOAc/EtOH/NaBH4 method followed by reduction to the amines using the IPA/KCOOH/Pd-C system.

1-(4-ethoxyphenyl)-2-nitroethene, 89% nitroalkane*, 85% amine hydrochloride*, 97% by HPLC**.
1-(4-ethoxyphenyl)-2-nitropropene, 86% nitroalkane*, 85% amine hydrochloride*, 98% by HPLC**.
1-(2,5-dimethoxyphenyl)-2-nitroethene, 94% nitroalkane*, 82% amine hydrochloride*, 98% by HPLC**.
1-(2,4-dimethoxyphenyl)-2-nitropropene, 90% nitroalkane*, 91% amine hydrochloride*, 98% by HPLC**.
1-(2,4,6-trimethoxyphenyl)-2-nitropropene, 96% nitroalkane*, 94% amine hydrochloride*, 98% by HPLC**.

* Isolatetd yield
** Purity by HPLC, calculated as area %.

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