Author Topic: Reduction of nitro to amine - Zn/N2H4.HCOOH  (Read 11272 times)

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Chimimanie

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Dimethoxy-phenylethyl alcohols
« Reply #20 on: April 13, 2003, 05:16:00 PM »
Hi!

Oxidation by mercury(II) salts.  I.  Hydroxyalkylation of aromatic rings by mercurated ethylene and propylene. M. Julia, E. Colomer and R. Labia Bulletin de la Societe Chimique de France  (1972),   (11),  4145-8

This is a translation of a french article which describe the synthesis of various dimethoxy-phenylethanols (and propan-2-ols). Those alcohols can be halogenated or tosylated and then swapped with azide/reduction or subjected to the one-pot synthesis described above. The advantage of this method is that it is easy (much easier than lithiation/ethylene oxyde or propylene oxyde) and OTC. The disadvantage is of course the use of mercury salts, which are obviously hazardous. Anyway i like this reaction, it open a new road to 2C-H from dimethoxy benzene in two steps (with the second step beeing the (not OTC) PPh3/CCl4/NaN3 reaction) with an acceptable yield.

This reaction should only bee done by educated individuals, with the skills and knowledge. Mercuric vapors are toxics, mercuric salts are toxics, organomercuric compounds are even more deadly. Metallic mercury is hazardous to the environnement, it should bee recycled to the mercuric acetate for another batch.

They say than direct ammonolyse might bee possible once the organomercuric compound is synthetised, without passing through the alcohol stage.

Fluoboric acid is used here, but it can bee replaced by perchloric acid (but that is more dangerous) or BF3.

Experimental

3,4-dimethoxy-phenyl beta-ethanol acetate

In a 500 mL three necked RBF equipped with a stirrer and a condenser is put 0.1 mol (32g) of mercuric acetate in 150 mL of acetic acid. A stream of ethylene is bubbled in till half an hour after the total dissolution of the mercuric salt. There is then added 0.2 mol (31g) of veratrol and 5 mL of a 40% water solution of fluoboric acid. After 3 hours at 80°C, 20g of metallic mercury is obtained (100%) and the product is extracted with CHCl3. Yield 13.5g (60% based on Hg) of 3,4- dimethoxy-phenylethanol acetate (bp 130-133°C). The acetate is then saponified in ethanolic KOH with a yield of 90%.  

The alcoylation of the three dimethoxybenzenes (2,5-, 2,4- and 3,4-) by mercurated ethylene or propylene is done by the same way than with ethylene and veratrol. The six phenylethyl acetates are obtained with yields of 60%.

The six alcohols obtained after saponification are caracterised with their o-naphtyl urethanes or identified with authentic samples.


Dimethoxy phenyl-2 ethanols and their Naphtyl-urethanes
3,4- mp=128°C (urethane); 47°C (alcohol)
2,5- mp=151°C
2,4- mp=134°C; 65°C

Dimethoxy phenyl-propan-2-ols and their Naphtyl-urethanes
3,4- mp=92°C; 40-42°C
2,4- mp=104°C
2,5- no mp given.

when Ar=2,5 dimethoxyphenyl no crystallised naphtyl urethane could be obtained

EDIT:

Another preparation for 2,5-dimethoxyphenyl-propan-2-ol (by lithiation) is in

Post 426585 (missing)

(Antoncho: "Not quite easy, but .....", Russian HyperLab)
, thank to our Official Russian Translator, Antoncho. Better yield but harder chemistry.

Chimimanie

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Recycling mercury
« Reply #21 on: July 29, 2003, 10:38:00 AM »
This method goes well for recycling mercury into mercury(II) acetate:

Hg metal -> HgSO4:

First, attack Hg metal with conc. H2SO4, like in

https://www.thevespiary.org/rhodium/Rhodium/chemistry/mercurychloride.html

, the reaction mixture must bee heated to at least 200°C and more preferably to a little more, like 250° or so, to see bubbling and crystal of HgSO4 formed in those bubble. A hot oil bath could bee used for a few hours, then the end of the reaction finished with a burner or heat gun, or all the attack could bee made on those heat sources, but beeware Hg vapors (as well as SO3 [cough])! ALWAYS use a tubing to vent outside the vapor! Hg metal vapors are toxics!

Well, now you have the HgSO4 in H2SO4, let it cool, then pour off the H2SO4, dissolve in water the HgSO4, filter if you find it wise to do so...

HgSO4 -> yellow HgO:

Prepare a solution of NaOH in iced water, and setup an ice bath. Slowly add the cold NaOH solution to the cold mercury sulfate solution, you will see some yellow HgO come then dissolve, after a while, when enough NaOH is added (use a somewhat big excess), you will have the flask full of yellow HgO crystals. When you find the precipitation is finished, filter at buchner, you could dry it with small quantity MeOH then et2O if you want. Dispose properly of the filtrate, and test if there is some remaining mercury in it, by adding a few more NaOH solution.

Yellow HgO -> Mercury(II) acetate: [1],[2]

        HgO    +    2 CH3COOH     =     Hg(CH3COO)2    +    H2O
MM     216,6              120.1                    318.7                18.0

A solution of 20g of yellow HgO in 30 mL of 50% CH3COOH is prepared on a waterbath. It is filtered through a jacketed filter heated with hot water, and the filtrate is cooled with ice. The crystals are suction-dried and washed with ethyl acetate. The product is recrystallized from hot ethyl acetate or from hot water slighty acidified with acetic acid. The salt is dried in a vacuum dessicator over CaCl2.

Some more facts about mercuric acetate: [1],[2]

Use: as a mercurizing and oxidizing agent and for the absorption of ethylene. ;)

Properties: Nacreous, light-sensitive crystalline flakes. On storage acquires a yellow tinge and an odor of CH3COOH (formation of a basic salt). MP: 178-180°C, decompose at higer temperatures.

Solubility: (0°C) 25g, (19°C) 36.4g / 100mL water and about 100g at 100°C with partial dec.). The compound in 0.2N aqueous solution is approximatively 30% hydrolized; the yellow basic salt precipitates on diluting or heating; soluble in ethyl acetate. d 23 3.286.

References:
[1] Wagenknecht, Juza in Handbook of Preparative Inorganic Chemistry, vol. 2, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) pp 1120-1121.
[2] Gmelin-Kraut. Hdb. anorg. Chem., 7th ed., V2, 826, Heidelberg, 1914, modified.


Safety:

-Beware Hg metal vapors.
-Beware Hg salts intake.
-Absolutely beeware organic Hg exposure  :o !

Interesting links for toxicity:

http://www.atsdr.cdc.gov/toxprofiles/tp46.html



Q: And why to not do the direct Hg metal to Hg diacetate transformation with peracetic acid???
A: look DOI:

10.1007/s002040050563



The source of methylmercury was most likely inadvertent synthesis. This may have followed the pattern suggested for the Minamata epidemics where the synthesis was also inadvertent. According to this scheme (Irukayama 1977) the first step is the oxidation of acetate to peracetic acid:

CH3COOH + O <-> CH3COOOH


and the second step is the formation of methylmercury from peracetic acid and inorganic mercury:

CH3COOOH + HgX2 -> CH3HgX + CO2 + HX


Peroxide, inorganic mercury salt and acetate, the essential ingredients of this reaction, were present in the reactor served by the patients. Compared with mercury vapour such a synthesis increased the risk of intoxication because methylmercury acetate is 5.4 times more volatile than elemental mercury (Swensson and Ulfvarson 1863), it is more toxic and the neurological damage is irreversible.




Hell, better to avoid CH3COOOH + HgX2 -> CH3HgX + CO2 + HX then  ;) .


Rhodium

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Nitro -> Amine with Mg/Hydrazinium Monoformate
« Reply #22 on: June 07, 2004, 05:03:00 PM »
Magnesium/Hydrazinium Monoformate: A new Hydrogenation System for the Selective Reduction of Nitro Compounds
K. Abiraj, Shankare Gowda, D. Channe Gowda

Synth. React. Inorg. Met.-Org. Chem. 32(8), 1409-1417 (2002)

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitro2amine.mg-n2h4-hcooh.html)

Abstract
The nitro group in aliphatic and aromatic nitro compounds, which also contain reducible substituents such as alkenes, nitriles, carboxylic acids, phenols, halogens, esters, etc., is selectively and rapidly reduced at room temperature to the corresponding amine in good yield by employing hydrazinium monoformate in the presence of magnesium powder. It was observed that, hydrazinium monoformate is more effective than hydrazine or formic acid or ammonium formate and reduction of the nitro group occurs without hydrogenolysis in the presence of low-cost magnesium compared to expensive metals like palladium, platinum, ruthenium, etc.


java

  • Guest
Reduction of Aromatic Nitro Compounds
« Reply #23 on: July 06, 2004, 10:44:00 AM »
Reduction of Aromatic Nitro Compounds under Solvent-free Conditions
using Alumina-supported Hydrazine/FeNH4(SO4)2·12H2O


Abstract
Aromatic nitro compounds were easily reduced to the corresponding amino compounds with hydrazine
hydrate supported on alumina in the presence of FeNH4(SO4)2?12H2O

.
Journal of the Chinese Chemical Society, 2004, 51, 569-570



RESULTS AND DISCUSSION
Microwave irradiation has been success fully applied in organic synthesis. Recently, reactions
facilitated by microwaves under solvent-free conditions have attracted more attention be cause
of their enhanced selectivity and milder reaction conditions. Recyclability of the inorganic solid
supportis often possible thus rendering the procedure relatively environmentally acceptable.
In this way, we successfully reduced the aromatic nitro compounds with hydrazine hydrate
supported on alumina in the presence of FeNH4(SO4)2-12H2O.

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