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Reduction of nitro arene by Fe/ammonium chloride; o-toludine

SyntheticPage 538
DOI: 10.1039/SP538
Submitted Feb 13, 2012, published Feb 13, 2012
Ramesha Ramakrishna (ramesha63@hotmail.com)


			Reaction Scheme: Reduction of nitro arene by Fe/ammonium chloride

Chemicals Used

o-nitrotoluene
Iron powder
Ammonium chloride
Methanol

Procedure

To a 500 mL three necked flask carrying a mechanical stirrer, thermometer pocket was charged methanol (250 mL) followed by o-nitrotoluene (50 g, 0.36 mol) and ammonium chloride (100 g). To this, iron powder (100 g, 1.79 at. Eq) was added under stirring and refluxed for 7h. Once TLC shows completion of the reaction, the reaction mixture was cooled to about 40 oC and added water (100 mL. It is very important to add water before distillation of methanol. If methanol is removed without addition of water, there is a possibility of uncontrolled exothermic reaction leading to explosion). Distil almost 90% methanol under vacuum. Cool to room temperature and add dichloromethane (250 mL, toluene or ether also can be used) and stir for 10 min. Filter the black sludge through a bed of celite or silica. Wash the celite with dichloromethane (100 mL). The combined filtrates were mixed and washed with water (150 mL). The dichloromethane layer was concentrated under reduced pressure to give ortho- toluedine as pale yellow liquid 36 g (92%).

Author's Comments

 1. This reaction is milder compared to Iron-acid reduction.

2. This reaction can also be done in stainless steel vessel. This has been scaled upto 100 kg batches. This offers great advantage in industrial scale preperation.

3. The product from this reduction is normally pure and does not require further purification.

4. Use of electrolytic grade iron reduces the reduction time from 7 to about 2-3 h.

5. This is a general method applicable to any nitro to amine reduction.

6. It is very important to add water before recovery of methanol to avoid exothermic reaction.

 

Data

1H NMR (300 MHz): δ 2.09 (s, 3H), 3.47 (s, br, 2H), 6.58 (d, J = 7.6 Hz, 1H), 6.67 (t, J = 7.6 Hz, 1H), 6.98-7.01 (m, 2H).

13C NMR (100 MHz): δ 17.4, 115.0, 118.7, 122.4, 127.1, 130.6, 144.8.

 


Lead Reference

Modified procedure of-

Krishnamurthy Ramadas & Natarajan Srinivasan, Synthetic Communications, 1992, 22(22), 3189–3195.

 

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Keywords: amines, ammonium chloride, aromatics/arenes, Iron, nitro, reduction

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