Nucleophilic aromatic substitution with ethyl cyanoacetate; 2-carboxyethyl- 2'-nitro-4'-chloro benzyl cyanide
SyntheticPage 557
DOI:
10.1039/SP557
Submitted May 03, 2012, published May 07, 2012
Ramesha Ramakrishna (
ramesha63@hotmail.com)
A contribution from
ramesha
Chemicals Used
2,5-Dichloronitrobenzene -commercial ,purity by GC min 98%
Ethylcyanoacetate - from S. D. Fine Chem, LR grade
Potassium carbonate powder
Tetrabutylammonium bromide - S D Fine Chem, LR grade
Dimethyl formamide
Ethyl acetate
Procedure
Dimethylformamide (30 mL), 2,5-dichlorobenzene (9.6 g, 0.05 mole), ethyl cyanoacetate (6.2 g, 0.055 mol) are charged to a 100 mL round bottomed flask. To this tetrabutylammonium bromide(0.5 g, 5% by weight to dichloronitrobenzene) was added, followed by powder potassium carbonate (7.6 g, 0.055 mol) all at once and stirred at room temperature (25-35 oC) for 16 hours. Reaction mixture turns dark red in 10-15 min. TLC shows complete disappearance of 2,5-dichloronitrobenzene after about 15 h. The reaction mixture diluted with ethylacetate (200 mL) and added into water (200 mL). The reaction mixture was acidified to about pH 6 with dilute HCl. At this time the dark red color turns to light yellow. Water layer was separated and discarded. Ethyl acetate was given water wash and dried over sodium sulphate( 25-30 g). The ethyl acetate layer thus obtained was concentrated to get the condensed product as a viscous oil - 12.8 g. This is purified by column chromatography using petroleum ether: ethyl acetate (97:3) on silica gel to get 10.7 g (79%)
Author's Comments
1. It is important to use powder potassium carbonate for the complete reaction. Granular potassium carbonate gives low yield/incomplete conversion.
2. The reaction medium turns red because of the formation of potassium salt of the product.
3. It is essential to acidify the reaction mixture during workup. This has two advantages. 1-high yield, 2- better colour for the product.
4. The active Methylene here is very reactive and can be further functionalized easily.
Data
1H NMR (300 MHz): 8.22 (S, 1H), 7.73 (s, 2H), 5.63 (s,1H), 4.30 (q, 4H), 1.32 (t, 6H)
13C NMR (75 MHz): 163.12, 147.66, 136.70, 134.41, 132.48, 126.26,123.66, 114.06, 64.09, 40.80, 24.70, 13.83.
Lead Reference
Other References
V.M.Vlasov, " Nucleophilic substitution of the nitro group, fluorine, chloride in aromatic compounds".
Russian Chemical Review,
1990, 59, 514-530.
http://dx.doi.org/10.1070/RC1990v059n06ABEH003540
Supplementary Information
1H NMR DCNB.bmp13C NMR DCNB.bmp
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Keywords: aromatics/arenes, dichloronitrobenzene, esters, Ethylcyanoacetate, nucleophilic, substitution
