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Nucleophilic Acylation with Aromatic Aldehydes to 2 Bromoacetonitrile: An Umpolung Strategy for the Synthesis of Active Methylene Compounds

[ Vol. 17 , Issue. 7 ]

Author(s):

Shailesh Singh, Jyoti Tiwari, Deepali Jaiswal, Amit Kumar Sharma, Jaya Singh, Vandana Singh* and Jagdamba Singh*   Pages 518 - 524 ( 7 )

Abstract:


Background: A novel one-pot N-heterocyclic carbene (NHC)-catalysed acylation of 2- bromoacetonitrile with aromatic aldehydes is reported. The protocol involves carbonyl umpolung reactivity of aldehydes in which the carbonyl carbon attacks nucleophilically (as d1 nucleophile) on the electrophilic terminal of 2-bromoacetonitrile to afford 3-aryl-3-oxopropanenitrile. The salient features of this procedure are short reaction time, operational simplicity, ambient temperature, no by-product formation and high yields.

Materials and Methods: A flame-dried round bottom flask was charged with Imidazolium salts (3a) (0.20 mmol). Aldehyde 1a (1.0 mmol), 2-bromoacetonitrile 2 (1.0 mmol), and THF / t-BuOH 5 mL; 10:1) were added at positive nitrogen pressure followed by the addition of DBU (0.15 mmol) through stirring. The resulting yellow- orange solution was stirred at room temperature for 5-6 h. After completion of the reaction (TLC monitored), the reaction mixture was concentrated under reduced pressure. The product was purified using hexane / EtOAc (10:1) as an eluent to provide analytically pure compound 4a. Physical data of representative compounds and the NMR spectroscopic data are in agreement with the literature value.

Results and Discussion: The salient features of this procedure are short reaction time, operational simplicity, ambient temperature, no by-product formation and high yields.

Conclusion: To sum up, we have developed a convenient, efficient and one-pot route for 3-oxo-3- phenylpropanenitrile synthesis from NHC promoted direct nucleophilic acylation of aromatic aldehydes using 2- bromoacetonitrile. This method provided a wide range of products and good yields. To best of our knowledge, this is the new report for the synthesis of 3-oxo-3-phenylpropanenitrile through NHC promoted nucleophilic acylation of aromatic aldehyde.

Keywords:

N-heterocyclic carbene, tetrahydrofuran, DBU, active methylene compound, aromatic aldehydes, nucleophilic acylation.

Affiliation:

Department of Chemistry, University of Allahabad, Allahabad-211002, Environmentally Benign Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad-211002, Environmentally Benign Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad-211002, Environmentally Benign Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad-211002, Department of Chemistry, LRPG College, Sahibabad, Ghaziabad- 201005, Department of Chemistry, University of Allahabad, Allahabad-211002, Environmentally Benign Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad-211002

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