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

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Author(s): Shailesh Singh, Jyoti Tiwari, Deepali Jaiswal, Amit Kumar Sharma, Jaya Singh, Vandana Singh, Jagdamba Singh*

Journal Name: Current Organic Synthesis

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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 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.

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 addition of DBU (0.15 mmol) through a 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 literature value.

Results: 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-oxo3-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, nucleophilically.

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(E-pub Ahead of Print)
DOI: 10.2174/1570179417666200615153536
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