Sodium Borohydride as the Only Reagent for the Efficient Reductive Alkylation­ of Malononitrile with Ketones and Aldehydes

Abstract

An efficient and convenient method for the synthesis of primary and secondary monosubstituted malononitriles has been developed. In this method, sodium borohydride in isopropanol has a catalytic effect on the initial condensation between malononitrile and aldehydes or ketones at 0 °C. The sodium borohydride also simultaneously acts as a reagent and reduces the unsaturated intermediate formed in situ by the condensation. This simple reductive alkylation method effectively consumes all malononitrile and selectively produces only monosubstituted malononitriles. Unsymmetrically disubstituted malononitriles are prepared via alkylation of these monosubstituted derivatives.

Key words

malononitrile - ketones - aldehydes - condensations - reductions

References

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8

Isolated yield for the previous one-pot method (ref. 5) was 83% and the reaction time was 10 min for the condensation step. The current yield was 78% in ≤6 min for both steps.

15

The second portion of NaBH₄ was added after 90 min.

19

Additional trimethylacetaldehyde was added after 60 min.

21

The second portion of NaBH₄ was added after 20 min.