Mechanistic aspects of the Strecker aminonitrile synthesis
- 1 January 1971
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 325-329
- https://doi.org/10.1039/j29710000325
Abstract
Asymmetric α-aminonitriles could not be prepared by the Strecker procedure catalysed by optically active acids or bases. Benzylideneaniline reacted readily and quantitatively with hydrogen cyanide to give α-cyanobenzylaniline, while mandelonitrile reacted very slowly with aniline, indicating that benzylideneaniline or a Schiff base may be an intermediate for the Strecker synthesis. The addition of hydrogen cyanide to benzylideneaniline in acetonitrile–methanol at 25 °C follows a third-order rate equation: –d[Ar1CHNAr2]/dt=k[Ar1CHNAr2][HCN][MeOH]. The rate is higher in protic dipolar solvents than in aprotic non-polar solvents. An electron-releasing group on either of the rings increases the rate with Hammett ρ values of –1·11 in the benzylidene and –1·39 in the aniline ring. A mechanism involving methanol-catalysed addition of hydrogen cyanide to benzylideneaniline is postulated and discussed.Keywords
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