Cyanomethine Explained

Cyanomethine (4-amino-2,6-dimethylpyrimidine) is an amino and methylated derivative of pyrimidine with the chemical formula, belonging to a class named cyanalkines.^[1]

Properties and synthesis

Cyanomethine is a strongly basic^[2] colourless to white crystalline solid. It is soluble in water and slightly soluble in alcohol.^[3] It is prepared by the trimerisation of acetonitrile with sodium or potassium,^[4] with the corresponding metal cyanide and (possibly 2-methylimidazole or 3-methylpyrazole; iminoacetonitrile has been identified^[5]) as the main byproducts.^[6] It can also made by reaction of sodium methoxide and acetonitrile.^[1]

The correspondence of the three acetonitrile units to a tautomer of cyanomethine is:

At higher pressure, sodium methoxide instead catalyzes trimerization to form 2,4,6-Trimethyl-1,3,5-triazine.^[7]

2,6-Diethyl-5-methyl-4-pyrimidinamine (cyan(o)ethine) is an analogous structure that can be made by trimerization of propionitrile.^[1]

Cyanomethine can form complexes with platinum(II) and platinum(IV) compounds.^[8]

Notes and References

1. Polymerisation of Nitriles, Journal of the Chemical Society. (1890). United Kingdom: Chemical Society.page 1158
2. Karrer, P. (1950). Organic Chemistry. page 819
3. Roscoe, H. E. (1881). A Treatise on chemistry volume 3, 1881.page 523-524
4. Miller, W. A., McLeod, H. (1880). Elements of Chemistry: Theoretical and Practical, page 174
5. Derivatives of Hydrocyanic Acid. Competition Science Vision. Jan 2001 page 1494
6. Methyl cyanide, Thorpe, T. E. (1895). A Dictionary of Applied Chemistry. United Kingdom: Longmans.page 575
7. T. L. Cairns, A. W. Larchar, and B. C. McKusick, The Trimerization of Nitriles at High Pressures, J. Am. Chem. Soc. 1952, 74, 22, 5633–5636Publication Date: November 1, 1952https://doi.org/10.1021/ja01142a028
8. Kovala-Demertzi, D. Platinum(II) and platinum(IV) complexes of 2-amino-4,6-dimethylpyrimidine. Transition Met Chem 15, 23–26 (1990). https://doi.org/10.1007/BF01032225