Investigation of the H3PO4-Promoted Reaction of Benzaldehydes, Ethyl Acetoacetate or Ethyl Cyanoacetate or Malononitrile in the Presence of Urea as a Route to Pyrimidin-2-ones and 2-Iminochromenes
Ishmael B. Masesane *
Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana
Ngonye Keroletswe
Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana
Runner R. Majinda
Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana
*Author to whom correspondence should be addressed.
Abstract
The H3PO4-promoted reactions of benzaldehydes, active methylene compounds and urea are reported. Benzaldehydes, ethyl acetoacetate and urea react in the presence of H3PO4 to give substituted pyrimidin-2-ones in 49-84% yields. The three-component reaction failed when either ethyl cyanoacetate or malononitrile were used instead of ethyl acetoacetate and only the aldol products were formed. However, the reaction of salicylaldehydes and ethyl cyanoacetate or malononitrile gave 2-iminochromenes in moderate to high yields. Some of the prepared pyrimidin-2-ones exhibited weak antibacterial and antifungal activities. The 3-acetoxy-2-iminochromenes showed moderate antimicrobial activities whereas the 3-cyano-2-iminochromenes were inactive against all the test organisms.
Keywords: Benzaldehyde, pyrimidin-2-one, Biginelli reaction, phosphoric acid, 2-iminochromene