Aim and Objective: Citrus Juice as an efficient, cost-effective and green catalyst
employed for one-pot synthesis of various β-substituted enaminones through the reaction of β-
dicarbonyl compounds with different primary amines in a solvent-free conditions on silica gel as
solid surface using grindstone technique in high yields and short reaction times. The presented
procedure is operationally simple, practical and green.
Material and Methods: The wide application of this procedure is demonstrated by the use of various
substituted amines to react with β-dicarbonyl compounds. The method was successfully applied for
primary amines (15 entries) and the related enaminones were well synthesized in good to excellent
yields. Melting points were measured on an Electro thermal 9100 apparatus. 1HNMR and 13C NMR
spectra were recorded on a FTNMR BRUKER DRX 500 Avence spectrometer. Chemical shifts were
given in ppm from TMS as internal references and CDCl3 was used as the solvent as well. The IR
spectra were recorded on a Perkin Elmer FT-IR GX instrument. The chemicals used in this work
were purchased from Merck and Fluka chemical companies.
Results: Grinding synthesis of citrus juice catalyzed enamination of 1,3-dicarbonyls (acetylacetone,
methyl and ethyl- 3-oxobutanoate) with various primary amines ( aromatic and aliphatic) under
solvent-free silica supported conditions was examined and studied (15 entries) and the obtained
enaminones were well synthesized in good to excellent yields. Furthermore, the effect of various
catalysts on the yield and reaction time for grinding synthesis of 3-phenylamino- but- 2- enoic acid
ethyl ester (1) by this method has evaluated as well.
Conclusion: a novel, efficient and green protocol for the grinding synthesis of enaminones using
citrus juice as natural catalyst has been presented. This methodology is user friendly, green and low
cost procedure under mild reaction condition with faster reaction rates. The citrus juice is
inexpensive and non-toxic which makes the process convenient, more economic and benign.
Furthermore, applying grindstone technique in solvent-free conditions, use of silica gel as a solid and
heterogeneous surface in reaction, high yields of products, cleaner reaction profiles, and availability
of the reagents makes this method a better choice for synthetic chemists.