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Chapter 1
Synthesis of functionalized pyrimidines
Figure-13
Lewis acid such as, Indium (III) chloride was emerged as a powerful Lewis
catalyst imparting high region and chemo selectivity in various chemical
transformations. B. C. Ranu and co-workers 30 have reported indium (III) chloride
(InCl 3 ) as an efficient catalyst for the synthesis of 3,4-dihydropyrimidn-2(1H)-ones
(Figure-14). A variety of substituted aromatic, aliphatic and heterocyclic aldehydes
have been subjected to this condensation very efficiently. Thiourea has been used
with similar success to provide the corresponding dihydropyrimidin-2(1H)-thiones.
Figure-14
Majid M. Heravi et al. has reported a simple, efficient and cost-effective
method for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones by one pot
three-component cyclocondensation reaction of a 1,3-dicarbonyl compound, an
aldehyde and urea or thiourea using 12-tungstophosphoric acid 31 and 12-
molybdophosphoric acid 32 as recyclable catalyst (Figure-15).
Figure-15
Hydroxyapatite doped with ZnCl 2 , CuCl 2 , NiCl 2 and CoCl 2 efficiently
catalyzes the three components Biginelli reaction between an aldehyde, ethyl
acetoacetate and urea in refluxing toluene to afford the corresponding
dihydropyrimidinones in high yields. 33
Sc(III)triflate catalyzes the three-component condensation reaction of an
aldehyde, a β-ketoester and urea in refluxing acetonitrile to afford the corresponding
3,4-dihydropyrimidin-2(1H)-ones in excellent yields (Figure-16). The catalyst can be
recovered and reused, making this method friendly and environmentally acceptable. 34
Department of Chemistry, Saurashtra University, Rajkot-360005 8