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Chapter 1
Synthesis of functionalized pyrimidines
1.7 Experimental section
Thin-layer chromatography was accomplished on 0.2-mm precoated plates of
silica gel G60 F 254 (Merck). Visualization was made with UV light (254 and 365nm)
or with an iodine vapor. IR spectra were recorded on a FTIR-8400 spectrophotometer
using DRS prob. 1 H (300 MHz), 1 H (400 MHz), 13 C (75 MHz) and 13 C (100 MHz)
NMR spectra were recorded on a Bruker AVANCE II spectrometer in CDCl 3 and
DMSO. Chemical shifts are expressed in δ ppm downfield from TMS as an internal
standard. Mass spectra were determined using direct inlet probe on a GCMS-QP 2010
mass spectrometer (Shimadzu). Solvents were evaporated with a BUCHI rotary
evaporator. Melting points were measured in open capillaries and are uncorrected.
General synthetic procedure for the 3,4-dihydropyrimidine-2-(1H)-ones
(ASM-01a-e).
A 100mL round bottom flask equipped with magnetic stirrer and septum was
charged with the methyl 4-methyl-3-oxopentanoate (0.01M), aldehyde (0.01M) and
urea (0.015M). Few drops of DMF were added to the reaction mixture as a catalyst.
The reaction mixture was then heated at 145-150 o C for 15-30 minutes. The progress
of reaction was monitored by thin layer chromatography. The reaction mixture was
allowed to cool at rt. Then, methanol (20 mL) was added and the resulting mixture
was refluxed for 30 min. The solid separated upon cooling was filtered, washed with
methanol and dried. The products thus obtained (ASM-01a-e) were directly used for
the next step.
General synthetic procedure for the 2-hydroxypyrimidine derivatives
(ASM-02a-e).
In a 100mL round bottom flask equipped with magnetic stirrer and
thermometer was added nitric acid (60%) (10 mL). To the nitric acid slowly added
ASM-01a-e (10 mmol) at 0 o C. After complete addition, the mixture was stirred at
this temperature for 30 min. The progress of reaction was monitored by thin layer
chromatography. The reaction mixture was poured into cold water and neutralized
with saturated sodium bicarbonate solution. The solid separated was filtered, washed
with water and dried. The crude products (ASM-02a-e) were directly used for the
next step.
Department of Chemistry, Saurashtra University, Rajkot-360005 25