S. El Kazzouli et al. / Tetrahedron Letters 44 (2003) 6265–6267
6267
Table 2. Imidazo[1,2-a]pyridines and imidazo[1,2-a]-
pyrimidines synthesized on base labile linker
linker is an efficient way to generate this class of
compounds.
Supplementary material
Spectroscopic characterization (1H, 13C NMR and MS)
for compounds 1, 3, 7, 8, 9, 10, 12, 13 is available
on-line.
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It should be noted, that all reactions reported here were
performed on a scale (typically 200–250 mg beads; 0.7
mmol/g or 0.87 mmol/g) allowing the isolation of at
least 20 mg of crude product. In some cases, yields of
products purified by flash chromatography were
reported in parentheses. The structure of all compounds
was established by 1H, 13C NMR and mass
spectroscopy.
Six different imidazo[1,2-a]pyridines and two imi-
dazo[1,2-a]pyrimidines were synthesized by this route
on Rink amide resin (Table 1). Unfortunately, use of
this solid support does not allow to obtain a total
conversion (50–80% after six steps) even with a double
coupling (twice 8 equivalents and 72 h).
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Furthermore, four examples of imidazo[1,2-a]pyridines
and two imidazo[1,2-a]pyrimidines were synthesized on
the base labile resin (Table 2). In this case, both conver-
sions and purities were excellent after six steps.
Although the reaction times are long in agreement with
experiments performed in solution,6 use of base labile