Abstract
The deproto-metalation reactions of pyrimidine and pyrazine were
regioselectively carried out using lithium tris(2,2,6,6-tetramethylpiperidino)cadmate
in tetrahydrofuran at room temperature. This result was demonstrated
by subsequent trapping with iodine to afford 4-iodopyrimidine
and 2-iodopyrazine in 71% and 63% yields, respectively.
The same reaction performed on pyridazine afforded a mixture of
the 3- and 4-iodo derivatives (55% and 41% yields,
respectively). From pyrazine, access to the 2,5-diiodo derivative
(40% on a 25 mmol scale) proved possible using a larger
amount of base (1 equiv instead of 0.33).
Key words
metalations - cadmium - lithium - heterocycles - iodine
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